Gut Microbiota and Host Immune System in Cancer

The mammalian gut is inhabited by more than 100 billion symbiotic microorganisms. The microbial colony residing in the host is recognised as microbiota. One of the critical functions of microbiota is to prevent the intestine against exogenous and harmful pathogen colonization mediated by various mechanistic pathways involving direct competition for limited nutrients and regulation of host immunity. Cancer accounts for one of the leading causes of mortality arising from multifactorial abnormalities. The interconnection of microbiota with various pathological conditions including cancer is recently being researched extensively for analysing tumor induction, progression, inhibition and diagnosis. The diversified microbial colony inhabiting the human gut possesses a vast and distinct metabolic repertoire complementary to the mammalian enzyme activity in the liver as well as gut mucosa which facilitates processes essential for host digestion. Gut microbiota is often considered the critical contributor to defining the biochemical profile of diet thus impacting the health and disease of the hosts. This chapter mainly focuses on understanding the complex microbial interaction with cancer either negatively or positively which may help to conceive novel precautionary and therapeutic strategies to fight cancer.