Cancer Flashcards

Question

What are the hallmarks of cancer?

Answer 1

Used to be 6 now 10. First 6 is original 1. Self –sufficient • Normal cells need growth signals to move from a quiescent (resting) to active proliferating state • These signals are transmitted into the cell via growth factors binding transmembrane receptors and activating downstream signalling pathways 2. Insensitive to anti-growth signals 3. Anti-apoptotic 4. Pro-invasive and metastatic 5. Pro-angiogenic 6. Non-senescent 7. Dysregulated metabolism 8. Evades the immune system 9. Unstable DNA 10. Inflammation

Answer 2

``` Top to bottom: Ligand-binding site Membrane Kinase domain C-terminal region with lots of tyrosine (for autophosphorylation) ```

Answer 3

HER2 – amplified and over-expressed in 25% breast cancer EGFR – over-expressed in breast and colorectal cancer, lung cancer PDGFR- glioma (brain cancer) VEGF – prostate cancer, kidney cancer, breast cancer FGFR (head and neck cancers, myeloma) Therefore increased kinase cascade and signal amplification

Answer 4

1) Monoclonal antibodies - momab (derived from mouse antibodies) - ximab (chimeric) e.g cetuximab - zumab (humanised) e.g. bevacizumab trastuzumab - mumab (fully human) e.g. panitumumab Humanized monoclonal antibody, murine regions (black) interspersed within the light (light gray) and heavy (dark gray) chains of the Fab portion. Chimeric antibody murine component (black) of the variable region of the Fab section is maintained integrally. Monoclonal antibodies target the extracellular component of the receptor Neutralise the ligand Prevent receptor dimerisation Cause internalisation of receptor Also activate Fcgamma-receptor-dependent phagocytosis or cytolysis induces complement-dependent cytotoxicity (CDC) or antibody-dependent cellular cytotoxicity Examples: bevacizumab binds and neutralised VEGF, improving survival in colorectal cancer Cetuximab targets EGFR 2)Small molecule inhibitors Bind to the kinase domain of the tyrosine kinase within the cytoplasm and block autophosphorylation and downstream signalling. Small molecule inhibitors act on receptor TKs but also intracellular kinases - therefore can affect cell signalling pathways Examples of SMIs inhibiting receptors: erlotinib (EGFR), gefitinib (EGFR), lapatinib (EGFR/HER2), sorafinib (VEGFR) SMIs inhibiting intracellular kinases: Sorafinib (Raf kinase) Dasatinib (Src kinase) Torcinibs (mTOR inhibitors) By acting on receptors (either externally or internally), targeted therapies block cancer hallmarks (e.g VEGF inhibitors alter blood flow to a tumour, AKT inhibitors block apoptosis resistance mechanisms) WITHOUT the toxicity observed with cytotoxics BUT CAN DEVELOP RESISTANCE AND EXPENSIVE

Answer 5

• Mutations in ATP-binding domain (e.g BCR-Abl fusion gene (Philadelphia) and ALK gene, targeted by Glivec - imatinib and crizotinib respectively) • Intrinsic resistance (herceptin effective in 85% HER2+ breast cancers, suggesting other driving pathways) • Intragenic mutations • Upregulation of downstream or parallel pathways

Answer 6

• Single stranded, chemically modified DNA-like molecule 17-22 nucleotides in length • Complementary nucleic acid hybridisation to target gene hindering translation of specific mRNA • Recruits RNase H to cleave target mRNA • Good for “undruggable” targets RNA interference • Single stranded complementary RNA • Has lagged behind anti-sense technology – especially in cancer therapy • Compounds have to be packaged to prevent degradation - nanotherapeutics • CALAA-01 targeted to M2 subunit of ribonucleotide reductase. Phase I clinical trials in cancer –results awaited

Answer 7

It is found in G1 and cell monitors its own size and external signals. The cell is now committed in the cell cycle and does not require any more GF’s.

Answer 8

An oncogene over expressed in many tumours A transcription factor which stimulates the expression of cell cycle genes and is need to enter S phase

Answer 9

Tyrosine phosphorylation provides docking sites for adapter proteins Protein-protein interactions: protein binding – bringing proteins together Proteins are modular and contain domains, i.e. functional and structural units that are copied in many proteins Some domains are important in molecular recognition – have no enzymatic function of their own, simply bring other proteins together E.g. Grb2 binds to SH3 - proline-rich regions (constitutive) and SH2 (phosphorylation tyrosine (transient)

Answer 10

1) exchange factors e.g. SOS activates 2) GTPase activating proteins inactivate RAS must be bound to plasma membrane to be activated Oncogenically activated: To increase the amount of active GTP-loaded Ras by: -preventing GAP binding -preventing GTP hydrolysis

Answer 11

Extracellular signal-regulated kinase | It’s a type of MAPK cascade (mitogen-activated protein kinase)

Answer 12

Cdks (cyclin-dependent kinases) Present in proliferating cells throughout cell cycle Activity is regulated by: -interaction with cyclins -phosphorylation Cyclins - transiently expressed at specific at specific points in the cell cycle - regulated at level of expression - synthesised then degraded Cyclins bind to and activate Cdk(s) triggering different events in the cell cycle Cdks phosphorylation proteins (on serine or threonine) to drive cell cycle progression E.g. nuclear lamins (causes breakdown of nuclear envelope) E.g. retinoblastoma protein (pRb) - tumour suppressor - inactivated in many cancers Regulation of Cdks by phosphorylation Requires activating phosphorylation AND removal of inactivating phosphorylation Cyclins activate Cdks but also alter substrate specificity Substrate accessibility changes through cell cycle Cyclical activation - Cdks become sequentially active and stimulate synthesis of genes required for next phase

Answer 13

Cdk1/cycB active. Mitosis on hold - key substrates phosphorylated Signal from fully attached kinetochores causes cyclin B to be degraded: - Cdk1 inactivated - key substrates dephosphorylated - mitosis progresses

Answer 14

INK4 family and CIP/KIP family G1 phase CKIs - inhibit Cdk4/6 by displacing cyclin D S phase CKIs - inhibit all Cdks by binding to the Cdk/cyclin complex CKI must be degraded to allow cell cycle progression

Answer 15

Oncogenes (derived from normal proto-oncogenes) -EGFR/HER2, mutationally activated or overexpressed in many breast cancers (herceptin antibody for the treatment of HER2-positive metastatic breast cancer) -Ras, mutationally activated in many cancers (inhibitors of membrane attachment) -cyclin D1, over expressed in 50% of breast cancers -B-Raf, mutationally activated in melanomas (kinase inhibitors in trials) -c-Myc, overexpressed in many tumours Higher up in signal, harder to treat because affects more pathways Tumour suppressors - RBC, inactivated in many cancers - P27KIP1, underexpression correlates with poor prognosis in many malignancies

Answer 16

Carbon ring structures can be easily activated chemically because chemically reactive Also can interchange easily e.g. thymine —> uracil by removal of methyl group. Base modifications prevent replication or cause mutations: Deamination - the primary amino groups of nucleic acid bases are somewhat unstable. They can be converted to ketogroups in reactions like cytosine to uracil Chemical modification - e.g. hyper-reactive oxygen (hydrogen peroxide, peroxide radicals .etc.) can modify DNA bases. A common product of thymine oxidation is thymine glycol. Hyper-reactive oxygen species are also generated by ionising radiation (x-rays, gamma rays) Many environmental chemicals can modify DNA bases (including food), frequently by addition of a methyl or other alkyl group (alkylation). Addition of larger molecules defines “adducts” - carcinogens can cause them Photodamage - ultraviolet light is absorbed by the nuclei acid bases, and the resulting influx of energy can induce chemical changes. The most frequent photo products are the consequences of bond formation between adjacent pyramid Ines with one strands (intra-DNA damage) e.g. thymidine react with each other to form thiamine dimer Nick - radiation can break phosphodiester bond Gap - lots of breaks/nicks Thymine dimer - distortion of helix Base pair mismatch - because of change in base

Answer 17

Chemicals (carcinogens) - dietary - lifestyle - environmental - occupational - medical - endogenous - metabolisms?? Radiation -ionising Generates free radicals in cells including oxygen free radicals - super oxide radical O2• , hydroxyl radical HO• Possess unpaired electrons - electrophilic and therefore seek out electron rich DNA - cause nicks e.g. ring-opened guanine and adenine -solar Form pyramidine (thymine) diners - skin cancer -cosmic Damage from carcinogens: - DNA adducts and alkylation - Base diners and chemical cross-links - Base hydroxylations (reactive oxygen) and abasic sites formed (base destroyed but DNA structure underlying it intact) The importance of DNA damage: - DNA damage can lead to mutation - mutation may lead to cancer - damaging DNA is an important strategy in cancer therapy (chemotherapy)

Answer 18

Mammalian metabolism Phase I - liver -addition of functional groups e.g. oxidation, reduction, hydrolysis -mainly cytochrome p450 mediated Phase II -conjugation of phase I functional groups e.g. sulphation, glucoronidation, acetylation, methylation, amino acid and glutathione conjugation (generates polar -water soluble metabolites) Polycyclic aromatic hydrocarbons: -common environmental pollutants -formed from combustion of fossil fuels and tobacco E.g. Two step epoxidation of B[a]P - mutation in lung cancer causes by tobacco smoke Epoxidaiton of aflatoxin B1 - formed by Aspergillus flavus mould, stored peanuts Metabolism of 2-napthylamine - past components of dye-stuffs, bladder cancer - nitrenium ion end up in urine and change pH causing cancer

Answer 19

The greater the persistence of damage then the greater the chance of mutagenic event. P53 is a tumour suppressor gene, p53 is kept inactive by MDM2. MDM2 lost if p53 activated P53 is a TF so can turn on different pathways to respond to damage e.g. DNA repair in response to DNA replication stress, double-strand breaks .etc. Types of DNA repair: - direct reversal of DNA damage - Base excision repair (mainly for apurinic/apyrimidinic damage - lost base) - nucleotide excision repair (mainly for bulky DNA adducts) - during or post replication repair - DNA mismatch repair DNA mismatch repair: -mismatches that arise during replication are corrected by comparing the old and new strands (proof-reading) Bulge in DNA = wrong base, recognised by MSH and MCH protein, bind to bulge, nucleus cuts out base and then polymerase restores correct sequence -other systems deal with mismatches generated by base conversions such as those which result from deamination Direct DNA repair: Involves the reversal or simple removal of the damage by the use of proteins which carry out specific enzymatic reactions E.g. photolyases (activated by normal light, not UV) repair thymine diners Excision repair of DNA damage: For nicks 1) Damage to G but not to phosphodiester backbone 2) remove base without affecting phosphodiester bone by DNA-glycosylase 3) AP-endonuclease cuts open nuclear strand 4) DNA polymerase adds correct base 5) DNA lipase For gaps, e.g. caused by big adduct groups 1) damage to both base and DNA 2) endonuclease - forms nicks around mutation 3) helicase removes phosphodiester bond and bases 4) DNA polymerase corrects base 5) DNA ligase Double strand break repair: Double-strand breaks are made: • Under physiological conditions during somatic recombination and transposition. e.g. Transient base pairing of V(D)J recombination • During Homologous Recombination. • As a result of ionizing radiation and oxidative stress induced DNA damage. 1) following a double sytrand break, a 3’-5’ exonuclease exposes a 5’ single-strand overhand until it finds a sequence which matches together 2) transient base pairing of several nucleotides enables ends to come together 3) DNA polymerisation 4) nucleolytic processing 5) ligation Non-homologous repair- if oevrlangs font match, Ku proteins hold DNA together forcing repair Summary: Direct reversal of DNA damage ▪ photolyase splits cyclobutane pyrimidine-dimers ▪ methyltransferases & alkyltransferases remove alkyl groups from bases Base excision repair (mainly for apurinic/apyrimidinic damage) ▪ DNA glycosylases & apurinic/apyrimidinic endonucleases + other enzyme partners ▪ A repair polymerase (e.g. DNA Polb) fills the gap and DNA ligase completes the repair. Nucleotide excision repair (mainly for bulky DNA adducts) ▪ Xeroderma pigmentosum proteins (XP proteins) assemble at the damage .A stretch of nucleotides either side of the damage are excised. ▪ Repair polymerases (e.g. DNA Pold/b) fill the gap and DNA ligase complete the repair. During- or post-replication repair ▪ mismatch repair ▪ recombinational repair

Answer 20

* Xeroderma Pigmentosum * severe light sensitivity * severe pigmentation irregularities * early onset of skin cancer at high incidence • elevated frequency of other forms of cancer • frequent neurological defects ``` Trichothiodystrophy • sulphur deficient brittle hair • facial abnormalities • short stature • ichthyosis (fish-like scales on the skin) • light sensitivity in some cases Cockayne's syndrome • dwarfism • light sensitivity in some cases • facial and limb abnormalities • neurological abnormalities • early death due to neurodegeneration ```

Answer 21

Normally: Carcinogen damage leading to altered DNA —> apoptosis —> cell death Carcinogen damage leading to altered DNA —> efficient repair —> normal cell Problem: Carcinogen damage leading to altered DNA —> incorrect repair/ altered primary sequence —> DNA replication and cell division: fixed mutations —> transcription/translation giving aberrant proteins OR carcinogenesis if critical targets are mutated: oncogenes, tumour suppressor genes

Answer 22

Alkylating agents - alkylate to cause DNA damage and apoptosis Agents that make bulky agents e.g. cisplatin Agents that induce double strand breaks e.g. ionising radiation

Answer 23

Testing for DNA damage: in vitro bacterial gene mutation assay —> in vitro mammalian cell assay —> in vivo mammalian assay —> investigate in vivo mammalian assay Bacterial (Ames) test for mutagenicity of chemicals 1) chemical to be tested and rat liver enzyme preparation-s9 (cytochrome p450 activity) added into bacteria that do not synthesis histidine(aa required to grow) e.g. salmonella strain -mutation 2) conversion of chemical to active metabolism 3) carcinogenic agents may correct defective mutation in salmonella, bacteria acquire ability to synthesise histidine and colonies can be seen on Petri dish Detecting DNA damage in mammalian cells -chromosomal aberrations: Treat mammalian cells with chemical in presence of liver s9. Look for chromosomal damage In vitro micronucleus assay: Cells treated with chemical and allowed to divide Binucleate cells assessed for presence of micronuclei Can stain the kinetochore proteins to determine if chemical treatment caused clastgenicity (chromosomal breakage) or aneuploidy (chromosomal loss) If DNA becomes very damaged, it gets budded as micronucleus Murine bone marrow micronucleus assay: Treat animals with chemical and examine bone marrow cells or peripheral blood erythrocytes for micronuclei

