Peptostreptococcus stomatis promotes colonic tumorigenesis and receptor tyrosine kinase inhibitor resistance by activating ERBB2-MAPK

Peptostreptococcus stomatis ( P. stomatis ) is enriched in colorectal cancer (CRC), but its causality and translational implications in CRC are unknown. Here, we show that P. stomatis accelerates colonic tumorigenesis in Apc Min/+ and azoxymethane/dextran sodium sulfate (AOM-DSS) models by inducing cell proliferation, suppressing apoptosis, and impairing gut barrier function. P. stomatis adheres to CRC cells through its surface protein fructose-1,6-bisphosphate aldolase (FBA) that binds to the integrin α6/β4 receptor on CRC cells, leading to the activation of ERBB2 and the downstream MEK-ERK-p90 cascade. Blockade of the FBA-integrin α6/β4 abolishes ERBB2-mitogen-activated protein kinase (MAPK) activation and the protumorigenic effect of P. stomatis . P. stomatis -driven ERBB2 activation bypasses receptor tyrosine kinase (RTK) blockade by EGFR inhibitors (cetuximab, erlotinib), leading to drug resistance in xenograft and spontaneous CRC models of KRAS-wild-type CRC. P. stomatis also abrogates BRAF inhibitor (vemurafenib) efficacy in BRAF V600E -mutant CRC xenografts. Thus, we identify P. stomatis as an oncogenic bacterium and a contributory factor for non-responsiveness to RTK inhibitors in CRC.