L14

Question 1

What is cancer

Answer 1

• Diseases in which abnormal cells divide without control.

- Cancer cells can spread to other tissues/organs through the blood and lymph systems.

Question 2

Cancer cells are characterized by:

Answer 2

• increased proliferation (division) rate
• invasive potential
• high metabolic rate
• altered morphology
• resistance to apoptosis (cell death)

Question 3

Proto-oncogenes are normal genes that encode:

Answer 3

• regulatory proteins
• growth factors
• growth factor receptors
  (control cell growth)

Question 4

Oncogenes are mutated proto-oncogenes:

Answer 4

• Constitutively expressed (gain of function) = Unregulated protein expression
• Only one mutated copy is sufficient (dominant)
• Causes uncontrolled cell proliferation

Question 5

DNA repair genes encode protein involved in DNA repair

Answer 5

• Mismatch repair
• Double-stranded DNA breaks
• Base excision repair…etc.
  (Prevent cancer initiation)

Question 6

Tumour suppressor genes encode protein involved in:

Answer 6

• Inhibition of the cell cycle
• Induction of apoptosis (programmed cell death)
  (Prevents cancer promotion)

Question 7

Mutated forms of DNA repair genes or tumour suppressor genes can result in:

Answer 7

• Non-function (loss of function) – Cannot make functional proteins
• Two mutant copies required (recessive)
• Prevents DNA repair (cancer initiation)
• Allows survival of mutated cells (cancer progression)

Question 8

BRCA2 gene (DNA repair gene)

Answer 8

Encodes the BRCA2 protein involved in double-stranded DNA break repairs by
homologous recombination.

Mutated non-functional BRCA2: mutation persists and cell proliferates

Question 9

p53 gene (tumour suppressor gene)

Answer 9

Encodes a transcriptional regulator activated in response to DNA damage.

Mutated non-functional p53 gene: mutated cells survive and proliferate

Question 10

Acquired mutations:

Answer 10

• Most common cause of cancer (sporadic cancer).
• Induced or Spontenous mutation occurs in somatic cells.
• Non-heritable. May result from a single dominant mutation or two recessive mutations
• Example: UV radiation and skin cancer

Question 11

Inherited (germline) mutations:

Answer 11

Inherited (germline) mutations:
• 5% to 20% of all cancers.
• Mutations in gametes (sperm or egg)
• Heritable. Offspring carry the mutation in every cell.
• Increases the risk for cancer development
(requires a second additional mutation in the somatic cell).
• Example: BRCA1/2 gene mutation = increased risk of breast cancer.

Question 12

Genetic therapies aim at:

Answer 12

1. Replacing defective genes
2. Fixing mutated genes
3. Making diseased cells more evident to the immune system.

Question 13

Cancer and DNA methylation

Answer 13

1. Increase expression and activity of DNA methyltransferase enzymes
2. Hypermethylation of promotor CpG islands (represses gene expression)
3. Hypermethylated of CpG islands can lead to mutations