Answer 24

1) harmful cells (e.g. cells with viral infection, DNA damage) 2) developmentally defective cells (e.g. B lymphocytes expressing antibodies against self antigens) 3) excess/ unnecessary cells: (embryonic development: brain to eliminate excess neurones; liver regeneration; sculpting of digits and organs) 4) obsolete cells (e.g. mammary epithelium at the end of lactation) 5) exploitation - chemotherapeutic killing of cells

Answer 25

Necrosis - unregulated cell death associated with trauma, cellular disruption and an inflammatory response Apoptosis (programmed cell death) - regulated cell death; controlled disassembly of cellular contents without disruption; no inflammatory response Necrosis: - plasma membrane becomes permeable - cell swelling and rupture of cellular membranes, organelles swell, chromatin condenses - release of proteases leading to autodigestion and dissolution of the cell - localised inflammation Apoptosis: Latent phase - death pathways are activated, but cells appear morphologically the same Execution phase - loss of microvilli and intercellular junctions - permeability of epithelium compromised - cell shrinkage, epithelium closes around - permeability resorted - loss of plasma membrane asymmetry (phosphatidylserine lipid appears in outer leaflet) - imbalance in lipid composition - chromatin and nuclear condensation - DNA fragmentation - Formation of membrane blebs - fragmentation into membrane-enclosed apoptotic bodies - apoptosis bodies phagocytosis by neighbouring cells and macrophages Plasma membrane remains intact - no inflammation Apoptosis-like PCD - some, but not all, features of apoptosis. Display of phagocytise recognition molecules before plasma membrane lysis Necrosis-like PCD - variable features of apoptosis before cell lysis; “aborted apoptosis”

Answer 26

1. The executioners – Caspases 2. Initiating the death programme • Death receptors • Mitochondria 3. The Bcl-2 family 4. Stopping the death programme 1) cysteine-dependent aspartate-directed proteases - cleave at specific sites -executioners of apoptosis -activated by proteolysis -cascade of activation Inactive at start - regulation, autofolded on itself Initiator and effector; initiator = trigger apoptosis by cleaving and activating; effector = carry out the apoptotic programme Cleave at: - CARD (cascade recruitment domain) - DED (death effector domain) - homotypic (same type) protein-protein interactions e.g. cascade would dimerise with cascade

Answer 27

Cleave and inactivate proteins or complexes (e.g. nuclear lamins leading to nuclear breakdown) -loss of function Activate enzymes (incl. protein kinases; nucleases .e.g. Caspase-Activated DNase, CAD) by direct cleavage, or cleavage of inhibitory molecules - gain of function Both the above apply to monomeric substrates and multiprotein complexes

Answer 28

Death by design - receptor-mediated (extrinsic) pathways Death by default - mitochondrial (intrinsic) death pathway

Answer 29

Anti-apoptotic - promote cell survival (mitochondrial) Bcl-2 Bcl-xL ``` Pro-apoptotic (move between cytosol and mitochondria) Bid Bad Bax Bak ```

Answer 30

1. Phosphorylates and inactivates Bad 2. Phosphorylates and inactivates caspase 9 3. Inactivates FOXO transcription factors (FOXOs promote expression of apoptosis-promoting genes) 4. Other, e.g. stimulates ribosome production and protein synthesis

Answer 31

They regulate programmed cell death in the extrinsic pathway by: - binding to procaspases and preventing activation - binding to active caspases and inhibit their activity

Answer 32

Bcl-2, Bcl-xL: intrinsic pathway FLIP, IAPs: extrinsic pathway Growth factor pathways via PI3’K and PKB/Akt

Answer 33

Harmful (oncogenic) cells e.g. cells with viral infection, DNA damage Chemotherapeutic killing of tumour cells e.g. dexamethasone stimulates DNA cleavage

Answer 34

Vasculogenesis (bone marrow progenitor cell) Angiogenesis (sprouting) Arteriogenesis (collateral growth) You have inhibitors (e.g.angiostatin) activators (VEGF) and factors required for maturation and integrity (platelets) to regulate angiogenesis.

Answer 35

Hypoxia is a trigger for angiogenesis: - HIF: hypoxia-inducible transcription factor, controls regulation of gene expression by oxygen - pVHL: Von Hippel-Lindau tumour suppressor gene, controls levels of HIF - inhibits HIF when needed. In hypoxia, VHL detaches from HIF, binds to DNA —> VEGF VEGF and its receptors - 5 members = VEGF-A, VEGF-B, VEGF-C, VEGF-D and placental growth factor (PIGF) - three tyrosine kinase receptors: VEGFR-1, VEGFR-2, VEGFR-3 and co-receptors (Nrp1 and Nrp2) - VEGFR-2 is the major mediator of VEGF-dependent angiogenesis, activating signalling pathways that regulate endothelial cell migration, survival, proliferation 1) tip/stalk selection - one cell gets bound by GF and forms tip, cells sitting below = stalk and push tip up VEGF binds to cell —> top cell —> drives formation of new blood vessels and tells neighbouring cells to become stalk cells VEGF/Notch signalling: I) in stable blood vessels, DII4 and natch signalling maintain quiescence II) VEGF activation increases expression of DII4 III) DII4 drives Notch signalling, which inhibits expression of VEGFR2 in the adjacent cell IV) DII4-expressing tip cells acquire a motile, invasive and sprouting phenotype V) Adjacent cells (stalk cells) form the base of the emerging sprout, proliferate to support sprout elongation 2) tip cell navigation and stalk cell proliferation 3) branching coordination 4) stalk elongation, tip cell fusion, and lumen formation 5) perfusion and vessel maturation 6) stabilisation and quiescence

Answer 36

Macrophages play a significant role in both physiological and pathological angiogenesis Macrophages carve out tunnels in the ECM providing avenues for capillary infiltration Tissue-resident macrophages can be associated with angiogenic tip cells during anastomosis.

Answer 37

Modulator role Haemostasis (physiological angiogenesis) - vascular development - wound healing Thrombosis (pathological angiogenesis) - atherosclerosis - rheumatoid arthritis - diabetic retinopathy

Answer 38

Form endothelial junctions Tight junctions and adherens junctions in endothelial cells - constitutively expressed at junctions - homophonic interaction mediates adhesion between endothelial cells and intracellular signalling - controls contact inhibition of cell growth - promotes survival of EC Mural cells (pericytes) hep to stabilise the neovessels - pericytes produce molecules to stabilise such as angiopoietin/Tie-2 system - VEGF pathway drives things, angiopoietin/Tie-2 act as modulators Angiopoietin-Tie2 ligand-receptor system - Ang-1 and Ang-2 are antagonistic ligand of the Tie2 receptor - Ang-1 binding to Tie2 promotes vessel stability and inhibits inflammatory gene expression - Ang-2 antagonises Ang-1 signalling, promotes vascular instability and VEGF-dependent angiogenesis

Answer 39

Tumours less than 1 mm^3 receive oxygen and nutrients by diffusion from host vasculature - don’t need angiogenesis Larger tumours require new vessel network. Tumour secretes angiogenic factors that stimulate migration, proliferation and neovessel formation by endothelial cells in adjacent established vessels - don’t release all factors, not same as normal physiology New vascularised tumour no longer relies solely on diffusion from host vasculature, facilitating progressive growth The angiogenic switch - a discrete step in tumour development that can occur at different stages in the tumour-progression pathway, depending on the nature of the tumour and its microenvironment

Answer 40

- irregularly shaped, dilated, tortuous - not organised into definitive venues, arteriolar and capillaries - leaky and haemorrhagic, partly due to the overproduction of VEGF - perivascular cells often become loosely associated - some tumours may recruit endothelial progenitor cells from the bone marrow

Answer 41

Cancer associated fibroblasts (CAFs) secrete ECM, pro-angiogenic growth factors e.g. VEGFA Pericytes are loosely associated with tumour-associated blood vessels (TABVs) and this favours chronic leakage in tumours. This is enhanced by angiopoietin 2. Platelets -link between cancer progression and thrombocytosis -activated platelets are a source of: Pro-angiogenic factors: VEGFA, platelet-derived growth factors (PDGFs), FGF2 Angiostatin molecules: thrombospondin 1, plasminogen activator inhibitor 1 (PAI1), endostatin -pro-angiogenic mediators and proteases support the proliferation and activation of CAFs -tumours cause platelet activation, aggregation and degranulation -disrupting platelet function does not obviously impaired tumour angiogenesis, however the overall outcome of platelet activation in tumours appears to be pro-angiogenic

Answer 42

Therapies to inhibit VEGF signalling: - antibodies against VEGF - molecules affecting signalling pathways - molecules blocking receptors VEGF inhibition by soluble VEGFR1 (Flt-1) reduces tumour growth 1) cells stably transferred with control or sFlt-1 plasmid to promote Flt-1 (VEGFR1) expression 2) VEGFR1 binds to VEGF and mops it up preventing it from stimulating angiogenesis 3) Flt-1 expression reduces tumour growth in vivo, without affecting tumour cell growth in vitro: effect on vasculature ``` Anti-VEGF humanised MAb: Avastin Side effects and limited efficacy -no overall survival advantage over chemo alone Side effects: -GI perforation -hypertension -proteinuria -venous thrombosis -haemorrhage -wound healing complications ``` Anti-angiogenic therapies: strategies Anti-angiogenic therapy which normalises vasculature -reduces hypoxia -incraese efficacy of conventional therapies Sustained/aggressive anti-angiogenic therapy -may damage healthy vasculature leading to loss of vessels, creating vasculature resistant to further treatment and inadequate for delivery of oxygen/ drugs.

Answer 43

VEGF inhibition aggravates hypoxia because block blood vessels, increasing tumour’s production of other angiogenic factors or increases tumour invasiveness Tumour vessels maybe less sensitive to VEGF inhibition due to vessel lining by tumour cells or endothelial cells derived from tumours Tumour cells that recruit pericytes maybe less responsive to VEGF therapy Tumour cell vasculogenic mimicry (vascular mimicry) describes the plasticity of aggressive cancer cells forming de novo vascular networks

Answer 44

Novel molecular mechanism (non-VEGF targets) ``` Other diseases: Age-related macular degeneration (AMD) -abnormal growth of choroidal blood vessels -leaky vessels cause oedema -visual impairment ``` Anti-VEGF therapy: Lucentis used for this Avastin is used off-label

Answer 45

Tumours are complex 3D structures with their own unique micro environments Studies are performed in 2D Also, tumours receive nutrients and therapeutics through the vasculature which is not included in any in vitro tumour models Tumour-on-a-chip platform develops a micro physiological system that incorporates human cells in a 3D ECM, supported by perfumed human microvessels

Answer 46

Microfilaments Regulation of actin dynamics Cytoskeleton proteins Signalling proteins

Answer 47

1) homeostasis 2) genetic alterations 3) hyper-proliferation 4) de-differentiation - disassembly cell-cell contacts, loss polarity 5) invasion - increased motility, cleavage ECM proteins Form a tumour mass - benign and break the basement membrane/ dissociate completely have high motility and cleave ECM proteins —> essential so they can migrate

Answer 48

1) epithelial cells in primary tumours are tightly bound together 2) metastatic tumour cells become mobile mesenchyme-type cells and enter the bloodstream 3) metastatic cells then travel through the bloodstream to a new location in the body 4) metastatic cells exit the circulation and invade a new organ 5) cancer cells lose their mesenchymal characteristics and form a new tumour

Answer 49

Two types individual and collective Individual - ameoboid e.g. lymphoma, leukaemia - mesenchymal (single cells) Collective - cluster/cohorts - epithelial cancer, melanoma - multicellular strands/ sheets -epithelial cancer, vascular tumours Factors involved: - integrins - receptors of ECM proteins - proteases - digest ECM - cadherins - induce differentiation in epithelial cells - metastatic collective cells grace these so they can interact with the other cells and be transported - pull cells together - gap junctions - allow communication with each other The above factors are higher in collective cells than indict dual so their metastatic potential is much higher than individual cells - can still maintain attachment with each other while being transported.

Answer 50

1) cells migrate and drag cells behind 2) differentiate to produce alveoli for lactation 3) cut vasculature => bruise - need to regrow - leader cells (tip cells) drives cells to vasculature 4) detached cluster Similar to mammary glands but tumour cells have no sense of direction E.g. migration of primary glial cells - recognise neighbouring cells and stop in scratch wound Migration of a glial tumour cell - cells continue to grow and don’t recognise neighbouring cells EGF leads to upregulation of genes involved in: -cytoskeleton regulation -motility machinery Tumour cells metastasis

Answer 51

Stimuli to move: - organogenesis and morphogenesis - wounding - growth factors/ chemoattractants - dedifferentiation (tumours) Where to go? Directionality (polarity) When to stop? Contact-inhibition motility - recognition of neighbouring cells How to move? Specialised structures (focal adhesion, lamellae, filopodium Attachment to substratum (ECM proteins) Cells attach to ECM via integrins -focal adhesions - close contact with ECM -filamentous actin - organised in bundles at specific orientations Structures shed got motilityL - filopodia: finger-like protrusions rich in actin filaments - lamellipodia: sheet-like protrusions rich in actin filaments - cells can form contacts over larger area of cell Control is needed: - within a cell to coordinate what is happening in different parts - regulate adhesion/ release of cell-extracellular matrix receptors - from outside to response to external influences - sensors e.g. GF and nutrients; directionality Motility: hapoptatic (stroll in park) versus chemotatic (purpose - go to stops, drives cell to specific location)

Answer 52

1) extension - can produce lamellar to go forward 2) adhesion - stabilise adhesion 3) translocation 4) de-adhesion Like rock climbing: - filopodia - sense rock - lamellar - grab rock, translocate - push yourself up

Answer 53

