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POM GENETICS > Cancer Genetics > Flashcards

Cancer Genetics Flashcards

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1
Q

What is a cancer?

A

An abnormal growth of cels which tend to proliferate in an uncontrolled manner, and in some cases, to metastasize

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2
Q

What causes cancer cells to behave abnormally?

A

Changes in the DNA sequence of key genes which are known as cancer genes

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3
Q

What are the two causes for mutations in DNA?

A

Tumour supressor genes being silenced or oncogenes being over-expressed

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4
Q

What are the 14 hallmarks of cancer?

A

PAIN GUARDS TEES

Polymorphic microbiomes
Activating invasion and metastasis
Inducing or accessing vasculature
Non Mutational epigenetic reprogramming

Genome instability and mutation
Unlocking phenotypic plasticity
Avoiding immune destruction
Resisting cell death
Deregulating cellular metabolism
Senescent cells

Tumor-promoting inflammation
Evading growth suppressors
Enabling replicative immortality
Sustaining proliferative signalling

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5
Q

What is deregulating cellular metabolism?

A

Involves a metabolic reprogramming that leads to a high production of lactate.

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6
Q

What is phenotypic plasticity?

A

Describes the ability of cancer cells to undergo dynamic, nongenetic cell state changes that amplify cancer heterogeneity to promote metastasis and therapy evasion.

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7
Q

What is sustaining proliferative signalling?

A

Cancer cells are able to divide even without receiving these signals which leads to an uncontrolled proliferation of these abnormal cells.

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8
Q

What is a benign tumour?

A

A mass of well-differentiated cells that grows slowly, is capsulated and lacks the ability to invade neighbouring tissue or metastasise

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9
Q

How do you get to subclones with individual genotypes?

A

Normal cell-> founder cell-> subclones with individual genotypes

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10
Q

What is a malignant tumour?

A

A tumour which is not self limited in growth, cells are poorly differentiated and capable of invading into adjacent tissues = metastasis

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11
Q

What is late cancer?

A

1-10 more driver mutations

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12
Q

What four things can cause cancer?

A
  • Radiation
  • Chemicals
  • Viruses
  • Hereditary alteration in genes which make a person more susceptible to cancer
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13
Q

What is the difference between benign and malignant tumours? (4)

A

benign grow slow, malignant fast
benign is well differentiated, malignant is not
benign is capsulated, malignant is not
benign cannot metastasize or invade neighbouring tissue, malignant can

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14
Q

What type of cancers have epithelial tissue origin?

A

Carcinomas

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15
Q

What are common types of carcinomas?

A

Lung, breast and colon cancer

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16
Q

What is the name given to cancers which arise from cells found in the connective tissues of the body? What are examples of connective tissue?

A

Sarcomas

bone, cartilage, fat, vascular, or hematopoietic tissues

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17
Q

What are cancers that arise in lymph nodes and tissues of the body’s immune system called?

A

Lymphomas

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18
Q

What are cancers that arise from immature blood cells that grow in the bone marrow called?

A

Leukaemia

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19
Q

What is the most common cancer in children?

A

Acute lymphoblastic leukaemia

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20
Q

What type of mutation can be passed on to off-spring?

A

Germline mutations can be passed on

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21
Q

What type of mutations can’t be passed onto offspring?

A

Somatic mutations

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22
Q

A gene change in which cells cause germline mutations?

A

Reproductive cells

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23
Q

What are somatic mutations also known as?

A

Acquired or sporadic mutations

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24
Q

What are the seven types of mutations?

A

deletions
insertions
aneuploidy
inversions
translocations
single base mutations
chromosome instability

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25
Q

What is a deletion mutation?

A

When one or more nucleotide is removed from the DNA

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26
Q

what is a duplication mutation?

A

When one or more copies of a gene or region of a chromosome are made

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27
Q

What is an inversion?

A

Reversing the orientation of a chromosomal segment

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28
Q

What is a driver mutation?

A

A mutation which contributes to cancer growth

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29
Q

When does a passenger mutation occur?

A

A mutation which occurs during cancer growth

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30
Q

What type of studies can help identify cancer germline mutations?

A

Positional cloning linkage studies through gene mapping and gene indentification

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31
Q

What are the three types of point mutations?

