Metformin suppresses pancreatic tumor growth with inhibition of NFκB/STAT3 inflammatory signaling

Objectives To further elucidate the anticancer mechanisms of metformin against pancreatic cancer, we evaluated the inhibitory effects of metformin on pancreatic tumorigenesis in a genetically engineered mouse model and investigated its possible anti-inflammatory and antiangiogenesis effects. Methods Six-week-old LSL-Kras G12D/+;Trp53 F2-10 mice (10 per group) were administered once daily intraperitoneally with saline (control) for 1 week or metformin (125 mg/kg) for 1 week (Met-1wk) or 3 weeks (Met-3wk) before tumor initiation. All mice continued with their respective injections for 6 weeks after tumor initiation. Molecular changes were evaluated through quantitative polymerase chain reaction, immunohistochemistry, and Western blotting. Results At euthanasia, pancreatic tumor volume in the Met-1wk (median, 181.8 mm 3) and Met-3wk (median, 137.9 mm 3) groups was significantly lower than those in the control group (median, 481.1 mm 3; P = 0.001 and 0.0009, respectively). No significant difference was observed between the Met-1wk and Met-3wk groups (P = 0.51). These results were further confirmed using tumor weight and tumor burden measurements. Furthermore, metformin treatment decreased the phosphorylation of nuclear factor κB and signal transducer and activator of transcription 3 as well as the expression of specificity protein 1 transcription factor and several nuclear factor κB-regulated genes. Conclusions Metformin may inhibit pancreatic tumorigenesis by modulating multiple molecular targets in inflammatory pathways.