Flashcards in Oncogenic Viruses Deck (55)
What is the objective of this lecture?
1. To know the mechanisms by which viruses can cause cancer
2. To know which viruses cause cancer in humans, and how this can be prevented.
What are proto-oncogenes that control the growth of cells?
1. myc - transcription factor
2. sis - platelet-derived growth factor
3. erb B - growth factor receptor
how do some retroviruses cause cancer in animal?
1. some contain oncogene and express them in infected cells
2. some can insert their promoter into a chromosome and cause expression of regional oncogene
p53 protein can be inactivated by
retinoblastoma protein (pRB) can be inactivated by
What are the two viruses that are specific-specific?
1. SV 40 virus
2. Adenoviruses (various serotypes)
SV 40 virus
1. a primate virus that causes cell transformation and cancer in rodents
2. transforms human cells to a malignant state
3. express T antigen which inactivated p53 and pRB
a group of human viruses, some of which cause cell transformation and cancer in rodents, but only cause colds and sore throats in people
What are the 5 viruses that cause cancer in humans?
1. human papillomaviruses
2. Epstein-Barr virus
3. Hepatitis virus (HBV and HCV)
4. Human T-cell lymphotropic virus (HTLV-1 and HTLV-2)
5. Kaposi sarcoma herpes virus (KSHV, HHV8)
1. low risk types, such as HPV-2 and HPV-4 cause warts
2. high risk types, such as HPV-16 and HPV-18 cause squamous cell carcinomas of the cervix, penis, and orpharynx
In HPV, E6 and E7 genes function in same way as
T antigen of SV40
In HPV, the progression to carcinoma is
slow, requiring many years
HPV vaccines consist of
empty virus capsids
HPV vaccines reduce the incidence of
cervical intraepithelial neoplasia (CIN)
What is a herpes virus that causes mononucleosis?
what is a herpes virus associated with childhood lymphoma (Burkitt's) in parts of Africa and in patients with AIDS?
What is the characteristics of Burkitt's lymphoma?
1. tumors express a latent viral antigen of uncertain function
2. have a translocated oncogene (myc) which is overexpressed.
EBV is also associated with
naso-pharyngeal cancer in Asia
What are the co-factors of EBV infection?
malaria infection in Africa and food preservatives in Asia
What do hepatitis viruses (HBV and HCV) cause?
chronic hepatitis that predisposes to cirrhosis and liver cancer after many years
Hepatitis is prevalent in
Africa and Asia
What is the characteristics of Human T-cell lymphotropic virus (HTLV-1 and HTLV-2)?
1. RNA virus
2. but with no oncogene
What is the molecular basis of HTLV?
tax gene causes overexpression of interleukin-2 and the receptor for interleukin-2. other proteins dysregulate RNA metabolism
3. blood borne
What does HTLV lead to?
leukemia and lymphoma
HTLV is prevalent
Kaposi sarcoma herpes virus (HHV8) is associated with
Kaposi's sarcoma in pts with HIV. (unknown mech)
all of the cancerous features (abnormal chromosomes,immortal, not contact inhibited etc) can be induced experimentally by
platelet derived growth factor
signal transduction from surface receptors