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Micro 2014 Unit 1 > Oncogenic Viruses > Flashcards

Oncogenic Viruses Flashcards

1
Q

What is the objective of this lecture?

A
  1. To know the mechanisms by which viruses can cause cancer

2. To know which viruses cause cancer in humans, and how this can be prevented.

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2
Q

What are proto-oncogenes that control the growth of cells?

A
  1. myc - transcription factor
  2. sis - platelet-derived growth factor
  3. erb B - growth factor receptor
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3
Q

how do some retroviruses cause cancer in animal?

A
  1. some contain oncogene and express them in infected cells

2. some can insert their promoter into a chromosome and cause expression of regional oncogene

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4
Q

p53 protein can be inactivated by

A

viral protein

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5
Q

retinoblastoma protein (pRB) can be inactivated by

A

viral proteins

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6
Q

What are the two viruses that are specific-specific?

A
  1. SV 40 virus

2. Adenoviruses (various serotypes)

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7
Q

SV 40 virus

A
  1. a primate virus that causes cell transformation and cancer in rodents
  2. transforms human cells to a malignant state
  3. express T antigen which inactivated p53 and pRB
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8
Q

Adenovirus

A

a group of human viruses, some of which cause cell transformation and cancer in rodents, but only cause colds and sore throats in people

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9
Q

What are the 5 viruses that cause cancer in humans?

A
  1. human papillomaviruses
  2. Epstein-Barr virus
  3. Hepatitis virus (HBV and HCV)
  4. Human T-cell lymphotropic virus (HTLV-1 and HTLV-2)
  5. Kaposi sarcoma herpes virus (KSHV, HHV8)
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10
Q

Human papillomaviruses

A
  1. low risk types, such as HPV-2 and HPV-4 cause warts

2. high risk types, such as HPV-16 and HPV-18 cause squamous cell carcinomas of the cervix, penis, and orpharynx

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11
Q

In HPV, E6 and E7 genes function in same way as

A

T antigen of SV40

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12
Q

In HPV, the progression to carcinoma is

A

slow, requiring many years

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13
Q

HPV vaccines consist of

A

empty virus capsids

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14
Q

HPV vaccines reduce the incidence of

A

cervical intraepithelial neoplasia (CIN)

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15
Q

What is a herpes virus that causes mononucleosis?

A

EBV

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16
Q

what is a herpes virus associated with childhood lymphoma (Burkitt’s) in parts of Africa and in patients with AIDS?

A

EBV

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17
Q

What is the characteristics of Burkitt’s lymphoma?

A
  1. tumors express a latent viral antigen of uncertain function
  2. have a translocated oncogene (myc) which is overexpressed.
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18
Q

EBV is also associated with

A

naso-pharyngeal cancer in Asia

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19
Q

What are the co-factors of EBV infection?

A

malaria infection in Africa and food preservatives in Asia

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20
Q

What do hepatitis viruses (HBV and HCV) cause?

A

chronic hepatitis that predisposes to cirrhosis and liver cancer after many years

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21
Q

Hepatitis is prevalent in

A

Africa and Asia

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22
Q

What is the characteristics of Human T-cell lymphotropic virus (HTLV-1 and HTLV-2)?

A
  1. RNA virus

2. but with no oncogene

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23
Q

What is the molecular basis of HTLV?

A

tax gene causes overexpression of interleukin-2 and the receptor for interleukin-2. other proteins dysregulate RNA metabolism
3. blood borne

24
Q

What does HTLV lead to?

A

leukemia and lymphoma

25
Q

HTLV is prevalent

A

in Caribbean

26
Q

Kaposi sarcoma herpes virus (HHV8) is associated with

A

Kaposi’s sarcoma in pts with HIV. (unknown mech)

27
Q

all of the cancerous features (abnormal chromosomes,immortal, not contact inhibited etc) can be induced experimentally by

A

viruses

28
Q

sis (protooncogenes)

A

platelet derived growth factor

29
Q

ras (protoconcogenes)

A

signal transduction from surface receptors

30
Q

Inactivation of p53 or Rb allows cells

A

to proliferate and accumulate other mutaitons

31
Q

E2F

A

stimulates cell cycle (Rb blocks E2F and stop the cell cycle)

32
Q

oncogenes are

A

overexpressed in some human cancers

33
Q

RNA oncogenic viruses

A

carry activated oncogenes, or insert their promoter and activate an oncogene

34
Q

DNA oncogenic viruses

A

degrade cell cycle genes

35
Q

Adenovirus E1A and E1B are

A

analogous to T antigen and are always expressed in transformed cells (not responsible for any human cancers)

36
Q

what are SCID X1?

A

IL-2 receptor deficiency in newborns

37
Q

oncogenes may have which function in normal cells?

A

surface receptors for growth factors

38
Q

EBV causes

A
  1. Burkitt’s lymphoma

2. Naso-pharyngeal cancer

39
Q

E6 binds

A

p53 (leads to degradation by ubiquitin pathway)

40
Q

E7 binds

A

non-phosphorylated Rb (prevents its interaction with E2F)

41
Q

Transfection of cells with E6/E7

A

leads to immortalization

42
Q

E2 gene in HPV normally

A

suppresses E6 and E7

43
Q

loss of E2 function, because of integration

A

therefore allows over-expression of E6 and E7

44
Q

EBV in western world causes

A

mononucleosis

45
Q

EBV in vitro can

A

transform human B cells

46
Q

Burkitt lymphoma caused by EBV

A
  1. endemic in African malaria belt
  2. affects pre-pubertal boys
  3. maxilla most common site
  4. contains EBV and expresses genes continually
47
Q

EBV can also cause

A

naso-pharyngeal cancer

48
Q

Naso-pharnygeal cancer

A
  1. endemic in South China, vietnam, arctic eskimls
  2. contains EBV and express genes continually
  3. Environmental co-factors involved
  4. IgA antiboides to EBV capsi antige predict tumors or recurrences
49
Q

pathogenesis of EBV related lymphomas

A

q 8-14 translocation puts myc gene under control of an immunoglobulin promoter

50
Q

B-cell lymphomas in the Western world

A
  1. Most B cell lymphomas are EBV negative
  2. seen in pts with AIDS or long term immunosuppression - SCID or graft recipients
  3. may regress if immune function is restored
51
Q

Hepatitis B virus

A
  1. liver cancer indcidenc is higher in countries with endemic HBV infection
  2. HBV is a risk factor for cancer
52
Q

retroviruses can cause

A

cancer in animals by transmission of activated oncogenes or by insertional activation of an oncogene

53
Q

DNA viruses can cause cancer through

A

effects of the T antigen or its equivalent (SV40, adenoviruses, HPV) which target the p53 and pRb genes)

54
Q

what are the effects of HBV vaccine?

A
  1. universal immunization of newborns can lead to 50% reduction of HCC in adolescent (or eliminate HCC)
55
Q

Hepatitis B virus

A
  1. Liver cancer incidence is higher in countries with endemic HBV infection
  2. HBV is a risk factor for cancer
  3. Prospective studies show greater risk with cirrhosis of liver, or high level expression of viral genes

Micro 2014 Unit 1 (7 decks)

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