A

Silent, non-sense and mis-sense

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32
Q

What affect does UV radiation have on the DNA?

A

forms covalent bonds between two adjacent pyrimidines (C and T) in the DNA molecule which causes cross linking, resulting in the formation of a dimer

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33
Q

What happens in the dimer formed due to UV radiation is not repaired?

A

Most DNA polymerases will insert 2 adenine opposite the dimer, resulting in a mutation

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34
Q

What does oncogene issues generally result in?

A

An increase in some form of protein activity, or a loss of regulation

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35
Q

Describe the process multistep carcinogenesis?

A
  1. begins with mutation in tumour supressor gene which therefore allows excessive cell proliferation
  2. proliferating cells tend to acquire additional mutations
  3. overtime the accumulated damage can yield a malignant, metastatic tumour
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36
Q

what type of protein is RAS?

A

A GTPase

37
Q

What state is RAS in when GDP is bound?

A

It is inactive

38
Q

Does Ras bind GDP or GTP with a higher affinity?

A

GTP

39
Q

When Ras binds GTP, what state is Ras then in?

A

Active state

40
Q

How does GAP ensure that Ras is not always active?

A

GTPase Activating protein hydrolyses the GTP into GDP so Ras is turned off

41
Q

What happens when RAS is constantly stuck in the active form?

A

the cell extensively proliferates causing cancer as RAS controls a lot of cellular signalling pathways

42
Q

What is the two hit hypothesis? and how does it relate to mutations to tumour supressor genes?

A

The two hit hypothesis states that both alleles that code for a particular protein must be affected before an affect is manifested.

Most mutations to tumour supressor genes are recessive, meaning in order for a particular cell to become cancerous, both of the alleles for the cells tumour supressor genes must be mutated

43
Q

What do mutations in tumour supressor genes result in?

A

A loss of function, as they can no longer stop the cell from proliferating uncontrollably

44
Q

what is the first event in the two hit hypothesis?

A

AN inherited mutation - however inheriting one germ line copy of the damaged gene is not sufficient

45
Q

What is the second hit in the two hit hypothesis?

A

When the second (good) copy in the gene pair is mutated - causing cancer

46
Q

What is p53?

A

a tumour supressor protein that is encoded by the TP53 gene

47
Q

What does p53 do?

A

Unwinds DNA region from histone
RNA polymerase then does its thing

48
Q

Loss of the TP52 gene gene due to mutation or deletion occurs in what percentage of human cancers?

A

> 50%

49
Q

What is Li-Fraumeni syndrome?

A

an inherited condition which is characterised by an increased risk for certain types of cancers

50
Q

What mutagens can cause damage to the TP53 gene?

A

Chemicals, radiation or viruses

51
Q

What is a retinoblastoma?

A

Cancer of the retina

52
Q

What does Rb protein do?

A

Prevents excessive cell growth by inhibiting cell cycle progression until a cell has made all the necessary checks in the G1 phase

53
Q

What transcription factor does retinoblastoma protein bind?

A

E2F

54
Q

What has to happen to the Rb for the E2F to be released?

A

Rb has to be phosphorylated - this leads to transcription

55
Q

How do cancer cells evade the immune response?

A

activation of the checkpoint pathways such as PD-1 send negative signals to the cell to stop if from attacking the tumour cell

56
Q

how does nivolumab work?

A

binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2,so the negative signals cannot be sent anymore

57
Q

What is positional cloning?

A

A lab technique used to locate the position of a disease associated gene along a chromosome

58
Q

Which type of mutation tends to cause clonal expansions?

A

Driver mutations

59
Q

What is the life-time risk of developoing cancer in a particular tissues correlated with?

A

How often the stem cells in that tissue divide

60
Q

How are most cancer causing mutations involving oncogenes acquired?

A

Chromosome rearrangements and gene duplications

61
Q

What does the translocation between chromosome 9 and 22 result in?

A

The formation of the ABL-BCR1 gene which makes elevated tyrosine kinase activity - leads to more cell proliferation

(abnormal chromosome 22)

62
Q

What do proto-oncogenes turn on?

A

Genes that cause oncogenes to be turned on

63
Q

What condition is caused by a mutation in the RET gene?

