CASP9 and liver cancer: Under the near-infrared laser irradiation, both in the tail vein injection group and the intratumor injection group, a large area of necrosis in the tumor tissue, as well as the up-regulation of apoptotic proteins including cleaved caspase-3 and cleaved caspase-9 were observed; these findings significantly differed from those of the blank control group, indicating that CuS-BSA NPs could induce liver cancer cells apoptosis to inhibit tumor growth during the treatment of photothermal therapy, in addition to causing coagulation necrosis of liver cancer cells through high temperature.