Lecture Content Flashcards
1
Q
What are carcinomas?
A
Arise from epithelial cells and account for around 90% cancers.
2
Q
What is an adenocarcinoma?
A
A cancer which has arisen from glandular tissue e.g. breast.
3
Q
What are sarcomas?
A
Arise from connective tissue and muscle.
4
Q
What are leukaemias?
A
Blood cell derived sarcomas
5
Q
What is a benign tumour?
A
Cells resemble normal cells. Tend to be localised. Often surrounded by a fibrous capsule. Usually require little treatment. Surgical removal may be needed.
6
Q
What are malignant tumours?
A
Less well differentiated than normal cells.
Grow and divide more rapidly.
High nucleus to cytoplasm ratio, fewer specialised structures.
More difficult to treat, less definition.
Invade surrounding tissues.
Enter circulation, seed at different sites - metastasis.
7
Q
What are protooncogenes?
A
These are genes which are normally involved with cell growth control, which can be converted to oncogenes.
8
Q
What are oncogenes?
A
Genes which when undergo GAIN OF FUNCTION mutation result in uncontrolled cell growth.
9
Q
What are tumour suppressor genes?
A
Genes which restrain cell growth, promote cell death and promote DNA repair.
Loss of function leads to excessive growth or damaged cells.
10
Q
How does the nucleus to cytoplasm ratio differ between tumour cells and normal cells?
A
Higher in tumour cells, there are fewer specialised structures found.
11
Q
Why must both copies of a tumour suppressor gene be lost before malignant effects occur?
A
Two hit hypothesis.
If one copy remains, the protein can still be created.
12
Q
How do TSGenes and oncogenes differ regarding the two hit hypothesis?
A
THH implies that both alleles that code for a particular protein must be affected before an effect is manifested. This is because if only one allele is damaged, the second can still produce the correct protein.
13
Q
What are some exceptions to the ‘two-hit’ rule regarding tumour suppressor proteins?
A
p53 mutations can function as a “dominant negative”, meaning that a mutated p53 protein can prevent the function of normal protein from the un-mutated allele.
14
Q
The transcription of tumour suppressor genes can be blocked by ________ of ______ residues in the ______ region.
A
Transcription of Tumour suppressor genes can be blocked by methylation of cytosine residues in promoter region.
15
Q
What is epigenetics?
A
The study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself.
16
Q
Epigenetic changes usually involve modifications to________. Also related are: _____
A
Epigenetic changes usually involve modifications to histone proteins. Also related are: miRNAs.
17
Q
Cancer cells usually contain _____ mutations.
A
3-7.
18
Q
What are the lifestyle factors for cancer development? [4]
A
- Environmental exposure
- Occupation
- Smoking = 40% cancer deaths. Tobacco smoke contains ~81 carcinogens.
- UV/Radiation exposure
19
Q
What type of diet is best for cancer prevention?
A
Mediterranean, eastern is worst.
20
Q
What is a proto-oncogene?
A
A proto-oncogene is an unmutated gene functioning normally to control cell growth, that has the potential to be mutated into an oncogene.
21
Q
Ras is an example of a proto-oncogene which can be mutated via____________
A
Point mutation.
22
Q
HER2 is an example of a proto-oncogene which can be mutated via___________
A
Gene amplification caused by template slipping leading to multiple copies of a gene coding for more protein.
23
Q
Bcl-abl Philadephia is an example of an oncogene caused by________
A
Chromosomal translocations where two separate chromosomes switch locations.
24
Q
What does the c- prefix to c-jun and c-fos indicate?
A
Indicate these are the wildtype/normal version of genes identified as proto-oncogenes.
25
What is the only human oncogenic retrovirus?
HTLV – Human T cell Leukaemia Virus
26
What is the Src gene?
It is a protooncogene, codes for the Src protein, a non-receptor tyrosine-protein kinase. The role of this protein is to phosphorylate specific tyrosine residues in other proteins, ultimately enhancing cell growth.
27
What is the structure of the Src protein?
Src protein contains a C-terminus tyrosine residue, which when phosphorylated, binds to its own SH2 domain inactivating the protein.
28
How does the Src protein become active in normal function?
The Src protein becomes active and unfolds following C-terminus tyrosine dephosphorylation by phosphatases. This goes against the normal convention of protein phosphorylation resulting in activation.
