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Cancer Week > Year 1 Cancer: a genetic disease > Flashcards

Year 1 Cancer: a genetic disease Flashcards

1
Q

What are some examples of inherited genetic mutations?

A
  • BRCA1/2
  • DNA repair genes (XP)
  • RB1
  • ATM
  • APC
  • P53
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2
Q

What are some examples of acquired mutations?

A
  • Ras
  • P53
  • ATM
  • epigenetics
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3
Q

What are some examples of external factors which can influence cancer?

A
  • smoking tobacco
  • alcohol
  • diet
  • exercise
  • solar radiation
  • ionising radiation
  • industrial asbestos
  • pharmacological chemotherapeutic agents
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4
Q

What are some examples of infections which can cause cancer?

A
  • HPV
  • Epstein Barr Virus
  • Hepatitis B Virus
  • Helicobacter Pylori and gastric adenocarcinoma
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5
Q

How can immunosuppression cause cancer?

A
  • increased cancers in AIDs and transplant patients
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6
Q

What are the 3 types of mutations found in oncogenes?

A
  • point mutations (Ras)
  • chromosomal rearrangements (Bcl-2)
  • gene amplification (HER2)
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7
Q

How does h-ras involve a point mutation?

A
  • GGC to GTC, glycine to valine
  • bladder cancer
  • single nucleotide exchange
  • activates oncogene
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8
Q

What is an example of a chromosomal translocation?

A
  • c-myc translocation places gene under control of highly active regulator from Ig gene
  • Burkitt lymphoma
  • also Bcl-2
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9
Q

Where is Bcl-2 upregulated?

A
  • anti-apoptotic protein
  • chromosomal translocation
  • leukaemias
  • non-Hodgkin lymphoma
  • small cell lung cancer
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10
Q

What is an example of gene amplification?

A
  • HER2 (breast cancer)
  • EGFR (small cell lung cancer)

overexpression of both

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11
Q

What mutations occur in p53?

A
  • tumour suppressor gene
  • point mutations
  • missense
  • single nucleotide substitution
  • TF p53 can no longer bind to DNA
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12
Q

What mutations happen in ATM gene?

A
  • DNA repair gene
  • role in repair of DNA double strand breaks
  • many point mutations
  • DNA repair impaired and mutations accumulate in other genes
  • cerebellar cells particularly affected = ataxia
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13
Q

What are susceptibility genes?

A
  • inherited mutations in genes
  • tumour suppressor genes
  • oncogenes
  • DNA repair genes
  • cell cycle control genes
  • genes stimulating angiogenic pathway
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14
Q

What is penetrance?

A
  • proportion of individuals carrying a pathogenic variant who will manifest the disease
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15
Q

What is the significance of methylation in tumour suppressor genes?

A
  • hypermethylation at CpG islands
  • inhibits transcription of gene
  • if tumour suppressor gene = no DNA repair = loss of tumour suppressor gene expression
  • hypomethylation in 3’ untranslated regions = genomic instability = promotes translocation
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16
Q

What is the significance of DNMT3B?

A

DNA methyltransferase 3 beta

  • expressed strongly in colon carcinoma cells
  • intense expression in aggressive carcinomas
  • high methylation = highly aggressive carcinomas
17
Q

How is DNA damaged?

A
  • replication errors in S phase
  • spontaneous damage altering base sequences
  • mutagenic damage (endogenous and exogenous)
18
Q

What are examples of endogenous mutagenic DNA damage?

A

indirect acting carcinogens which require metabolic activation:

  • polycyclic aromatic hydrocarbons
  • alcohol
19
Q

What are some examples of exogenous mutagenic DNA damage?

A

direct acting carcinogens:

  • oxygen species
  • chemical mutagens
  • x-rays
  • UV radiation
20
Q

What are the causes of spontaneous DNA damage?

A
  • proofreading errors
  • deamination of bases
  • depurination (linking purine A/G to deoxyribose removing base)
  • depyrimidination
  • oxidation
21
Q

What can smoking cause?

A

double strand breaks
lots of carcinogens = polycyclic aromatic hydrocarbons
- formation of DNA adducts
- BP formed = benzopyrene (fused benzene rings)
- cytochrome p450 formed = ultimate carcinogen producing chemical species and highly reactive mutagenic DNA
- lung cancer
- BPDE forms adduct with guanosine in lung epithelial cells

22
Q

How can DNA adducts form in oral and oesophageal cancers?

A
  • acetaldehyde break down forms deoxyguanosine and converts to weak mutagen (DNA adduct)
  • then converts to stronger mutagen
23
Q

What can radiation cause?

A
  • indirect = creation of free radicals which damage bases/break DNA backbone
  • direct = alpha/beta particles or x-rays create ions which break sugar phosphate backbone = pyrimidine dimers
24
Q

What are some examples of cancers with pyrimidine dimers?

A
  • melanosomes

- basal cell carcinomas

25
Q

What causes XP?

A
  • defect in human nucleotide excision repair
26
Q

What are the symptoms of XP?

A
  • light sensitive
  • risk of sunlight induced cancer
  • neurological abnormalities
27
Q

What is the difference between non-melanoma and cutaneous melanoma?

A
  • non melanoma = basal cell and squamous cell skin cancer at UV exposed sites
  • cutaneous melanoma (melanocytes)
28
Q

How can viruses cause cancer?

A
  • HPV -> cervical cancer (sex)
  • Epstein Barr Virus -> Burkitts Lymphoma, Hodgkins Lymphoma (saliva/blood/transplants)
  • leukaemia virus type 1 -> Adult T cell leukaemia (mother to child, sex, blood transfusion)
  • Hep B and C -> hepatocellular carcinoma (blood trans, organ trans, needles)
  • H. pylori -> gastric adenocarcinoma via indirect inflammatory effects on gastric mucosa and direct epigenetic effects on cells
  • schistosomiasia -> squamous cell and transitional cell bladder cancer

Cancer Week (12 decks)

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