Paper II
Question
Oncogenic viruses
Answer
Oncogenic viruses are viruses causally associated with the development of human malignancy, typically through mechanisms that disrupt normal host cell-cycle control, tumour suppressor function, or DNA repair, or through chronic inflammation-driven carcinogenesis.
Important examples and associated malignancies:
- Human Papillomavirus (HPV), high-risk types (16, 18, etc.) — cervical carcinoma (and other anogenital and oropharyngeal cancers); oncoproteins E6 (inactivates p53) and E7 (inactivates Rb) drive malignant transformation.
- Hepatitis B virus (HBV) and Hepatitis C virus (HCV) — hepatocellular carcinoma, via chronic inflammation/cirrhosis and, for HBV, also direct viral genome integration into host DNA.
- Epstein-Barr virus (EBV) — Burkitt lymphoma (endemic African form, associated with c-myc translocation), nasopharyngeal carcinoma, certain Hodgkin lymphomas, and post-transplant lymphoproliferative disease in immunosuppressed patients.
- Human T-cell Lymphotropic Virus type 1 (HTLV-1) — Adult T-cell Leukaemia/Lymphoma (ATLL).
- Human Herpesvirus 8 (HHV-8/KSHV) — Kaposi’s sarcoma, particularly in AIDS patients.
- Merkel cell polyomavirus — Merkel cell carcinoma (a rare skin cancer).
Clinical/public health significance: recognition of these associations underlies major cancer-prevention strategies — HPV vaccination for cervical cancer prevention, HBV vaccination for hepatocellular carcinoma prevention, and screening/antiviral treatment of chronic HBV/HCV infection to reduce long-term cancer risk.