29
How does V-src (the protein resulting from the mutated v-src oncogene) differ from normal Src protein structure and activity?
V-src differs from normal srs in that the C-terminus is truncated, leading to an inability to enter the inactive state and thus having constitutive/basal activity, and abnormal cell growth.
30
What is the normal role of Bcl-abl?
Anti-apoptotic, pro-survival genes. Translocates next to genes coding for B cell immunoglobulin production, hence highly expressed and highly pro-survival.
31
What is HPV? (4)
1. Human papilloma virus
2. Oncogenic DNA virus - integrates viral DNA into host genome - permanently transforming host cells.
3. Causes warts and other benign epithelial growths
4. Causes cervical cancer
32
What are the main 3 proteins produced as a result of HPV infection?
E5
E6
E7
33
How does HPV have oncogenic effects?
The proteins it encodes for interefere with proteins that control cell growth.
34
The HPV produced E5 subunit binds to:
E5 binds to platelet derived growth factor receptor (PDGFR) causing constitutive activation.
35
The HPV produced E6 subunit binds to:
E6 and E7 inhibit the TSGs p53 and pRb respectively.
36
The HPV produced E7 subunit binds to:
E6 binds to the TSG p53.
| E7 binds to pRb.
37
How does HPV produced E6 lead to p53 degrdation?
E6, in associated with host E6-associated protein (which has ubiquitin ligase activity), acts to ubiquinate p53, leading to proteosomal degradation.
38
How does HPV produced E7 result in the cell cycle progressing?
E7 competes for retinoblastoma protein (pRb) binding, freeing the transcription factor E2F to transactivate its targets, pushing the cell cycle forward.
39
EGFs drive cell proliferation by binding and activating _______ leading to activation of the _________ pathway and the __________ pathway.
EGFs drive cell proliferation by binding and activating EGFRs leading to activation of the Ras/MAPK pathway (cell growth) and the PI3K-PKB pathway (cell survival).
40
The Ras/MAPK pathway is involved with____
Cell growth regulation
41
The PI3K-PKB pathway is involved with____
Cell survival
42
What happens to the EGFR when EGF binds?
Two EGFR dimerise.
Kinase domains trans- and auto-activate.
These active kinase domains can then phosphorylate signalling molecules.
43
What causes the ErbB oncoprotein?
The loss/deletion of the extracellular ligand binding domain of EGF. Leading to constitutive activation of kinase domains.
44
What causes the Neu oncoprotein?
Point mutation leading to replacement of the hydrophobic Valine in the transmembrane region of HER2 with a charged Glutamine.
This Gln is energetically unfavourable in a lipid environment, leading to the two chains dimerising, independent of ligand presence, to minimise disruption to the membrane.
45
What is HER2 positive breast cancer?
This is where amplification of WT HER2 has occured. Person becomes overly sensitive to low levels of the ligand. However there is no mutation in the receptor itself.
This is caused by the template slipping leading to multiple copies of the gene or the gene being near to areas of high rates of transcription.
46
What is iressa?
A small molecule inhibitor that blocks ATP binding site in the kinase domain of EGFR. The first selective inhibitor developed.
47
What is tarceva?
Small molecule inhibitor that blocks the ATP binding site in the kinase domain of EGFR.
48
What is herceptin?
This is a drug that targets HER2 positive cancer only.
49
What percentage of women with breast cancer are HER2 positive?
25%.
| HER2 + is associated with aggressive tumours and reduced survival rate.
50
How can we target HER2 positive breast cancer?
Herceptin/trastuzumab (recombinant humanised monoclonal antibody.
51
How does herceptin/trastuzumab work?
It is a recombinant humanised monoclonal antibody (MAb) against the extracellular domain of the HER2 protein.
Multiple MOAs: blocks MAPK + pI3K activation, downregulates receptor, decreases srs activation, increases PTEN activation etc.
52
What are the negatives to herceptin use? (4)
1. Expensive MAb
2. Resistance can occur if mutations alter epitope.
3. Only targets HER2 positive
4. Potentially cardiotoxic (expressed in heart)
53
What is Ras?
Ras protein family members belong to a class of protein called small GTPase, and are involved in transmitting signals within cells, subsequently switching on other proteins and ultimately genes involved with cell growth.
