Viral Oncogenesis II Flashcards
What is Merkel Cell Carcinoma (MCC)
highly aggressive neuroendocrine carcinoma of the skin w/ a high propensity of recurrence and metastasis
5-year disease-specific survival rate for Merkel Cell Carcinoma (MCC)
60%
virus associated with Merkel Cell Carcinoma (MCC)
Merkel cell polyomavirus (MCV)
how common is the Merkel cell polyomavirus
rare but incidence is rapidly increasing
is Merkel Cell Polyomavirus associated with all Merkel Cell Carcinoma
it is associated with most of it but not all of it; about 20 - 30% of cases of MCC do not have the MCV virus and have a distinct pathoetiology
genome that Hep B and C are associated with
Hep B - DNA
Hep C - RNA
organ that Hep B and Hep C virus infect
they infect and damage the liver so you get classical symptoms of jaundice and liver enzyme release
80% of all Primary Hepatocellular Carcinoma (PHC) can be attributed to what virus
chronic HBV infection
prognosis if a pt has PHC
usually fatal – one of the three most common causes of cancer mortality in the world
what type of virus is HBV
Hepadnavirus (class VII)
how is HBV spread
blood or needles, sexual contact, and
perinatally
median incubation period of HBV
3 months which then icterus symptoms begin
what do 5-10% of pts with PHC eventually develop
chronic hepatitis
percentage of the world’s population that has been infected with HBV and how many die from it annually
1/3 of world infected
1-2 million deaths/year
why has the incidence of HBV gone down
vaccination
HBV has a tissue tropism for what organ and what happens when in that organ
liver
integrates into the host chromosome and stimulate cell growth
oncoprotein associated with HBV
HBx
type of virus is Hep C
flavivirus (Class IV so (+) ssRNA)
how long does it take for Hep C to develop into cancer
10-50 years (30 years being median)
when someone contract HCV acute infection, what are the three fates
- 15%: recovery and clearance
- 15%: cirrhosis rapid onset
- 70%: persistent infection with 40% being asymptomatic and other 30% definitely leading to chronic hepatitis
of the 30% of those with HCV that eventually become chronic hepatitis, what is their fate
- 6% liver failure
- 20% cirrhosis
- 4% hepatocellular carcinoma
only known retrovirus known to cause cancer in humans
HTLV-1 (RNA tumor virus)
what do retroviruses carry with their regular genes
they carry oncogenes that they can integrate at particular sites in the host cell
example of fast acting and slow/transacting RNA tumor cancer
fast: acute leukemia or sarcoma
slow: leukemia
what is significant about leukemia virus’ replication (including HTLV-1)
replication is competent but they cannot transform cells in vitro
how long does it take for HTLV-1 to cause cancer
after a long latency period usually about 30 years
how does HTLV-1 promote cell growth
in more indirect ways than the oncogene encoding viruses
what is associated with myelopathy (tropical spastic paraparesis)
Adult acute T-cell lymphocytic leukemia (ATLL) and HTLV 1
is HTLV-1 only associated with neoplastic diseases
no they are also associated with nonneoplastic neurologic disorders
what is the importance of HTLV-1 having the tax protein
activates promoters in LTR region and specific cellular genes (promote outgrowth of the cell)
importance of HTLV-1 integrating near cellular growth controlling genes
enhancer and promoter gene sequences can promote expression of growth-stimulating proteins
importance of Tax protein being immunogenic
eventually cells will evolve and there will be selection for cells that do not have tax hence pushing cells towards having proteins like HBZ that compensates for loss of tax by taking up its function – cells basically become immortal
most common among those w/ inherited immune deficiency, autoimmune disease, or HIV
Non-Hodgkin’s lymphoma
increase the risk of developing non-Hodgkin’s lymphoma
Viral infections: HTLV-1, hepatitis C, and EBV
mechanism by which cell growth is promoted (viral transformation/ immortalization)
either removing the growth suppressors or enhancing growth activators
