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Microbiology > Oncogenic Viruses > Flashcards

Oncogenic Viruses Flashcards

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1
Q

What percentage of cancers are caused by viruses?

A

15-20%

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2
Q

Viruses are the leading causes of which types of cancer?

A

Liver, cervical

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3
Q

What are the general mechanism by which viruses cause cancer?

A

Activate signalling pathways (cytokines)
Release cell cycle control
Infected cell destruction/clearance leads to unplanned regeneration

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4
Q

Why is the presence of viral genomes in a tumor not sufficient to say the virus caused the tumor?

A

It may be a coincidental spot of replication of the virus

It may be due to contamination of the assay

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5
Q

What are the epidemiologic criteria to be considered a cancer-causing virus?

A

Coincident geographic distribution of infxn, cancer
Higher incidence of viral markers in cases vs control references
Viral markers should precede cancer
Reduction in infection rats should reduce cancer rates

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6
Q

What are virologic criteria to be considered a cancer-causing virus?

A

Virus should transform cells in vitro
Virus genome present in tumor but not normal cells
Tumor induction in experimental animals

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7
Q

What are the six known human cancer viruses?

A 
Human T-Lymphotrophic Virus Type 1 (HTLV1)
KSHV
EBV
HPV
Hep B
Hep C
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8
Q

What is the difference between immortalized cells and transformed cells?

A

Immortalized cells retain original properties but grow indefinitely. Transformed cells are immortalized but lose many growth properties.

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9
Q

What were early viruses identified to cause cancer?

A

Avian Leukemia and Rous Sarcoma Virus

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10
Q

What are v-oncogenes?

A

Oncogenes contained in the viral genome that are transducing agents themselves, leading to rapid cancer formation.

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11
Q

What are c-oncogenes?

A

Oncogenes or proto-oncogenes in the human genome that can be activated to overstimulate by a virus.

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12
Q

What are transducing oncogenic viruses?

A

I.e. Rous Sarcoma Virus
Contain v-oncogene
100% of tumor formation
Rapid tumor formation

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13
Q

What are Nontransducing oncogenic viruses?

A

No v-oncogene, but can activate c-oncogenes via integration
Intermediate tumor time
High rate of tumor formation

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14
Q

What are nontransducing, long latency oncogenic Viruses?

A

HTLV1
Contain a v-oncogene unrelated to c-oncogenes
low rate of tumor formation
months to years to tumor formation

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15
Q

Through signaling pathways, explain how dna and rna tumor viruses can cause cancer.

A

They can increase/dysregulate kinase cascades, leading to increased cell division.

Can upregulate gene expression by introducing new transcription factors

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16
Q

What is a principal difference between v- and c-oncogenes in terms of activity?

A

V-oncogenes are always active.

17
Q

What is the result of a v-oncogene that is always on?

A

Loss of signaling control and inappropriate grwoth

18
Q

How do nontransducing retroviruses work?

A

They use insertional activation. Strong promoters or enhancers located in virus genome lead to unregulated overexpression of nearby c-oncogenes

19
Q

How does HTLV work?

A

A long-latency retrovirus, causing T cell leukemia and lymphoma. infects and transforms CD4 T cells, through Tax. Tax stimulates Ikk to cause Ikb degradation, freeing NFkB to direct transcription. Leads to immortalization of T cells with transformation as well.

20
Q

Explain EBV

A

Latent in B cells and leads to burkitts lymphoma and hodgkins lymphoma, and NPC
LMP1 activates kinase cascade that localized NFkB, which causes nuclesu to immortalize

21
Q

What is KSHV?

A

Kaposi’s sarcoma, encoding several oncogenes that produce cytokines resulting in transformatino. Mess up GPCR.

Alters cell control, through v-cyclin production, activating cdk6

22
Q

What is HPV?

A

Undergoes lytic replication in some cells. Others don’t allow lytic activity, so it transduces them. Integrated into host dna.

E6 BINDS TO P53
E7 BINDS TO RB (inactivating It)

23
Q

How do hepbc work?

A

The constant clearance of infxted cells leads to unintended uncontrolled proliferation and cancer

Microbiology (4 decks)

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