Clinical Studies Fusobacterium in Colonic Flora and Molecular Features of Colorectal Carcinoma

Fusobacterium species are part of the gut microbiome in humans. Recent studies have identified overrepresentation of Fusobacterium in colorectal cancer tissues, but it is not yet clear whether this is pathogenic or simply an epiphenomenon. In this study, we evaluated the relationship between Fusobacterium status and molecular features in colorectal cancers through quantitative real-time PCR in 149 colorectal cancer tissues, 89 adjacent normal appearing mucosae and 72 colonic mucosae from cancer-free individuals. Results were correlated with CpG island methylator phenotype (CIMP) status, microsatellite instability (MSI), and mutations in BRAF, KRAS, TP53,CHD7, andCHD8. Whole-exome capture sequencing datawere also available in 11 cases. Fusobacteriumwas detectable in 111 of 149 (74%) colorectal cancer tissues and heavily enriched in 9% (14/149) of the cases. As expected, Fusobacterium was also detected in normal appearing mucosae from both cancer and cancer-free individuals, but the amount of bacteria was much lower compared with colorectal cancer tissues (a mean of 250fold lower for Pan-fusobacterium). We found the Fusobacterium-high colorectal cancer group (FB-high) to be associatedwithCIMPpositivity (P1⁄4 0.001),TP53wild-type (P1⁄4 0.015),hMLH1methylation positivity (P1⁄4 0.0028), MSI (P1⁄4 0.018), and CHD7/8mutation positivity (P1⁄4 0.002). Among the 11 cases where whole-exome sequencing datawere available, two thatwere FB-high cases also had the highest number of somaticmutations (amean of 736 per case in FB-high vs. 225 per case in all others). Taken together, our findings show that Fusobacterium enrichment is associated with specific molecular subsets of colorectal cancers, offering support for a pathogenic role in colorectal cancer for this gut microbiome component. Cancer Res; 74(5); 1311–8. 2014 AACR. Introduction The non–spore-forming, anaerobic Gram-negative bacterium Fusobacterium is part of the normal flora in the human mouth and gut mucosa. Fusobacterium species are highly heterogeneous and some species have been recognized as opportunistic pathogens implicated in inflammatory diseases of both the mouth, such as periodontitis, and the gut, such as appendicitis and inflammatory bowel diseases (IBD; refs. 1–5). Two recent studies have linked Fusobacterium species with colorectal cancer. These studies demonstrated that Fusobacterium nucleatum (F. nucleatum) and whole Fusobacterium species (Pan-fusobacterium) were abundant in colorectal cancer tissues compared with adjacent normal mucosa (6, 7). Several infectious bacteria and viruses were previously associatedwith neoplasia such as humanpapillomavirus in cervical cancer (8), Kaposi sarcoma-associated herpes virus in Kaposi sarcoma (9), and Epstein–Barr (EBV) virus in lymphomas and gastric cancer (10). Fusobacterium in colorectal cancer provided a novel concept, in that a part of the normal intestinal microflora may be relevant to tumorigenesis. However, the previous studies could not exclude the possibility that the presence of Fusobacterium in colorectal cancer is an epiphenomenon related to local changes triggered by the neoplastic process. Colorectal cancers are characterized by specific genetic and epigenetic lesions. Besides common mutations in TP53, KRAS, and APC genes (11, 12), epigenetic alterations in colorectal cancers are frequent, particularly gene promoter DNA methylation. Classification of colorectal cancers according to mutation and DNA methylation status has identified distinct subtypes based on the CpG island methylator phenotype (CIMP; ref. 13). Typical high-level CIMP (CIMP-high, CIMP1) colorectal cancers are associated with microsatellite instability (MSI) Authors' Affiliations: Fels Institute for Cancer Research & Molecular Biology, Temple University School of Medicine, Philadelphia, Pennsylvania; Department of Gastroenterology, Fujita Health University School of Medicine, Toyoake; First Departments of InternalMedicine and Molecular Biology, Sapporo Medical University, Sapporo; Department of Gastroenterology, Akita Red Cross Hospital, Akita; Department of Pathology, Iwate Medical University,Morioka; Division ofMolecular Oncology, AichiCancer Center Research Institute, Nagoya, Japan; Division ofOVP, Department of Clinical Cancer Prevention, Cancer Prevention and Population Sciences; Center for Cancer Epigenetics, The University of Texas MD Anderson Cancer Center, Houston; and Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, Texas Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Corresponding Author: Tomomitsu Tahara, Temple University School of Medicine, 3307 N, Broad Street, Room 154 PAHB, Philadelphia, PA 19140. Phone: 215-707-4300; Fax: 215-707-1454; E-mail: [email protected] doi: 10.1158/0008-5472.CAN-13-1865 2014 American Association for Cancer Research. Cancer Research www.aacrjournals.org 1311 on July 15, 2017. © 2014 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from Published OnlineFirst January 2, 2014; DOI: 10.1158/0008-5472.CAN-13-1865