Arsenic Sulfide Induces Apoptosis And Autophagy Through The Activation Of ROS/JNK And Suppression Of Akt/mTOR Signaling Pathways In Osteosarcoma

Osteosarcoma?OS?is the most common malignant bone tumor in children and adolescents and arises from cells of mesenchymal osteoblast origin,with highly aggressive and early systemic metastases.80-90%of osteosarcoma patients occurs most commonly in the long bones of limbs?femur and tibia?.Due to the advances of surgery and the development of multi-agent and doseintensive chemotherapy,the 5-year overall survival rate for osteosarcoma increased from less than 20%to 75%in the past three decades.However,approximately 20%of affected patients have metastasis at presentation,and almost all patients with recurrent osteosarcoma have metastatic disease.The 5-year survival rate decreases drastically to 20%in patients in whom pulmonary metastases are detected at diagnosis.Therefore,it is still urgent to develop novel drug and more effective therapeutic approaches for osteosarcoma treatment.Arsenic compounds,a natural medicinal agent,have been widely used in Traditional Chinese Medicine?TCM?for more than 2,000 years.There are mainly three types of arsenic compounds:arsenic trioxide?As₂O₃?,arsenic disulfide?As₂S₂?and arsenic trisulfide?As₂S₃?.As₂O₃ has excellent efficacy in treating acute promyelocytic leukemia?APL?.The Food and Drug Administration?FDA?approved As₂O₃ for clinical application to the treatment of APL in 2000.Because of the remarkable clinical achievement of As₂O₃,researchers have been focusing on the medicinal value of As₂S₂ in cancer treatment.Compared with As₂O₃,As₂S₂ has the advantages of oral adminstration safety,hypotoxicity and abundant resources.Recent studies have reported that As₂S₂ exhibited potential antitumor activity in various malignancies,including hematological malignancies,gastric cancer,hepatocellular carcinoma and pancreatic carcinoma.However,whether As₂S₂ suppresses the growth of human osteosarcoma and its underlying molecular mechanisms have never been investigated.In this study,we demonstrated that As₂S₂ inhibits the osteosarcoma cells proliferation in a dose-and time-dependent manner.And we found that As₂S₂ potently suppressed cell proliferation by inducing G2/M phase arrest in various osteosarcoma cell lines.Also,treatment with As₂S₂induced 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 Reactive oxygen species?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,As₂S₂ in 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.