Tumour Formation and Development Flashcards

Question

Outline the effect of TANs

Answer 1

Can be both pro- and anti-tumour depending on phenotype. N1 = anti-tumour (pro-inflammatory) * Direct killing of cancer cells: ADCC, direct cytotoxicity (perforin) * Immune recruitment: IL-8, CXCL2, TNFα * Increased ROS production (expression of NADPH oxidase) - increases efficacy of radiotherapy and chemotherapy. N2 = pro-tumour (anti-inflammatory) - elevated levels ⇒ poor prognosis * Stimulate angiogenesis (VEGF) * Cytokine release (IL-6, IL-10) * Suppression of immune cells (PD-L1 expression) * Promote EMT: MMP9 release

Answer 2

Almost all research in in mouse models: * Major differences in TAN expression and influence * Observations mainly from xenotransplants in humanised mice: TANs in these have been heavily selectively modeified to survive in mouse - may not be representative. * Not a full immune system present (interaction with other immune cells limited which is a major effect of signalling).

Answer 3

Hypoxia occurs when oxygen demand exceed supply (shortage of Ox) * Commonly occurs in a tumour (since high metabolic rate) - is a hallmark of cancer * Cellular responses to hypoxia are protective, reversible and short-lived (turned off after 48hrs) * However, these same responses facilitate cancer development (e.g. stimulation of proliferation, angiogenesis, activaiton of survival genes etc...) * Therefore, this system is hijacked by cancer cells. Becomes a permanent response which is non-reversible, extreme and damaging.

Answer 4

Hypoxia induces gene expression changes which alter cell behaviour and metabolism. HIF is a master regulator. * Try to reduce hypoxia by promoting angiogenesis (bring in more O2) * Increase survival of cells while hypoxia occurs (in the short-term) through gene expression changes (e.g upregulate Nf-kB and downregulate Bcl-2) * Change energy metabolism to reduce oxygen usage (OxPhos to glycolysis)

Answer 5

Hypoxia changes gene expression including HIF activation * Encourages the release of angiogeneic factors (VEGF, FGF) in extreme amounts * Leads to rushed and copious proliferation of endothelial cells * Disorganised and leaky vessels result * Increases hypoxia as diffusion distances can actually increase * Causes +ve feedback

Answer 6

Extreme hypoxia and hypoxic response (e.g. angiogenesis) is a hallmark of cancer Observation/diagnosis: * Identfying tumours (e.g. pimonidazole which becomes reduced in hypoxia environment leading to adduct formation (trapped in area). Link to radio or fluorescence tracer. * Good for metastasis detection (not seen on a normal scan) Treatment: * Identifying metastases for targeted treatment * Target results of hypoxia (e.g. anti-angiogenc drugs) * Localise treatment to tumour (e.g. hypocia activated prodrugs HAPs or hypoxia activated theragnostic prodrugs HATP) (limited to solid tumours)

Answer 7

* Reduces efficacy of radiotherapy (oxygen enhancement theory that O2 produces ROS from radiotherapy, increasing local damage). - improved using radiosensitisers (carbogen; vit B3) * Damaged blood vessels may reduce ability for immunotheraputic drugs to access tumour

Answer 8

* When O2 low: less oxygen to allow E3 ligase activity (e.g. including Von-Hippel Lindau) * Less degradation of HIF-1/2a, more HIF-alphas become stable (normal 1/2 life is 3 mins) * HIFs (HIF-1α + 1β & HIF-2α + 1β) * Bound HIFs translocate to the nucleus and act as TFs **oxygen independent HIF activation can also occur (through mutation e.g. VHL disease).**

Answer 9

Since they are master regulators they are almost ubiquitiously expressed and necessary for survival. * Cannot use knock-outs form birth * Need to manipulate in a localised area * Manipulation or inhibition in treatment can have severe side-effects Treatment therefore often used in conjunction with another treatment