``` G-actin = small soluble subunits F-actin = large filamentous polymer ``` Actin filament has polarity - plus and minus end Signal such as a nutrient source —> disassembly of filaments and rapid diffusion of subunits —> reassembly of filaments at a new site Filament organisation and structure: - lamellipodium: branched and crosslinked filaments - filopodium: bundle of parallel filaments - stress fibres - antiparallel contractile strictures (thick bundle of actin) Depending on the proteins they bind to, actin filaments have different functions and are in different states e.g. motor proteins (contract), bundling, cross-linking, nucleating, capping

Answer 54

1) Nucleation For polymerisation to occur, you need nucleating of 3 monomers together - not very stable Arp3 + Arp2 and other proteins —> ARP complex ARP complex + actin monomers —> nucleated actin filament Limiting step in actin dynamics - formation of trimmers to initiate polymerisation 2) elongation Free actin monomer —> actin filament via actin-profilings complex Actin-thymosin complex blocks, restricts availability of G monomers to form actin filament Profilin competes with thymosin for binding to actin monomers and promotes assembly Monomer binding: profilin Sequestering: b4-thymosin, ADF/cofilin (do not inhibit polymerisation) 3) capping 4) severing Stop growing of filament Like bottle cap at end to prevent addition of monomers Capping proteins: + end = Cap Z, gelsolin, fragments/severin - end = tropomodulin, Arp complex Severin proteins: Gelsolin ADF/ cofilin Fragmin/severin Depending on stimulus = capping or severing If not chopped, straight to monomeric form then they can form adhesion points for growth Need coordination between capping and severing In unsevered population, actin filaments grow and shrink relatively slowly In severed population, actin filaments grow and shrink more rapidly ``` 5) cross-linking and bundling Group filaments Proteins involved: -a-actinin = dimer cross-link filament -fibrin -filamin - angle -spectrin = stabilise cortico structures of cells -villin -vinculin -dystrophin - link filaments to plasma membrane ``` 6) branching Branching protein = Arp complex Branching at 70 degrees 7) gel-sol transition by actin filament severing The network is maintained at some sort of rigidity of membrane in cytoskeleton If cell needs to protrude membrane/ cytoplasm - need to loosen up —> cleave some crosslink proteins so they are not connected to each other Gel (rigid) —> sol (can flow)

