IGF1 and hepatocellular carcinoma: To explore whether IGF-1R is involved in inducing the resistance of HCC cells to sorafenib, SK-Hep1 and HepG2 cells were treated with single-drug sorafenib (4 μM), IGF-1 (100 ng/ml) + sorafenib (4 μM), IGF-1 (100 ng/ml) + sorafenib (4 μM) + PPP (100 nM) and IGF-1 (100 ng/ml) + sorafenib (4 μM) + siRNA2 (IGF-1R) for 24 h, respectively.