54
Mutations often occur at what positions on Ras?
Positions 12 or 61, present in many human tumours, e.g. 90% of pancreatic tumours.
55
Why is EGFR targeting less effective in tumours caused by Ras mutations?
Ras is downstream of the EGFR and therefore targeting the receptor itself may not be efficacious if Ras is constitutively active.
56
What are the less defined mechanisms of action of herceptin? [5]
1. Downregs receptor
2. Decreases srs activation
3. Increases PTEN activation
4. Induces cell cycle arrest.
5. Potentially increase apoptosis through Fc region being detected by cytotoxic T cells and NK cells.
57
How can Ras mutations be targeted if the EGFR is not a valid target?
Ras has a fatty acid modification which tethers it to membranes.
Inhibitors of this modification (farnesyl transferase inhibitors, FTI) have been developed - these are peptidomimetics.
Don't work well in humans due to compensatory mechanisms that exist.
58
How can mutations to Raf/ how can Raf be targeted during cancer treatment?
Nexavar is a kinase inhibitor approved for the treatment of kidney and liver cancers. It inhibits Raf, but also has MOA by inhibiting VEGFR and PDGFR.
59
What are tumour suppressor genes?
Genes that code for proteins that normally play a role in inhibiting both growth and tumour formation.
60
What does loss of function of tumours suppressor genes lead to?
Tumours! Loss of growth inhibition occurs when mutations cause a loss of function of these genes.
61
Tumour suppressor gene mutations are normally recessive, why is this?
One intact allele is usually sufficient to inhibit unchecked growth, so mutations in both alleles would be needed for full loss of function.
62
What is haploinsufficiency?
Alternative mechanism suggested for particular tumour suppressor genes.
One normal allele produces half (haplo-) of the quantity of protein produced by normal cells and this is not enough to suppress tumour formation. Particularly occurs in genes that regulate DNA repair and the DNA-damage response.
63
What is the APC hereditary mutation?
Precancerous intestinal polyps, increased risk of colon cancer.
64
What is the BRCA1 hereditary mutation?
60% probability of inheriting breast cancer compared to 2% with two WT alleles.
65
What is the retinoblastoma protein?
pRb is a tumour suppressor protein that is dysfunctional in several major cancers. Gene name: RB or RB1.
66
What is the function of pRb, the retinoblastoma protein?
1. Prevent excessive cell growth by inhibiting cell cycle progression until a cell is ready to divide. When the cell is ready to divide, pRb is phosphorylated, becomes inactive and allows the cell cycle to progress.
2. It is a recruiter for several chromatin remodeling enzymes such as methylases and acetylases.
67
How many forms of retinoblastoma are there?
2.
One is a familial form which is inherited.
The other is a sporadic form.
60% inherited, 40% sporadic.
68
Why do those sufferers of inherited retinoblastoma have an increased risk of developing other cancers later in life whereas those with sporadic retinoblastoma do not?
In the familial form, a mutated allele is inherited along with a normal allele. In this case, should a cell sustain only one mutation in the other RB gene, all Rb in that cell would be ineffective at inhibiting cell cycle progression, allowing cells to divide uncontrollably and eventually become cancerous. Furthermore, as one allele is already mutated in all other somatic cells, the future incidence of cancers in these individuals is observed with linear kinetics. However, in the sporadic form, both alleles would need to sustain a mutation before the cell can become cancerous. This explains why sufferers of sporadic retinoblastoma are not at increased risk of cancers later in life, as both alleles are functional in all their other cells.
69
How does Rb restrict the cells ability to replicate DNA?
It inhibits the progression from G1 (first gap phase) to S (synthesis phase) of the cell division cycle.
pRb is normally bound to E2F - preventing the transcription of genes required for S phase.
a LOF in pRb means that E2F is free all the time, independent of growth factors, and cells are constantly pushed through S phase leading to uncontrolled proliferation.
70
How does pRb become phosphorylated during the cell cycle?
Growth factors are activated eg through ras/MAPK pathway from EGFR, this leads to transcription of cyclin D1 which binds to Cyclin dependent kinase 4, which then phosphorylates pRb.
71
A loss of function to p16 has what impact on the cell?
LOF p16 removes the ability of the cell to halt the cell cycle in order to repair damaged DNA. Mutations are passed on to daughter cells and accumulate.
