Microbiota in cancer development and treatment

Abstract

Purpose: Human microbiota comprises of a variety of organisms ranging from bacterial species to viruses, fungi, and protozoa which are present on the epidermal and mucosal barriers of the body. It plays a key role in health and survival of the host by regulation of the systemic functions. Its apparent functions in modulation of the host immune system, inducing carcinogenesis and regulation of the response to the cancer therapy through a variety of mechanisms such as bacterial dysbiosis, production of genotoxins, pathobionts, and disruption of the host metabolism are increasingly becoming evident.

Methods: Different electronic databases such as PubMed, Google Scholar, and Web of Science were searched for relevant literature which has been reviewed in this article.

Results: Characterization of the microbiome particularly gut microbiota, understanding of the host-microbiota interactions, and its potential for therapeutic exploitation are necessary for the development of novel anticancer therapeutic strategies with better efficacy and lowered off-target side effects.

Conclusion: In this review, the role of microbiota is explained in carcinogenesis, mechanisms of microbiota-mediated carcinogenesis, and role of gut microbiota in modulation of cancer therapy.

Keywords: Cancer therapy; Carcinogenesis; Gut microbiota; Microbiome.

Fig. 1

Microbiota and Carcinogenesis. Microbiota plays a key role in maintenance of host physiological functions as well as disease development through interference with the immune system. When disrupted, i.e., dysbiosis in microbiota, can lead to cancer development. Furthermore, several factors such as intake of antibiotics, defined transplant of microbiome, as well as lifestyle of the host modulates carcinogenesis and the response to cancer therapy

Fig. 2

Mechanism of modulation of carcinogenesis by microbiota. Translocation of microbiota across extraintestinal sites leads to induction of inflammatory responses that are activated through microorganism-associated molecular patterns (MAMPS) which subsequently activate TLRs leading to several on-site and off-site effects that promote carcinogenesis. Meanwhile, genotoxicity induced by the genotoxins and ROS produced by bacteria also lead to development of cancer. Microbiota also interferes with the metabolic activities of the host that can result in either suppression of carcinogenesis by SCFAs or promotion by cancer-inducers