STAT3 and cancer: Nevertheless, the overlapping downstream signaling of leptin and IL-6 (such as Stat3 and mTOR/eIF4E), as well as our findings that hepatic leptin signaling can partially compensate for IL-6Rα deficiency in HCC development, prompts further investigation of intracellular signaling cascades the therapeutic inhibition of which might help to prevent cancer deaths of millions of affected people per year.