STAT3 and neoplasm: On the other hand, metformin treatment-associated AMPK independent anti-cancer/anti-tumor/anti-proliferative and pro-apoptotic effects reportedly involve the inhibition the complex 1 of the mitochondrial electron transport chain (ETC) and/or Rag GTPases and/or signal transducer and activator of transcription-3 (STAT3) and activation of regulated DNA damage-1 (REDD1; also known as DNA damage-inducible transcript-4-DDIT4) (Figure 2) [51].