Pks‐positive Escherichia coli in tumor tissue and surrounding normal mucosal tissue of colorectal cancer patients

Abstract A significant association exists between the gut microbiome and colorectal carcinogenesis, as well as cancer progression. It has been reported that Escherichia coli ( E. coli ) containing polyketide synthetase ( pks ) island contribute to colorectal carcinogenesis by producing colibactin, a polyketide‐peptide genotoxin. However, the functions of pks + E. coli in initiation, proliferation, and metastasis of colorectal cancer (CRC) remain unclear. We investigated the clinical significance of pks + E. coli to clarify its functions in CRC. This study included 413 patients with CRC. Pks + E. coli of tumor tissue and normal mucosal tissue were quantified using droplet digital PCR. Pks + E. coli was more abundant in Stages 0–I tumor tissue than in normal mucosal tissue or in Stages II–IV tumor tissue. High abundance of pks + E. coli in tumor tissue was significantly associated with shallower tumor depth (hazard ratio [HR] = 5.0, 95% confidence interval [CI] = 2.3–11.3, p < 0.001) and absence of lymph node metastasis (HR = 3.0, 95% CI = 1.8–5.1, p < 0.001) in multivariable logistic analyses. Pks + E. coli ‐low and ‐negative groups were significantly associated with shorter CRC‐specific survival (HR = 6.4, 95% CI = 1.7–25.6, p = 0.005) and shorter relapse‐free survival (HR = 3.1, 95% CI = 1.3–7.3, p = 0.01) compared to the pks + E. coli ‐high group. Pks + E. coli was abundant in Stages 0–I CRC and associated with CRC prognosis. These results suggest that pks + E. coli might contribute to carcinogenesis of CRC but might not be associated with tumor progression.