72
What is p16?
p16 is an inhibitor of cyclin dependent kinases such as CDK4 and CDK6. These latter kinases phosphorylate pRB which results in progression from G1 phase to S phase.
73
What is p53?
An evolution to prevent tumour development. It is usually present at low levels in cells, complexed to inhibitor protein MDM2.
74
What impact do stress signals have on MDM2 inhibitor protein?
They inhibit MDM2 which allows the activation of p53: transcription regulation occurs.
75
What type of stress responses can inhibit MDM2 and thus allow p53 to function?
DNA damage
Oncogenic activity
Cytokine activation
Hypoxia
76
What are the functions of p53?
Promotes apoptosis, cell cycle arrest and DNA repair.
77
Why is p53 not really classed as a recessive TSGene?
As p53 acts as a tetramer, it requires all 4 components to be functional. a LOF in one allele has a high chance of producing a protein tetra that is non-functional (15/16).
78
How is p53 commonly inactivated?
Carcinogens in cigarette smoke can cause mutations in the DNA binding motifs of the protein. Benzo(a) pyrine is metabolised in the liver into a potent mutagen.
Causes G>T transversions in DNA. (R175, R248, R273)
79
What is aflatoxin?
Fungal metabolite that leads to G>T transversions at R249 of p53, inactivating it. Causing liver cancer.
80
What is the cancer stem cell hypothesis?
1. Problems with the notion of cancer arising from mature cells.
2. Cells need to live long enough (18mths) to accumulate enough mutations (3+) to become malignant.
3. Cancers arising from a single mature cell shouldn't be able to differentiate into the multiple cell types with distinct properties and morphology observed in tumours.
4. The cancer stem cell hypothesis suggests that malignant tumours are initiated and maintained by a population of tumour cells which share features with adult stem cells.
81
Pluripotent stem cells
Able to differentiate into many different cell types, unspecialised cells that can reproduce themselves and/or generate more specialised cells indefinitely.
82
Asymmetric stem cell division
One daughter cell retains the exact characteristics of the parent, the other one becomes more specialised and decreases in proliferation.
83
Schematic representation of asymmetric stem cell division
Stem cell ---> stem cell + restricted potential stem cell (multipotent)
Multipotent cell ---> multipotent cell + progenitor cell (unipotent cell)
Unipotent cell ---> unipotent cell + terminally differentiated cell.
84
How are the growth pathways for adult stem cells controlled?
Adult stem cells normally exist in a stem cell niche, where the stem cell is surrounded by niche cells/nurse cells which pump out growth suppression factors. When repair or replacement is needed, growth pomoter factors are used instead --> asymmetric division.
85
What are the ways in which a cancer stem cell could develop?
1. Shift in the programmed decline in replication potential: cancer stem cell arising from a progenitor cell.
2. Cancer cells that arose from normal stem cells can adapt to a different niche allowing their expansion.
3. Cancer cells that arose from normal stem cells can become niche-independent, and self-renewal becomes cell-autonomous.
4. Expansion of the normal stem cell niche permits the expansion of cancer stem cells that arose from a normal stem cell.
86
What is Wnt?
Proto-oncogene that is present in mutated form in 90% of colon cancers. Not normally active in normal cells.
87
What is the result of mutation to the Wnt pathway?
LOF to TSGene APC and/or increased levels of beta-catenin which could lead to more cyclin D --> more cell cycle progression --> increased cell growth.
88
Why is the notion of cancer arising from mature cells problematic?
Mature cells dont tend to prolierate - but cancer is a disease of proliferating cells.
Cancer is caused by an accumulation of mutations in a single cell (clonal disease) - but most cells have a finite lifetime and cannot acquire the 3+ mutations needed.
Only certain cells are possible of recolonisation and can cause tumours, suggesting heterogeneity.
89
How may the normal stem cell niche permit expansion of a cancer stem cell?
The cancer stem cell may arise from a normal cell and cause the niche to expand. The CSC may adapt to a different niche allowing their expansion (metastasis). Possibly in a predictable manner or become niche dependent.
90
What is the Wnt pathway?
Wnt + Frizzled receptors = sequested GSK-3 = released beta-catenin to act as TF = c-myc and cyclin D expression = proliferation.