Answer 10

HIF structure has 'druggable pocket' found by Wu et al 2015. Drugs developed: * HIF-2a inhibitors (Belzutifan): for clear cell renal carcinoma (ccRCC). Patients survived for >1 year (not seen before) * Mostly used in conjunciton with other drugs

Answer 11

* Low-oxygen induced tracers (e.g. pimonidazole) * Measure metabolic genes 'hypoxia induced signature' (29 specific genes give good profile of hypoxic respones)

Answer 12

* Understanding that kidney cells only express HIF-2α * Therefore hypoxia induces major HIF-2α activaiton (whether oxygen dependent or independent) * HIF-2α inhibitors therefore particularly effective * Success of Belzutifan for ccRCC

Answer 13

* Patients with VHL disease are not very responsive to HIF-2α inhibition (despite having elevated HIF-2α ) * Reaction would be expected if VHL only activated HIF-2α pathway (and knock-on effects)

Answer 14

Changes in oxPhos * Reduced OxPhos * electrons are shunted from complex IV * Increased ROS production * ROS can interact with Fe (in **Fenton reaction** to produce highly toxic OH- * More intermediates are present which can act as regulators in themselves. Consequences: * Epigenetic change which promotes mutation How could fats help? * Fats can be used to provide electrons for OxPhos (attempts to protect mt from caspase which would lead to apoptosis) * Allows limited OxPhos to continue which limits ROS and subsequent damage * Downregulates Bcl-2 as a survival mechanism

Answer 15

Paget's hypothesis that cancer cells and microenvironment need to combine for successful tumourigenesis. Particular areas of the body provide right conditions for specific cancer to grow. Explains why models with identical cancer cell mutation profile may not grow in different areas/animals.

Answer 16

Clonal mutant tumours have same chance of survival but most do not survive. A handful do. Niches of those that survive show significantly more stromal remodelling (Alcolea et al 2014 - induced oesophageal tumours using DEN (nitrosamine)). Pre-tumour phenotype stroma is sufficient to induce tumour properties in carcinogen free epithelium (Skrupsleyte et al)

Answer 17

Goes from anti-tumour to tumour permissive (immunosuppressive state). Due to: - Upregulation of exhaustion - Increase in CAF numbers (wound healing response) - Upregulation of M2-like immunosuppressive cells (TAMs; e.g. CD163+) and downregulated M1

Answer 18

Skrupskelyte et al 2024 Mice exposed to DEN form many epithelial tumours. Most are cleared after 10 days. 1. The surviving tumours showed a phenotypically distinct niche ("niche+") (i.e. this changed from the minority to dominating niche) with more extreme stromal remodelling (a 'stromal nest') at a nascent stage. 2. Showed a high fibroblast population which encourages tumour growth and survival. Author suggests this is a 'pre-cancer niche' which encourages tumour growth.

Answer 19

Skrupskelyte et al 2024 Pre-cancer niche stroma was grown with healthy epithelium (where no carcinogen was present) - Healthy epithelium took on tumour like-morphology - Proliferation of healthy epithelium reached almost tumour like levels - Suggests signalling from PCN stroma was sufficient to induce this change - Stroma may not just be responding to tumour signalling; it may be driving it.

Answer 20

Altered gene expression: *E.g. YAP/TAZ mechanotransductor translates a mechanical signal into a change in TFs. Is sufficient for tumour initiation. Causing physical damage/stress: *Increased BM stiffness correlated with development of invasive sarcoma-like phenotype *'Fold like' structure rather than budding indicates sarcoma vs. basal cell carcinoma has more tension and is correlated to severe invasion and poor prognosis (Fiore et al 2022)

Answer 21

Amplification/activation is associated with tumour initiation and growth in many cancers (liver; breast) *Synergistically activates many genes controlling entrance to S phase of cell cycle. *Leads to self-renewal of cells (which resemble stem cells)

Answer 22

Fiore et al 2022: increased membrane stiffness leads to increased likelihood of developing invasive sarcoma-like phenotype. 1. Increased stiffness increases chance of developing 'fold' (invasive sarcoma) rather than 'budding' (non-invasive basal carcinoma) phenotype (structure) of growth 2. Fold has increased tensile stress on BM leading to loss of membrane integrity and invasion 3. Leads to: Metastasis; difficulty in treating and worse prognosis

