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Y2 GENETICS IN MEDICINE > Familial Cancer > Flashcards

Familial Cancer Flashcards

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1
Q

What are the 2 categories of genes that are involved in genetic development of cancer?

A
  1. caretaker genes involved in DNA repair and carcinogen metabolism
  2. gatekeeper genes involved in cell cycle control and programmed cell death
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2
Q

What is TP53 involved in?

A

it is a gene that ensures an individual cell does not divide too rapidly or become unregulated

it causes a cell to undergo apoptosis

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3
Q

What type of gene is TP53?

What happens if it goes wrong?

A

It is a gatekeeper gene

If it goes wrong, it will not stop an unregulated cell from dividing and cancer may develop

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4
Q

What are the 2 categories of environmental factors involved in cancer development?

A
  1. macro-environment

2. micro-environment

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5
Q

What are examples of macro-environmental factors?

A

chemicals, viruses, radiation, physical agents

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6
Q

What are examples of micro-environmental factors?

A

oxyradicals, hormones, growth factors

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7
Q

What is the background behind cancer development?

A

a series of genetic changes occur within cells leading to increasingly abnormal behaviour and histology

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8
Q

What are the 7 stages involved in multi-stage carcinogenesis?

A
  1. normal epithelium
  2. hyperproliferated epithelium
  3. early adenoma
  4. intermediate adenoma
  5. late adenoma
  6. carcinoma
  7. metastasis
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9
Q

What is meant by penetrance?

A

the percentage of individuals with a gene change that develop a condition

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10
Q

If you come from a family that has a cancer predisposition, when will you develop the cancer?

A

You are not destined to get the cancer

Penetrance describes the chance you will develop the cancer

This is influenced by genetic variations and environmental factors

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11
Q

What is the role of gatekeeper genes?

A

they regulate tumour growth, monitor and control cell division/death and prevent accumulation of mutations

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12
Q

What is the role of caretaker genes?

A

they improve genomic stability e.g. through repair of mutations

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13
Q

What is the role of landscaper genes?

A

they control the surrounding stromal environment

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14
Q

What does the likelihood of developing cancer depend on?

A

the importance of the gene function that has been mutated

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15
Q

Can sporadic cancers be inherited?

A

sporadic cancers are not inherited

they occur at random

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16
Q

What is the chance of developing cancer from an adenomatous polyp?

A

5%

The cancer that develops would be sporadic

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17
Q

What would happen if there was a change in a gatekeeper gene?

What is the chance of cancer developing?

A

multiple polyps would develop

there is >95% chance of developing cancer from these polyps

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18
Q

What would happen if there was a change in a caretaker gene?

What is the chance of developing cancer?

A

a polyp would develop and there is a 70% chance this would become malignant

the penetrance is lower than a mutation in a gatekeeper gene

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19
Q

What would happen if there was a mutation in a landscaper gene?

what is the chance of developing cancer?

A

hamartomatous polyps would develop

there is a 10-20% chance these will develop into cancer

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20
Q

What is the role of tumour suppressor genes?

A

they protect cells from becoming cancerous

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21
Q

What happens if there is loss of function of tumour suppressor genes?

A

this increases the risk of cancer

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22
Q

What are examples of tumour suppressor genes?

A

APC

BRCA 1/2

TP53

Rb

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23
Q

What is the role of oncogenes?

A

They regulate cell growth and differentiation

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24
Q

What happens if there is a mutation in an oncogene?

A

Gain of function from activating mutations increases the risk of cancer

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25
Q

What are examples of oncogenes?

A

growth and signal transduction factors

RET gene

transcription factors

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26
Q

What is the overview of Knudson’s Two Hit Hypothesis?

A

In sporadic cancer, two hits are required in a single cell

In inherited cancer, only one additional hit is required in a single cell

27
Q

In someone with a genetic predisposition to cancer, how could a mutation lead to tumour formation?

A

If a sperm contains a mutation, all of the cells of the offspring contain one copy of the mutation

A tumour begins to form when the second copy of the gene gains a mutation

28
Q

How does cancer development differ in someone who does not have a genetic predisposition to cancer?

A

If someone does not carry a mutation, both alleles of a gene need to be mutated in order for a tumour to form

Often the first allele is mutated and the second one becomes mutated later in life

29
Q

What pattern of inheritance increases cancer risk?

A

autosomal dominant

30
Q

If someone has a cancer syndrome, what is the chance that they will pass this onto their offspring?

Why?

A

They have a 50% chance of passing on the mutated gene

Cancer syndromes show an autosomal dominant inheritance pattern

31
Q

What are examples of 3 autosomal recessive cancer syndromes?

A
  1. MUTYH associated polyposis
  2. Faconi anaemia
  3. ataxia telangiectasia
32
Q

If each parent is a carrier of one mutated allele for a cancer syndrome, what is the chance of the child inheriting the cancer risk?

A

1 in 4

It is autosomal recessive and the child must inherit both mutated copies of the gene

33
Q

When taking a family history, what 4 factors must be taken into account?

