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This study was carried out to investigate the anti-tumor effect and mechanism of hiporfin-mediated photodynamic therapy (hiporfin- PDT) in osteosarcoma. We found that hiporfin accumulated mainly in the cytoplasm of osteosarcoma cells in a time and concentration-dependent manner. Hiporfin- PDT inhibited the proliferation, induced apoptosis and produced cell cycle arrest at G2 M in osteosarcoma cell lines. Hiporfin- PDT increased the expression of cleaved-caspase-3, cleaved PARP-1, Bax and RIP1 while it decreased the expression of Bcl-2; in addition, low concentration of hiporfin increased LC3 conversion. Furthermore, cell death caused by hiporfin- PDT could be rescued by Nec-1 but not by Z- VAD- FMK. Production of reactive oxygen species was increased after hiporfin- PDT. In vivo studies showed a significant decrease in tumor volume and weight after hiporfin- PDT in all three tumor mouse models investigated (subcutaneous and orthotopic). Histological analysis showed widespread cell apoptosis and necrosis after treatment. Immunohistochemistry also showed upregulation of cleaved-caspase-3 and downregulation of Bcl-2 after hiporfin- PDT. These results indicate that hiporfin- PDT exhibits a killing effect in osteosarcoma both in vitro and in vivo, which is associated with apoptosis and necroptosis, while autophagy plays a protective role. All these findings shed light on a potential future clinical use for hiporfin in the treatment of osteosarcoma. [ABSTRACT FROM AUTHOR]

Fullerene C60 nanocrystals (nano‐C60) possess various attractive bioactivities, including autophagy induction and calcium/calmodulin‐dependent protein kinase IIα (CaMKIIα) activation. CaMKIIα is a multifunctional protein kinase involved in many cellular processes including tumor progression; however, the biological effects of CaMKIIα activity modulated by nano‐C60 in tumors have not been reported, and the relationship between CaMKIIα activity and autophagic degradation remains unclear. Herein, nano‐C60 is demonstrated to elicit reactive oxygen species (ROS)‐dependent cytotoxicity and persistent activation of CaMKIIα in osteosarcoma (OS) cells. CaMKIIα activation, in turn, produces a protective effect against cytotoxicity from nano‐C60 itself. Inhibition of CaMKIIα activity by either the chemical inhibitor KN‐93 or CaMKIIα knockdown dramatically promotes the anti‐OS effect of nano‐C60. Moreover, inhibition of CaMKIIα activity causes lysosomal alkalinization and enlargement, and impairs the degradation function of lysosomes, leading to autophagosome accumulation. Importantly, excessive autophagosome accumulation and autophagic degradation blocking are shown to play an important role in KN‐93‐enhanced‐OS cell death. The synergistic anti‐OS efficacy of KN‐93 and nano‐C60 is further revealed in an OS‐xenografted murine model. The results demonstrate that CaMKIIα inhibition, along with the suppression of autophagic degradation, presents a promising strategy for improving the antitumor efficacy of nano‐C60. [ABSTRACT FROM AUTHOR]