Answer 23

Bansaccal et al 2023 SmoM2 expression is associated with the development of basal cell carcinoma on the ear. *SmoM2 expression in ear epidermis led to BCC tumour initiation but did not in back ear epidermis (instead proliferating laterally forming a growth rather than invading vertically) *Back skin is stiffer with a much denser collagen I network *Breakdown of this (collagenase treatment) followed by overexpression of SmoM2 did lead to tumour initiation Also used UVB expression to test this (however, this may have other effects which also overcome BCC resistance e.g. mutation of different pathways).

Answer 24

1. VEGF binds to VEGFR2 (VEGFR1 is decoy receptor) 2. Induces endothelial cells to becomes a tip cells and stalk cells 3. Tip cells are highly migraitory and stalk cells are highly proliferative 4. Forms new sprout which eventually matures into a new vessel (hollows and propoer structure formed) 5. Tip cells signal to neighbouring cells to inhibit their formation into a new vessel (for effective vessel network).

Answer 25

* Angiogenesis is the production of new blood vessels * Tumour microenvironment leads to excessive production of angiogenic signals (from tumour cells, TA immune cells...) * Leads to excessive and dysregulated angiogenesis which causes tumour growth (+ve feedback) * Promotes tumour growth, invasion and metastasis.

Answer 26

* Leaky vessels: weaker tight gap junctions allowing fluid leakage and making it easier for tumour cells to invade (metastasis) * Vessels may be too small or rough to transport RBCs so oxygen not delivered (increases hypoxia) * Vessel network not orderly (e.g. inconsistant distances between vessels which may increase diffusion distance leading to hypoxia) * Excessive exposed endothelial cells: express PD-1 which may lead to immunosuppression

Answer 27

* Many tumours are associated with dense vessel micronetwork which is correlated with poor outcome * Xenografts whihc fail to induce vascular response do not grow (i.e. angiogenesis is required) * Blocking angiogenesis inhibits tumour growth (Zahalka et al), anti-angiogenics (e.g. Belvacitumab against VEGF-A in colon, sunitinib against insulomas) have been successful).

Answer 28

* Some tumours show decreased vessel density (NSCLC) * May be due to development of 'angiogenic independent' mechanisms to vascularise. E.g. vascular independence (i.e. use glycolysis), vessel co-option, mimicary * Therefore anti-angiogenic drug will not inhibit * Fast evolution of cancer allows adaptation around pathway being inhibited (e.g. downregulate VEGF and upegulate FGF) - limits long term efficacy. * Major side-effects since angiogenesis is a widespread and necessary mechanism in healthy tissue.

Answer 29

* Only have drug activate in tumour environment (e.g. like HAPs or pimonidazole)

Answer 30

Warburg effect = phenomenon of cancer cells switching to aerobic glycolysis. No inherent energy advantage (reduces ATP produced per mole). Advantage: product recycling of TCA intermediates * Ribose for nucleotides * Acetyl CoA for fatty acids (can further support metastasis e.g. Ferraro et al) * Glucose intermediates for non-essential amino acids * Creates mutagenic environment which progresses tumour (ROS and Fenton reaction (OH- radicals))

Answer 31

Can allow tumour to survive in different environments: * E.g. Ferraro et al: breast tumour metastasis to brain requires de novo fatty acid synthesis (since fats don't pass BBB). Could be a target for treatment. Cause more mutations: * Directly: metabolites can modify proteins e.g. succination - where fumarate reacts with cystine changing structure (epigenetic changes) * Increase ROS production causing damage and mutation.

