Pathogens and Carcinogenesis: A Review

SIMPLE SUMMARY: An increasing number of cancer cases has been reported throughout the years. Most cancers are linked to unhealthy lifestyles and genetic inheritance. Nevertheless, unknown to many, infection from microorganisms (bacteria, viruses, fungi) and sometimes, parasites, can also lead to cancer development. For these cancers, the infection may inflict mechanical injury on host cells, whilst gene products or protein secretion from the microorganism further alters host cell activity, leading to abnormal cell development and growth. Due to the cancer-causing characteristic of these microorganisms, they have been classified as definite biological agents that cause cancer. This review describes the cancer development process caused by some of these microorganisms and highlights strategies to prevent or treat the associated cancers. ABSTRACT: Cancer is a global health problem associated with genetics and unhealthy lifestyles. Increasingly, pathogenic infections have also been identified as contributors to human cancer initiation and progression. Most pathogens (bacteria, viruses, fungi, and parasites) associated with human cancers are categorized as Group I human carcinogens by the International Agency for Research on Cancer, IARC. These pathogens cause carcinogenesis via three known mechanisms: persistent infection that cause inflammation and DNA damage, initiation of oncogene expression, and immunosuppression activity of the host. In this review, we discuss the carcinogenesis mechanism of ten pathogens, their implications, and some future considerations for better management of the disease. The pathogens and cancers described are Helicobacter pylori (gastric cancer), Epstein-Barr virus (gastric cancer and lymphoma), Hepatitis B and C viruses (liver cancer), Aspergillus spp. (liver cancer), Opisthorchis viverrine (bile duct cancer), Clonorchis sinensis (bile duct cancer), Fusobacterium nucleatum (colorectal cancer), Schistosoma haematobium (bladder cancer); Human Papillomavirus (cervical cancer), and Kaposi’s Sarcoma Herpes Virus (Kaposi’s sarcoma).