Infection and cancer: Multi-directorial relationship

Abstract

The World Health Organization estimates more than two million cancer cases per year (more than 20 % of the global cancer burden) are attributable to chronic infections, making them the second most preventable cause of cancer. It appears that persistent infections are the leading causes for some of the most important human cancers, such as stomach cancer, cervical cancer and liver cancer. However, fundamental principles regulating the effector functions of immune cells in the tumor environment during systemic infections and host and microbial molecules and pathways that can be targeted for treatment or prevention of cancer progression are not yet well characterized. Identifying these pathways can affect health across populations, creating opportunities to reduce the impact of cancer by preventing or treating infection. The fact that certain chronic infections lie at the root of 20 % of human cancers is expected to render their primary prevention more practicable. On the other side, immunosuppression associated with tumor progression, as well as cancer therapy, predisposes cancer patients to the development of either new infections or reactivations of latent infections. This chapter briefl y introduces four main parts of the book and stresses the importance of recognition of different aspects of interactions between infectious agents and neoplastic processes. Specifi cally, part one provides an overview on the role of chronic infection in cancer development, i.e., infection-associated cancers. Part two focuses on infection diseases induced by cancer treatment, i.e., cancer-associated infections. Part three opens the opportunity to understand the interaction between immune reactions associated with independent development of infection in tumor-bearing hosts, i.e., omorbid development of cancer and infection. And part four discusses viral and bacterial based approaches to cancer therapy.