Answer 32

Mutations to enzymes in the TCA cycle: * PGL1 gene (SDH mutation): halts TCA cycle increasing ROS and hypoxia signalling (Glycolysis upregulated) = mutation rate increases. Paraganliomas result. * Fumarate hydratase (FH) mutation leads to RCC and leiomyomas * VHL disease signalling hypoxia (manifests in similar way since VHL also requires 2-α-ketoglutarate from TCA cycle) * Isocitrate dehydrogenase (IDH) mutations in gliomas - leads to D-2 hydroxyglutarate which disrupts histone methylation (aberrant gene expression)

Answer 33

Promote cancer: Globig et al: * NA secretion onto β1 receptors induces PD-1 expression on T-cells which induces exhaustion * Ablation of receptor prevents progression to exhaustion Protect against: Guillot et al 2022 * SNS is protective for pancreatic cancer * Sympathectomy increases CD163+ (through β2-adrenergic sginalling) population which correlates with worse outcome

Answer 34

Regulatory: * Myeloid derived suppressor cells * Tregs (higher number correlates with worse prognosis) * Tumour associated macrophages (ITAMs) - M2s are immunosuppressive (tumour promoting) Active: * M1 ITAMs (pro-inflammatory) * NK cells * DCs * CD8+ cells - crucial for *control of cancer* (respond to tumour antigens) * CAFs Signalling by cancer promotes immunosuppression (e.g. M1 to M2 switch)

Answer 35

Major part of +ve feedback system inducing progression of cancer 1.Cancer cells are present and reproduce 2.Replication and growth causes damage to the surrounding tissue 3.Immune activation and immune cells recruited = wound healing state (both by cancer cells and damaged healthy cells) 4.Signals recruiting immune cell also suppress immune control cells and signals 5.Recruited cells cause changes to microenvironment (EMT transition) (e.g. more damage) 6. Leads to an environment encouraging growth and repair = Facilitates growth of tumour (back to 1.) 7. Eventually invasion and metastasis occurs to start the cycle somewhere else

Answer 36

It is difficult since they are a highly heterogeneous group (this may be part of the problem...they may not be one group) Identified using a combination of shape and chemical markers (fibroblast activation protein (FAP), F specific protein (FSP1))

Answer 37

ssRNA-seq revealed (and is revealing) more functionally heterogeneous sub-populations. A few examples: - Wound-healing (h-CAFs): proliferation, collagen and ECM deposition) - Myofibroblasts (myCAFs): mechanical architects of ECM (highly destructive and invasion promoting, lots of anti-muscle antibodies) - Inflammatory CAFs (IL-8 and IL-11, IL-1β) stimulating proliferation - generally tunourigenic

Answer 38

M1 inflammatory: * Induced by complement activation (C3a/C5a) * Produce inflammatory signals: IFNγ, TNFα, IL-1β * Nitric oxide production (iNOS) = pathogen clearance M2 promotes repair: * Induced by IL-4, high C3b, TGF-β * Produce TGF-β, IL-10 * Induce proliferation Problem: realistically there are more than 2 catagories (>100 subtypes have been identified).

Answer 39

* UV exposure is common cause with similar tumour specific antigens being highly expressed. * These TSAs make good targets for CD8+ cells which can directly kill cancer cells * Therefore upregulation of CD8+ cells (e.g. using PD-1 blocker) is effective and has fewer sideeffects (at least in surounding area)

Answer 40

Hiding: * Downregulation of antigen presenting (MHC I decrease) * Reduced access Reduced recruitment of immune system: * Downregulation of B7 receptors → reduced CD28 co-stimulatory activity → reduced T cell activation and increased anergy of naive T cells * Immune privilege: dysrupted vascular may not present correct selectins (P and E) for immune recruitment * Downregulation of pro-inflammatory signals Immunosuppression: * Upregulation of immune suppresive signals (e.g. TGF-β and IL-10) * Upregulation of PD-L1 * TAM, CAFs

Answer 41

Kamiya et al: protective in breast cancer through repression of PD-1 on lymphocytes. * Xenograft model in humanised mice * Genetic stimulation fo PSNS nerves reduced tumour burden * (Previous correlation evidence) Patients with worse outcomes showed lower PSNS innervation

