Sulfated polysaccharide-protein complex sensitizes doxorubicin-induced apoptosis of breast cancer cells in vitro and in vivo.

The present study aimed to investigate the effect of sulfated polysaccharide-protein complex (SPPC) on the antitumor effect of doxorubicin (Dox) on MDA-MB-231 breast cancer cells in vitro and in vivo. MTT and Annexin V/propidium iodide staining assays demonstrated that SPPC selectively sensitized MDA-MB-231 cells to Dox-induced cytotoxicity. The half maximal inhibitory concentration of Dox against MDA-MB-231 cells was decreased from 5.3 to 1.5 µM when it was used concomitantly with 5 µM SPPC. SPPC potentiated Dox-induced apoptosis in breast cancer cells via the mitochondrial apoptosis signaling pathway by activating caspase-3 and caspase-9. Notably, the caspase inhibitor Z-VAD-fmk diminished the effect of SPPC on Dox-mediated apoptosis. Furthermore, combination treatment with SPPC and Dox markedly reduced the growth of breast cancer xenografts in mice. The present study demonstrated that SPPC was able to enhance the antitumor effect of Dox on breast cancer cells, thus suggesting that SPCC may be used to reduce the cumulative dose of Dox and its associated toxicities in the chemotherapy of breast cancer and other types of cancer.