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FHHD > Clinical Cancer Genetics > Flashcards

Clinical Cancer Genetics Flashcards

1
Q

What are polymorphisms

A

Changes in the DNA sequence that occur commonly in the population

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2
Q

What are germ line mutations

A

Different from polymorphisms and are rare inherited mutations that increase the risk of cancer significantly

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3
Q

How does genetic and environmental factors affect cancer risk

A

Different for different cancers
Lung cancer is very environmental
Retinoblastoma is mostly inherited

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4
Q

Give examples of inherited cancers

A
  • Retinoblastoma
  • Multiple endocrine tumours
  • Breast cancer
  • Colon cancer
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5
Q

How many mutations are usually required to form a human tumour cell

A

Evidence suggest at least 4 pathways must be mutated and that there are 3-6 rate limiting steps in the development of most cancers

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6
Q

What types of cancer gene are there

A

Oncogenes

Tumour suppressor gene

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7
Q

How do onco and tumour suppressor genes associated with cancer

A

Oncogene - gain of function or increased function associated with cancer

Tumour Suppressor gene - Loss of function or reduced function associated with cancer

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8
Q

What is a proton-oncogene

A

A normal gene that can become an oncogene due to mutations or increased expression

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9
Q

What proteins do proton-oncogenes code for

A

Proteins that help to regulate cell growth and differentiation

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10
Q

What processes are proton-oncogenes often involved in

A

Signal transduction

Mitogenic signals

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11
Q

What is oncogene activation

A

This is the conversion of a proton-oncogene to an oncogene

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12
Q

What is the restriction point of the cell cycle

A

This is the point near the end of the G1 phase of the cell cycle where beyond this point the cells will absolutely complete the cell cycle

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13
Q

What do Kinases do

A

These add phosphate to amino acids like serine (threonine kinases) or tyrosine (tyrosine kinases)

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14
Q

What do phosphatases do

A

Removes phosphate from amino acids

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15
Q

What do cyclins and cyclin dependent kinases (CDKs) do

A

These form complexes and the cyclins are regulatory and activate the CDKs

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16
Q

What is a major target of the cyclins

A

The retinoblastoma tumour suppressor gene that it phosphorylates at multiple points throughout the cell cycle

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17
Q

How do growth factors work

A
  • Growth factors bind to receptors
  • G-protein switch
  • Kinase cascade
  • Activates transcription factors
  • Changes in gene expression
  • Cells instructed to synthesis DNA
18
Q

How do Epidermal growth factors work

A
  • Binds to EGF receptor
  • “Ras” g protein is activated
  • Activates series of kinases called Raf/MEK/ERK kinases - part of the mitogen activated protein kinase complex
  • ERK kinase activates transcription factors AP1 (fos/jun proteins)
  • Cyclin D1 transcribed
  • Cells instructed to synthesis DNA
19
Q

How does the MYC proton-oncogene contribute to cancer

A
  • Starts when a chromosomal translocation moves an enhancer sequence within the vicinity of the MYC gene
  • The MYC gene codes for widely used transcription factors
  • When the enhancer sequence is wrongly placed, these transcription factors are produced at much higher rates
20
Q

How does the philadephia chromosome associate with choleric myelogenous leukaemia

A

The BCR (breakpoint cluster region) is moved next to a kinase called ABL

This chromosome is caused is caused by the translocation of pieces from chromosomes 9 and 22

BCR-ABL codes for a receptor tyrosine kinase that is constitutively active leading to uncontrolled cell proliferation

21
Q

What proton-oncogenes are activated by increased gene copy number

A
  • ERB1 - epidermal growth factor receptor
  • CCND1 - cyclin D1
  • MYC
22
Q

Name a few tumour suppressors genes and what cancers they are associated with then the fail

A
  • RB1 - retinoblastoma
  • APC - colon cancer
  • TP53 - Breast cancer
  • BRCA1 and BRCA2 - Breast and Ovarian cancer
  • MSH1 - colon cancer
23
Q

Explain the two-hit hypothesis

A

If you inherited a mutated tumour suppressor gene then you were more likely to get the cancer as you might only need one more mutation for the tumour cells to be formed

24
Q

What are the 2 types of tumour suppressor genes

A

Gatekeeper

Caretaker

25
Q

Describe the function of gatekeeper tumour suppressor genes

A

These regulate tumour growth by controlling proliferation or promoting cell death

26
Q

Describe the function of caretaker tumour suppressor genes

A

These are generally DNA repair genes or genes that otherwise protect the genome from acquiring or retaining DNA damage

27
Q

How much risk is associated with gatekeeper gene inactivation

A

Very large more than 1000 fold because only one further mutation is required to initiate neoplasia

28
Q

How much risk is associated with the inactivation of a caretaker gene

A

Smaller increase about 5-50 fold as there are up to 3 further mutations required to initiate neoplasia

29
Q

How can the type of inheritance of some tumour suppressor genes affect the risk of cancer

A

Recessive = less likely as either 2 come to make a baby with it or needs an extra germ line mutation along with the 2 somatic gatekeeper mutations e.g. ATM gene

30
Q

Describe the function and risk of failure of the pRB gatekeeper gene

A

Control of the restriction point and can lead to retinoblastoma and osteosarcoma

31
Q

Describe the function and risk of failure of the CDKN2A (p16^INK4A protein) gatekeeper gene

A

Control of restriction point by inhibiting cyclin D1 and can lead to melanoma

32
Q

Describe the function and risk of failure of the TP53 gatekeeper gene

A

Control of cell cycle and apoptosis and metabolism and can lead to breast cancer and many others

33
Q

Describe the function and risk of failure of the APC gatekeeper gene

A

Controls the cell cycle, apoptosis and differentiation and can lead to colon cancer

34
Q

Name some types of caretaker gene and their function

A
  • Nucleotide excision repair genes
  • Mismatch repair genes - repair of mismatched DNA
  • BRCA1 and 2 - recombinational repair
35
Q

What cancers can result from nucleotide excision repair genes

A

Skin cancers

36
Q

What cancers can result from mismatch repair genes

A

Colon cancer

37
Q

What cancers can result from BRCA1 and 2 genes

A

Breast and Ovarian cancer

38
Q

What can viruses do to create viral oncogenes

A

They can recruit and modify versions of proton-oncogenes to activate them OR activate them by inserting powerful viral enhancer sequences next to them as in human Burkitt’s lymphoma with EBV and MYC

39
Q

What is the most important human virus that can lead to cancer and how does it work

A

Human Papillomavirus that encodes proteins E6 that inhibits and destroys p53 and E7 destroys RB1 proteins, causes cervical cancer

40
Q

What does the p16^INK4A protein do

A

It restrains the cyclin D1 and CDK4 complex that normally takes you through the cell cycle restriction point

FHHD (21 decks)

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