Viruses and cancer. Causal associations

Area of Science:

• Oncology
• Virology
• Epidemiology

Background:

• Viruses are implicated in a significant proportion of human cancers.
• Establishing definitive causal links between specific viruses and cancers is complex.
• Several viruses are considered candidate oncogenic agents in human carcinogenesis.

Purpose of the Study:

• To review general challenges in establishing virus-cancer causality.
• To assess the strength of evidence for causal associations between candidate oncogenic viruses and associated human cancers.
• To identify areas where evidence is strong, moderate, incomplete, or inconclusive.

Main Methods:

• Literature review and synthesis of existing evidence.
• Evaluation of established guidelines for determining viral carcinogenicity.
• Categorization of virus-cancer associations based on current scientific consensus.

Main Results:

• Strong causal links exist for Hepatitis B virus (HBV) and hepatocellular carcinoma, and Human T-cell Leukemia/Lymphoma Virus type 1 (HTLV-1) and adult T-cell leukemia/lymphoma.
• Epstein-Barr virus (EBV) shows a moderate causal association with African Burkitt's lymphoma.
• Associations for EBV with Hodgkin's disease and non-Hodgkin's lymphoma, and Hepatitis C virus (HCV) with hepatocellular carcinoma are incomplete or inconclusive.
• The role of Human Papilloma Viruses (HPVs) in cervical carcinoma requires further investigation with current techniques.

Conclusions:

• The strength of evidence varies significantly for different virus-cancer associations.
• HBV and HTLV-1 represent clear examples of viral oncogenesis.
• Further research is needed to clarify the roles of EBV, HCV, and HPV in specific human cancers.