Answer 42

A tumour where only 20% of cells are hypoxic requires double the radiation dose for same effect * Causes double the toxicity

Answer 43

2-HG is a molecule produced from the conversion of α-ketoglutarate: * IDH converts it into D-2-HG, build up can occur from mutant IDH * MDH converts into L-2-HG, build up can occur during hypoxia

Answer 44

Direct effects from the build up of D-2-HG (or L-2-HG) * Immunosuppression * Direct inhibitor of lactate dehydrogenase (promotes glycolysis) Indirect effects from the reduction of α-ketoglutarate * Reduces TCA and increases glycolysis: more intermediates for growth. * Alters activity of PHDs (α-ketoglutarate dependent enzyme) - D increases activity, L decreases activity * Role in epigenetic expression (hypermethylation): Reduce TET activity meaning more methylation of DNA occurs (silences genes) * Reduces endosatin synthesis

Answer 45

Normally: 1. Prolyl hydroxylases (PHDs) usually hydroxylate HIF-α 2. Makes HIF-α a target for degredation by VHL Effect of 2-HG: * D-2-HG *increases* PHD activity, so more HIF is degraded * L-2-HG *decreases* PHD activity so HIF is stabilised (increase hypoxia signalling) * Balance between the two determines HIF stability

Answer 46

Disrupts T-cell activity: direct inhibition of LH increases glycolysis in T cells: * Inhibits proliferation * Inhibits cytokine production Reduces complement Reduces granzyme B concentration (Notarangelo 2022) decreasing

Answer 47

Changes to: 1. Metabolism 2. Vascularisation 3. Epigenetic expression

Answer 48

Drop in α-ketoglutarate (build up of both or either D or L 2-HG) * Reduce activity of TET demethylation enzymes * Increases methylation of genes * Makes them harder to transcribe * Leads to silencing (Liu et al) Effects: * Thought to immunosuppress *

Answer 49

* Zahalka: prostate, GEMM * Magnon et al: prostate, xenograft * Globig: PDAC, GEMM * Guillot: PDAC, xenograft * Renz: PDAC, GEMM * Kamiya: breast, xenograft

Answer 50

1 in 4 cells carry a positively selected mutation in a cancer gene...in cancer free tissues. Found in a study of eye lids from many individuals.

Answer 51

Zhao et al CD146+ CAFs maintain ER+ expression on breast tumour cells. Encourages growth.

Answer 52

* Number of nerves * Coverage area in a slice * Concentration of neurotransmitters, enzymes (e.g. TH)

Answer 53

Activates Rho-G and cdc42: * Lead to intracellular Ca2+ release which moves actin, extending lamellipodia * Selective overexpression of these factors causes extension in specific patterns e.g. cdc42 causes many small filopodia to extend. * Increases migraition ability

Answer 54

* Tumour cells express P-selectin * Makes platelets stick to the outside * Creates a barrier to avoid immune recognition/damage * Increases hypercoagulability (better for metastasis)

Answer 55

Liver heavily immune associated. * Fatty liver disease or alcholoism cause long term inflammation * Inflammation causes damage ot cells (e.g. ROS and NOS) which eventually causes mutations in tumour suppressor or oncogenes (Evidence since IL-6 KOs in liver cells reduce risk of HCC) **Does seem to be a driver**

Answer 56

Brain is an immune priviledged site with fewer types of immune cells e.g. brain macrophages. Generally less immune driven. * Initial mutations generally before immune involvement (e.g. EGFR, IDH) * Anti-inflammatory drugs show less success **Seems to be a modulator not a driver**

Answer 57

BRCA1/2: tumour suppressor genes which lead to uncontrolled proliferation when mutated * Treatment with PARP inhibitor causes catastrope (PARP inhibitors prevent repair via ssbr, therefore cells also BRCA deficient cannot repair = die but healthy cells can use other mechanisms). Hereditary IDH mutations: * Associated with glioma development * Disruption to metabolism

Tumour Formation and Development Flashcards

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