91
Why has down-regulation of secreted Frizzled-related proteins (SFRPs) been observed in breast cancers?
SFRPs are Wnt inhibitors.
92
Inactaviting mutations in APC are found in what?
Up to 80% of sporadic colon cancers. Also seen is activating mutations of beta-catenin (TF) for c-myc and cyclinD = cell proliferation.
93
What is OMP-54F28?
Wnt targeting therapy that has entered clinical trials. Shown to decrease tumour cell proliferation and CSC numbers in lung, beast and pancreatic tumours.
94
Beta-catenin release by Wnt + frizzled receptor binding GSK-3 sequestion results in:
Release of beta-catenin which acts as a TF for c-myc and CyclinD = cell proliferation.
95
In the absence of Wnt bound receptor, what is the situation of beta-catenin?
Without receptor bound Wnt, B-catenin is located in the cytosol in complex with APC/CK1/Axin/GSK3.
It becomes phosphorylated by CK1 and GSK3 and then ubiquitinated by B-TrCP and degraded.
96
What occurs to beta-catenin when Wnt is bound?
B-cat becomes free to be accumulate and translocate to the nuclues and bind DNA bindin proteins such as TCF, causing changes in gene expression.
97
What is beta-catenin phosphorylated by?
CK1 and GSK3
98
What is beta-catenin ubiquitinated by?
B-TrCP then degraded by a proteasome.
99
What is the normal function of TCF that is impaired when B-catenin is allowed to accumulate following Wnt + receptor binding?
TCF, in complex with Groucho, normally occupies and represses its target genes.
B-cat displaces groucho, and recruits transcriptional coactivators and histone modifiers to drive target gene expression: c-myc and cyclin D -> cell proliferation.
100
What is hedgehog (HH)?
Hedgehog is a ligand, of which there are three types:
Sonic (SHH)
Desert (DHH)
Indian (IHH).
Which binds to its receptor patched (PTCH1/2) and frees smoothened to release gli and drive proliferation (GLI1, GLI2 and GLI3).
101
How many different HH ligands are there?
```
Three:
Sonic (SHH)
Desert (DHH)
Indian (IHH).
Which binds to its receptor patched (PTCH1/2) and frees smoothened to release gli and drive proliferation (GLI1, GLI2 and GLI3).
```
102
What do HH ligands bind to?
Sonic (SHH)
Desert (DHH)
Indian (IHH).
Which binds to its receptor patched (PTCH1/2) and frees smoothened to release gli and drive proliferation (GLI1, GLI2 and GLI3).
103
What is the result of HH ligands binding to the patched receptor?
Sonic (SHH)
Desert (DHH)
Indian (IHH).
Which binds to its receptor patched (PTCH1/2) and frees smoothened to release gli and drive proliferation (GLI1, GLI2 and GLI3).
104
What impact does the release of GLI by HH binding have?
Sonic (SHH)
Desert (DHH)
Indian (IHH).
Which binds to its receptor patched (PTCH1/2) and frees smoothened to release gli and drive proliferation (GLI1, GLI2 and GLI3).
105
The transcription factor GLI1 is highly expressed where?
In 26% of primary glioblastoma mulforme (GB) and 57% of cell lines, while the ligand SHH is expressed in GBM-derived tumourspheres.
106
What is the evidence that HH ligands can lead to cancer? (3)
1) SHH is highly expressed in GBM-derived tumourspheres.
2) SHH is expressed more highly in breast cancers compared with normal tissue.
3) Increased transcription of SHH and its downstream target GLI2 are revealed in colon cancers.
107
What is Vismodegib?
The first drug approved for the treatment of basal cell carcinoma (BCC) which targets hedgehog signalling.
108
What are telomeres?
Tandem repeats found on the ends of chromosomes and which aid chromosomal replication.
109
How do telomeres lead to cell apoptosis?
DNA polymerases cannot copy right to the end of the chromosomes --> telomeres shorten by 100-200 bases with each round of DNA replication.
When these telomeres get too short they are recognised as damaged DNA and p53 is activated to induce senescence.
110
What are telomerases?
Reverse transciptase enzymes containing RNA template to add TTAGGG repeats to chromosome ends. They are only found in rapidly dividing cells and germ line cells.
