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MoD > L21 - Carcinogenesis - molecular hallmarks of cancer cells > Flashcards

L21 - Carcinogenesis - molecular hallmarks of cancer cells Flashcards

1
Q

what 2 mechanisms are responsible for the conversion of normal cells into nepotistic cells?

A
  • oncogene activation

- tumour supressor gene inactivation

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2
Q

What do caretaker genes do?

A

Maintain genetic stability by repairing damaged DNA and replication errors

  • DNA repair genes
  • controlling accuracy of mitosis
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3
Q

What do mutated forms of caretaker genes cause?

A

genomic instability as unable to correctly repair damaged DNA

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4
Q

What are 2 types of TSG?

A
  • gatekeepers

- caretakers

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5
Q

What do gatekeepers do?

A

Play important roles in regulating normal growth

  • negative regulators of the cell cycle and proliferation
  • positive regulators of apoptosis
  • positive regulators of cell differentiation
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6
Q

What types of mutations occur in TSGs?

A
  • point mutations
  • deletions/insertions
  • chromosomal rearrangements
  • epigenetic silencing (promoter methylation)
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7
Q

Every cell in the body will carry the ‘1st hit’ in what circumstances?

A

In the case of familial cancer syndromes

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8
Q

Why is a ‘2nd hit’ required for complete loss of function of a TSG?

A

one copy of the gene is enough to control; cell proliferation/apoptosis/repairing DNA due to mutations within TSGs being RECESSIVE .

Both copies of TSG have to be mutated for inactivated for complete loss of function.

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9
Q

Familial cancer syndromes can involve inheritance of a mutant copy of what?

A

A gatekeeper or caretaker gene (TSG)

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10
Q

What is the risk of cancer for a carrier of a mutant copy of a TSG?

A

70-90% lifetime risk of developing cancer, depending on the syndrome

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11
Q

What TSG gene is involved in retinoblastoma cancer syndrome?

A

RB1 (gate)

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12
Q

What TSG gene is involved in Li-Fraumeni cancer syndrome?

A

p53 (gate/care)

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13
Q

What TSG gene is involved in Familial adenomatous polyposis cancer syndrome?

A

APC (gate)

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14
Q

What TSG gene is involved in Familial breast cancer syndrome?

A

BRCA1, BRCA2 (care)

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15
Q

What TSG gene is involved in Hereditary non-polyposis colorectal cancer syndrome?

A

hMLH1, hMSH2 (care)

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16
Q

What are the principal tumours in Li-Fraumeni syndrome?

A

Sarcomas

Breast

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17
Q

What are the principal tumours in FAP?

A

Colorectal

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18
Q

What are the principal tumours in HNPCC?

A

Colon

Endometrial

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19
Q

What are the stages from proto-oncogene to cancerous cell?

A
  • proto-oncogene
  • cancer-promoting agent (UV light, chemicals etc)
  • oncogene
  • cancerous cell
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20
Q

What do mutations in proto-oncogenes lead to?

A

Activated versions of or increased expression of proto-oncogenes (gain of function)

Oncogenes

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21
Q

What are the different types of mechanism of oncogene activation?

A
  • translocation
  • point mutation
  • amplification
  • insertion
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22
Q

What are the 10 hallmarks of cancer cells?

A
  • sustaining proliferative signalling
  • evading groet suppressors
  • avoiding immune destruction
  • replicative immortality
  • promoting inflammation
  • invasion and metastasis
  • inducing angiogenesis
  • genome instability and mutation
  • resisting cell death
  • deregulating cellular energetics
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23
Q

what is meant by the hallmark self-sufficiency in positive growth signals?

A

Tumour cells acquire the ability to grow in the absence of EGF (epidural growth factor) which would bind to its receptor to encourage a cell to grow and differentiate.

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24
Q

Which family is the oncoprotein RAS part of?

A

It is a member of a family of guanine nucleotide binding proteins called G-proteins

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25
Q

What does the Rb protein do?

A

It is a key regulator of the cell cycle by preventing progression from G1 to S phase

NB: -ve GFs inhibit progression of cell cycle by activating Rb

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26
Q

What is Rb protein activated by?

A

Negative growth factors

  • they inhibit progression of cell cycle by activating Rb protein
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27
Q

What does Rb protein stand for?

A

Retinoblastoma protein

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28
Q

Give an example of a negative growth factor

A

Transforming growth factor beta (TGFbeta)

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29
Q

How can cancer cells escape inhibition of proliferation by negative growth factors?

A

They can acquire mutational inactivation, or epigenetic silencing, of the RB tumour suppressor gene.

