Shikonin promotes adriamycin­induced apoptosis by upregulating caspase­3 and caspase­8 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 B­cell lymphoma 2­associated X protein (Bax), caspase­3, caspase­8, and poly (ADP­ribose) polymerase (PARP). Flow cytometry was used to analyze cell cycle and cell death. The survival rate of cells decreased significantly in a dose­ and time­dependent manner when treated with a combination of SK and ADM. Western blot analysis revealed increased expression levels of Bax, caspase­3, caspase­8 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 caspase­3­ and caspase­8­dependent apoptosis. SK may be a potential enhancer in the treatment of drug­resistant primary osteosarcoma.

Arsenic sulfide induces apoptosis and autophagy through the activation of ROS/JNK and suppression of Akt/mTOR signaling pathways in osteosarcoma.

Osteosarcoma is a common primary malignant bone tumor, the cure rate of which has stagnated over the past 25-30 years. Arsenic sulfide (As2S2), the main active ingredient of the traditional Chinese medicine realgar, has been proved to have antitumor efficacy in several tumor types including acute promyelocytic leukemia, gastric cancer and colon cancer. Here, we investigated the efficacy and mechanism of As2S2 in osteosarcoma both in vitro and in vivo. In this study, we demonstrated that As2S2 potently suppressed cell proliferation by inducing G2/M phase arrest in various osteosarcoma cell lines. Also, treatment with As2S2 induced apoptosis and autophagy in osteosarcoma cells. The apoptosis induction was related to PARP cleavage and activation of caspase-3, -8, -9. As2S2 was demonstrated to induce autophagy as evidenced by formation of autophagosome and accumulation of LC3II. Further studies showed that As2S2-induced apoptosis and autophagy could be significantly attenuated by ROS scavenger and JNK inhibitor. Moreover, we found that As2S2 inhibited Akt/mTOR signaling pathway, and suppressing Akt and mTOR kinases activity can increase As2S2-induced apoptosis and autophagy. Finally, As2S2in vivo suppressed tumor growth with few side effects. In summary, our results revealed that As2S2 induced G2/M phase arrest, apoptosis, and autophagy via activing ROS/JNK and blocking Akt/mTOR signaling pathway in human osteosarcoma cells. Arsenic sulfide may be a potential clinical antitumor drugs targeting osteosarcoma.