Virology Chapter 16

5. What is mainly responsible for the reduction in the incidence of HBV cancers worldwide? A) Better cancer screening B) Abstinence programs C) Improved blood screening D) Availability of an HBV vaccine

D) Availability of an HBV vaccine Ans: D

8. Which of the following is not a way hepatitis B virus (HBV) can be transmitted? A) Contact with blood and body fluids B) Sharing of needles C) Passed from infected mother to child D) Sexual contact

D) Sexual contact Ans: D

10. Which assay can be used to determine whether a virus can transform cells in culture? A) Soft agarose assays B) ELISA C) Plaque assay D) PCR

A) Soft agarose assays Ans: A

2. Which of the following is not a characteristic of transformed cells? A) Anchorage dependence B) Lack of contact inhibition C) Changes in membrane structure and function D) Rapid division

A) Anchorage dependence Ans: A

4. Explain the difference between v-oncogenes, c-oncogenes, and proto-oncogenes.

Ans: A proto-oncogene is a normal copy of a gene involved in normal cell growth and differentiation. A c-oncogene is a mutated form of a proto-oncogene that causes abnormal cell growth. Lastly, a v-oncogene is a homolog of a cellular proto-oncogene that when expressed can result in abnormal cell growth and differentiation.

3. Explain why the incidence of Burkitt's lymphoma is relatively low despite the fact that the majority of the world's population is infected with EBV.

Ans: Burkitt's lymphoma appears to predominate in individuals with weakened immune systems. This includes individuals suffering from AIDS and children in Central Africa chronically infected with malaria.

6. List some of the alterations observed in cancer cells present in the body.

Ans: Cancer cells in the body tend to express higher levels of oncogene mRNA, exhibit loss of tumor suppressor function and altered patterns of DNA methylation, produce increased amounts of growth factors, divide uncontrollably, express increased levels of enzymes involved in nucleic acid synthesis, exhibit increased telomerase activity, and are able to evade host immunosurveillance.

7. Explain how altered telomerase activity contributes to the development of cancer.

Ans: During the normal aging process, telomeres at the ends of host chromosomes gradually shorten with each cycle of cell division. At a certain point the shortened telomere signals the cell to stop dividing and undergo apoptosis. Cancer cells typically express elevated levels of the enzyme telomerase, which causes the telomere length to be maintained. Thus, cancer cells never receive the signal to stop dividing.

1. True or False? Viral oncogenes expressed by DNA tumor viruses are not essential for replication.

Ans: False

1. Explain why immunity is both a benefit and a hurdle to virotherapy.

Ans: Host immunity can greatly impact the efficacy of virotherapy. Stimulation of the host immune system by oncolytic viruses appears to activate antitumor immunity, improving the efficacy of virotherapy. However, immune responses directed at the oncolytic virus can cause the virus to be eliminated from the body before it has had a chance to damage the tumor.

4. ____________ infections, common among sexually active adults and adolescents, are associated with cancers of the cervix, anus, and penis.

Ans: Human papillomavirus Alternative ans: HPV

2. Provide a definition for metastasis.

Ans: Metastasis is when a transformed cell or clump of cancer cells separate from the initial site of the tumor and spread to other locations in the body. Metastatic cancers are usually more difficult to treat than localized cancers.

1. ____________ is the leading cancer among men in the United States.

Ans: Prostate cancer

8. Detail how oncolytic viruses can be engineered to target tumor cells and spare healthy cells.

Ans: Scientists have engineered oncolytic viruses to express tissue-specific promoters such that the viruses express viral genes only in certain tissues and not in others. Additionally, oncolytic viruses have been engineered to attach to cell surface receptors that are either more abundant or exclusively expressed on cancer cells compared to healthy, normal cells.

5. List the DNA viruses shown to cause cancer in humans.

Ans: The DNA viruses known to cause cancer in humans include Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, hepatitis B virus, hepatitis C virus, and human papillomavirus.

2. True or False? About 20% of human cancers are associated with viruses.

Ans: True

3. True or False? Progressive telomere shortening is a normal part of aging in humans.

Ans: True

4. True or False? Adenoviruses have not been associated with cancer in humans.

Ans: True

5. True or False? An optimized oncolytic virus should be capable of being administered intravenously.

Ans: True

5. The large T antigen of SV-40 interacts with the tumor suppressor _______, disabling cell cycle control and allowing cellular transformation to take place.

Ans: p53

3. Platelet-derived growth factor (PDGF) and the transcription factor c-myc are ____________ involved in the stimulation of normal cell growth and division.

Ans: proto-oncogenes

2. Due in part to increased levels of ___________ activity, cancer cells never receive a signal to stop dividing.

Ans: telomerase

9. What explains the high incidence of scrotal and testicular cancer among 18th-century chimney sweeps? A) Radiation exposure B) Exposure to carcinogens C) Activation of endogenous human retroviruses D) Infection with Epstein-Barr virus

B) Exposure to carcinogens Ans: B

7. Which of the following is an important characteristic for a potential oncolytic virus? A) Capable of establishing latency B) Induces apoptosis C) Enters the nucleus of target cells D) Resistance to antiviral drugs

B) Induces apoptosis Ans: B

6. What is the nature of the Cervarix vaccine? A) Live, attenuated B) Viruslike particles C) Inactivated D) Subunit

B) Viruslike particles Ans: B

3. Temin and Baltimore shared the 1975 Nobel Prize in physiology or medicine for: A) demonstrating the efficacy of virotherapy. B) discovering reverse transcriptase. C) linking endogenous human retroviruses with schizophrenia. D) discovering viral oncogenes.

B) discovering reverse transcriptase. Ans: B

4. What disease does HTLV primarily cause? A) Hepatocellular carcinoma B) Burkitt's lymphoma C) Adult T cell leukemia D) Kaposi's sarcoma

C) Adult T cell leukemia Ans: C

1. Which of the following viruses has not been shown to cause cancer in humans? A) Kaposi's sarcoma-associated herpesviruses B) Hepatitis B virus C) Simian virus 40 D) Epstein-Barr virus Ans: C

C) Simian virus 40 Ans: C