Theme 2: Intestinal microbiome and clinical efficacy of antitumoral drugs and radiotherapies. Despite an extensive research on the interplay between chronic inflammation and development of cancer, it is now a prerequisite to understand how alterations in the microbiome that are commonly found within and outside the tumor may profoundly affect responsivness to antitumoral drugs and radiotherapies. In this context, Dr LF. Poulin aims at understanding how sensing of microorganisms by phagocytes may regulate tumor immune surveillance with a specific interest on the myeloid commitment shift. Understanding this paradigm is of importance because the plasticity of the tumor microenvironment influences therapeutic resistance. To this end, our highly interdisciplinary research program is funded by the National “Plan Cancer 2014-2019” and benefits from a continued fruitful collaborative research approach gathering complementary inputs on biostatistics, metagenomics and oncology. Ultimately, we anticipate the improvement of decision-making for therapy through the identification of easy-to-use biomarkers from the gut microbiota at all stages of intestinal tumorigenesis.