Survival mechanism of pancreatic tumor bacteria and their ability to metabolize chemotherapy drugs.

Pancreatic cancer (PC) remains one of the most lethal malignancies, with limited treatment efficacy. While surgical resection is the most effective option, chemotherapy with agents such as 5-fluorouracil (5-FU) and gemcitabine may improve survival. Intraductal papillary mucinous neoplasms (IPMNs) are pancreatic cystic tumors and important precursor lesions frequently detected during PC screening. Emerging evidence suggests that IPMNs can harbor a distinct tumor microbiome, but the microbial persistence and potential influence on cancer treatment remain poorly understood. In this study, we analyzed bacterial isolates from clinical IPMN samples and investigated their interactions with chemotherapeutic agents using functional assays and whole-genome sequencing (WGS). We found that most isolates reduced the cytotoxic effect of 5-FU and gemcitabine on pancreatic cancer cell lines (PANC-1, AsPC-1, and Capan-2). WGS revealed that the Gammaproteobacteria strains were enriched in genes associated with antibiotic resistance, drug transport, and virulence compared to the Bacilli strains. Further pathway analysis showed that Gammaproteobacteriawere enriched in pyrimidine metabolism pathways, while Bacilli were enriched in purine metabolism. These findings indicate that IPMN-associated bacteria are metabolically active and capable of modulating chemotherapy drug efficacy. Together, our findings suggest that the microbial adaptation mechanisms supporting bacterial survival within tumor lesions also enable them to interact with pyrimidine analogs. This underscores the importance of elucidating the functional roles of tumor-associated microbiota in modulating the tumor microenvironment and treatment efficacy. IMPORTANCE: Chemotherapy is a primary treatment for pancreatic cancer, and emerging evidence indicates that the gut microbiota can modulate its efficacy. While most studies have focused on gut-residing microbes, characterization of intra-tumoral microbes within the pancreas remains limited. Here, we report new insights into metabolic interactions between chemotherapeutic agents and patient-derived pancreatic tumor bacteria. These bacteria were isolated from intraductal papillary mucinous neoplasms (IPMNs), the main precursors to pancreatic cancer. Our findings demonstrate that patient-derived pancreatic tumor bacteria tolerate two commonly used chemotherapeutic drugs, 5-fluorouracil (5-FU) and gemcitabine, and can attenuate their cytotoxic effects on pancreatic cancer cells. Through whole-genome and transcriptomic analyses, we further reveal potential adaptation mechanisms that could enable these bacteria to persist in the tumor microenvironment and metabolize chemotherapeutics.