Calycosin induces apoptosis via p38-MAPK pathway-mediated activation of the mitochondrial apoptotic pathway in human osteosarcoma 143B cells

Previous studies have demonstrated that calycosin is a natural phytoestrogen with a similar structure to estrogen, which can inhibit cell proliferation and induce apoptosis in a variety of tumors. Calycosin exerts potential pharmacological effects on osteosarcoma cells by inducing apoptosis. The aim of the present study was to elucidate the specific molecular mechanism of calycosin-induced apoptosis in osteosarcoma cells. Cell proliferation was determined by an MTT assay. Annexin V/PI and JC-1 staining were used to detect apoptosis and mitochondrial dysfunction, respectively, by flow cytometry. Western blot analysis was used to detect the expression of caspases or mitochondrial proteins. The results revealed that calycosin reduced the cell viability of human osteosarcoma 143B cells, induced apoptosis and increased the loss of mitochondrial membrane potential (MMP). In addition, calycosin increased the expression of the proapoptotic antiapoptotic proteins cleaved caspase-3, cleaved caspase-9, cleaved poly(ADP-ribose) polymerase and Bcl-2-associated X protein (Bax), and decreased the expression of the antiapoptotic proapoptotic protein B-cell lymphoma-2 (Bcl-2), thus altering the Bax/Bcl-2 ratio. In addition, the expression levels of cytochrome c were markedly decreased in the mitochondria and increased in the cytoplasm following calycosin treatment. Furthermore, calycosin treatment induced p38-mitogen-activated protein kinase (MAPK) phosphorylation, whereas the p38-MAPK inhibitor BIRB 796 markedly reversed cell viability, apoptosis and loss of MMP in 143B cells. These results suggested that calycosin inhibited osteosarcoma 143B cell growth via p38-MAPK regulation of mitochondrial-dependent intrinsic apoptotic pathways.