INS and pancreatic neoplasm: Metformin antitumour mechanism is still being speculated, but possible explanations involve AMPK activation with downregulation of specificity protein (Sp) transcription factors [7] and inhibition of the insulin/insulin-like growth factor-I (IGF-I) receptor activation [8], In vitro experiments using human pancreatic cancer cells showed that metformin abolished signalling normally induced by insulin through G protein-coupled receptor [9].