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30
Q

What does P53 do?

A

Induces cell cycle arrest to allow repair of DNA damage

But also induces apoptosis if there is too much damage

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31
Q

What does TP53 inactivation lead to?

A

Loss of apoptotic response

This is the most common genetic abnormality in human tumours (>50% of tumours)

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32
Q

Which syndrome does inherited mutation of TP53 cause?

A

Li-Fraumeni syndrome

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33
Q

Why is sustained angiogenesis important in cancer cells?

A

Tumours greater than 2mm need to stimulate a new blood supply (angiogenesis) or the cells in the middle of the growth will die from lack of oxygen/nutrients

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34
Q

How do cancer cells carry out angiogenesis?

A

Growth factors/angiogenic factors such as vascular endothelial growth factor are often produced by tumours and these stimulate growth of new vessels

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35
Q

What do VEGF do?

A

Stimulates growth of new vessels

Actively recruits endothelial cells that process to construct new capillaries and vessels

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36
Q

Tumour cells which are able to invade new tissues show which feature?

A

Loss of E-cadherin through mutation or hypermethylation of the gene

37
Q

What does loss of E-caherin result in?

A

Epithelial-mesenchymal transition (EMT)

38
Q

What does metastasis involve?

A

The spread of malignant cells via the blood/lymphatic system to secondary sites and the formation of secondary tumours

39
Q

What is CA-125 serum antigen used for?

A

Used in the detection and monitoring of ovarian cancer - but not very sensitive or specific

40
Q

Overexpression of which gene is found in around 30% of breast tumours? And what does it code for?

A

HER2

Codes for a positive growth factor receptor

So over expression causes cells to become more responsive to, or independent of, positive growth factors.

41
Q

Which drug targets HER2 and what type of drug is it?

A

Herceptin

It is an antibody drug targeted to HER2

42
Q

What does herceptin do?

A

It dampens the effects of an overactive HER2 receptor

43
Q

what is a proto-oncogene?

A

Normal genes that promote cell proliferation,

survival and angiogenesis

44
Q

what is an oncogene?

A

mutated versions/increased expression of proto-oncogenes,

causing
increased/uncontrolled activity of expressed proteins

45
Q

what does on oncogene do?

A
  • cause aberrant cell proliferation
  • survival/inhibition of apoptosis
  • angiogenesis [feeding the growing tumour mass]
46
Q

do oncogenes allow for gain or loss of function?

A

Oncogenes are dominant gain-of-function: 1 mutant copy of the gene acts dominant to the
remaining normal parental gene

47
Q

Explain how insertion allows for oncogene activation.

A

Insertion of a promoter or enhancing gene (by retroviruses) near an oncogene = increased
expression of porto-oncogene

48
Q

what is a Antioncogene?

A

gatekeepers (tumour suppressor gene)

49
Q

Carcinogens induce what molecular abnormalities in TSGs that cause reduced/lack of protein
expression/function?

A
  • inactivating point mutations
  • deletions
  • translocations
  • epigenetic silencing
50
Q

are mutations within TSGs dominant or recessive?

A

recessive

51
Q

what familial cancer is associated with loss of the APC gene?

A

(Familial adenomatous polyposis) -

colorectal cancer syndrome

52
Q

what does the APC gene control?

A

a TSG that controls proliferation

53
Q

what does the p53 gene control?

A

regulates apoptosis

54
Q

what affect to negative growth factors have on a mutated or inactive Rb protein?

A

negative growth factors would have no affect and so proliferation/growth would continue

55
Q

inactivation of Rb gene is common in tumours, what does this result in?

A
  • resistance to negative growth factors

- continuous proliferation

56
Q

what is the mechanism that allows the hallmark avoiding immune destruction?

A

binding of PD-1 antigen on T cell and PD-L1 receptor on tumour cell inhibiting T cell from killing tumour cell

57
Q

What is the PD-1/PD-L1 pathway?

A

The PD-1 (programmed cell death-1) receptor (also known as CD279) is expressed on the surface of T cells. Its ligands, PD-L1 (CD274) and PD-L2 (CD273), are commonly expressed on the surface of dendritic cells or macrophages. PD-1 and PD-L1/PD-L2 and act as co-inhibitory factors, which halt the development of the T cell response.

PD-1/PD-L1 interaction ensures that the immune system is activated only at the appropriate time in order to minimize the possibility of chronic autoimmune inflammation.

58
Q

what is the role of PD-1/PD-L1 in cancer cells?

A

PD-L1 expressed on the tumor cells binds to PD-1 receptors on the activated T cells, which leads to the inhibition of the T cells.

