Fig. 6

Antitumor action of metformin. The drug could inhibit the tumor cell proliferation by various mechanisms; A by ceasing the insulin/insulin-like growth factor 1 (IGF-1) signaling pathway, B by blocking the activity of complex I of the oxidative phosphorylation, C by interrupting the Kreb’s cycle pathway through carboxylation of α-ketoglutarate, thus inhibiting the pathway for lipogenic citrate synthesis, D by enhancing apoptosis via targeting AMPK and mTOR pathways or via targeting STAT-3 pathway either directly or through AMPK. LKB-1 liver kinase B-1, AMP adenosine monophosphate