Combination of sorafenib and YC-1 induced S cell cycle arrest and apoptosis of HCC cells. HepG2 cells were treated with combination of sorafenib (5 μmol/L) and YC-1 (10 μmol/L) or either drug for 48 h. A, Cell cycle was assayed by PI/RNAse staining. B, The treated cells were assayed for apoptosis by annexin V/PI staining. C, Apoptosis in situ was assessed by Hoechst 33258 staining. D, Cell extracts were subjected to western blot analysis and expression of PARP, cleaved PARP, capase 9, capsase 8 and cleaved caspase 8 was detected. Actin served as loading control.