Published in the revue PNAS on November 11, 2019, this manuscript reports a collaborative contribution by Prof. Philippe Sansonetti, Institut Pasteur Paris and now head of The Center for Microbes, Development and Health, Institut Pasteur Shanghai, and Prof. Iradj Sobhani, head Gastroenterology Department, Henri Mondor Hospital, France. The work takes a closer look at the environmental stressors expected to influence the occurrence of colorectal cancer, particularly changes in the composition of the gut microbiota (i.e. dysbiosis). 

Beyond the usual correlations observed in the patient cohorts studied here, the manuscript establishes a causality link by demonstrating that the dysbiotic gut microbiota of patients affected by colorectal cancer, when transplanted into germ-free mice, induce histological alterations that are characteristic of a precancerous state (i.e. aberrant intestinal crypts) and epigenetic signatures, particularly changes in DNA methylation in genes that are similarly affected in cancer patients. Moreover, these alterations can be linked to a restricted set of microbial species, thereby offering a simple biomarker that may accelerate and amplify the detection of individuals at risk of developing colorectal cancer.