Integrating the microbiome into the barrier theory of cancer

Abstract

Abstract The barrier theory of cancer integrates environmental, genetic, and infectious contributions to oncogenesis into a single framework. The full spectrum of symbiotic influences on oncogenesis, however, still needs to be brought into this framework, particularly for symbionts that are classified as commensals or mutualists. This paper contributes to this goal by presenting evidence that these symbionts may improve the effectiveness of immunological defenses against cancer and by drawing attention to the interactions between parasitic and mutualistic microbes in relation to oncogenesis. Although integration of protective symbionts with the barrier theory encompasses a variety of interactions, we highlight one particular aspect: effects of symbionts on the host’s ability to attack tumor cells through the relaxation of immune checkpoints.

Keywords

• cancer
• disease biology
• evolutionary medicine
• host–parasite interactions
• immune checkpoint
• microbiome