• Department of Pathology, New York University School of Medicine, 560 First Avenue, New York, NY 10016, USA.
• Department of Pathology, New York University School of Medicine, 560 First Avenue, New York, NY 10016, USA; Department of Medicine, New York University School of Medicine, 560 First Avenue, New York, NY 10016, USA; Department of Veterans Affairs New York Harbor Healthcare System, 423 East 23rd Street, Room 6030W, New York, NY 10010, USA. Electronic address: zhiheng.pei@med.nyu.edu.

The cause of colorectal cancer (CRC) is multifactorial, with genetic, molecular, inflammatory, and environmental risk factors. Recently, the gut microbiota has been recognized as a new environmental contributor to CRC in both animal models and human studies. An additional interplay of the gut microbiome with inflammation is also evident in studies that have shown that inflammation alone or the presence of bacteria/bacterial metabolites alone is not enough to promote tumorigenesis. Rather, complex interrelationships with the gut microbiome, inflammation, genetics, and other environmental factors are evident in progression of colorectal tumors.