Molecular Neoplasia 3

Question 1

15. Distinguish between hereditary and sporadic cancers

Answer 1

hereditary cancers are passed down through germ cells where sporadic cancers are caused by mutation in somatic cells

Question 2

17. Describe the mechanisms of initiation, promotion and progression in relation to the genome and the development of cancer

Answer 2

initiation: mutation that occurs at single cell, is irreversible, dose dependent and there are a finite number of critical gene targets
promotion: reversible and environmentally modulated, exerts effect over extended time by increased proliferation or decreased apoptosis through receptor action, requires initiation
progression is the final irreversible stance, through the acquisition of multiple mutation and major genetic changes

Question 3

18. List the four best understood causes of mutation associated with cancer development.

Answer 3

chemicals
radiation
biologic organisms (viruses)
inheritance

Question 4

16. Explain dominant and recessive inheritance patterns with regard to the cancer phenotype and name at least one example of each.

Answer 4

autosomal dominant (1 mutation inherited, 1 acquired) ie. retinoblastoma or Li-Fraumeni or APC even though tumor suppressor alleles are considered recessive

autosomal recessive (both mutant copies must be inherited) ie. ataxia telangctasia and XP

Question 5

19. Contrast chemical carcinogens that are initiators v. promotors. What is the difference between direct acting and indirect acting, give examples of both.

Answer 5

initiators react with DNA in a way that is irreversible but not sufficient for tumor formation alone
promotors are not tumorigenic themselves but the can induce cellular proliferation or expansion of an initiated cell

direct are weaker and require metabolism to be activated ie. alkylating agents
indirect are more potent i.e.. polycyclic aromatic hydrocarbons

Question 6

20. Contrast between electromagnetic and particulate radiation, how do each lead to cancer?

Answer 6

electromagnetic spectrum include UV, gamma and X rays
particulate radiation includes a, B particles, protons and neutrons

ionizing radiation has the potential to knock an electron from orbit, creating a free radical

Question 7

22. How can DNA viruses lead to cancer in humans?

Answer 7

virus can insert gene product that can directly or indirectly inactivate host protooncogens or inactivate tumor suppressor genes; can also induce chronic cell injury or lead to loss of normal immune surveillance

Question 8

21. List the cancers associated with each of the following viruses: HPV, EBV, HBV, herpes virus-8, HTLV-1 and 2

Answer 8

HPV types 16, 18 cervical
EBV gene products E6-7 interact with Rb and p53- Burkit lymphoma
HBV- increased chronic inflammation- hepatocellular carcinoma
HHV8- kaposi sarcoma
HTLV-1 (RNA)- adult T-cell leukemia
HIV (loss of immunosurveilience)- kaposi sarcoma

Question 9

23. List the tumors associated with infections by H. pylori, Schistomsoma and Opisthorchis viverrini.

Answer 9

H. Pylori: gastric and duodenal peptic ulcer along with gastric carcinoma and gastric lymphoma

Schistosomiasis: bladder cancer