Oncogenic Viruses (4) Flashcards
Features of human cancer cells?
1- make tumors if transported to animals 2- undifferentiated 3- Immortal 4- Not contact inhibited 5- Abnormal Chromosomes
True or False: All of the features of human cancer cells can be induced experimentally by viruses
True
What do the following proto-oncogenes do:
myc src ras sis erbB fms LMO2
myc: transcription factor
src: membrane signaling of growth factor binding
ras: signal transduction from surface receptors
sis: platelet-derived growth factor
erbB: growth factor receptors
fms: growth factor receptor
LMO2: Hematopoiesis
Which teo genes control cell cycle?
p53 and Rb
How do retroviruses cause cancer?
1- contain oncogenes and express them in infected cells
2- insert its promotor into a chromosomes and causes expression of regional oncogenes
What is the mechanism through which DNA viruses cause cancer?
DNA viruses encode proteins that disturb the cell cycle and prevent apoptosis
What is the SV40 virus?
Primate virus that causes cell transformation and cancer in rodents and human cells
What protein does SV40 express? What does it do?
T antigen
Inactivated p53 and Rb
What vaccine was SV40 found in?
It was a contaminant in early polio vaccines
What are adenoviruses?
a group of human viruses, some of which cause cell transformation and cancer in rodents
What are the viral proteins of adenoviruses? When are they expressed?
E1A and E1B (they are analogous to T antigen)
They are always expressed in transformed cells
Name some viruses that are the cause of animal cancers (
1- Breast cancer in mice…mouse mammary tumor virus
2- Sarcoma….sarcoma viruses of cats, chicken, rodents
3- Feline leukemia…Feline leukemia virus (FeLV)
4- Lymphoma of chickens….Marek’s disease virus
What virus is the HPV virus related to?
SV40
What are the low risk types of HPV? The intermediate types? The High risk types?
What disease is each associated with?
Low risk: type 4, 6, 8; warts
Intermediate risk: type 11; laryngeal papilloma
High risk: type 16, 18; cervical, pharyngeal cancer
What are the viral proteins of HPV? What are thier functions?
E6: binds p53
E7: binds Rb
E2: suppressor that switch off effects of E6 and E7
What happens with loss of E2?
Loss of function allows over expression of E6 and E7 and cell immortalization
What is the pathogenesis of cervical cancer?
Normal Epithelium —> CIN I/ II —> CIN III —> Cancer
What is the function of the 2 vaccines for HPV?
Reduce incidence of CIN, to prevent cervical cancer
What does the Epstein- Barr Virus cause in the western world? In africa? In Asia?
Western world: Mono
Africa: Burkitt’s lymphoma
Asia: Naso-pharyngeal cancer
What is Burkitt’s lymphoma?
A B cell lymphoma in which myc is overexpressed
What predicts tumor recurrence with Epstein Barr virus?
IgA antibodies to EBV capsid antigen
Where is the highest incidence of hepatitis B (and associated cancer) ?
Africa and Asia
His hep B infection preventable?
Yes, there is a vaccine
What is the pathogenesis of Hep B virus?
Tumor cells contain integrated HBV but no consistent expression of any viral proteins in cancer cells and no activation of cellular oncogene
