Virus Oncogenicity

Front 1

1. Cancer results when 2 types of cellular control systems are corrupted. What are these 2 systems?

Back 1

1. Systems that are designed to promote cell proliferation

2. Safeguard systems which are supposed to protect against irresponsible cell growth.

These control systems are composed of genes and the proteins they encode, and these systems can malfunction when the structure of the genes which comprise them is altered by DNA mutation.

Front 2

2. It is estimated that 5 control system mutations are required to produce most common cancers. True/False

Back 2

True. Because this takes a long time, this is why most cancers occur later in life.

Front 3

3. Viruses are known to directly cause cancer. True/False

Back 3

False. Viruses tend to contribute to cancer formation. They act as risk factors.

Front 4

4. List 4 kn own oncogenic viruses.

Back 4

1. Hepatitis B

2. hepatitis C

3. HTLV(human T cell leukemis virus)

4. Human papilloma virus

Front 5

5. App. 20%$ of long term hepatitis B carriers can be expected to contract liver cancer(hepatocellular carcinoma). True/False

Back 5

True.

Front 6

6. What is a genotoxin?

Back 6

These are toxins that originate within the body as toxic byproducts of normal cellular metabolism. These can damage cellular DNA.

In a hepatitis B infected liver cells must proliferate to replacethose which have been killed by the immune response to the infection. This extra proliferation increases the risk that these liver cells will divide before DNA damage can be repaired.

Front 7

7. More than 90% of Hepatits B associated liver cancers contain at least partial hepatitis B genomes that have been inserted into a cellular chromosome. True/False

Back 7

True. It is believed that the virus has some untoward negative effect on these cells. This unknown effect is referred to as a viral X protein. It is essential for viral reproduction.

This protein can inactivate, the important tumor suppressor p53 gene protein. If DNA damage is extensive, the p53 protein will trigger the cell to commit suicide. The p53 is the guardian of the protein.

Front 8

8. SV40 and polyoma viruses are associated with cancer in animals. True/False

Back 8

True.

Front 9

9. Only about 12 human papilloma types are considered oncogenic. true/False

Back 9

True. HPV 16- and 18 are usually found in cervical cancers. HPV 31, 33 and 45 are found less frequently. HPV infections alone do not cause cancer(cervical), because less than 1% of women infected with general HPV will ever suffer from this disease. 95% of cervical cancers HPV has been detected.

Front 10

10. What are HPV proteins E6 and E7?

Back 10

HPV encodes 2 proteins, E6and E7 which are essential for keeping infected epithelial cells in the proliferative mode required for viral infection.

E6 and E7 proteins are more disruptive of the cell cycle than are their non oncogenic variants.

The oncogenic E7 protein binds more strongly to the cellular pRB protein than does the non oncogenic version of E7, and gives cells a bigger kick to cause them to proliferate.

Front 11

11. Oncogenic E6 protein promotes the degradation of the cellular p53 tumor suppressor. True/False

Back 11

True.

Front 12

12. In HPV infected cells, the viral genomes usually exist as circular, ds DNA molecules. True/False

Back 12

True. These float free in the nucleus of an infected cell unassociated with host chromosomes. This is because HPV does not encode an integrase protein which can facilitate the precise integration of viral DNA into cellular chromosomes.

Front 13

13. What occurs often as a result of HPV DNA being imprecise?

Back 13

Viral genes are usually disrupted or lost when the viral DNA is pasted into a cellular chromosome. The loss of this viral information inactivates the virus, so integration of its DNA into the genome of a cell is a dead end event for the virus.

Front 14

14. In HPV, does the inactivation of viral genes always disrupt all phases of the virus?

Back 14

No. ironically, genes encoding E6 and E7 are almost always founf intact in cervical cancer cells.

In some instances, the gene for a viral protein E2, which normally helps keep E6 and E7 at relatively low levels, is deleted during the integration event.

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15. In HPV, as long as the viral genome is not integrated into the chromosome of an infected cell, the added strength of E6 and E7 is of little value. True/False

Back 15

True.

Front 16

16. In HPV, what is the significance of the transformation zone in the cervix?

Back 16

HPV can infect other areas of the female reproductive tract(vulva and vagina), most HPV cancers occur in this transformation zone. This is the area where the epithelium changes from the multilayered, squamous epithelium of the vaginato the single layered epithelium of the endocervix.

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17. Where are PaP smears taken from?

Back 17

They are cultured from the transformation zone, and are useful in diagnosing cervical cancer in the early stages.

Front 18

18. HPV types can cause warts on the exterior genitals. True/False

Back 18

True. Most of these warts are caused by non oncogenic HPV genotypes(HPV-6/11. Individuals are commonly infected with more than one genotype at a time, the presence of genital warts

may signal a possible infection with oncogenic genotypes.

HPV penile cancer is rare, because the penis has no transformation zone.

Front 19

19. Do other transformation zones exist elsewhere in the body?

Back 19

Yes. One exists in the respiratory tract, where the multilayered, stratified squamous epithelium of the vocal chords meets the pseudostratified epithelium that lines the trachea. This is the primary target for respiratory HPV infections.

Front 20

20. about 10% of patients with Hep C induced cirrhosis of the liver eventually suffer from liver cancer(hepatocellular carcinoma. True/False

Back 20

True. This may arise 3 decades post infection.

Front 21

21 List 2 Hep. C viral proteins that have been shown to inactivate p53.

Back 21

Core protein

NS5A

Front 22

22. About 2 % of those infected with HTLV-1, will eventually contract a blood cell cancer. True/False

Back 22

True. many or most suffer no real effects as a result of having this virus. The blood cell cancer is adult T cell leukemia. It is usually diagnosed in the 4th or 5th decade of life.

The viral tax protein tends to dysregulate the cells control systems, and T cells are stimulated over and over again.