Answer 55

High blood pressure - requires contraction of blood vessels Duchenne Muscular Dystrophy (muscle wasting) -dystrophin protein truncated Bulbous Pemphigoid (autoimmune disease) -epithelial connection to basement membrane - destabilised Alzheimer’s (neurodegenerative - depositis of protein - cytotoxicity

Answer 56

Disassembly, nucleation, branching, severing, capping and bundling used in extension Polymerisation also in extension Gel/sol transition and attachment ECM in adhesion Contraction in translocation Detachment in de-adhesion Lamellar protrusion - polymerisation, disassembly, branching, capping Filopodia - actin polymerisation, bundling, crosslinking

Answer 57

1) ion flux changes (I.e. intracellular calcium - cytoskeleton proteins can bind to Ca2+ to activate protein) 2) phosphoinositide signalling (phospholipid binding) - P13K signalling, cytoskeleton proteins can change properties when bound 3) kinases/phospjhatases (phosphorylation cytoskeleton proteins) e.g. MAPK 4) signalling cascades via small GTPases

Answer 58

Rho subfamily (found in GDP bound form - activated as GTP bound form) of small GTPases belongs to the Ras super-family Family members: Rac, Rho, Gdc42 Rho is upregulated in cancers Inactivated by release of Pi Participate in a verity of cytoskeletal processes These proteins are activated by receptor tyrosine kinase, adhesion receptors and signal transduction pathways Expression levels up-regulated in different human tumours Activation of: Cdc42 —> filopodia Rac—> lamellipodia (large lamellar not localised) Rho —> stress fibres (lots of force when contract) Actin binding proteins regulated by Rac/cdc42 1) extension - Rac in actin polymerisationa nd branching 2) adhesion - Rac, Rho in focal adhesion, assembly 3) translocation - Rho in stress fibres, tension, contraction 4) De-adhesion - Rho Cdc42 - filopodia and polarised mobility

Answer 59

Term used to describe the way cells interact with their external environment and their reactions to this, particularly proliferative and motile responses of cells Chemical: hormones, growth factors, ion concs, ECM, molecules on other cells, nutrients and dissolved gas (O2/CO2) concs Physical: mechanical stresses, temperatures, the topography or layout of the ECM and other cells Although all external factors may influence cell proliferation, the ones to be considered here, in relation to cancer cell behaviour, are:- • Growth factors • Cell-cell adhesion • Cell-ECM adhesion Lamellipod allows adhesion of tissue cells to matrix surface Cell-spreading is not a passive, gravity dependent event. Energy is required to modulate cell adhesion and the cytoskeleton during spreading. When cell spreads, less blebbing Cells require to be binding to extracellular matrix to be fully competent for responding to soluble growth factors. ``` • in suspension, cells do not significantly synthesise protein or DNA • cells require to be attached to ECM ( and a degree of spreading is required) to begin protein synthesis and proliferation (DNA synthesis) • attachment to ECM may be required for cell survival .i.e. anchorage dependence Most cells need matrix ```

Answer 60

(A) in interstitial matrix (type 1 collagen), mammary epithelium does not differentiate to secretory cells (B) in basal lamina (basement membrane) matrix, mammary cells organise into “organoids” and produce milk proteins. Cell-ECM adhesion molecules • Cells have receptors on their cell surface which bind specifically to ECM molecules • these molecules are often linked, at their cytoplasmic domains, to the cytoskeleton • this arrangement means that there is mechanical continuity between ECM and the cell interior

Answer 61

Integrins are heterodimer complexes of a and b subunits that associate extracellularly by their “head” regions. Each of the “leg” regions spans the plasma membrane. Ligand-binding occurs at the junction of the head regions Integrins • more than 20 combinations of a/b known which each bind specifically to short peptide sequence on ECM proteins • For example a5b1 fibronectin receptor binds arg-gly-asp ( RGD) • peptide sequences such as RGD are found in more than one ECM molecule, e.g. RGD found in fibronectin, vitronectin, fibrinogen plus others • most integrins link to the actin cytoskeleton via Focal adhesions actin-binding proteins (exeption: a6b4 integrin (green) complex found in epithelial hemidesmosomes, linked to the cytokeratin (intermediate filament) network) • integrin complexes cluster to form focal adhesions (most) or hemidesmosomes (a6b4) • these clusters are involved in signal transduction • Some integrins also bind to specific adhesion molecules on other cells (e.g. avb3 binds to PECAM-1(CD31) and aIIbb2 to ICAM-1 on endothelial cells in inflammation) - important in immune system and blood clotting Signalling to and from ECM receptors • ECM receptors (e.g. integrins) can act to transduce signals • e.g. ECM binding to an integrin complex can stimulate the complex to produce a signal inside the cell, • i.e. “outside-in” integrin signalling Integrin signalling involves conformational changes to the complex Integrin complexes can adopt “flexed” and “extended” molecular confirmations. Switching between these confirmations affects their ability to bind their ligands, and their signalling. In this way, cell-ECM adhesion, and signals, can be switched on and off. Outside-in signalling • a cell can receive information about its surroundings from its adhesion to ECM • e.g. the composition of the ECM will determine which integrin complexes bind and which signals it receives • this can alter the phenotype of the cell The amount of force that is generated at a focal adhesion depends on both the force generated by the cytoskeleton (F cell) and the stiffness of the ECM Some proteins can stretch and open up, exposing new sites Integrins recruit cytoplasmic proteins which promote both signalling and actin assembly Signalling to and from ECM receptors a signal generated inside the cell (e.g. as the result of hormone binding to receptor) can act on an integrin complex to alter the affinity of an integrin (i.e. alter its affinity for its ECM binding) this is “inside-out” intergin signalling (e.g. in inflammation or blood-clotting, switching on adhesion of circulating leukocytes) Summary of the conformational changes to the integrin complexes during activation and signalling: -low affinity = bent confirmation, weak or no binding to ligand High affinity = extended confirmation, strong binding to ligand - ECM ligand binds and causes the further opening of the legs. This exposes the binding sites for the recruitment of cytoplasmic signalling molecules - outside-in activation; signals into the cells - signal from inside the cell acts on the integrin complex to promote the switch to the extended high-affinity conformation: “inside-out” activation; switches adhesion on

Answer 62

At high density, cells compete for growth factors. When cells in culture form a con fluent mono layer, they cease proliferating and slow down many other metabolic activities. This used to be known as contact inhibition of cell division May be competition for external growth factors rather than cell-to-cell contact Density-dependence of cell-division

Answer 63

Two signals required: - growth factor (density dependence); ERK MAP Kinase cascade - ECM (anchorage dependence) Mechanism of anchorage dependence - growth factor receptors and integrin signalling complexes can each activate identical signalling pathways (e.g. MAPK) - individually this activation is week and/or transient - together activation is strong and sustained - the separate signalling pathways act synergistically

Answer 64

Short-term: transient interactions between cells which do not form stable cell-cell junctions Long-term: stable interactions resulting in formation of cell-cell junctions Cell-cell contact between non-epithelial cells When most non-epithelial cells collide, they do not form stable cell-cell contacts. They actually repel one another by paralysing motility at the contact site, promoting the formation of a motile front at another site on the cell, and moving off in the opposite direction This is contact inhibition of locomotion and is responsible for preventing multi layering of cells in culture and in vivo Long-term cell-cell contacts Upon contact, some cell types strongly adhere and form specific cell-cell junctions (adherents junctions, desmosomes, tight junctions, gap junctions) This iOS true of epithelial cels, which form layers and neurones forming synapses Cell-cell junctions in epithelia Junctions are usually arranged as online ours belts (zonula) or as discrete spots (macula) Contact-induced spreading of epithelial cells Contact between epithelial cells leads to the mutual induction of spreading, so that the total spread area of the contacted cells is greater than that of the sum of the two separated cells. This could result in a stable monolayer Cell-cell adhesion affecting cell proliferation -No cell-cell junctions, activated MAPK, decreased p27KIP1, high proliferation (-Ca2+; + adhesion blocking antibody) -Cell-cell junctions form, inactive MAPK, increased p27KIP1, low proliferation (+Ca2+; -adhesion blocking antibody) Junctions are Ca2+ dependent

Answer 65

Catenins bind to cadherins B-catenin; a-catenin bind to cadherins (Ca2+-dependent, homophilic cell adhesion molecule - bind to identical molecules on adjacent cells) and actin filament Adenomatous polyposis coli (APC) - inherited colon cancer: there are a number of familial types The APC gene-product is a protein involved in the degradation of the junction-associated molecule, b-catenin (forms junction with actin cytoskeleton) In normal state - b-catenin bound to cadherin roaming junctions at plasma membranes of adjacent cells In cytoplasm: -when bound to APC, APC complex active and leads to raid degradation -when APC complex active, bound to LEF-1, goes to nucleus to cause gene transcription, leading to cell proliferation

Answer 66

When bound to cadherin at the membrane, b-catenin not available for LEF-1 binding and nuclear effects Normally, cytoplasmic b-catenin rapidly degraded If b-catenin cytoplasmic levels rise as a result of inhibition of degradation or loss of cadherin-mediated adhesion, b-catenin/LEF-1 complex enters nucleus and influences gene expression, leading to proliferation Other: Clustering of cadherins after cell-cell contact is known to alter the activation of small GTPases .e.g. Rac is activated, Rho is inhibited: this can influence proliferation Some growth factor receptors are associated with cell-cell junctions. This reduces their capacity to promote proliferation

Answer 67

- proliferate uncontrollably (lose density dependence of proliferation) - are less adherent and will multilayer (lose contact inhibition of locomotion and anchorage dependence) - epithelia breakdown cell-cell contacts - not Hayflick limited, express telomerase I.e. cancer If the gene coding for a component of a signalling pathway is mutated so that the protein is constitutively active, that pathway will be permanently on Receptors, signalling intermediates and signalling targets (e.g. transcription factors) are protooncogenes This is the mechanism of short-circuiting leading to uncontrolled proliferation as a result of loss of growth factor dependence .etc. Oncogene: mutant gene which promotes uncontrolled cell proliferation Porto-oncogene: normal cellular gene corresponding to the oncogene Neither growth factor (density dependence) or ECM signals (anchorage dependence) required to stimulate proliferation. Can invade

