S2145 A Possible Microbiome Signature in Invasive Cancer

Introduction: Although a link between cancer and the gut microbiome has been proposed, these associations are poorly understood. In the present study, we sought to investigate the composition and relative abundance of the gut microbiome of patients with both invasive and localized cancer compared to those of healthy adults without a history of cancer. Methods: Stool samples from 72 participants, n = 19 adults without a history of cancer (controls), n = 37 adults with invasive cancer, and n = 16 adults with localized cancer were analyzed to compare the abundance of gut microbes. DNA was extracted, purified, quantitated, and normalized prior to library preparation utilizing shotgun methodology. Libraries were then indexed and sequenced on the NextSeq 550 platform using High-Output Kits V.2.5 for 300 cycles. T-tests were used to compare overall and between-group differences in the relative abundances of each highly prevalent bacterial genus. Results: When compared to control subjects, patients with aggressive cancer had significantly lower abundance of Bifidobacterium (P = 0.002), and Eubacterium (P = 0.027). Concurrently these patients also had elevated abundance of Bacteroides (P < 0.0001) and Parabacteroides (P = 0.037). When patients with localized cancer were compared to healthy controls, Bacteroides was also found to be significantly elevated (P = 0.008), and both Bifidobacterium (P = 0.036), and Eubacterium (P = 0.026) were found to be depleted. When patients with aggressive cancer were compared to patients with localized cancer, no significant differences were observed. Conclusion: Adults with a history of invasive cancer had a large gap between the levels of Bifidobacteria and Bacteroides. Aggressive cancers appear to have a higher gap than localized cancers, when compared to healthy control. Further, larger studies are needed to clearly elucidate how the relative abundance of specific genera may influence cancer pathogenesis and treatment response.