Tanshinone I restrains osteosarcoma progression by regulating circ_0000376/miR-432-5p/BCL2 axis.

Circular RNAs (circRNAs) have been identified as important regulators in cancer progression. Nevertheless, little is known about the biological function of circ_0000376 in the progression of osteosarcoma (OS). Cell viability, colony formation ability, apoptosis, and motility were analyzed by Cell Counting Kit-8 assay, colony formation assay, flow cytometry, and transwell assays. Cellular glycolytic metabolism was analyzed using commercial kits. RT-qPCR and Western blot assay were performed to analyze RNA and protein expression in OS tissues and cells. Starbase software was used to establish circRNA-microRNA (miRNA)-messenger RNA linkage, and intermolecular interaction was verified by dual-luciferase reporter assay. Xenograft tumor assay was conducted to analyze the effects of Tanshinone I (Tan I) and circ_0000376 on xenograft tumor growth in vivo. Tan I treatment suppressed the viability, migration, invasion, and glycolysis and triggered the apoptosis of OS cells. Tan I treatment markedly down-regulated circ_0000376 expression in OS cells. The addition of circ_0000376 plasmid largely rescued the malignant behaviors of OS cells upon Tan I exposure. Circ_0000376 interacted with miR-432-5p in OS cells. Circ_0000376 overexpression-mediated protective effects in Tan I-induced OS cells were partly attenuated by the accumulation of miR-432-5p. miR-432-5p bound to the 3' untranslated region (3'UTR) of B-cell leukemia/lymphoma 2 (BCL2) in OS cells. miR-432-5p interference-induced effects in Tan I-treated OS cells were partly overturned by the silence of BCL2. Circ_0000376 can act as miR-432-5p sponge to up-regulate BCL2 expression in OS cells. Circ_0000376 silencing contributed to the anti-tumor effect of Tan I on the growth of xenograft tumors in vivo. Tan I exerted an anti-tumor role in OS progression by targeting circ_0000376/miR-432-5p/BCL2 axis.