111
What can telomerase levels indicate with regards to the level of their expression in tumour cells?
High levels indicative of poor prognosis.
112
What is Imetelstat?
A modified 13-mer olinucleotide, binds directly to the template region of the RNA component of human telomerase.
113
Why are conventional drug therapies less effective at killing CSCs in a tumour?
Conventional drug therapies rarget rapidly proliferating cells while CSCs are slower dividing --: can lead to a recurrence in cancer driven by these unkilled CsCs
114
Acetylation of histones has what impact on the rate of transcription
Increased transcription rate can occur from the acetylation of histones.
115
What are most common changes which impact levels of gene expression (epigenetics)?
DNA methylation
| Histone acetylation
116
What is metastasis a measure of?
The ability of cancer cells to break away from a site of origin, travel to and then recolonise at a distant site,
117
What is the fundamental difference between benign and malignant growths?
The ability to mestasise.
>50% solid tumours have metastasised at the time of diagnosis.
The appearance of metastases is a poor sign of prognosis.
118
What are the mechanisms of metastasis?
Depends on a break down in cell-cell adhesion and degradation of basal lamina.
119
In metastasis, mutations to what causes a relaxation in cell to cell adhesion?
Mutations in E-cadherins causes a relaxation in cell to cell adhesion.
120
A change in expression of _______ allows cancer cell movement through ECM.
A change in expression of integrins allows cancer cell movement through ECM.
121
In order to metastasise, tumours must be able to induce surrounding stromal cells to produce ____ to digest the ECM.
In order to metastasise, tumours must be able to induce surrounding stromal cells to produce MMPs to digest the ECM.
122
What is the first pass organ in terms of metastasis?
This is the first organ that tumour cells encounter after they have entered the bloodstream at the origination site.
123
Where do tumour cells tend to recolonise?
Tumour cells tend to recolonise in tissue which have similar growth factors or have been prepared to receive tumour cells.
124
Angiogenesis
The growth of new blood vessels - highly needed for the growth of tumours.
125
When does angiogenesis normally occur and how is it controlled?
Angiogensis normally occurs during embryogenesis, wound healing and during the menstrual cycle.
It is controlled by a range of growth factors and inhibitors.
126
What growth factors and inhibitors are involved with angiogenesis?
Angiogenic GFs: FGF, VEGF, PDGF
Inhibitors: angiostatin, endostatin.
127
The Angiogenic process
1. Surrounding cells release ___________.
2. These bind to ________ on nearby endothelial cells.
3. The endothelial cells are activated and produce _________.
4. The _______ digest the _________________.
5. The endothelial cells ___________ and _________ out of the vessel.
6. Adhesion molecules and _____________ aid the formation of the growing blood vessel.
7. The new vessels are stabilised by __________ cells and ________.
1. Surrounding cells release angiogenic factors --> 2. Which bind to receptors on nearby endothelial cells --> 3. Endothelial cells activated and produce enzymes --> 4. These enzymes digest the basment membrane --> 5. The endothelial cells then migrate out of the vessel --> 6. Adhesion molecules and MMPs aid the formation of the growing blood vessel --> 7. The new vessels are stabilised by smooth muscle cells and pericytes.
128
Angiostatin + Endostatin
Angiogenesis inhibitors
129
Why is angiogenesis so important in cancer?
Without BV formation tumour limited to 1-2mm diameter. New BV needed for oxygen and nutrients for cells at centre of tumour.
Mutations in the tumour cells lead to the production of angiogenic factors and new BV formation.
130
What is VEGF?
Vascular endothelial growth factor - secreted by tumours, triggered by oncogenes and by hypoxia-mediated stabilisation of TF which drives VEGF.
131
What is the impact of tumour secretion of VEGF?
Angiogenesis.
132
What are sunitinib and sorafenib?
VEGF receptor inhibitors.
133
What is Avastin?
Humanised monoclonal antibody anti VEGFA, inhibits tumour blood vessel growth.
134
Why can avastin not be used long term?
Could impair natural wound healing.
135
What is avastin not effective against?
Works well on newly formed/growing tumours, not on already established tumours.
136
What is avastin particularly good at?
Preventing metastases/acting on newly formed tumours.
137
What are novel therapies for preventing angiogenesis based around?
A new to target newly formed blood vessels and yet differentiate between established and neovasculature.
