Viruses and cancer Flashcards
What fraction of all cancers worldwide is caused by viruses?
1/4 of all cancers worldwide are caused by viruses.
What is one method of investigating viruses in cancer?
Epidemiology: Look for geographical differences in populations and for overlap between viruses and cancers.
Example: Bile duct cancer in South East Asia.
What does the presence of virus in tumour tissue indicate?
Look for virus proteins/particles/DNA/RNA in tumour. Not necessarily causative.
What is a method to study mechanisms of viral oncogenesis?
Find plausible mechanistic ways in which virus would cause tumour using animal models.
Example: Inject virus into animal models.
What is the role of E6 protein in HPV?
E6 binds to p53, stopping it from causing cell cycle arrest and skipping DNA repair steps, increasing the risk of developing tumour cells.
What type of cancer does Papillomavirus cause?
Papillomavirus causes 100% of cervical cancer.
What percentage of head and neck cancers are caused by HPV?
HPV causes 50% of head and neck cancers.
What virus causes Kaposi’s sarcoma?
Kaposi’s sarcoma is caused by HHV-8, not HIV.
What is a common mechanism of viral oncogenesis?
Dysregulation of the cell cycle to turn the cell into a viral replication factory.
How do viruses induce host genome instability?
Viruses make host cells replicate too much, leading to other mutations and tumorigenesis.
What is the role of p53 in the cell?
p53 is the guardian of the genome, causing cell cycle arrest to fix DNA damage and inducing cell death.
How do viral proteins affect p53?
Viruses often have proteins that stop or inhibit p53, such as HPV E6.
What disease is associated with EBV?
EBV is associated with glandular fever/infectious mononucleosis and B cell lymphoma.
What chromosomal translocation is induced by EBV?
EBV induces chromosomal translocation involving chromosome 14 (gene IgH) and chromosome 8 (Myc).
What is the link between Hepatitis B and cancer?
Chronic Hepatitis B infection increases the risk of hepatocellular carcinoma (HCC) by 100 times.
What is the role of HBV X protein (HBx)?
HBx binds to p53, sequestering it into an inactive complex, preventing it from functioning.
What does SV40 polyomavirus do?
SV40 polyomavirus produces Large T protein, which binds and sequesters p53 and Rb, allowing cell cycle progression.
What is Merkel cell polyomavirus (MCV)?
MCV is a dsDNA virus that infects Merkel cells and is responsible for 100% of Merkel cell carcinomas.
What are the high-risk types of Papillomavirus?
High-risk types include HPV 16, 18, and 31.
What is the purpose of L1 proteins in HPV?
L1 proteins form virus-like particles (VLPs) that can be used to make vaccines.
What is Gardasil 9?
Gardasil 9 is a vaccine made from VLPs of HPV types 6, 11, 18, 31, 45, 52, and 58.
What happens to HPV DNA in cervical cancer cells?
In cervical cancer cells, viral DNA is integrated into the host genome in 85% of cases.
What is the effect of inactivating E6 and E7 in HPV-infected cells?
Inactivating E6 and E7 can revert cancer cells back to normal cells, providing proof that the virus is involved in cancer development.
What does HPV E6 do to p53?
HPV E6 causes proteolytic degradation of p53 using E6AP.
What is the function of HPV E7?
HPV E7 binds Rb, targeting it for degradation, which leads to cell cycle progression.
