IGF1R and hepatocellular carcinoma: Compared with single-drug sorafenib, IGF-1 + sorafenib treatment reduced the decrease of mitochondrial potential induced by sorafenib in HCC cells; however, the mitochondrial potential of HCC cells was significantly decreased in treatments in which binding of PPP inhibited the activation of IGF-1R or binding of siRNA2 interfered with the expression of IGF-1R independent of IGF-1 (Fig. 4 A).