A

Multiple Endocrine Neoplasia Type 2 (MEN2)

64
Q

What type of cancer do people with multiple endocrine neoplasia type 2 develop?

A

a form of thyroid cancer called medullary cancer of the thyroid

65
Q

What is the nature of most loss-of-function mutations that occur in tumour suppresor genes?

A

Recessive

66
Q

What three things make cancer cells genetically unstable?

A

Unable to stop the cell cycle to allow time for repair
Unable to carry out efficient repair
Unable to undergo apoptosis

67
Q

What do DNA repair genes do?

A

Code for proteins whose normal function is to correct errors which arise when cells duplicate prior to cell division

68
Q

What factors is the rate of DNA repair dependant on? (3)

A

Cell type, age of cell and extracellular environment

69
Q

After a cell has accumulated alot of DNA damage, what are the three states it can enter into

A

Dormancy
Apoptosis / programmed cell death
Unregulated cell division = cancer

70
Q

What can mutations in DNA repair genes lead to?

A

Failure to repair which in turn allows mutations to accumulate
`

71
Q

How do viruses cause DNA damage?

A

Insert their genomes into the DNA of the host cell, which can disrupt important regulatory genes

72
Q

What does the E7 protein from HPV do to promote cancer?

A

Binds to Rb to promote its degradation which allows cells to divide faster and

73
Q

What are three viruses associated with cancer?

A

Papillomavirus
Hepatitis Virus
Epstein-Barr Virus

74
Q

What has lead to the discovery of many common low risk variants for different cancers in recent years?

A

Genome wide association studies

75
Q

What does the two-hit hypothesis predict?

A

That the chances for a cell with a germ-line mutation to get a second hit ie a somatic mutation is much higher than the chances of a non-carrier to get two hits in the same cell

76
Q

What is tumour heterogeneity?

A

Describes the observation that different tumour cells can show distinct morphological and phenotypic profiles, including cellular morphology, gene expression, metabolism, motility, proliferation, and metastatic potential.

This phenomenon occurs both between tumours (inter-tumour heterogeneity) and within tumours (intra-tumour heterogeneity)

77
Q

What are driver mutations?

A

Those that drive cancer initiation and progression

They can result in the acquisition of 1 or more of the hallmarks of cancer

78
Q

What are passenger mutations?

A

Those that don’t drive cancer initiation and progression

79
Q

What are proto-oncogenes?

A

Type of normal gene that produces a protein that promotes cell growth and proliferation

Driver mutations in a proto-oncogene could lead to cancer

A proto-oncogene with driver mutations is called an oncogene (Genes which stimulate the cell cycle)

80
Q

What are tumour suppressor genes?

A

Type of normal gene that produces a protein that helps limit cell growth and proliferation

Driver mutations in tumour suppressor gene could lead to cancer

Genes which halt the cell cycle

81
Q

What is Knudson hypothesis?

A

aka the 2 hit hypothesis

It is the hypothesis that most tumour suppressor genes require both alleles to be inactivated to cause a phenotypic change

82
Q

What is a germline mutation?

A

Mutation in the reproductive cells (egg or sperm). Germline mutations are passed on from parents to offspring.

Entire organism carries the mutation

83
Q

What are somatic mutations?

A

Mutation in any cell fo the body except the germ cells. They are not passed on from parents to offspring.

Path of the affected area carries the mutation

84
Q

What is the cancer gene census?

A

Ongoing effort to catalogue those genes which contain mutations that have been causally implicated in cancer.

85
Q

What are cancer-risk genes?

A

We all carry certain genes that are normally protective against cancer. These genes correct any DNA damage that naturally happen when cells divide.

Inheriting faulty versions or “variants” of these genes significantly raises your risk of developing cancer, because the altered genes cannot repair the damaged cells, which can build up and form a tumour. E.g., BRCA1 and BRCA2

86
Q

Why is melanoma of the skin mostly C–>T mutations?

A

Because radiation causes this mutation

87
Q

What are the most common mutated genes in pancreatic cancer?

A

KRAS & TP53

88
Q

What are the ways to treat cancer? (5)

A

Surgery
Chemotherapy
Radiotherapy
Targeted therapy
Immunotherapy

POM GENETICS (9 decks)

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