A
  1. include maternal and paternal sides
  2. include at least 3 generations
  3. confirm the type of cancer and the age of diagnosis
  4. confirm this if possible through medical records, cancer registries, death certificates
34
Q

What are the 4 clues that point towards a sporadic cancer diagnosis?

A
  1. onset at an older age
  2. only one cancer in the individual
  3. family members are unaffected
  4. the type of cancer is rarely genetic (lung, cervical)
35
Q

What are the 4 clues that point towards a familial cancer diagnosis?

A
  1. onset at younger age
  2. multiple primary cancers in the individual
  3. other family members are also affected
  4. the cancers are the same type or genetically related
36
Q

What is diagnostic testing and when is it performed?

A

it is performed on DNA from a relative affected with cancer

it tries to identify the familial mutation

37
Q

What is predictive testing and when is it performed?

A

If a mutation is identified within a family, predictive testing for the specific mutation is offered to other relatives

This determines whether or not they are at risk

38
Q

What is retinoblastoma?

What gene is affected?

A

It is a childhood ocular cancer caused by defects in the retinoblastoma (Rb1) gene

39
Q

How many children per year in the UK are affected by retinoblastoma?

A

around 30-50

it is very rare

40
Q

From which cells does a retinoblastoma affect?

What age group is usually affected?

A

cancer rapidly develops from immature cells of the retina

it almost exclusively affects young children

41
Q

What are the BRCA 1/2 genes usually involved in?

In which populations are mutations commonly seen?

A

They are involved in DNA repair

Common mutations occur in Jewish and other founder populations

42
Q

What % of breast cancer cases are the BRCA1/2 genes responsible for?

A

10% of cases of breast cancer under 40

43
Q

What is the risk of ovarian and breast cancers with BRCA1/2?

A

Risk of breast cancer is 80%

Risk of ovarian cancer is 40% with BRCA1 and 10-20% with BRCA2

44
Q

What other cancers do BRCA1/2 show an increased risk of?

A
  1. prostate
  2. melanoma
  3. male breast cancer
45
Q

What is the risk of breast cancer in males with the BRCA2 gene?

A

7%

The penetrance of problems is less severe in men

46
Q

What is familial adenomatous polyposis (FAP)?

What causes it?

A

A mutation in the APC tumour suppressor gene

Leads to hundreds of bowel polyps (adenomas) from teens onwards

47
Q

What is the risk of bowel cancer if FAP is untreated?

What % of bowel cancers does it account for?

A

High risk (up to 100%) if it is untreated

accounts for around 1% of bowel cancers

48
Q

What are other features of familial adenomatous polyposis?

A

CHRPE

Desmoid tumours

Osteomas

49
Q

How is FAP detected and treated?

A

Through colonoscopies

A total colonectomy is performed in late teens/early 20s

50
Q

What is an alternative name for Lynch syndrome?

A

hereditary non-polyposis colorectal cancer (NHPCC)

51
Q

How are the polyps different in FAP and Lynch syndrome?

A

Lynch syndrome has polyps, but not polyposis (there are less)

52
Q

What causes Lynch syndrome?

A

mutations in mismatch repair genes

53
Q

What is the risk of bowel cancer in Lynch syndrome?

What % of bowel cancers is is accountable for?

A

60-80% risk of bowel adenomas or cancer from mid 20s onwards

accounts for 2-3% of bowel cancers

54
Q

What other cancer risks are associated with Lynch syndrome?

A

endometrial, ovarian, stomach and GU

55
Q

What are the 5 components of the Amsterdam criteria for HNPCC?

A
  1. at least 2 generations are affected
  2. one family member diagnosed with colorectal cancer before 50
  3. three relatives are affected
  4. FAP should be excluded
  5. tumours should be verified by pathological examination
56
Q

What is the routine for colonoscopy in patients with HNPCC?

A

They should have a colonoscopy every 18-24 months from age 25 onwards

57
Q

What are the benefits of colonoscopic screening in HNPCC?

A

Removal of polyps and early detection of cancer improves survival

58
Q

What preventative surgery is recommended in HNPCC?

A

prophylactic colectomy is NOT recommended

women may consider hysterectomy

59
Q

What type of screening is offered to BRCA1/2 gene carriers?

A

breast screening

annual MRI age 30-50

annual mammography from age 40 onwards

60
Q

What are the preventative measures for BRCA1/2 gene carriers?

A
  1. risk-reducing mastectomies and reconstruction
  2. risk-reducing BSO
  3. lifestyle changes
61
Q

What gene is implicated in Li Fraumeni syndrome?

A

P53 mutations

This is very rare

62
Q

What is the risk of cancer in Li Fraumeni syndrome?

What cancers is it associated with?

A

50% risk of cancer by age 40, with close to 100% lifetime risk

associated with breast, sarcoma, brain, adrenocortical and leukaemia

63
Q

What treatment is avoided in Li Fraumeni syndrome?

A

radiotherapy

the P53 gene makes someone vulnerable to radiation and carries a risk of inducing cancers

64
Q

Why is the prognosis of Li Fraumeni syndrome very poor?

A

there is very limited screening

an MRI can be conducted for the breast

Y2 GENETICS IN MEDICINE (11 decks)

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