Cancer Development

Question 1

What percentage of colorectal cancer patients have a FHx of this?

Answer 1

• ~25%
• The molecular basis is only understood in a small number of patients.
• Causative mutations are identified in only 5-6% of cases.

Question 2

What are 2 main types of familial colorectal cancer?

Answer 2

• Familial adenomatous polyposis (FAP).
• Hereditary non-polyposis colon cancer (Lynch Syndrome).

Question 3

What is the main difference between tumour suppressor genes and oncogenes?

Answer 3

• Tumour suppressor genes cause recessive mutations (loss of function).
• Oncogenes cause dominant mutations (gain of function).

Question 4

What is the primary genetic test for FAP?

Answer 4

• Direct gene sequencing.
• The older method is a protein truncation test.

Question 5

What is the primary genetic test for HNPCC?

Answer 5

• Immunohistochemical protein staining.
• Histological sections are stained for these 4 proteins. If it stains brown, the protein is present. If not, the protein is absent.

Question 6

What are the major types of mutation which cause FAP?

Answer 6

• Mostly nonsense or frameshift mutations.

Question 7

Where are the mutations which cause FAP?

Answer 7

Chromosome 5 q21-22

Question 8

What are the mutations which cause HNPCC?

Answer 8

• The gene defects which cause HNPCC are MSH2, MLH1, MSH6 and PMS2.