138
What is Vitaxin?
Antiangiogenic humanised Ab against Avb3 integrin
139
What is antineovascular therapy?
Based around the use of drug delivery systems such as liposomes to transport cyctoxic drugs to integrins.
140
What is vascular gene therapy?
Tries to correct or alleviate disease by delivery of genes.
It requires identification of appropriate gene and then specific delivery of that gene to the required area.
141
What is a humanised monoclonal anti-VEGFA antibody?
Avastin - prevents tumour blood vessel growth.
142
Humanised Ab against Avb3 integrin
Vitaxin.
143
What is a potential target for vascular gene therapy?
The E selectin adhesion molecule.
| Retroviruses can be used to specifically target rapidly proliferating cells by targeting EC specific promoter.
144
What was the seed and soil theory?
The idea that a cancer cell would have predisposition for certain tissues to spread to.
Prostate cancer usually metastasizes the bones.
145
When a cell is deficient in oxygen, it produces HIF. What is HIF and what is its purpose?
HIF: hypoxia-inducible factors, which stimulates the release of VEGF-A.
VEGF-A then bind to tyrosine kinase receptors (VEGFRs 1-3) on the cell surface causing them to dimerise and become activated --> bv growth.
146
Why do patients with leukaemia often have blood which appears 'milky'?
Too many white cells.
147
Myeloid leukaemias involve
Granulocytes, neutrophils, macrophages, mast cells.
148
Lymphoid leukaemias involve
T lymphocytes
| B lymphocytes
149
How are leukaemias classified?
1. Acute or chronic
| 2. Cell of origin: myeloid/lymphoid
150
What is the clinical presentation of chronic myeloid leukaemia (CML)?
Fatigue, anaemia, splenomegaly, hepatomegaly.
Elevated number of white cells in blood count.
All stages of granulocyte differentiation on blood smear.
151
What are the three clinical phases of CML?
1. Initial chronic phase, fairly mild.
2. Accelerated phase develops after 4 years (mutations must have time to accumulate)
3. Acute leukaemic phase - Blast crisis.
152
Why are splenomegaly and hepatomegaly presenting symptoms of cml?
White blood cells are filtered through the spleen: splenomegaly.
White cells broken down in the liver: hepatomegaly.
153
______ is mutated in 50% of AML
Ras is mutated in 50% AML
154
Leukaemogenesis is a ______________ process.
Leaukarmogenesis is a multifactorial process: there are numerous causes. Chromosomal abnormalities are common: additions, translocations, deletions or amplifications.
155
What are novel oncogenes?
Novel oncogenes are often associated with leukaemias.
156
95% of CMLs have ________ __________ between chromosomes ____ and _____.
95% of CMLs have reciprocal translocation between chromosomes 9 and 22.
157
CML is due to genetic alterations in ______ or _____ _______ cells.
CML is due to genetic alterations in stem or early progenitor cells.
158
CMLs often feature a fusion between _______ _______ ______ (BCR) and _____ _____ ______ forming BCR-ABL.
CMLs often feature a fusion between breakpoint cluster region (BCR) and Abl tyrosine kinase - BCR-ABL.
159
BCR-ABL has _______ tyrosine kinase activity.
BCR-ABL has elevated tyrosine kinase activity - dysregulated. This results in many intracellular signalling pathways becoming constitutively activated:
1. Ras pathway
2. Phosphoinositide-3 kinase pathway.
3. signal transducers and activators of transcription (STATS)
160
What does STATS stand for?
Signal transducers and activators of transcription (STATS)
161
C-Abl
Non-receptor protein tyrosine kinsase.
Found in cytoplasm and nucleus.
Known to be activated by DNA damage, during S phase and downstream of integrin signalling.
162
C-Abl is known to be activated by
DNA damage
During S phase
Downstream of integrin signalling
163
C-Abl is found
In the cytoplasm and the nucleus.
Nuclear c-Abl interacts with Rb and p53 to regulate gene transcription.
Cytoplasmic c-Abl plays a role in cell growth.
164
Nuclear c-Abl
Interacts with Rb and p53 to regulate gene transcription.
165
Cytoplasmic c-Abl
Appears to play a role in cell growth.
166
Drug name ending in nib =
small molecule inhibitor
167
Drug name ending in Mab
Antibody based
168
What is Glivec/ STI 571 / Gleevec?
