Mucus-invasive bacterial biofilms are identified on the colon mucosa of approximately 50% of colorectal cancer (CRC) patients and approximately 13% of healthy subjects. Here, we test the hypothesis that human colon biofilms comprise microbial communities that are carcinogenic in CRC mouse models. Homogenates of human biofilm-positive colon mucosa were prepared from tumor patients (tumor and paired normal tissues from surgical resections) or biofilm-positive biopsies from healthy individuals undergoing screening colonoscopy; homogenates of biofilm-negative colon biopsies from healthy individuals undergoing screening colonoscopy served as controls. After 12 weeks, biofilm-positive, but not biofilm-negative, human colon mucosal homogenates induced colon tumor formation in 3 mouse colon tumor models (germ-free ApcMinΔ850/+;Il10–/– or ApcMinΔ850/+ and specific pathogen–free ApcMinΔ716/+ mice). Remarkably, biofilm-positive communities from healthy colonoscopy biopsies induced colon inflammation and tumors similarly to biofilm-positive tumor tissues. By 1 week, biofilm-positive human tumor homogenates, but not healthy biopsies, displayed consistent bacterial mucus invasion and biofilm formation in mouse colons. 16S rRNA gene sequencing and RNA-Seq analyses identified compositional and functional microbiota differences between mice colonized with biofilm-positive and biofilm-negative communities. These results suggest human colon mucosal biofilms, whether from tumor hosts or healthy individuals undergoing screening colonoscopy, are carcinogenic in murine models of CRC.
Sarah Tomkovich, Christine M. Dejea, Kathryn Winglee, Julia L. Drewes, Liam Chung, Franck Housseau, Jillian L. Pope, Josee Gauthier, Xiaolun Sun, Marcus Mühlbauer, Xiuli Liu, Payam Fathi, Robert A. Anders, Sepideh Besharati, Ernesto Perez-Chanona, Ye Yang, Hua Ding, Xinqun Wu, Shaoguang Wu, James R. White, Raad Z. Gharaibeh, Anthony A. Fodor, Hao Wang, Drew M. Pardoll, Christian Jobin, Cynthia L. Sears