Viruses and Cancer L24

Question 1

A ___1___ arises when normal controls on cell proliferation are disrupted; a ___1___ may be benign or malignant.

A benign ___1___ may grow large, but do not ___2___ to other parts of the body.

A malignant ___1___ (cancer) have the ability to invade and destroy neighbouring tissue and ___2___ to other parts of the body (metastasize).

Answer 1

1. Tumour

2. Spread

Question 2

What is an oncogene?

Answer 2

Genes which promote unrestrained proliferation.

Question 3

What is a tumour suppressor gene?

Answer 3

Genes which prevent unrestrained proliferation.

Question 4

True or false? Cancer is usually the result of multiple “insults” to cell – viral infection is one of these insults.

Answer 4

True.

Question 5

Describe the HPV.

How many genotypes?

Structure?

Genome code type?

Answer 5

• > 100 genotypes
• icosahedral, non-enveloped virus
• ds DNA genome

Question 6

Describe the HPV life cycle.

Answer 6

• Virus transmitted by direct contact (esp. sexual) or fomites
• Enters basal layer of epidermis through microabrasions
• Receptor protein unknown – heparan sulphate may be low-affinity receptor
• Enters cell by endocytosis
• Uncoated in endosome
• DNA enters nucleus and is maintained as episome
• Assembly – not yet fully understood – L1 forms capsomeres in cytoplasm then relocates to nucleus, where L2 is added
• Released from dead cells sloughed off epithelial surface – exact mechanism unknown – may be facilitated by E4

Question 7

In order to replicate viral ___1___, cells must be actively dividing.
In uninfected epithelium the cells differentiate and stop dividing as they move up through the stratified layers.
E6 & E7 push the cells into ___2___ phase (DNA synthesis) – allows viral replication – increases cell proliferation.
E6 & E7 are normally held in check by ___3___.

Answer 7

1. Genomes
2. S
3. E2

Question 8

Abnormal cells in a pap smear may be described as what?

Answer 8

Cervical intraepithelial neoplasia (CIN) 1-3.

Dysplasia – mild, moderate, severe – cells are abnormal but not cancerous (do not invade nearby healthy tissue)

Question 9

What is the Cervical transformation zone?

Answer 9

Where stratified epithelium of the ectocervix (vaginal side) meets the columnar epithelium of the endocervix (uterus side).

Question 10

What can the pap smear prevent?

Answer 10

Cervical cancer.

Question 11

HPV16 & HPV18 are strongly linked to what?

Answer 11

Cervical cancer.

Question 12

Patterns of HPV gene expression change as epithelial cells terminally _____.

Answer 12

Differentiate

Question 13

Oncogenic proteins E6 and E7 bind to ___1___ and ___2___ respectively (tumour supressors).

Answer 13

1. p53

2. Rb