Infections and cancer: the “fifty shades of immunity” hypothesis

BMC Cancer

Table 1 Principal oncogenic agents and their participation to associated cancers

Oncogenic agents	Associated cancer	Contribution	Transmission	Prevention or elimination methods	Carcinogens classification	Ref
Macro-Parasites						[90, 91]
Schistosoma haematobium	Bladder cancer	30%	Water	Anti-helminthics
					Indirect
Opisthorchis viverrini and Clonorchis sinensis	Cholangioma liver cancer	15%	Food	Anti-helminthics
Bacteria
Helicobacter pylori	Stomach cancer	80%	Water, sanitation, food, saliva	Antibiotics, sanitation	Indirect	[92, 93]
Viruses						[92, 94, 95]
Epstein Barr Virus	Burkitt’s lymphoma, nasoparyngeal cancer	10–30%	Saliva	Antivirals for some illnesses
Hepatitis B and C	Liver cancer	80%	needles, sex	Vaccination (HBV), antivirals, blood screening
Human T lymphotropic virus	Adult T cell leukaemia	Almost 100%	Sex, needle, milk	No treatment	Direct and indirect
Human Papillomavirus	Cervical cancer	100%	Sex, saliva	Vaccination, pap smear
Human Herpesvirus 8	Kaposi sarcoma	Almost 100%	Sex, saliva	No treatment
Merkel cell polyomavirus	Merkel cell cancer	Almost 100%	Saliva	No treatment

Today, the World Health Organization acknowledges that at least 20% of cancers have an infectious origin [96]. For transmission section, “needles” includes blood transfusion, contaminated medical syringes and illicit intravenous drug use. A classification of oncogenic organisms has been proposed on the basis of their contribution to carcinogenesis [1]. When infection leads to introduction of viral oncogenes into the host genome, pathogens are considered to be direct carcinogens. These pathogens exploit the host in ways that interfere with mechanisms of cancer prevention (cell cycle arrest, apoptosis, restriction of telomerase and cell adhesion). Infectious organisms that induce immunosuppression, chronic inflammation and/or chromosomal instability, are referred to as indirect carcinogens as they may drive mutations and promote cancer cell proliferation

ISSN: 1471-2407