SM-164 enhances the antitumor activity of adriamycin in human U2-OS cells via downregulation of X-linked inhibitor of apoptosis protein

The antitumor effects of SM-164 and adriamycin (ADM) on human osteosarcoma U2-OS cells, the underlying mechanism are yet to be investigated. In the present study, U2-OS cells were divided into control, ADM, SM-164, and ADM + SM-164 groups. In addition, cells treated with both SM-164 and ADM were further divided into three subgroups: SM-164 + ADM, SM-164 + ADM + vector and SM-164 + ADM + X-linked inhibitor of apoptosis protein (XIAP) silencing groups. XIAP expression was achieved via transfection with shRNA lentiviral vectors. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect the expression of caspases-7, −9, and −3, poly ADP-ribose polymerase (PARP), XIAP, cellular inhibitor of apoptosis protein-1 (cIAP-1) and survivin. Cell viability and apoptosis were evaluated using MTT and flow cytometry assays, respectively. Compared with the control group, cell viability decreased, while apoptosis was increased in the ADM and SM-164-treatment group. ADM and SM-164 treatment promoted the expression of caspases-7, −9 and −3, and PARP, but reduced the expression of XIAP, survivin and cIAP-1. Compared with ADM + SM-164 group, XIAP silencing with ADM + SM-164 treatment further reduced cell viability, promoted apoptosis, increased caspase-7, −9 and −3, and PARP expression; however the expression of survivin and cIAP-1 were reduced. Combined ADM and SM-164 treatment may be considered as potential therapeutic agent in the treatment of osteosarcoma, possibly via reductions XIAP expression.