Answer 68

Adenoma (benign) - don’t invade locally Adenocarcinoma (malignant) - invade locally and metastasise • in addition to deregulated proliferation, a major feature of cancerous tumours is their ability to spread • most human cancers are carcinomas (i.e. of epithelial origin) • in order to spread to other sites (metastasis), cells must break away from the primary tumour, travel to a blood or lymph vessel, enter the vessel, lodge at a distant site, leave the vessel, and ultimately establish a secondary tumour Primary carcinoma cell metastasis • cell-cell adhesion must be down-regulated (e.g. cadherin levels reduced) • the cells must be motile • degradation of ECM must take place; matrix metaloproteinase (MMP) levels increased in order to migrate through basal lamina and interstitial ECM • the degree of carcinoma cell-cell adhesion is an indicator of how differentiated the primary tumour is, and indicates its invasiveness and the prognosis

Answer 69

- resisting cell death - sustaining proliferative signalling - evading growth suppressors - activating invasion and metastasis - enabling replication immortality - inducing angiogenesis - deregulating cellular energetic (less dependent on aerobic, more on anaerobic) - avoiding immune destruction - genome instability and mutation - tumour-promoting inflammation ``` Cell cycle Cycle checkpoints (growth arrest ensures genetic fidelity) - main, G1/S sense damage. G2/M right: duplication, identical and damage ``` Specific proteins accumulate/ are destroyed during the cycle Cyclins, cycle dependent kinases, cycle dependent kinase inhibitors Permanent activation of a cyclin can drive a cell through a checkpoint

Answer 70

Porto-oncogenes code for essential proteins involved in maintenance of cell growth, division and differentiation Mutation converts a proto-oncogene to an oncogene, whose protein product no longer responds to control influences Oncogenes can be aberrantly expressed, over-expressed or aberrantly active e.g. MYC, RAS, ERB, SIS Proto-oncogenes can be converted to an oncogene by a single mutation e.g. point mutations, frame shift .etc. Oncogenes activation Normal proto-oncogene can be changed in 4 ways: -mutation in the coding sequence (point mutation of deletion); aberrantly active protein -gene amplification (multiple gene copies); overproduction of normal protein -chromosomal translocation (chimaeric genes) = strong enhancer increases normal protein levels e.g. Burkitt’s lymphoma -insertional mutagenesis (e.g. viral infection) = fusion to actively transcribed gene overproduced protein or fusion protein is hyperactive .e.g. Philadelphia chromosome - BCR is an anti-apoptotic protect inserted into ABL Proteins involved in signal transduction are potential critical gene targets (proto-oncogenes): -tyrosine kinase receptor EC - met, neu -tyrosine kinase receptor IC - src, ret -G-protein coupled receptor - ras, gip-2 -kinases - raf, pim-1 -transcription factors - myc, fos, jun Can start cascade without appropriate signal Mutant RAS has aberrant activity • Upon binding GTP, RAS becomes active. • Dephosphorylation of the GTP to GDP switches RAS off. • Mutant RAS fails to dephosphorylate GTP and remains active. Oncogenes and human tumours - MYC - transcription factor - activated by translocation - nuclear - Burkitt’s lymphoma - JUN - transcription factor - overexpression/deletion - nuclear - lung

Answer 71

Typically proteins whose function is to regulate cellular proliferation, maintain cell integrity e.g. RB Each cell has two copies of each tumour suppressor gene Mutation or deletion of one gene copy is usually insufficient to promote cancer Mutation or loss of both copies means loss of control Knudson’s two hit hypothesis Sporadic cancer: 2 acquired mutations Hereditary cancer: 1 inherited and 1 acquired mutation Inherited cancer susceptibility ▪ Family history of related cancers. ▪ Unusually early age of onset. ▪ Bilateral tumours in paired organs. ▪ Synchronous or successive tumours. ▪ Tumours in different organ systems in same individual. ▪ Mutation inherited through the germline. Retinoblastoma ▪ Malignant cancer of developing retinal cells. ▪ Sporadic disease usually involves one eye. Hereditary cases can be unilateral or bilateral and multifocal. ▪ Due to mutation of the RB1 tumour suppressor gene on chromosome 13q14. ▪ RB1 encodes a nuclear protein that is involved in the regulation of the cell cycle. (CDK 4 and 6) ``` Functional classes of tumour suppressor genes ▪ Regulate cell proliferation ▪ Maintain cellular integrity ▪ Regulate cell growth ▪ Regulate the cell cycle ▪ Nuclear transcription factors ▪ DNA repair proteins ▪ Cell adhesion molecules ▪ Cell death regulators Suppress the neoplastic phenotype ``` Tumour suppressor genes and human tumours P53 - cell cycle regulator - nuclear - many cancers e.g. colon, breast, lung BRCA1 - cell cycle regulator - nuclear 0 breast, ovarian, prostate Although p53 is a tumour suppressor gene, mutants of p53 act in a dominant manner and mutation of a single copy is sufficient to get dysregualtion of activity - hard to target because can affect other functions APC tumour suppressor gene (familial adenomatous polyposis coli) - due to a deletion in 5q21 resulting in loss of APC gene (tumour suppressor gene) - involved in cell adhesion (anchoring/no according in stroma) and signalling (MAPK) - sufferers develop multiple benign adenomatous polyps of the colon - there is a 90% risk of developing colorectal carcinoma The tumour suppressor gene APC participates in the WNT signalling pathway APC protein is a negative regulator of b-catenin(cell division and adhesion) thereby preventing uncontrolled cell division Mutation of APC is a frequent event in colon cancer

Answer 72

Oncogene, defective tumour suppressor gene —> cell growth and proliferation —> cancer Analogy Normal genes (regulate cell growth) - tumour suppressor gene (break) working effectively 1st mutation (susceptible carrier) - tumour suppressor gene and active oncogene (accelerator) 2nd mutation or loss (leads to cancer) - accelerator and no brakes ``` The development of colorectal cancer Normal epithelium (problem with APC - tumour suppressor) —> hyperproliferative epithelium (problem with K-ras - oncogene)—> adenoma (problem with p53) —> carcinoma —> metastasis ``` Hyperplasia —> metaplasia —> dysplasia —> carcinogenesis Oncogene vs tumour suppressor gene Table Side note: COSMIC = catalogue of somatic mutations in cancer; important in precision medicine

Answer 73

Incidence: new cases of cancers Mortality: no of deaths Discrepancy because not all cancers are lethal Epidemiological transition: poorer countries moving towards western; mortality changes with food, environmental changes .etc.

Answer 74

Extent and rate of change that are informative: A rapid change in risk following migration implies that lifestyle/environment factors act late in carcinogenesis A slow change suggests that exposures early in life are the most relevant Persistence of rates between generations suggests genetic susceptibility is important in determining risk

Answer 75

Incidence is increasing for common cancer sites in both high-income (now with plateauing and even decreases) and low-income countries (e.g. colorectal, prostate) - effects of earlier diagnosis, screening, changes in risk factors Mortality is decreasing in most high-income countries, not in low income. Total burden is increasing because of demographic changes (ageing and population size) and westernisation of lifestyle Main risk factors: smoking, diet, alcohol Cancer is a leading cause of death 1. The epidemiology of cancer tells us that cancer incidence is related to: •Age •Common environmental causes •Geographical variation and secular trends There are several well defined risk factors for cancer, including smoking, diet and alcohol consumption. 2. The process of carcinogenesis is important in understanding the development of cancer. Important factors involved in this process include chemical carcinogens, radiation and oncogenic viruses 3. Inherited / familial cancers are rare, but have provided valuable information in understanding the process of carcinogenesis.

Answer 76

Reduction/ elimination of risk factors would lead to a substantial reduction in cancers and CVD, renal disease, hepatic, diabetes and neurological Smoking - at least 30% of all cancer deaths - smoking is associated with increased risk for at least 15 types - 90% of lung cancer deaths in men and 80% in women Diet -dietery fibre and colorectal cancer ``` Alcohol Oral cavity, pharynx, larynx, oesophagus, liver all types of alcohol mechanisms poorly understood synergism with tobacco balance with preventive effect for CHD ``` Anthropometry Measure of proportions of body e.g. BMI

Answer 77

1) be as lean as possible without being underweight 2) physically active, more than or equal to 30 mins 3) avoid sugary drinks, processed foods 4) veg and fruit 5) decrease alcohol 6) decrease salty foods 7) don’t use supplements Western Lifestyle: - Energy dense diet, rich in - fat, - refined carbohydrates - animal protein - Low physical activity - Smoking and drinking Consequences: - Greater adult body height - Early menarche - Obesity - Diabetes - Cardiovascular disease - Hypertension Infectious disease 16% caused by infectious agents HPV = cervix, head and neck EBV = Hodgkin’s lymphoma, Burkitt’s HCV, HBV = liver H. Pylori = stomach

Answer 78

Carcinoma: tumour of epithelial cells All glands meet at nipple Different cancer types for different glands E.g. lobular cancer for lobes, ductal cancer for ducts Mammary gland made up of 2 epithelial layers Second layer is myoepithelial cells - contractile properties - squeeze luminal epithelial - milk out of nipple A layer of myoepithelial cells, some of which are slightly vacuoloted is seen just around the luminal cells, making contact with the basement membrane

Answer 79

Normal —> benign/ in situ carcinoma —> medullary carcinoma/ carcinoma/ lobular carcinoma Medullary carcinoma - with lymphocytes - aggressive - not like original, have neuroendocrine secretory vesicles Carcinoma - Infiltrating ductal carcinoma - Greater than or equal to 80% in this category - many have no special type of histogocial structure

Answer 80

Immunohistochemical staining using antibodies against the Human Estrogen Receptor (ER) is informative The oestrogen receptor is activated upon binding oestrogen Gene expression is induced by binding to specific DNA sequences called oestrogen response elements The oestrogen-induced gene products increase cell proliferation, resulting in breast cancer Ligand = oestrogen (can pass cell membrane) ER - monomeric protein, nuclear receptor Dimer ER Bind to TATA —> gene expression Some important oestrogen regulated genes: -progesterone receptor (PR) -Cyclin D1 = regulation of cell cycle -c-myc = make sure cells don’t apoptosis -TGF-a = direct GF therefore cell growth and cell survival increases Normal mammary gland: Cells with ER don’t grow, surrounding cells grow Tumour: Oestrogen drives growth of tumour cells Some breast cancers like normal breast are sensitive to the effects of oestrogen ER is over expressed in around 70% of breast cancers = better prognosis In ER-positive case, estrogen regulates the expression of genes involved in cellular proliferation leading to breast cancer Oestrogen withdrawal or competition for binding to the ER using anti-oestrogens results in a response in about 70% of ER positive cancers, 5-10% of ER-negative cancers also respond An increased level of expression of ER indicates a good rognosis in female breast cancer but a worse in male (androgen receptor) Overstimulation of ER downregulates it therefore tumour regression but can relapse with incurable metastatic disease

