Basics of Tumor Virology

Question 1

Early observation: infect chickens w/ virus –> tumors. Belief that transformation was from regulated growth and cell division to unregulated growth and cell division

Question 2

Intro

Answer 2

*Some RNA and DNA viruses cause a stable, inheritable change result in poor or no control of cellular division (cellular transformation) in certain infected cells
*DNA tumor viruses lyse permissive (replicate totally in cell) cells; they only transform non-permissive (virus DNA not fully replicated) cells
*RNA tumor viruses transform permissive cells
*Some RNA tumor viruses carry oncogenes responsible for the transformation

ONCOGENES GO W/ RNA VIRUSES

Question 3

General Features of Cellular Transformation

Answer 3

*Carcinogenesis is a multistep process involving multiple genetic changes
*Cellular transformation is a stable, heritable change resulting in poor or no control of cellular growth
*Cellular transformation results in the alteration of cellular processes and properties which can result in altered morphology, growth control and cellular and biochemical properties
*All tumor viruses are DNA viruses or generate a DNA provirus (Retrovirus)
*Certain DNA and RNA viruses are associated or implicated in human cancers

Question 4

Association of Viruses w/ Human Cancers - KNOW THESE

Answer 4

ENter mannually from table …Papovviridae….

Question 5

Review of Cell Cycle

Answer 5

p110RB - a protein that, when phosphorylated, is the master break in the cell cycle. When functional, cell growth is normal

p53 - when active, turns on p21 which prevents kinases from phosphorylating p110RB (master break) which tells master protein to shut down–> uncontrolled growth. I think..

Question 6

Oncogenes

Answer 6

Cellular oncogenes (c-onc):
*Are mutated forms of normal cellular genes (proto-oncogenes)
*Code for a heterogeneous group of proteins that are involved in normal cell division or differentiation pathways (Table 2)
*Abnormal expression or regulation lead to cellular transformation or cancerous growth

Question 7

Oncogenes, Ctd.

Answer 7

Viral oncogenes (v-onc):
Are copies of cellular oncogenes which have been acquired by certain viruses during replication
Are present in the viral genome
Are responsible for the cellular transforming activity of those viruses which contain them

Question 8

Tyrosine kinase (product of src oncogene) when expressed in unregulated form–>

Answer 8

somewhere downstream is unregulated growth

Question 9

Tumor Suppressor Genes

Answer 9

Are negative regulators of cellular growth
Are sometimes called anti-oncogenes or growth suppressor genes
Cause cellular transformation if the functional activity of both alleles is lost
Are exemplified by the retinoblastoma (Rb) (master break) gene and the p53 gene

Question 10

Tumor virus – Host Cell Interactions

Answer 10

Summary:

*DNA tumor viruses transform non-permissive cells; they kill permissive cells
*DNA tumor virus rarely produce tumors in the natural host (human DNA tumor viruses are the exception)
*RNA tumor viruses transform both permissive and nonpermissive cells and do produce tumors in the natural host