No abstract

Sarcoma, a rare form of cancer, is unlike the much more common carcinomas as it occurs in a distinct type of tissue. The potent antitumor effects of 18β-glycyrrhetinic acid (GA), a novel naturally derived agent, have been demonstrated in various cancers. However, the effect of GA on human sarcoma, and the underlying mechanisms, remain to be elucidated. In the current study, we show that GA inhibits sarcoma cell proliferation by inducing G0/G1-phase arrest. Exposure to GA resulted in the activation of caspase-3, -8, and -9, indicating that GA induced apoptosis through both extrinsic and intrinsic pathways. In addition, the autophagy pathway, characterized by the conversion of LC3-I to LC3- II, was activated, resulting in increased Beclin-1 protein levels, decreased p62 expression, and stimulation of autophagic flux. The present findings showed that GA stimulated autophagy by inducing endoplasmic reticulum (ER) stress via the IRE1–JNK pathway. Our data supported the prosurvival role of GA-induced autophagy when the autophagy pathway was blocked with specific chemical inhibitors. Finally, GA markedly reduced sarcoma growth, with little organ-related toxicity, in vivo. The present results suggest that the combination of GA with a specific autophagy inhibitor represents a promising therapeutic approach for the treatment of sarcoma.

Transcriptional co-activator with PDZ-binding motif (TAZ) is a downstream effector of the Hippo signaling pathway that participates in tumorigenesis. The aim of this study was to identify the miRNA counterpart for TAZ and elucidate the mechanism underlying the tumorigenic effect of TAZ. We demonstrated that TAZ is upregulated in osteosarcoma (OS) tissues and cell lines, and that TAZ overexpression can induce cell migration, invasion and proliferation. Moreover, miRNA-224 (miR-224), a TAZ phenocopy that functions downstream of TAZ, was found to be upregulated with TAZ overexpression. Further, a mechanistic study revealed that miR-224 functions by inhibiting the tumor suppressor, SMAD4, to support the proliferation and migration of OS cells. Our findings indicate that targeting TAZ and miR-224 could be a promising approach for the treatment of OS.