Imatinib mesylate. Small molecule which inhibits the proliferation of CML-derived cell lines in mouse models.
Blocks activity of Abl tyrosine kinases + PDGFbR and c-kit tyrosine kinases.
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How does Glivec work?
It blocks the activity of Abl tyrosin kinase.
It also blocks the activity of PDGFbR and c-kit tyrosine kinases.
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Is Glivec effective in all patients?
No - exists resistance to Glivec in some patients, for exmaple they might have amplification of the BCR-ABL mutation meaning doses given are below therapeutic level or there may be point mutations in BCR-ABL that prevent Glivec from binding.
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First signal transduction inhibitor to fully enter clinic
Gleevec - inhibitor of CML/abl kinases.
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How is cancer treatment similar to bacterial infection treatment?
The initial treatment can select for resistance.
Cancer cells can develop mutations that make them resistant to the drug of choice, then when the drug removes the cancer cells which are susceptibile it allows the resistant cancer cell population to expand.
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How are Dasatinib/Nilotinib better than Glivec?
They can bind to the active conformation of BCR-ABL and can therefore be effective in patients in which point mutation has led to Glivec resistance.
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Small molecule inhibitor of Abl tyrosine kinase.
Gleevec
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Mutation against which neither Dasatinib or Nilotinib are effective
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T3151 mutation.
JAK2 inhibitor (3rd gen) VX-680 is active in this mutant but caused cardiotoxicity.
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Two ways in which patients can 'resist' the use of Glivec
The BCR-ABL mutation is amplified so doses are ineffective.
The point mutations in BCR-ABL prevent Glivec from binding.
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What is GIST?
Gastro-intestinal stromal tumours.
Driven by constitutive c-kit receptor activity.
This receptor is blocked by Glivec.
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How is GIST treated?
Glivec blocks the consitutively active c-kit receptor.
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Iressa is more effective in
Those patients with a mutation leading to hyperactive EGFR.
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Patients with mutations in _______ will not respond to EGFR inhibitors.
Patients with mutations in K-Ras will not respond to EGFR inhibitors.
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What is an example of variations in patient drug metabolising enzymes leading to chemotherapy toxicity?
Thiopurinemethyltransferase TPMT can lead to chemotherapy Toxicity. (6-MP)
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What is TEL-PDGFb receptor fusion?
Associated with chronic myelomonocytic leukaemia (CMML).
The amino terminal region of TEL (transcription factor) becomes swapped with the tyrosine kinase domain of the PDGF receptor.
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How does the TEL-PDGFb receptor fusion lead to cancer?
The kinase is always active, the helix-loop-helix region of TEL induces oligomerisation.
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How can TEL-PDGFb kinase activity be inhibited?
GLIVEC
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Farnesyl Transferase Inhibitors
FTI: Ras targeting can be achieved with these peptidomimetics that inhibit the fatty acid modification which Ras relies on to become tethered to membranes.
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How can aflatoxin cause liver cancer?
Aflatoxin is a fungal metabolite that causes C>T transversions of p53, inactivating it.
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Haploinsufficiency refers to genes that___________
Alternative mechanism suggested for particular tumour suppressor genes.
One normal allele produces half (haplo-) of the quantity of protein produced by normal cells and this is not enough to suppress tumour formation. Particularly occurs in genes that regulate DNA repair and the DNA-damage response.
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How do cancer cells alter their motility?
Growth factors and cell adhesion molecules can signal into the cell and affect the
state of the actin cytoskeleton, which is important in mediating cell movement.
These signaling pathways interact with the cytoskeleton via the a small G-proteins
that are part of the Rho family
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Give an overview of invasion proces
Proteolysis creates a new space for a cancer cell to move into
Cells push out cytoplasmic processes at the front of the cell in the direction of travel
New adhesions to stroma are formed in these cytoplasmic extensions using integrins to anchor the cell in a new
position
Integrin signaling to Rho proteins leads to changes in actin filaments to form actin stress fibres
Stress fibres generate traction to pull the back of the cell forwards
De-adhesion at back of the cell (via down-regulation of cadherins if the back of the cell is connected to another
cancer cell or integrins if the back is connected to stroma) allows the cell to be pulled forwards