Answer 81

Surgery Radiation therapy Chemotherapy Endocrine therapy Side note: Adjuvant therapy: kill of any tumour cells broken away from tumour mass —> secondary tumours Neoadjuvant therapy given before surgery because too big tumour for surgery but less common because early detection

Answer 82

Can be achieved by: - ovarian suppression (pre-menopausal) - blocking’s oestrogen production by enzymatic inhibition - inhibiting oestrogen responses Hormonal control of target tissues Premenopausal Hypothalamus releases LHRH —> pituitary gland releases gonadotrophins —> ovary —> oestrogen and progesterone Pre/post menopausal LHRH—> ACTH from pituitary —> adrenal glands —> androgen —> oestrogen (by peripheral conversion - aromatisation, fatty tissue (also liver, muscle) has high levels of aromatase e.g. mammary gland) Ovarian ablation and suppression -surgical oophorectomy (removal of ovaries) -ovarian irradiation (radiation therapy) The major problems associated are morbidly and irreversibility - won’t be able to have children To overcome, treatments to produce ovarian ablation have been developed: Lutenising hormone releasing hormone (LHRH) agonists These bind to LHRH receptors in the pituitary leading to receptor down-regulation and suppression of LH release and inhibition of ovarian function, including oestrogen production REVERSIBLE E.g. goserelin, Buserelin, leuprolide, triptorelin Inhibiting oestrogen action Anti-oestrogens: Tamoxifen (nolvadex) - receptor recognises this as oestrogen even if don’t look alike —> no gene expression ICI 182,780 = Faslodex - bind to ER receptor but won’t activate transcription Tazmoxifen is a competitive inhibitor of oestradiol binding to the ER. Antioestorgens negate the stimulatory effects of oestrogen by blocking the ER causing the cell to be held at the G1 phase of the cell cycle —> death Tamoxifen is the endocrine treatment of choice in metastatic disease in postmenopausal women Few side effects Tamoxifen is a selective oestrogen receptor modulator (SERMs) -oestrogenic effects in bone - treat osteoporosis, maintain density -oestrogenic effects in CNS - treat atherosclerosis, lowers LDL and raises HDL but long term use may increase risk Undesirable: -subsequent thromboembolic episodes (liver) -endometrial thickening, hyperplasia and fibroids -hypothalamus incraeses vasomotor symptoms = hot flushes Toremifene - structural derivative of tamoxifen with similar antioestrogenic and oestrogenic properties Faslodex/ fulvestrant - no oestrogen-like effects so not to be used in osteoporosis and CVD patients but controls oestrogen stimulated growth, favourable over tamoxifen in decreasing tumour cell invasion and stimulation of endometrial carcinoma. First lien for advanced breast cancer and second line if tamoxifen fails Raloxifene - agonistic in bone and no activity in breast and uterus. Used in treatment of osteoporosis in post-menopausal Tamoxifen also reduces the incidence of contralateral breast cancer by a third - second breast cancer in other mammary gland which is independent of first so can prevent breast cancer Problems in using for prevention: -increased incidence of endometrial cancer -stroke -DVT -cataracts To overcome use raloxifene/Faslodex (SERM) or aromatase inhibitors Blocking oestrogen production by enzymatic inhibition Aromatase inhibitors In postmenopausal, major source of oestrogen from conversion of androstenedione or testosterone to oestrone -occurs at extra-adrenal or peripheral sites such as fat, liver and muscle -conversion catalysed by aromatase Aromatase consists of a complex containing a cytochrome P450 heme containing protein as well as the flavoprotein NADPH cytochrome P450 reductase. Aromatase catalyzes three separate steroid hydroxylations involved in the conversion of androstenedione to estrone. Aromatase can metabolise androsteindione, which is produced by the adrenal glands. This leads to the production of Estrone Sulphate, which is circulated in the plasma Can divide aromatase inhibitors into mechanism-based, suicide inhibitors (type I) and competitive inhibitors (type II) Type I: -chemically binds to active site and enzyme breaks down -irreversible E.g. exemestane, side effects include fatigue, nausea, hot flushes Type II: - bind reversibly to active site, blocks as long as it occupies the site e. g. anastrozole

Answer 83

* Progesterone is the dominant naturally occurring progestin * The poor absorption of progesterone has been overcome with some of the synthetic derivative progestins * Progestin response in the human breast is complex and influences both proliferation and differentiated function. * Progestins are used in the endocrine treatment of uterine and breast cancer with clinically proven antineoplastic properties. * Progestin therapy for metastatic breast cancer has been used principally as a second- or third-line therapy following selective estrogen * . The principal progestin used for metastatic breast cancer has been megestrol acetate Agonist which overstimulates receptor

Answer 84

•In treatment: >60% of ERa-positive tumours respond to endocrine therapy Anti-estrogens, e.g. tamoxifen Inhibitors of estrogen synthesis, e.g. exomestane clinical problem: • Initial response but eventual relapse • Relapse due to resistance during prolonged endocrine therapy • NOT due to tumours becoming ER-independent • Recent data shows that resistant tumours have mutated ER Solution- • Continue use endocrine therapies as these are successful • But, require additional therapeutic agents/ strategies for endocrine resistant, metastatic disease e.g. inhibitors of CDKs

Answer 85

``` Risk Factors - exposure to estrogens Early age of onset of menarche Late age to menopause Age at first full-term pregnancy Some forms of the contraceptive pill Hormone Replacement Therapy Obesity Diet, physical activity, height, medication (Aspirin) ``` Screening programme uses mammography between 50-64 now extended to 70 Test every 3 years

Answer 86

Front of colon lined by peritoneum Back lined by mesentery Colon is a hollow tube which starts in right iliac fossa Mucosa found in lamina propria and epithelium Cells are constantly proliferating and travel up colorectal crypt of Lieberkuhn Function - extraction of water from faeces (electrolyte balance) - faecal reservoir (evolutionary advantage) - bacterial digestion for vitamins (.e.g. B and K) Turnover Proliferation renders cells vulnerable APC mutation prevents cell loss —> mutation Normally we have protective mechanisms to eliminate genetically defective cells by: -natural loss -DNA monitors -repair enzymes

Answer 87

A polyp is any projection from a mucosal surface into a hollow viscus, and may be hyperplastic, neoplastic, inflammatory, hamartomatous .etc. An adenoma is a benign neoplasm of the mucosal epithelial cells Colonic polyp types - metaplastic/hyperplastic - adenomas - juvenile - Peutz Jeghers (mucosal hyperpigmentation) - lipomas - others (essentially any circumscribed intramucosal lesions) ``` Hyperplastic polyps -very common -often multiple -no malignant potential -15% have k-ras mutation -<5 cm (Serrated appearance (jagged edge) ```

Answer 88

``` Colonic adenoma types: -tubular -tubular/villus -villus (Flat) (Serrated) ``` Pedunculated adenoma - like stalk Sessile adenoma - flat Microscopic structure of adenomas: tubular -columnar cells with nuclear enlargement, elongation, multilayering and loss of polarity (nuclear) -increased proliferative activity -reduced differentiation -complexity/disorganisation of architecture E.g. colonic adenoma = mushroom like Villous - mutinous cells with nuclear enlargement , elongation, multilayering and loss of polarity - exophytic, frond-like extensions - rarely may have hypersecretory function and result in excess mucus discharge and hypokalaemia (potassium loss in GI tract)

Answer 89

Abnormal growth of cells with some features of cancer Indefinite, low grade and high grade (back to back glands) APC/FAP - 5q21 gene mutation - site of mutation determines, clinical variants (classic, attenuated, Gardner, Turoot) -many patients have prophylactic colectomy Large polyps have higher risk than small ones Progression from adenoma to carcinoma - Most CRCs arise form adenomas - adenomas and Ca similar distribution - adenomas usually precede cancer by 15 years - endoscopic removal of polyps decrease the incidence of subsequent CRC Genetic pathways: -Involves APC, K raise, Smads, p53, telomerase activation -Micro satellite instability - micro satellites are sequences prone to misalignment. Some microsatellites are in coding sequences of genes which inhibit growth or apoptosis e.g. TGFbR11 -mismatch repair genes (e.g MSH2). Recessive teens requiring 2 hits HNPCC - germline mutation in these genes Diagram Genetic predisposition as 2 main pathways: - FAP - inactivation of APC tumour suppressor gene - HNPCC - microsatellite instability Why is APC important in colon cancer? B-catering moves from cytoplasm to nucleus if APC doesn’t work - affect cell transcription, cell proliferation increases (uncontrolled) Role of p53 Diffuse positivity of p53 - p53 not working properly therefore cells trying to express p53 - accumulating non-functional p53 All this leads to colonic carcinoma - age Rae 50-80, dietary factors: high fat, low fibre, high red meat, refined carbohydrates

Answer 90

Food contains carcinogens Also contains anti cancer agents Heat modifies chemicals and so does bacteria HCAs (heterocyclic amines) found in red meat When cooked at high temperatures oxidation of PhIP can form complexes with deoxyguanosine in DNA —> mutagenesis Dietery deficiencies Folate and colorectal cancer -co-enzyme for nucleotide synthesis and DNA methylation MTHFR -deficiency leads to disruption in DNA synthesis causing DNA instability (strand breaks and uracil incorporation) —> mutations -decreased methionine synthesis leads to genomic hypomethylation and focal hypermethylation —> gene activation and silencing (May not need to know the above) Anti cancer food elements Vitamin C and vitamin E - ROS (reactive oxygen species) scavenger Polphenols (green tea, fruit juice) activate MAPK —> regulates Phase 2 detoxifying enzymes as well as other genes and reduced DNA oxidation Garlic associated with apoptosis

