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Cancer Cell Biology > 6 - Tumor Viruses > Flashcards

6 - Tumor Viruses Flashcards

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1
Q

What is the genetic origin of cancer attributed to?

A

oncogenic viruses

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2
Q

What is significant about the Rous sarcoma virus?

A

first discovered virus that can induce sarcomas in chickens

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3
Q

What type of genome (RNA or DNA) does the Rous Sarcoma Virus (RSV) have?

A

RNA

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4
Q

What are transforming retroviruses?

A

cancer-causing single-stranded RNA virus that uses reverse transcriptase to make ssDNA into dsDNA which integrates into host genome

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5
Q

If a virus wants the cell to move, how will it make the cell do this function?

A

induce cytoskeletal rearrangement = cells start to move and grow &raquo_space;> mobility

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6
Q

What is the key characteristics of the retrovirus life cycles that relates to cancer?

A

genome integrates and recombines with the host genome

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7
Q

How can viruses be passed onto the daughter cells?

A

when cells undergo cell division = viruses will multiply and split into daughter cells

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8
Q

How do viruses disrupt/cause cancers?

A

breaks host DNA &raquo_space;> inserts viral DNA after an active promoter = CAN activate genes that should be off OR deactivate genes that should be on (ie: tumor suppressor genes) | can insert viral DNA in non-protein encoding gene

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9
Q

What are the 2 hallmarks of cancer?

A

uncontrolled cell division | immortality = doesn’t die (as a population)

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10
Q

What are the mutations of most tumors?

A

mutated proto-oncogenes

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11
Q

How many mutations does a proto-oncogene need before the cell loses control?

A

one

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12
Q

How many mutations does a tumor suppressor gene need before the cell loses control?

A

two

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13
Q

Are all retroviruses, transforming retroviruses?

A

no

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14
Q

What are the 2 goals tumor viruses reach for?

A

cell survival | proliferation

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15
Q

What are 5 altered properties of a transformed cell due to transforming retroviruses?

A

loss of growth control (loss of contact inhibition in cultured cells) | tumor formation | mobility | reduced adhesion | chromosomal aberrations

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16
Q

What are the 2 mechanisms of gene activation by retroviral insertion?

A

promoter insertion | enhancer insertions

17
Q

What does the src gene cause? Is this gene normal?

A

sarcomas | normal in all cells

18
Q

How can a virus convert a proto-oncogene into an oncogene such as in the case of src?

A

by altering the gene sequence so it codes for a protein with abnormal activity | brought under control of powerful promoters or enhancers in the viral genome

19
Q

What is the purpose of the src gene?

A

involved in cell division

20
Q

Which cells will respond to a growth factor?

A

only those that have the receptor for the growth factor

21
Q

What was the first tyrosine kinase discovered and in what?

A

src gene in chickens

22
Q

Do viruses always insert their genome in the same sites in every cell?

A

not always

23
Q

What percent of cancers are associated with viral infections?

A

15% (number changes)

24
Q

What are the 4 ways viruses can give rise to tumor cells?

A

genetics | disrupt host gene | bring in own viral genes that can induce neoplasia | immune suppression

25
Q

What is the “hit and run” method of virus that can induce neoplasia?

A

virus leaves a mutation in the genome of a normal cell but the virus is not there anymore

26
Q

What is insertional mutagenesis?

A

virus DNA inserted in the host chromosome alters or destroys normal gene expression

27
Q

What can insertional mutagenesis cause?

A

immune suppression

28
Q

What are the most common types of papillomaviruses?

A

16 and 18 = transforms human keratinocytes

29
Q

What is the function of the HPV viral protein E2?

A

sticks to spindles when the cells divide so it takes a ride into the daughter cells

30
Q

What do at least 50% of cancers have mutated?

A

p53

31
Q

What is the role of p53?

A

guardian of the genome | inhibits cell cycle and induces apoptosis

32
Q

How can viruses inhibit p53?

A

some viral proteins can act on and inhibit p53

33
Q

What is E2F? Is it usually on or off?

A

transcription factor for cell cycle genes | usually off

34
Q

What is Rb?

A

discovered in retinoblastoma

35
Q

What is the function of Rb?

A

always active | binds and sequesters E2F (off) = no cell cycle genes (like cyclin)

36
Q

How is E2F activated?

A

phosphorylate Rb = changes shape and becomes inactive &raquo_space;> releases E2F = activated E2F

37
Q

What percent of people are infected with Epstein-Barr Virus?

A

95%

38
Q

What is HBV?

A

Hepatitis B virus | goes into liver and causes inflammatory response

39
Q

What are the 3 anti-oncogenes?

A

loss-of-function mutations | retinoblastoma (Rb) | p53

Cancer Cell Biology (17 decks)

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