Viruses and Cancer

Question 1

Why do viruses cause cancer?

Answer 1

• They disrupt normal cell control
• They damage DNA
• They interfere with the immune system’s tumour surveillance

Question 2

What are the main viruses that cause cancer?

Answer 2

• Human Papillomavirus
• HBV
• HCV
• EBV
• Kaposi’s sarcoma herpesvirus
• Human T-lymphotropic Virus type 1

Question 3

What cancer do hepatitis viruses cause?

Answer 3

Hepatocellular carcinoma

Question 4

What percentage of human cancers are viruses responsible for?

Answer 4

Around 15% of cancers can be linked to viruses

Question 5

What is oncogenesis?

Answer 5

The process by which normal cells transform into cancerous cells

Question 6

What are p53 and Rb examples of?

Answer 6

Host cell cycle regulators

Question 7

What are oncoproteins?

Answer 7

Proteins produced by oncogenes, which are genes that can transform normal cells into cancerous cells

Question 8

What are the oncoproteins involved in direct transformation of host cells by EBV?

Answer 8

EBNA-2
EBNA-3
LMP1

Question 9

What is the target of EBV oncoproteins?

Answer 9

• Rb
• CD40
• Bcl-2

Question 10

What is the effect of EBV oncoproteins?

Answer 10

Promotes B cell proliferation.
Inhibits apoptosis

Question 11

What are the oncoproteins involved in direct transformation of host cells by HBV?

Answer 11

Hbx

Question 12

What is the target of HBV oncoproteins?

Answer 12

• p53
• c-src

Question 13

What is the effect of HBV oncoproteins?

Answer 13

Disrupts apoptosis and promotes proliferation

Question 14

What are the oncoproteins involved in direct transformation of host cells by HCV?

Answer 14

Core
NS3
NS4B
NS5A

Question 15

What the targets of HCV oncoproteins?

Answer 15

p53
p21

Question 16

What is the effect of HCV oncoproteins?

Answer 16

Induces inflammation and suppresses cell cycle regulation

Question 17

What are the oncoproteins involved in direct transformation of host cells by HPV?

Answer 17

E6 and E7

Question 18

What are the targets for HPV oncoproteins?

Answer 18

p53
Rb

Question 19

What is the effect of HPV oncoproteins?

Answer 19

Inhibits tumour suppressors

Question 20

What some indirect mechanisms of viral oncogenesis?

Answer 20

• Chronic inflammation
• Immune suppression
• Insertional mutagenesis

Question 21

How is chronic inflammation an indirect mechanism of oncogenesis?

Answer 21

Drives constant tissue repair → higher mutation risk (e.g. HCV)

Question 22

How is immune suppression an indirect mechanism of oncogenesis?

Answer 22

Allows oncogenic viruses like EBV to reactivate and transform cells

Question 23

How is insertional mutagenesis an indirect mechanism of oncogenesis?

Answer 23

Disrupts cellular genes and increases oncogene expression (e.g HPV)

Question 24

Sentence to memorise for oncoproteins of HPV

Answer 24

In HPV infection, the viral proteins E6 and E7 promote oncogenesis by inactivating tumour suppressors p53 and Rb, respectively.
This leads to impaired apoptosis and uncontrolled cell proliferation

Question 25

Sentence to memorise for oncoproteins of HCV

Answer 25

In HCV infection, the core protein binds and inhibits p53, while NS5A suppresses the expression of p21, a key cell cycle regulator. This creates a pro-oncgenic environment through disrupted cell cycle control and chronic inflammation

Question 26

What are some effective strategies for preventing viral cancers?

Answer 26

Vaccination Treatment Early diagnosis Lifestyle choices

Question 27

What is an example of a viral vaccine that is important in preventing which cancers?

Answer 27

- HPV vaccine protects against high cancer risk serotypes of HPV (-16 & -18) which are responsible for the majority of cervical cancer

Question 28

What is the prevention of HCV-related cancers?

Answer 28

- No vaccine - Direct-acting antivirals offer curative treatment with >95% efficacy

Question 29

How does treatment of HCV minimise cancer risk?

Answer 29

- Reduce chronic inflammation and liver damage - Lowering cancer risk