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59 Cards in this Set

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What are the family of viruses that have been found to cause cancer?
Papillomaaviridae
Hepadnaviridae
Herpesviridae
Poxiviridae
Describe the mechanism of transformation for small DNA viruses.
induces S phase genes
Extend life of cell
Block action of normal regulatory proteins
Often tumor suppressor genes
describe the mechanism of Large DNA viruses
interact with extra-cellular growth factors or intracellular signaling systems
Results in perpetual cellular replication
Encode homologs of cellular genes involved in signaling
True or False
Tumor Suppressor genes are often deleted or damaged in cancer cells
True
True or False
50% of human tumors have p53 gene inactivated
True
what does p53 do in the cell?
p53 regulates G1 to S phase in the cell cycle
Active p53 inhibits progression from G1 to S phase
what is the function of pRb?
the pRb protein is a cell cycle regulator
it inhibits cells moving from G1 to S phase
how do Polymaviruses cause cancer?
these viruses also encode proteins that interfere with tumor suppressor factors
SV40 makes the larger T antigen which interferes with both pRb and p53
what produces SV40? what does it do?
Polymaviruses
-makes the larger T antigen which interferes with both pRb and p53
Is there a vaccine for HPV?
Yes
what types of HPV cause cervical carcinoma?
HPV types 16, 18, and 31
How does HPV act on the cell to cause cancer?
Two viral proteins, E6 and E7 maintain cells in S phase for virus replication and can immortalize cells
what is the function of protein E7 in the HPV virus?
Protein E7 interferes with pRb while protein E6 interferes with p53
E7: pRb
E6: _____
p53
what type of cell will the EBV infect?
EBV in a gammaherpesvirus that infects limited set of cells bearing the CD21 molecule
what type of cells is EBV limited to?
B-lymphocytes and a few types of epithelial cells
what main proteins does EBV viral DNA produce?
EBNA-1
+LMP1
what does LMP stand for in EBV?
Latent membrane protein
what is a fatal lymphoma of the head or neck caused by a virus?
Burkitt's Lymphoma
what do the lymphoma cells of Burkitt's lymphoma exhibit in its genome?
the lymphoma cell exhibits a chromosomal translocation (t8:14) which is relocation of c-myc
If the immune system is well intact will a Burkitt's lymphoma occur?
NO
loss of immune surveillance is necessary for this disease to develop
what are the 3 forms of Burkitt's lymphoma?
Ednemic Form
Sporadic Form
AIDS form
What type of co-infection is required for the formation of Endemic form of Burkitt's Lymphoma?
requires co-infetion with Plasmodium falciparum (malaria)
True or False
50% of cells found in an AIDS form of a Burkitt's lymphoma have EBV DNA present.
True
loss of immune surveillance due to HIV infection
what virus subset has been found to cause Hodgkin's disease (lymphoma)?
EBV
what is the etiological agent of Kaposi's Sarcoma?
HHV-8
Describe the pathogenesis in the mechanism of HHV-8
multifactorial viral neoplasia that is not well understood
not an aggressive tumor
due to lack of immune competence
What type of co-infection is required for the formation of Endemic form of Burkitt's Lymphoma?
requires co-infetion with Plasmodium falciparum (malaria)
True or False
50% of cells found in an AIDS form of a Burkitt's lymphoma have EBV DNA present.
True
loss of immune surveillance due to HIV infection
what virus subset has been found to cause Hodgkin's disease (lymphoma)?
EBV
what is the etiological agent of Kaposi's Sarcoma?
HHV-8
Describe the pathogenesis in the mechanism of HHV-8
multifactorial viral neoplasia that is not well understood
not an aggressive tumor
due to lack of immune competence
Is the HHV-8 caused tumor an aggressive tumor?
NO
not an aggressive tumor and the overt disease is due to lack of immune competence
what is described as " hit and run" transformation?
proposed mechanism for HSV (1 & 2) of a small part of the genome is a rearrangement of cellular genes
Is there a vaccine for Hepatits B?
YES
what type of cancer does Hepatitis B cause?
a member of the Hepadnaviridae family that causes a persistent infection of the liver
-there is a long incubation period before cancer develops
-Chronic HBV infection and increased proliferation of hepatocytes predisposes the patient to PHC
-Hepatocellular Carcinoma is a multifactorial disease
How do viruses cause cancer?
viruses encode proteins that perturb normal cellular regulation
-these proteins can upregulate cellular growth factors and disrupt regulatory brakes
this is a multistep/multifacotrial process
define oncogenesis
mechanism of the development of cancer
define Neoplasm
an abnormal new growth
define Retinoblastoma
a cancer of the retina
Sarcoma
a cancer of fibroblasts
How many kinds of RNA viruses are there?
three kinds of RNA viruses
What are the three RNA viruses?
Retroviruses & Hepatitis C (Flavivirus)
1. Non-acute transforming retroviruses
2. Acute transforming retroviruses
3. Trans-activating retroviruses
Human T-cell Leukemia is causes by what type of virus
Trans-acting retroviruses
Avian Sarcoma virus is caused by what type of virus
Acute transforming retroviruses
Murine leukemia virus is caused by what type of virus
Non-Acute transforming retrovirus
Are Non-acute transforming Retroviruses responsible for cancer in humans?
NO
do acute transforming retroviruses cause cancer in humans?
NO
these viruses are uncommon in nature and do NOT cause cancer in humans
how long is the incubation period until cancer is developed by an acute transforming retrovirus?
weeks
-the virus is defective and required a helper virus
what does the oncogen version of C-ras have transformed in it from the normal C-ras?
The oncogene version, v-ras has a change in codon for aa-12
what type of cancer may be linked to Prostate Cancer?
gamma retrovirus
what type of virus is uncommon in nature but causes cancer in humans?
Trans activating Tumor Viruses
what type of virus is considered a trans activating tumor virus?
Retroviris
How long is the incubation period for a trans activating tumor virus to cause cancer?
The incubation period until cancer develops is years
How do trans activating tumor viruses act on the cell to cause cancer?
The action of viral regulatory proteins on cellular genes immortalizes or transforms the cell
-the virus is replication competent
-the virus transforms a subset of lymphocytes
-after a long incubation period there will be numerous immortalized T-cells
When does Adult T-cell Leukemia occur?
occurs when an aggressive clone is generated by the trans activating tumor viruses
Describe the mechanism of HTLV Transformation.
1. Retrovirus carries an accessory gene, tax
2. tax may activate several cellular genes and initiate an autostimulating IL-2 loop
what family does Hepatits C virus belong to?
Flaviviridae
(+) ssRNA genome
-infection with virus predisposes patients to primary hepatocellular carcinoma
What is the mechanism of transformation for HCV?
HCV persistently infects hepatocytes
It causes continual destruction and regeneration of liver tissue
Continual induction of cell growth in the presence of an active immune response may lead to cancer