Microbiology Lecture 4. Flashcards
What are the 6 main differences between malignant cells and normal cells?
tumorigenicity, lack of differentiation, immortality, lack of contact inhibition, resistance to apoptosis, chromosome abnormalities
What are the cancers caused by a virus that have a vaccine?
cervical cancer (HPV vaccine) and hepatocellular cancer (hep B vaccine)
oncogene
surface receptors for growth factors in normal cells
How is growth and differentiation of cells regulated?
by numerous surface receptors and internal signaling pathways
myc
proto-oncogene transcription factor that controls growth of cell
sis
proto-oncogene that controls growth of cell - platelet-derived growth factor
erb B
proto-oncogene growth factor receptor
scr
proto-oncogene membrane signaling of growth factor binding
ras
porto-oncogene signal transduction from surface receptors
fms
proto-oncogene growth factor receptor
CMO2
proto-oncogene hematopoiesis
p53
proto-oncogene that controls cell cycle; stimulated by DNA damage to stop cell cycle
pRB
proto-oncogene that controls cell cycle; blocks E2F (which controls cell cycle regulation
Large T antigen
allows cell to proliferate without control by blocking p53 and RB
What is damage to DNA normally managed by?
pause in cell cycle, attempted repair of DNA, resumption of the cycle or apoptosis
oncogene specific to chronic myelogenous leukemia
abl
oncogene specific to breast cancer
her2/neu
What mechanisms do retroviruses cause cancer?
- contain oncogenes and express them in infected cells 2. insert their promoter into a chromosome and cause expression of regional oncogenes
What mechanism do DNA viruses use to be oncogenic?
encode proteins that disturb the cell cycle and prevent apoptosis (esp p53 and pRB)
SV40 virus
primate virus (species specific!!!) causes cell transformation and cancer in rodents - transforms human cells to malignant state by expressing T antigen - contaminant of early polio vaccines
adenoviruses
a group of human viruses, some of which cause cell transformation and cancer in rodents, but only cause colds and sore throats in people
E1A and E1B
analogous to T antigen
Which cancers are caused by a virus? What is the associated virus?
- cervical cancer: human papillomaviruses 2. Burkitt’s lymphoma: Epstein Barr virus 3. hepatocellular carcinoma: HBV 4. leukemia and lymphoma: HTLV-1 and HTLV-2 5. Kaposi’s sarcoma: KSHV, HHV8
What do low risk types of HPV cause?
warts
What do high risk HPVs cause?
squamous cell carcinomas of the cervix, penis, oropharynx
What are the E6 and E7 genes?
function the same way as T antigen of SV40 virus: E6 binds P53 (leads to degradation of ubiquitan pathway) and E7 binds Rb (prevents interaction with E2F)
Where are E6 and E7 genes present?
both low and high risk HPV - but have low affinity binding in low risk HPVs
What type of vaccine is the HPV vaccine?
empty virus capsid
Epstein Barr virus
herpes virus that causes mononucleosis in western world, childhood lymphoma (burkitt’s) in parts of Africa and AIDS patients, nasopharyngeal cancer in Asia
What is the translated oncogene present in Epstein Barr virus?
myc (which is overexpressed): translocated from chromosome 8 to 14 - becomes active, activating expression of other genes
Which virus can have tumors and recurrences predicted? How?
EBV by IgA antibodies
Hepatitis viruses (HBV and HCV)
cause chronic hepatitis that predisposes you to cirrhosis and liver cancer - prevalent in africa and asia
Human T-cell lymphotropic virus (HTLV-1 and HTLV-2)
RNA virus but with no oncogene - tax gene causes overexpression of IL-2 and IL-2 receptor - causes leukemia and lymphoma
Where is HTLV-1 and HTLV-2 prevalent?
caribbean countries
Kaposi Sarcoma Herpes Virus (KSHV, HHV8)
associated with Kaposi’s sarcoma in patients with HIV but uncertain mechanism
