Autophagy and intratumoral bacteria abundance influencing the prognosis of patients with pancreatic carcinoma

The biological and clinical significance of the intratumoral microbiota in pancreatic ductal adenocarcinoma (PDAC) remains poorly defined. Using oncogenic Kras-driven mouse models of pancreatic tumorigenesis and human pancreatic tissue from patients with non-metastatic PDAC treated with neoadjuvant (n = 62) or adjuvant therapy (n = 101), along with samples from intraductal papillary mucinous neoplasms (IPMN, n = 24), chronic pancreatitis (CP, n = 33), and healthy donors (n = 9), we determined tissue lipopolysaccharide (LPS), 16S rRNA sequencing, high-resolution quantitative multiplex immunofluorescence of autophagy markers (LAMP2, LC3B) and LPS, 16S rRNA fluorescence in situ hybridization (FISH) staining, and TLR4 signaling. In KrasCre mice, we identified significant bacterial accumulation in the pancreas, indicated by elevated LPS, increased FISH signals, enhanced TLR4 signaling, and activation of autophagy. Administration of exogenous LPS further amplified autophagy and TLR4 signaling, supporting a mechanistic link between microbial sensing and autophagy. In human tissue, both adjuvant and neoadjuvant PDAC samples showed significantly increased bacterial α- and β-diversity compared to controls, with similar enrichment in CP but not in IPMN, but with differed diversity patterns across the disease. Increased LPS levels along with elevated autophagy markers and abundant FISH-positive bacteria confirmed intratumoral colonization. Across four independent transcriptomic datasets PDAC samples showed elevated expression of bacterial-associated pathways (including TLR4) and autophagy-related genes. Clinically, higher autophagic activity of LAMP2_LC3B and increased densities of FISH-positive cells were independently associated with prolonged survival in both adjuvant and neoadjuvant or combined PDAC patients. Collectively, these findings link intratumoral microbial enrichment to enhanced autophagy/xenophagy and improved patient outcomes, suggesting that effective microbial handling within the tumor microenvironment favorably influences PDAC progression.