From promotion to management: the wide impact of bacteria on cancer and its treatment.

In humans, the intestine is the major reservoir of microbes. Although the intestinal microbial community exists in a state of homeostasis called eubiosis, environmental and genetics factors can lead to microbial perturbation or dysbiosis, a state associated with various pathologies including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Dysbiotic microbiota is thought to contribute to the initiation and progression of CRC. At the opposite end of the spectrum, two recently published studies in Science reveal that the microbiota is essential for chemotherapeutic drug efficacy, suggesting a beneficial microbial function in cancer management. The dichotomy between the beneficial and detrimental roles of the microbiota during cancer initiation, progression, and treatment emphasize the interwoven relationship between bacteria and cancer. Moreover, these findings suggest that the microbiota could be considered as a therapeutic target, not only at the level of cancer prevention, but also during management, i.e. by enhancing the efficacy of chemotherapeutics.