Metformin inhibits neutrophil extracellular traps-promoted pancreatic carcinogenesis in obese mice.

Obesity has been linked to a higher risk of pancreatic cancer. However, the mechanism by which obesity promote pancreatic carcinogenesis is still unclear. We investigated the effect of obesity on pancreatic carcinogenesis in Pdx1-Cre; LSL-KrasG12D+/- (KC) mice. Metformin was administrated to rescue the effects of obesity and NETs. The pro-tumorigenic effects of neutrophil extracellular traps (NETs) were further evaluated in vivo and vitro. We found that obesity significantly promoted the progression of murine pancreatic ductal intraepithelial neoplasia (mPanIN). The proliferation rate and epithelial-mesenchymal transition (EMT) of mPanIN ductal cells were increased in obese mice. More visceral adipocytes, PD-L1+ neutrophil infiltration and NETs formation were found in the pancreas of obese mice and visceral adipocytes could recruit neutrophils and promote NETs formation. The latter could induce an inflammatory response in ductal cells via TLR4-dependent pathways both in vivo and vitro, as demonstrated by upregulation of IL-1β. Metformin and DNase I significantly reversed the pro-tumorigenic effects of obesity and NETs in vivo and in vitro. Our study provides causal evidence for the contribution of obesity in promoting pancreatic carcinogenesis in genetic model and reveals the mechanism by NETs to regulate mPanIN progression.