Answer 91

``` Changes in bowel habit Bleeding PR (pre-rectal) Unexplained iron deficient anaemia ``` Mucous Bloating Cramps Constitutional (weight loss, fatigue) Macroscopic features Small carcinomas may be resent within large polyploid adenomas, pedunculated or sessile Can be distributed in caecum/ascending colon, transverse colon, descending colon, rectosigmoid ``` Microscopic structures Adenocarcinomas grade 1-3 Mutinous carcinomas Signet ring cell Neuroendocrine ```

Answer 92

proportion of gland differentiation relative to solid areas or nests and cords of cells without lumina ~ 10% well differentiated ~ 70% moderately differentiated ~ 20% poorly differentiated Dukes Classification Dukes A - growth limited to mucosa/submucosa - nodes negative Dukes B - growth into or beyond musc propria - nodes negative Dukes C1 - nodes positive - apical LN negative Dukes C2 - apical LN positive (A—>C, 5 year survival drops dramatically)

Answer 93

Screening is the practice of investigating apparently healthy individuals with the object of detecting unrecognised disease or people with an exceptionally high risk of developing disease, and of intervening in ways that will prevent the occurrence of disease or improve the prognosis when it develops. Screening for High Risk Colon Cancer Previous adenoma 1st Degree relative affected by colorectal cancer before the age of 45 2 affected first degree relatives evidence of dominant familial cancer trait including colorectal, uterine, and other cancers UC and Crohn’s disease Hereditable cancer families (include other sites) ``` Test characteristics simple and acceptable to the patient sensitive and selective The screening population should have equal access to the screening procedure. Cost effectiveness ```

Answer 94

Leukaemia is cancer of the blood Blood cancers are the most common cancers in men and women aged 15-24 Bone marrow disease, not all patients have abnormal cells in the blood Leukaemia results from a series of mutations in a single lymphoid or myeloid stem cell These mutations lead to cell showing abnormalities in proliferation, differentiation or cell survival leading to explanation of the leukaemia clone Cells involved: Myeloid stem cell —> erythroblast, megakaryoblast, myeloblast, moon last Lymphoid stem cell —> pre B lymphocytes, Pro T lymphocyte ``` Difference to other cancers • Leukaemia is different from other cancers • Most cancers exist as a solid tumour • However, it is uncommon for patients with leukaemia to have tumours • More often they have leukaemic cells replacing normal bone marrow cells and circulating freely in the blood stream • Leukaemia is different from other cancer because haemopoietic and lymphoid cells behave differently from other body cells • Normal haemopoietic stem cells can circulate in the blood and both the stem cells and the cells derived from them can enter tissues • Normal lymphoid stem cells recirculate between tissues and blood ``` • The concepts of invasion (local penetration) and metastasis (blood/lymphatics) cannot be applied to cells that normally travel around the body and enter tissues • We have to have other ways of distinguishing a ‘benign’ condition from a ‘malignant’ condition and haematologists usually use different words for these concepts • Leukaemias that behave in a relatively ‘benign’ manner are called chronic—that means the disease goes on for a long time • Leukaemias that behave in a ‘malignant’ manner are called acute—that means that, if not treated, the disease is very aggressive and the patient dies quite rapidly In summary: • Leukaemia results from acquired somatic mutation in a haemopoietic or lymphoid stem cells • A single cell gives rise to a clone of leukaemic cells that replace normal cells • Disease characteristics are due to (i) proliferation of leukaemic cells (ii) loss of function of normal cells

Answer 95

Leukaemia can be acute or chronic Depending on the cell of origin it can also be lymphoid or myeloid Lymphoid can be B or T lineage Myeloid can be any combination of granulocytic, monocytic, erythroid or megakaryocytic

Answer 96

Leukaemia is cancer of the blood Blood cancers are the most common cancers in men and women aged 15-24 Bone marrow disease, not all patients have abnormal cells in the blood Leukaemia results from a series of mutations in a single lymphoid or myeloid stem cell These mutations lead to cell showing abnormalities in proliferation, differentiation or cell survival leading to explanation of the leukaemia clone Cells involved: Myeloid stem cell —> erythroblast, megakaryoblast, myeloblast, moon last Lymphoid stem cell —> pre B lymphocytes, Pro T lymphocyte ``` Difference to other cancers • Leukaemia is different from other cancers • Most cancers exist as a solid tumour • However, it is uncommon for patients with leukaemia to have tumours • More often they have leukaemic cells replacing normal bone marrow cells and circulating freely in the blood stream • Leukaemia is different from other cancer because haemopoietic and lymphoid cells behave differently from other body cells • Normal haemopoietic stem cells can circulate in the blood and both the stem cells and the cells derived from them can enter tissues • Normal lymphoid stem cells recirculate between tissues and blood ``` • The concepts of invasion (local penetration) and metastasis (blood/lymphatics) cannot be applied to cells that normally travel around the body and enter tissues • We have to have other ways of distinguishing a ‘benign’ condition from a ‘malignant’ condition and haematologists usually use different words for these concepts • Leukaemias that behave in a relatively ‘benign’ manner are called chronic—that means the disease goes on for a long time • Leukaemias that behave in a ‘malignant’ manner are called acute—that means that, if not treated, the disease is very aggressive and the patient dies quite rapidly

Answer 97

Leukaemia can be acute or chronic Depending on the cell of origin it can also be lymphoid or myeloid Lymphoid can be B or T lineage Myeloid can be any combination of granulocytic, monocytic, erythroid or megakaryocytic

Answer 98

Leukaemia is cancer of the blood Blood cancers are the most common cancers in men and women aged 15-24 Bone marrow disease, not all patients have abnormal cells in the blood Leukaemia results from a series of mutations in a single lymphoid or myeloid stem cell These mutations lead to cell showing abnormalities in proliferation, differentiation or cell survival leading to explanation of the leukaemia clone Cells involved: Myeloid stem cell —> erythroblast, megakaryoblast, myeloblast, moon last Lymphoid stem cell —> pre B lymphocytes, Pro T lymphocyte ``` Difference to other cancers • Leukaemia is different from other cancers • Most cancers exist as a solid tumour • However, it is uncommon for patients with leukaemia to have tumours • More often they have leukaemic cells replacing normal bone marrow cells and circulating freely in the blood stream • Leukaemia is different from other cancer because haemopoietic and lymphoid cells behave differently from other body cells • Normal haemopoietic stem cells can circulate in the blood and both the stem cells and the cells derived from them can enter tissues • Normal lymphoid stem cells recirculate between tissues and blood ``` • The concepts of invasion (local penetration) and metastasis (blood/lymphatics) cannot be applied to cells that normally travel around the body and enter tissues • We have to have other ways of distinguishing a ‘benign’ condition from a ‘malignant’ condition and haematologists usually use different words for these concepts • Leukaemias that behave in a relatively ‘benign’ manner are called chronic—that means the disease goes on for a long time • Leukaemias that behave in a ‘malignant’ manner are called acute—that means that, if not treated, the disease is very aggressive and the patient dies quite rapidly

Answer 99

Leukaemia can be acute or chronic Depending on the cell of origin it can also be lymphoid or myeloid Lymphoid can be B or T lineage Myeloid can be any combination of granulocytic, monocytic, erythroid or megakaryocytic • Put all this together and we get: Acute lymphoblastic leukaemia (ALL) Acute myeloid leukaemia (AML) Chronic lymphocytic leukaemia (CLL) Chronic myeloid leukaemia (CML) Lymphoblastic: immature, lymphocytic: mature lymphocyte

Answer 100

• Leukaemia results from a series of mutations in a single stem cell • Some mutations result from identifiable (or unidentifiable) oncogenic influences • Others are probably random errors—chance events—that occur throughout life and accumulate in individual cells • The important leukaemogenic mutations that have been recognized include: - Mutation in a known proto-oncogene e.g. point mutations - Creation of a novel gene, e.g. a chimaeric or fusion gene - Dysregulation of a gene when translocation brings it under the influence of the promoter or enhancer of another gene • Loss of function of a tumour-suppressor gene can also contribute to leukaemogenesis—this can result from deletion or mutation of the gene • If there is a tendency to increased chromosomal breaks, the likelihood of leukaemia is increased • In addition, if the cell cannot repair DNA normally, an error may persist whereas in a normal person the defect would be repaired ``` • Inherited or other constitutional abnormalities can contribute to leukaemogenesis: -Down’s syndrome - Chromosomal fragility syndromes -Defects in DNA repair -Inherited defects of tumour-suppressor genes ``` ``` • Identifiable causes of leukaemogenic mutations include: -Irradiation -Anti-cancer drugs -Cigarette smoking -Chemicals—benzene ``` • Leukaemia, like cancer in general, can be seen as an acquired genetic disease, resulting from somatic mutation • Mutation in germ cells may bring favourable, neutral or unfavourable characteristics to the species • Somatic mutation may be beneficial*, neutral or harmful * A rare occurrence but can lead to reversion to normal phenotype in some cells in individuals with an inherited abnormality, e.g. an immune deficiency or bone marrow failure syndrome

Answer 101

In AML, cells continue to proliferate but they no longer mature so there is: -A build up of the most immature cells— myeloblasts or ‘blast cells’—in the bone marrow with spread into the blood -A failure of production of normal functioning end cells such as neutrophils, monocytes, erythrocytes, platelets Platelets can also be low because complicated by disseminated intravascular coagulation (platelets consumed) • In AML, the responsible mutations usually affect transcription factors so that the transcription of multiple genes is affected • Often the product of an oncogene prevents the normal function of the protein encoded by its normal homologue • Cell behaviour is profoundly disturbed • In CML, the responsible mutations usually affect a gene encoding a protein in the signalling pathway between a cell surface receptor and the nucleus • The protein encoded may be either a membrane receptor or a cytoplasmic protein • In CML, cell kinetics and function are not as seriously affected as in AML • However, the cell becomes independent of external signals, there are alterations in the interaction with stroma and there is reduced apoptosis so that cells survive longer and the leukaemic clone expands progressively • Whereas in AML there is a failure of production of end cells, in CML there is increased production of end cells

Answer 102

``` • Acute lymphoblastic leukaemia has an increase in very immature cells— lymphoblasts—with a failure of these to develop into mature T and B cells • In chronic lymphoid leukaemias, the leukaemic cells are mature, although abnormal, T cells or B cells ```