59
Q

how can we use PD-1/PD-L1 against cancer in immunotherapy?

A

we block the ligand PD-L1, PD-1 cannot bind and so T cell is not inhibited and acts on tumour cell

60
Q

what is the enzyme that allows the hallmark of replicative immortality?

A

telomerase

keeps building telomere so it doesn’t shorten

61
Q

what is the mechanism that allows the hallmark of inflammation promotion?

A

inflammation destroys cells and so promotes more to grow back (unscheduled when tumour cells are promoting inflammation)

62
Q

how are secondary tumours formed?

A

via metastasis

63
Q

what is the mechanism that allows the hallmark of resisting cell death?

A

Over expression of anti-apoptotic BCL2 - puts a halt on apoptosis = cancer cell survives.

64
Q

what does the BCL2 gene regulate?

A

cell death (apoptosis) by either inhibiting (pro-apoptotic) or inducing (anti-apoptotic) apoptosis.

65
Q

what is the mechanism that allows the hallmark of deregulated metabolism?

A

the Warburg effect

66
Q

what is the Warburg effect?

A

Cancer cells predominantly produce energy through a high rate of glycolysis followed by lactic acid fermentation even in the presence of abundant oxygen.

67
Q

what is a possible explanation of the Warburg effect?

A
  • damaged mitochondria due to the cancer
  • an effect associated with cell proliferation. Since glycolysis provides most of the building blocks required for cell proliferation, cancer cells (and normal proliferating cells) have been proposed to need to activate glycolysis, despite the presence of oxygen.
68
Q

Explain how translocation allows for oncogene activation.

A

chromosomal translocation which relocates a proto-oncogene to a new chromosomal site that leads to higher expression

69
Q

Explain how point mutation allows for oncogene activation.

A

A mutation within a proto-oncogene, or within a regulatory region (for example the promoter region), can cause a change in the protein structure, causing:

  1. an increase in protein (enzyme) activity
  2. a loss of regulation
70
Q

Explain how amplification allows for oncogene activation.

A

by insertion of multiple copies of an oncogene – increased expression

71
Q

what are the 3 genes that code for the RAS family of proteins?

A

KRAS
NRAS
HRAS

72
Q

list 5 oncogenes.

A 
RAS
MYC 
RAF
HER2
EGFR
73
Q

what are the 2 categories of TSGs?

A

antioncogenes/gate keepers

caretakers

74
Q

what molecular abnormalities do carcinogens induce in TSGs?

A
  • inactivating point mutations
  • deletions
  • translocations
  • epigenetic silencing

this causes reduced/lack of protein expression/function

75
Q

what is epigenetic silencing?

A

shutdown of gene expression via

methylation of CpG sequences (cytosine nucleotide is followed by a guanine) in promoter regions

76
Q

what familial cancer syndrome does a mutated RB1 TSG cause?

A

retinoblastoma

77
Q

what familial cancer syndrome does a mutated p53 TSG cause?

A

Li-Fraumeni

sarcomas, breast tumours

78
Q

what familial cancer syndrome does a mutated APC TSG cause?

A

familial adenomatous polyposis

colorectal cancer

79
Q

what familial cancer syndrome does a mutated BRCA1/2 TSG cause?

A

familial breast cancer

breast, ovarian tumours

80
Q

what familial cancer syndrome does a mutated hMLH1/2 TSG cause?

A

hereditary non-polyposis colorectal cancer

colon/endometrial tumours

81
Q

what serum marker can be used as an adjunct for liver/testicular cancer?

A

AFP

82
Q

what serum marker can be used as an adjunct for ovarian cancer?

A

CA125

83
Q

what serum marker can be used as an adjunct for testicular cancer?

A

hCG

84
Q

what serum marker can be used as an adjunct for prostate cancer?

A

PSA

85
Q

why is PSA no longer used to detect prostate cancer?

A
  • many noncancerous conditions also can increase a man’s PSA level
  • not sensitive or specific enough
  • PSA elevates as a mans prostate grows with age
86
Q

why should you always test for PSA before a prostate examination?

A

touching the prostate is enough for it to secrete PSA into the blood stream and you will get an elevated PSA result

87
Q

which serum markers are not used as an adjunct for diagnosis but for monitoring a cancer?

A
  • CEA (will not indicate which kind of cancer is present)
  • thyroglobulin (thyroid cancers – both those confined to the thyroid gland and those that have spread to other parts of the body)
88
Q

the KRAS mutation is associated with which type of cancer?

A

50% of colorectal cancers have a KRAS mutation

MoD (19 decks)

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