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

Abstract 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 alpha- and beta diversity compared with controls, while CP showed a similar enrichment pattern that IPMN lacks; the underlying microbial diversity differs fundamentally across these conditions. Increased LPS levels, along with elevated autophagy markers and abundant FISH-positive bacteria, support the presence of intratumoral bacteria. Across four independent transcriptomic datasets, PDAC samples showed elevated expression of bacteria-associated pathways (including TLR4) and autophagy-related genes. Clinically, higher autophagy-associated LAMP2-LC3B colocalization 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 increased autophagy-associated signaling and improved patient outcomes, suggesting that microbial signals within the tumor microenvironment were associated with favorable survival.