Answer 103

Accumulation of abnormal cells leading to – Leucocytosis, bone pain (if leukaemia is acute), hepatomegaly, splenomegaly lymphadenopathy (if lymphoid), thymic enlargement (if T lymphoid), skin infiltration Metabolic effects of leukaemic cell proliferation—hyperuricaemia (DNA break down) and renal failure (deposit of uric acid), weight loss, low grade fever, sweating Crowding out of normal cells leading to – anaemia, neutropenia, thrombocytopenia Haemorrhage and swelling of gums (infiltration of gums by leukaemic cells), chemotaxis, can also have intraventricular haemorrhage Loss of normal immune function as a result of loss of normal T cell and B cell function —a feature of chronic lymphoid leukaemia

Answer 104

Acute lymphoblastic leukaemia is largely a disease of children * Epidemiology suggests that B-lineage ALL may result from delayed exposure to a common pathogen or, conversely, that early exposure to pathogens protects * Evidence relates to family size, new towns, socio-economic class, early social interactions, variations between countries • Epidemiology also suggests that some leukaemias in infants and young children result from: -Irradiation in utero -In utero exposure to certain chemicals ? -Epstein–Barr virus infection • Rarely ALL results from exposure to a mutagenic drug

Answer 105

``` Resulting from accumulation of abnormal cells: • Bone pain • Hepatomegaly • Splenomegaly • Lymphadenopathy • Thymic enlargement • Testicular enlargement ``` Resulting from crowding out of normal cells • Fatigue, lethargy, pallor, breathlessness (caused by anaemia) • Fever and other features of infection (caused by neutropenia) • Bruising, petechiae, bleeding (caused by thrombocytopenia) • Leucocytosis with lymphoblasts in the blood • Anaemia (normocytic, normochromic) • Neutropenia • Thrombocytopenia • Replacement of normal bone marrow cells by lymphoblasts

Answer 106

* Blood count and film * Check of liver and renal function and uric acid * Bone marrow aspirate * Cytogenetic/molecular analysis * Chest X-ray On blood film can see: lymphoblasts, high nuclear:cytoplasmic ratio, lack of platelets Immunophenotyping Antibodies used to bind to antigen and have fluorescent markers Cytogenetic and molecular genetic analysis Can see leukaemogenic mechanisms Cytogenetic : karyotyping, extra chromosomes can be seen -hyperdiploidy = good prognosis, fusion gene/ translocation = poor prognosis Leukaemogenic mechanisms: • Formation of a fusion gene - translocation • Dysregulation of a proto-oncogene by juxtaposition of it to the promoter of another gene, e.g. a T-cell receptor gene • Point mutation in a proto-oncogene Specific to ALL: Chromosomes 12 an 21 showing EV6 and RUNX1, following translocation there is a fusion ETV6-RUNX1 gene on chromosome 12 This can be detected by two fluorescent probes, a green probe for ETV6 and a red probe for RUNX1; when a fusion gene is formed the two colours fuse to give a yellow fluorescent signal This technique is called fluorescence in situ hybridization —FISH (If cytogenetic analysis fails because cells don’t go into mitosis, FISH can be used to detect fusion gene)

Answer 107

• Supportive -red cells - anaemia -platelets - thrombocytopenia -antibiotics - infection • Systemic chemotherapy - widespread disease • Intrathecal chemotherapy - via lumbapuncture

Answer 108

Made up of epidermis, dermis and hypodermis. Hair follicle located in dermis, subcutaneous fat in hypodermis Dermis also contains collagen, elastin, GAGs, blood vessels, nerves, sweat glands Apocrine glands make viscous and smelly sweat (groins), eccrine - normal body sweat Dendritic cells, melanocytes, keratinocytes found in epidermis Structure of epidermis Cells important in skin cancer are keratinocytes and melanocytes Keratinocytes mature and rise up from base, basal —> spinous —> granular —> corneum and shed Exposed to UV radiation and undergo genetic mutation

Answer 109

Keratinocytes derived: E.g. basal cell carcinoma (pearly-grey, shiny, pinky with telangiectasia - dilated small capillaries), squamous cell carcinoma, aka non-melanoma skin cancer (NMSC) Melanocyte derived: E.g. malignant melanoma - dark irregular border Vasculature derived: E.g. Kaposi’s sarcoma, angiosarcoma Lymphocyte derived: E.g. mycosis fungoides Cause of cancer Accumulation of genetic mutation —> uncontrolled cell proliferation Examples of causes - genetic syndromes: Gorlin’s syndrome (underlying tendency to develop basal carcinomas), xeroderma pigmentosum (genetic defect in DNA repair) - viral infections: HHV8 in Kaposi’s sarcoma, HPV in squamous cell carcinoma - UV light: basal cell and squamous cell carcinoma, malignant melanoma - immunosuppression: drugs, HIV, old age, leukaemia

Answer 110

Sunlight benefits: • Essential for photosynthesis (plants) • Infrared spectra provide warmth • Effect on human mood • Stimulates the production of vitamin D in the skin • UVB most important wavelength in skin carcinogenesis Directly induces abnormalities in DNA e.g. mutations Induces photoproducts affecting cytosine and thymine - cross linking to form thymine dimers Usually repaired quickly by nucleotide excision repair - remove mutations • UVA 100 times more UVA penetrates to the Earth’s surface major cause of skin ageing contributes to skin carcinogenesis used therapeutically in PUVA therapy (used in psoriasis, eczema) Can form pyrimidine dimers but less effective Free radicals which damage DNA and cell membrane • UV damage to DNA leads to mutations in specific genes - cell division - DNA repair - cell cycle arrest Repair of UV induced DNA damage • Photoproducts are removed by a process called Nucleotide Excision Repair • Xeroderma pigmentosum (treated with removal of cancer ad sun protection) Genetic condition with defective Nucleotide Excision Repair Mutations that cause cancer 1. Mutations that stimulate uncontrolled cell proliferation Eg abolishing control of the normal cell cycle (p53 gene) 2. Mutations that alter responses to growth stimulating / repressing factors 3. Mutations that inhibit programmed cell death (apoptosis)

Answer 111

UV leads to keratinocyte cell apoptosis ‘Sun burn’ cells are apoptotic cells in UV overexposed skin Apoptosis removes UV damaged cells in the skin which might otherwise become cancer cells Photocarcinogenesis UV light —> p53 mutation —> skin cancer UV —> DNA damage —> repair of DNA (p52 stops cell division) —> normal cell UV —> damage too severe, unable to repair —> cell death, apoptosis Immunomodulatory effects of UV light • UVA and UVB effect the expression of genes involved in skin immunity Depletes Langerhans cells in the epidermis (involved in antigen presentation) • Reduced skin immunocompetence and immunosurveillance - no immune response to cause cell death, instead skin cancer develops Basis for UV phototherapy for eg psoriasis • Further increases the cancer causing potential of sun exposure

Answer 112

Host response to UV is determined by genetic influences especially skin phenotype Fitzpatrick Phototypes • 1 - Always burns never tans • II - Usually burns, sometimes tans • III - Sometimes burns, usually tans • IV - Never burns, always tans • V - Moderate constitutive pigmentation - Asian • VI - Marked constitutive pigmentation - Afrocaribean Melanin • Melanin pigmentation is responsible for skin colour • Produced by melanocytes within the basal layer of the epidermis • Skin colour depends on the amount and type of melanin produced not the density of melanocytes (which is fairly constant) = no of melanocytes between all skin types remain the same; it’s the amount of melanin they produce that differs Melanocytes = after sunlight exposure (UV), keratinocytes will send out paracrine messages - MSH which affects melanocytes to form melanin. Melanin taken up by keratinocytes and placed around nucleus = protection • Two types of melanin are formed: Eumelanin – brown or black Phaeomelanin – yellowish or reddish brown Melanin is formed from tryosine via a series of enzymes • MCR1 gene >20 gene polymorphisms Variation in eumelanin : phaeomelanin produced Explains different hair colour and skin types Melanin dictates skin sensitivity to UV damage

Answer 113

Malignant tumour of melanocytes -Melanocytes become abnormal -Atypical cells and architecture Caused by - UV exposure - Genetic factors Risk of metastasis: Pagetoid spread, atypical melatocyes because located in epidermis normally in basement membrane (resembles Paget’s) Lentigo maligna (melanoma in situ) - proliferation of malignant melanocytes within the epidermis - no risk of metastasis - irregular shape - light and dark brown colours - size usually > 2 cm Lentigo maligna melanoma - local invasion - superficial spreading - lateral proliferation of malignant melanocytes - invade basement membrane - risk of metastasis - melanocytes in dermis and epidermis - radial growth phase - heading outwards and vertical growth phase - downwards ``` Diagnosis of superficial spreading malignant melanoma ABCD rule Asymmetry Border irregular Colour variation (dark brown-black) Diameter > 0.7 mm and increasing Erythema ``` Nodular malignant melanoma Vertical proliferation of malignant melanocytes (no previous horizontal growth) Risk of metastasis Nodular melanoma arising within a superficial spreading melanoma - downward proliferation of malignant melanocytes - following previous horizontal growth - nodule developing within irregular plaque - prognosis will become worse Acral lentiginous melanoma Pigmented plaques/lumps on sole Amelanotic melanoma Non-pigmented ``` Overall types of malignant melanoma: • Superficial spreading • Nodular • Lentigo maligna melanoma • Acral lentiginous • Amelanotic ``` Melanoma recognition - ABCD • Asymmetry • Border • Colour • Diameter Prognosis of melanoma can be found by using Breslow thickness; see depth of invasion from granular epidermis to where it extends

Answer 114

- family history of melanoma - ultraviolet irradiation - intermittent burning exposure in unacclimatised fair skin - personal history of melanoma - skin type I, II

Answer 115

Keratoacanthoma grows rapidly into a volcano like shape ``` SCC from keratinocytes, if well differentiated it will make keratin Malignant tumour of keratinocytes Caused by: -UV exposure -HPV -Immunosuppression May occur in scars or scarring processes Risk of metastasis ```

Answer 116

``` Malignant tumour arising from basal layer of epidermis Caused by: -sun exposure -Genetics Slow growing Invades tissue, but does not metastasise Common on face Glistening, telangiectasia Can be nodular, superficial ```

Answer 117

Mycosis fungoides Cutaneous and cell lymphoma Looks like psoriasis Kaposi’s sarcoma HIV and HHV8 associated - rises from endothelial cells of lymphatics Epidermodysplasia veruciformis Rare autosomal recessive condition Predisposition to HPV induced warts and SCCs

Cancer Flashcards

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