Carcinogens

Question 1

Which type of cancer is most common and why?

Answer 1

Carcinomas, because the epithelium comes into greatest contact with the environment, and so, carcinogens.

Question 2

What is the evidence for an environmental cause of cancer?

Answer 2

Study of Japanese hawaiians. Cancer rates changed over years from country of origin to country of residence.

Question 3

Give some carcinogenic viral agents

Answer 3

HPV
Epstein Barr
Hepatitis B and C
Helicobacter pylori

Question 4

Describe tumour promoter

Answer 4

Increase cell proliferation but do not damage DNA. Usually extrinsic eg inflammatory environment

Question 5

Describe tumour initiators

Answer 5

DNA damaging agents

Question 6

What is the evidence for the requirement of both initiators and promotors for tumour development?

Answer 6

Application of both over different time periods to rats lead to the development of papilloma sand carcinomas.

Question 7

Give a test for mutagenicity

Answer 7

The Ames test

Question 8

Give some examples of DNA repair genes associated with familial cancer syndromes

Answer 8

Li fragment syndrome - sarcomas, breast, colon - TP53, CHK2 - DNA damage alarm protein and kinase signalling DNA damage.
Bloom - BLM - DNA helicase, replication
Werner - WRN - exonuclease and DNA helicase, replication
Breast - BRCA1, BRCA2 - homology-directed repair of dsDNA breaks.

Question 9

Give types of DNA repair

Answer 9

Mismatch repair
Methylguanine dna methyltransferase
Base excision repair
Nucleotide excision repair

Question 10

Describe the Ames test

Answer 10

Homogenised rat liver is mixed with the test compound
Add to salmonella bacteria unable to grow without additive histidine
Count number of bacterial colonies that have undergone mutation enabling them to grow without histidine.