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Principles of Disease > Genetic Predisposition to Cancer > Flashcards

Genetic Predisposition to Cancer Flashcards

1
Q

Cancer is a genetic disease of

A

somatic cells

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2
Q

Most cancers happen by

A

‘chance’ or due to envinronmental factors

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3
Q

Somatic mutations

A
  • Occur in nongermline tissues

- Are nonheritable

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4
Q

Germline mutations

A
  • Present in egg or sperm
  • Are heritable
  • Cause cancer family syndromes
  • All cells affected in offspring
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5
Q

Different genetic processes associated with Cancer

A
  • Oncogenes
  • Tumour suppressor genes
  • DNA damage-response genes
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6
Q

Proto-oncogenes =

A

normal gene that codes for proteins to regulate cell growth and differentiation.

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7
Q

Mutations can change a proto-oncogene into

A

an oncogene

  • Oncogenes can accelerate cell division
  • Cancer arises when stuck in “on” mode
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8
Q

Tumour suppressor genes

A
  • The cell’s brakes for cell growth
  • Genes inhibit cell cycle or promote apoptosis or both
  • Cancer arises when both brakes fail
    ‘Two – hit’ hypothesis (Knudson 1971)
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9
Q

The Two-Hit Hypothesis example

A

First hit in germline of child
- Second hit (tumor)

not everyonewho has the gene will develop the cancer but they have a higher risk of having it than someone who doesnt have the first hit.

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10
Q

oncogenes are

A

dominant genes in effect

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11
Q

tumour suppressor genes are

A

recessive genes in effect

- second mutation or loss results in cancer

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12
Q

DNA damage-response genes

A

The repair mechanics for DNA

- Cancer arises when both genes fail, speeding the accumulation of mutations in other critical genes

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13
Q

HNPCC Results From

A

Failure of Mismatch Repair (MMR) Genes

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14
Q

Mismatch Repair Failure Leads to

A 
Microsatellite Instability (MSI)
- addition of nucleotide repeats
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15
Q

MMR corrects errors that

A

spontaneously occur during DNA replication like single base mismatches or short insertions and deletions

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16
Q

Cells with abnormally functioning MMR tend to

A

accumulate errors.

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17
Q

Microsatellites (aka Simple Sequence Repeats SSR) are

A

repeated sequences of DNA, can be made of repeating units of 1 – 6 base pairs

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18
Q

MSI (changes in microsatellite sequences) is the

A

phenotypic evidence that MMR is not functioning normally – genetic hypermutability

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19
Q

BENIGN =

A

lacks ability to metastasize. Rarely or never become cancerous.
Can still cause negative health effects due to pressure on other organs.

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20
Q

DYSPLASTIC =

A

‘benign’ but could progress to malignancy.
Cells show abnormalities of appearance & cell maturation. Sometimes referred to as ‘pre-malignant’.

(NB distinguish from ‘hip dysplasia’ which is macroscopically abnormal but not pre-malignant!)

21
Q

MALIGNANT =

A

not ‘benign’. Able to metastasize.

NB distinguish from ‘malignant hypertension’, ‘malignant hyperthermia’

22
Q

Tumour suppressor genes that are common dominantly inherited cancer syndromes

A

BRAC1, BRAC2
APC
P53
RB

23
Q

Mutation of P53 leads to

A

Li-Fraumeni syndrome

24
Q

Oncogenes that are common dominantly inherited cancer syndromes

A

RET

25
Q

Mutation of RET causes

A

MEN2 (multiple endocrine neoplasia)

familial medullary thyroid cancer

26
Q

DNA repair (mis-match repair) that are common dominantly inherited cancer syndromes

A

MLH1, MSH2, MSH6,

PMS1, PMS2

27
Q

mutations of MLH1, MSH2, MSH6, PMS1 or PMS2 can lead to

A

HNPCC/Lynch syndrome

28
Q

Autosomal recessive syndromes =

A

both copies of the gene have inherited mutations

- MYH polyposis

29
Q

New (de novo) mutation occurs in

A

germ cell of parent

- no family history of hereditary cancer syndrome

30
Q

de novo mutations are common in:

A
  • Familial adenomatous polyposis
  • Multiple endocrine neoplasia 2B
  • Hereditary retinoblastoma
31
Q

How do we look for an inherited cancer predisposition syndrome?

A

TAKE A FAMILY HISTORY!

32
Q

Most Cancer Susceptibility Genes Are

A

Dominant With Incomplete Penetrance.

  • May appear to “skip” generations
  • Individuals inherit altered cancer susceptibility gene, not cancer
33
Q

Features of Retinoblastoma

A
  • Most common eye tumor in children
  • Occurs in heritable and nonheritable forms
  • Identifying at-risk infants substantially reduces morbidity and mortality
34
Q

Heritable Retinoblastoma is

A

Usually bilateral

  • some in family history
  • inccreased risk of osteosarcoma, other sarcoma, melanoma
  • less than one years old
35
Q

Inheritable retinablastoma is

A

unilateral

  • no family history
  • no risk of secondary primaries
  • around 2 years old
36
Q

Risk Factors for Breast Cancer

A
  • Ageing
  • Dietary factors (eg: alcohol)
  • Lack of exercise
  • Family history
  • Late menopause
  • Estrogen use
37
Q

Genes contributing to familial ovarian cancer

A 
BRCA1
BRCA2
TP53
RAD51C
RAD51D
Mis-match repair gene
38
Q

Genes contributing to familial breast cancer

A 
BRCA1
BRCA2
TP53
PALB2
PTEN
39
Q

BRCA1-Associated Cancers:

Lifetime Risk

A

likelihood of having secondary breast cancer and ovarian cancer.
- Possible increased risk of other cancers (eg, prostate, colon)

40
Q

BRCA2-Associated Cancers:

Lifetime Risk

A

occurs in men too.

Increased risk of prostate, laryngeal, and pancreatic cancers (magnitude unknown)

41
Q

Risk Factors for Colorectal Cancer (CRC)

A
  • Ageing
  • Personal history of CRC or adenomas
  • High-fat, low-fibre diet
  • Inflammatory bowel disease
  • Family history of CRC
42
Q

Clinical Features of HNPCC

A
  • Early but variable age at CRC diagnosis (~45 years)
  • Tumor site throughout colon rather than descending colon
  • Extracolonic cancers: endometrium, ovary, stomach, urinary tract, small bowel, bile ducts, sebaceous skin tumors
43
Q

Untreated polyposis leads to

A

100% risk of cancer

44
Q

Attenuated FAP is

A

Later onset (CRC ~age 50)

  • Few colonic adenomas
  • Not associated with CHRPE
  • Upper GI lesions
  • Associated with mutations at 5’ and 3’ ends of APC gene
45
Q

Attenuated FAP is associated with mutations at

A

5’ and 3’ ends of APC gene

46
Q

Recessive MYH polyposis have

A

Similar clinical GI features to attenuated FAP

47
Q

Managing cancer risk in Adenomatous Polyposis syndromes can be done through

A
  • Surveillance
  • Surgery
  • Chemoprevention
48
Q

Mutation testing is now being carried out routinely on certain cancers, to

A

identify familial mutations and to target therapies

Principles of Disease (27 decks)

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