Carcinogenesis

Question 1

What are the steps to chemical carcinogenesis?

Answer 1

1. Initiation: Irreversible and not sufficient for tumor formation
2. Mutation: irreversible
3. Promotion: Reversible

Question 2

Differentiate direct acting compounds from indirect acting compounds

Answer 2

Direct acting compounds do not require chemical transformation. Indirect acting compounds require metabolic conversion.

Question 3

Name some direct acting compounds.

Answer 3

Alkylating agents, Anticancer drugs and acylating agents

Question 4

Name some indirect acting compounds

Answer 4

Aromatic amines, amides

Question 5

Name some carcinogenic promoters

Answer 5

Alcohol, cigarette smoke, virus, hormones and bile salts

Question 6

What can UV exposure lead to?

Answer 6

Leads to formation of pyrimidine dimers in DNA, which are repaired by nucleotide excision.

Question 7

Discuss Xeroderma Pigmentosum

Answer 7

Autosomal recessive; Inability to repair UV-induced DNA damage

Question 8

Discuss Heliobacter pylori and carcinogenesis

Answer 8

Oncogenic strains contain cytotoxin gene A which penetrates gastric epithelial cells. Gastric adenocarcinoma is mediated by increased cellular proliferation to repair epithelial damage in background of chronic inflammation.