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PoD > Genetic Predisposition to Cancer > Flashcards

Genetic Predisposition to Cancer Flashcards

1
Q

What are somatic cells?

A

Cells that do not reproduce

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2
Q

Where do somatic mutations arise from?

A

Occurs in non-germline tissue and are non-heritable

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3
Q

Where do Germline mutating rise from?

A

Present in egg or sperm and are inheritable - cause cancer family syndromes

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4
Q

What genes are associated with cancer?

A

Oncogenes, tumour suppressor genes and DNA damage-response genes

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5
Q

What are proto-oncogenes?

A

Normal gene that codes for proteins to regulate cell growth and differentiation

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6
Q

What are oncogenes?

A

Mutated proton-oncogenes that can accelerate cell division

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7
Q

What is you first mutation that leads to cancer development and what are its effects?

A

Oncogenes - causes uncontrolled cell proliferation

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8
Q

What are tumour suppressor genes?

A

Control cell cycle - by inhibition or initiating apoptosis but when its action fails cancer arises

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9
Q

What is the two-hit hypothesis?

A

Two mutations required for cancer to arise
First mutation can be inherited making individual susceptible carrier and then a second mutation or loss of certain gene leads to cancer

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10
Q

Second mutation that can cause cancer?

A

Loss of tumour suppressor genes

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11
Q

What are DNA damage-response genes?

A

Repair mechanics for DNA - cancer will arise when both genes fail, speeding the accumulation of mutations in other critical genes

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12
Q

What are mismatch repair (MMR) genes?

A

Correct error that spontaneously occurs during DNA replication (single base mismatch, short insertions or deletions etc)

If gene is defective, faulty DNA is not repaired and leads to mutated DNA

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13
Q

What does MMR failure lead to?

A

Microsatellite instability (MSI) - phenotypic evidence that MMR is not functioning properly as MMR failure accumulates error like simple sequence repeats (SSRs)

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14
Q

Describe benign tumours

A

Cannot metastasise, and rarely becomes cancerous but can still cause negative health effects due to pressure on other organs

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15
Q

Describe dysplastic tumours

A

They are benign tumours but could progress to malignancy

Cells have abnormal appliance and cell maturation - “pre-mailgnant”

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16
Q

Describe Malignant tumours

A

Able to metastasise

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17
Q

What gene process is affected in Breast/Ovarian cancer and how?

A

Mutated BRCA1, BRCA2 genes alter Tumour suppressor genes

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18
Q

What gene process is affected in Li-Fraumeni syndrome and how?

A

Mutated P53 alters Tumour suppressor gene

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19
Q

What is a De Novo mutation?

A

New mutation which occurs in germ cell of parent in people with no family history of hereditary cancer syndrome

20
Q

In what cancers are De Novo mutations common in?

A

Familial adenomatous polyposis
Multiple endocrine neoplasia 2B
Hereditary retinoblastoma

21
Q

What kind of genes are cancer susceptibility gene?

A

Dominant with incomplete penetrance - people with condition which hasn’t developed into cancer

22
Q

In pedigree charts, what does a circle (or square) with a line though the middle indicate?

A

That person is a susceptible carrier

23
Q

Features of Retinoblastoma

A
  • 1/20 000 children
  • Common eye tumour in children
  • Can be hereditary or sporadic
  • Identify susceptible infants to reduce morbidity and motility
24
Q

Where is the mutation in Retinoblastoma?

A

Germline mutation in RB1 gene

25
Q

Nonheritable vs heritable: Features on the tumour in RB cancer

A

Non- unilateral

H - bilateral (both eyes)

26
Q

Nonheritable vs heritable: Features on the risk of second primaries in RB cancer

A

Only in heritable - osteosarcoma, other sarcomas, melanoma

27
Q

Risk factors for breast cancer

A
  • Ageing
  • Dietary factors (alcohol)
  • Lack of exercise
  • Late menopause
  • Early menarche
  • Nulliparity
  • Estrogen use
28
Q

What genes contribute to breast cancer and how?

A

BRCA1 and BRCA2 - normal genes code for tumour suppressor genes so a mutation in them leads to faulty TSG

29
Q

What process is affected in HNPCC (hereditary non-polyposis colon cancer) and by what genes?

A

MLH1, MSH2, MSH6, PMS1, PMS2 alter MMR gene so that it doesn’t repair DNA

30
Q

What is the function of the BRCA1 gene?

A

Checkpoint mediator, involved in DNA damage signalling and repair and chromatin remodelling

31
Q

Function of BRCA2

A

DNA repair by homologous recombination

32
Q

What are BRCA1-Associated cancers?

A
  • Breast cancer
  • Secondary primary breast cancer
  • Ovarian cancer

Increased risk of other cancers - i.e. prostate, colon

33
Q

What are BRCA2-Associated cancers?

A
  • Breast cancer
  • Ovarian cancer
  • Male breast cancer

Increased risk of prostate, laryngeal and pancreatic cancers

34
Q

Risk factors for Colorectal Cancer (CRC)

A
  • Ageing
  • History of CRC or adenomas (dysplastic)
  • High fat, low-fibre diet
  • Inflammatory bowel disease
  • Family history of CRC
35
Q

Adenoma to Carcinoma sequence

A
  1. Normal epithelium
  2. APC mut. - Hyperproliferative epithelium
  3. k-ras mut. - Adenoma
  4. p53 mut. - Carcinoma
36
Q

What is the nonpolyposis hereditary CRC syndrom?

A

HNPCC - few to no adenoma

37
Q

Types of polyposis Hereditary CRC syndromes?

A

FAP - severe colonic polyposis
AFAP - less severe
MAP - varying degrees

38
Q

Clinical feature of HNPCC

A
  • Early but variable age at CRC diagnosis (~45yrs)
  • Tumour through colon
  • Extracolonic cancers: endometrium, ovary, stomach, UT, small bowel, bile ducts, sebaceous skin ducts
39
Q

Clinical features of FAP

A
  • Penetrance of adenomas >90%
  • Risk of extracolonic tumours - upper GI, desmoid, osteoma, thyroid, brain - usually benign but pressure effect)
  • CRHPE my be present (spot on retina)
  • Untreated leads to 100% risk of cancer
40
Q

What is attenuated FAP (AFAP)?

A

Less sever colonic polyposis with a later onset in life.

Few colonic adenoma but still dysplastic so can develop into tumour

Upper GI and associated with mutations as 5’ and 3’ ends of APC gene

41
Q

What is recessive MYH polyposis?

A
  • Similar clinical features to AFAP
  • Common mutation in mut. MYH gene
  • Recessive inheritance
42
Q

What are modifier genes?

A

Genes that influence expression of another gene

May explain families with history of cancer and no indemnities mutation and the difference in cancer penetrance in families with same mutation

43
Q

How to manage cancer risk in adenomatous polyposis syndromes

A
  • Surveillance
  • Surgery
  • Chemoprevention
44
Q

Predictive gene tests problems

A
  • Not always possible or required
  • Problems of gene variant of unknown significance (VUS) - whether it’ll develop into cancer
  • For adult onset cancers, predictive gene test. not offered until adult hood
45
Q

What is exome sequencing?

A

Looking at specific part of gene

46
Q

What is genome sequencing?

A

Looking at entire genome (code)

47
Q

How do most people develop cancers?

A

Most due to sporadic mutations and only a small number due to inherited mutations

PoD (35 decks)

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