Intestinal microbiota enhances pancreatic carcinogenesis in preclinical models

Area of Science:

• Oncology
• Microbiology
• Gastroenterology

Background:

• Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death with limited understanding of host factors influencing its development.
• The role of the host microbiota in carcinogenesis is increasingly recognized, but its specific involvement in PDAC remains unclear.

Purpose of the Study:

• To investigate the influence of the host microbiota on pancreatic carcinogenesis and PDAC progression.
• To determine if intrapancreatic bacteria are present in PDAC and if their composition correlates with the disease.

Main Methods:

• Antibiotic-mediated microbial depletion in KrasG12D/PTENlox/+ mice models of PDAC.
• 16S rRNA PCR and sequencing to detect and analyze bacterial presence in murine and human pancreatic tissues.
• Xenograft studies in Nod-SCID mice comparing microbiota-intact and depleted conditions.
• Immunohistochemistry and RNA sequencing to assess immune suppression and oncogenic pathway regulation.

Main Results:

• Microbial depletion in mice led to a decreased proportion of poorly differentiated PDAC tumors.
• Approximately 50% of PDAC-bearing mice harbored intrapancreatic bacteria, also detected in human pancreatic specimens, but composition did not differentiate PDAC from non-PDAC tissue.
• Microbial depletion in xenograft models increased time to tumor formation, reduced tumor size, and attenuated growth, independent of intratumoral bacteria.
• Microbiota-intact xenografts exhibited innate immune suppression and differential regulation of oncogenic pathways.

Conclusions:

• The intestinal microbiota plays a significant role in PDAC progression, potentially through long-distance mechanisms.
• Intrapancreatic bacteria are present in PDAC but may not be the sole drivers of tumor acceleration.
• Findings open new research avenues into the gut-pancreas axis in pancreatic carcinogenesis.