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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
HTLV is prevalent
in Caribbean
26
Kaposi sarcoma herpes virus (HHV8) is associated with
Kaposi's sarcoma in pts with HIV. (unknown mech)
27
all of the cancerous features (abnormal chromosomes,immortal, not contact inhibited etc) can be induced experimentally by
viruses
28
sis (protooncogenes)
platelet derived growth factor
29
ras (protoconcogenes)
signal transduction from surface receptors
30
Inactivation of p53 or Rb allows cells
to proliferate and accumulate other mutaitons
31
E2F
stimulates cell cycle (Rb blocks E2F and stop the cell cycle)
32
oncogenes are
overexpressed in some human cancers
33
RNA oncogenic viruses
carry activated oncogenes, or insert their promoter and activate an oncogene
34
DNA oncogenic viruses
degrade cell cycle genes
35
Adenovirus E1A and E1B are
analogous to T antigen and are always expressed in transformed cells (not responsible for any human cancers)
36
what are SCID X1?
IL-2 receptor deficiency in newborns
37
oncogenes may have which function in normal cells?
surface receptors for growth factors
38
EBV causes
1. Burkitt's lymphoma | 2. Naso-pharyngeal cancer
39
E6 binds
p53 (leads to degradation by ubiquitin pathway)
40
E7 binds
non-phosphorylated Rb (prevents its interaction with E2F)
41
Transfection of cells with E6/E7
leads to immortalization
42
E2 gene in HPV normally
suppresses E6 and E7
43
loss of E2 function, because of integration
therefore allows over-expression of E6 and E7
44
EBV in western world causes
mononucleosis
45
EBV in vitro can
transform human B cells
46
Burkitt lymphoma caused by EBV
1. endemic in African malaria belt 2. affects pre-pubertal boys 3. maxilla most common site 4. contains EBV and expresses genes continually
47
EBV can also cause
naso-pharyngeal cancer
48
Naso-pharnygeal cancer
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
pathogenesis of EBV related lymphomas
q 8-14 translocation puts myc gene under control of an immunoglobulin promoter
50
B-cell lymphomas in the Western world
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
Hepatitis B virus
1. liver cancer indcidenc is higher in countries with endemic HBV infection 2. HBV is a risk factor for cancer
52
retroviruses can cause
cancer in animals by transmission of activated oncogenes or by insertional activation of an oncogene
53
DNA viruses can cause cancer through
effects of the T antigen or its equivalent (SV40, adenoviruses, HPV) which target the p53 and pRb genes)
54
what are the effects of HBV vaccine?
1. universal immunization of newborns can lead to 50% reduction of HCC in adolescent (or eliminate HCC)
55
Hepatitis B virus
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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