Fecal Bacteria Act as Novel Biomarkers for Noninvasive Diagnosis of Colorectal Cancer

Abstract

<b>Purpose:</b> Gut microbiota have been implicated in the development of colorectal cancer. We evaluated the utility of fecal bacterial marker candidates identified by our metagenome sequencing analysis for colorectal cancer diagnosis.<b>Experimental Design:</b> Subjects (total 439; 203 colorectal cancer and 236 healthy subjects) from two independent Asian cohorts were included. Probe-based duplex quantitative PCR (qPCR) assays were established for the quantification of bacterial marker candidates.<b>Results:</b> Candidates identified by metagenome sequencing, including <i>Fusobacterium nucleatum</i> (<i>Fn</i>), <i>Bacteroides clarus</i> (<i>Bc</i>), <i>Roseburia intestinalis</i> (<i>Ri</i>), <i>Clostridium hathewayi</i> (<i>Ch</i>), and one undefined species (labeled as <i>m7</i>), were examined in fecal samples of 203 colorectal cancer patients and 236 healthy controls by duplex-qPCR. Strong positive correlations were demonstrated between the quantification of each candidate by our qPCR assays and metagenomics approach (<i>r</i> = 0.801-0.934, all <i>P</i> < 0.0001). <i>Fn</i> was significantly more abundant in colorectal cancer than controls (<i>P</i> < 0.0001), with AUROC of 0.868 (<i>P</i> < 0.0001). At the best cut-off value maximizing sum of sensitivity and specificity, <i>Fn</i> discriminated colorectal cancer from controls with a sensitivity of 77.7%, and specificity of 79.5% in cohort I. A simple linear combination of four bacteria (<i>Fn</i> + <i>Ch</i> + <i>m7</i>-<i>Bc</i>) showed an improved diagnostic ability compared with <i>Fn</i> alone (AUROC = 0.886, <i>P</i> < 0.0001) in cohort I. These findings were further confirmed in an independent cohort II. In particular, improved diagnostic performances of <i>Fn</i> alone (sensitivity 92.8%, specificity 79.8%) and four bacteria (sensitivity 92.8%, specificity 81.5%) were achieved in combination with fecal immunochemical testing for the detection of colorectal cancer.<b>Conclusions:</b> Stool-based colorectal cancer-associated bacteria can serve as novel noninvasive diagnostic biomarkers for colorectal cancer. <i>Clin Cancer Res; 23(8); 2061-70. ©2016 AACR</i>.