Shikonin promotes adriamycin-induced apoptosis by upregulating caspase-3 and caspase-8 in osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor. Cancer cells employ a host of mechanisms to develop resistance to adriamycin (ADM) or other chemotherapeutic drugs. Shikonin (SK), an active constituent extracted from a Chinese medicinal herb, has been shown to cooperate with ADM in the treatment of osteosarcoma and certain other types of cancer by contributing to the response rate of chemotherapy and the side effects. The aim of the present study was to investigate the role and underlying mechanism of SK in chemotherapy for osteosarcoma. In the present study, a CCK-8 assay was performed to assess cell survival rate in vitro. Western blot analysis was performed to determine the expression levels of B-cell lymphoma 2-associated X protein (Bax), caspase-3, caspase-8, and poly (ADP-ribose) polymerase (PARP). Flow cytometry was used to analyze cell cycle and cell death. The survival rate of cells decreased significantly in a dose-and time-dependent manner when treated with a combination of SK and ADM. Western blot analysis revealed increased expression levels of Bax, caspase-3, caspase-8 and PARP in U2OS and MG63 cells 48 h following treatment with SK and ADM. Flow cytometric analysis showed that the combined treatment of SK and ADM significantly induced apoptosis in the osteosarcoma cells. Taken together SK cooperated with ADM to promote apoptosis, possibly by inducing caspase-3- and caspase-8-dependent apoptosis. SK may be a potential enhancer in the treatment of drug-resistant primary osteosarcoma.