Molecular and pathology features of colorectal tumors and patient outcomes are associated with Fusobacterium nucleatum and its subspecies animalis.

Background: Fusobacterium nucleatum activates oncogenic signaling pathways and induces inflammation to promote colorectal carcinogenesis. Methods: We characterized F nucleatum and its subspecies in colorectal tumors and examined associations with tumor characteristics and colorectal cancer (CRC) specific survival. We conducted deep sequencing of nusA, nusG, and bacterial 16s rRNA genes in tumors from 1,994 CRC patients and assessed associations between F nucleatum presence and clinical characteristics, CRC-specific mortality, and somatic mutations. Results: F nucleatum, which was present in 10.3% of tumors, was detected in a higher proportion of right-sided and advanced-stage tumors-particularly subspecies animalis. Presence of F nucleatum was associated with higher CRC-specific mortality (hazard ratio [HR], 1.97; P=0.0004). This association was restricted to non-hypermutated, microsatellite-stable tumors (HR, 2.13; P=0.0002) and those who received chemotherapy (HR = 1.92, CI: 1.07-3.45, p-value = 0.029). Only F nucleatum subspecies animalis, the main subspecies detected (65.8%), was associated with CRC-specific mortality (HR, 2.16; P=0.0016)-subspecies vincentii and nucleatum were not (HR, 1.07, P=0.86). Additional adjustment for tumor stage suggests that the effect of F nucleatum on mortality is partly driven by a stage shift. Presence of F nucleatum was associated with microsatellite instable tumors, tumors with POLE exonuclease domain mutations, ERBB3 mutations, and suggestively associated with TP53 mutations. Conclusions: F nucleatum, and particularly subspecies animalis, was associated with a higher CRC-specific mortality and specific somatic mutated genes. Impact: Our findings identify the F nucleatum subspecies animalis as negatively impacting CRC mortality which may occur through a stage shift and its effect on chemoresistance.