MiR-195-5p has been shown to play an essential role in human cancer progression. Nevertheless, the biological role of miR-195-5p in osteosarcoma development remains unclear. In this study, real-time PCR was performed to examine the miR-195-5p expression in human osteosarcoma cell lines. CCK-8 assay and Transwell assay were carried out to measure the effect of miR-195-5p on cell proliferation and invasion. Luciferase reporter assay was used to identify the targets of miR-195-5p. The results showed that miR-195-5p was significantly downregulated in osteosarcoma cells. Forced expression of miR-195-5p significantly inhibited cell proliferation, suppressed cell migration and invasion, compared with wild-type and control-transfected osteosarcoma cells. Luciferase reporter assay revealed that miR-195-5p binds to the 3'-untranslated region (UTR) of Naked cuticle homolog 1 (NKD1), indicating that NKD1 was a novel target of miR-195-5p. NKD1 mRNA and protein levels were reduced after overexpression of miR-195-5p. Moreover, silencing of NKD1 significantly inhibited the proliferation and invasion of osteosarcoma cells. Accordingly, our results support a tumor suppressor role of miR-195-5p in osteosarcoma through inhibiting NKD1, and it may be a promising therapeutic target for osteosarcoma.

Osteosarcoma (OS) is a rare malignancy of bone associated with poor clinical outcomes. The antitumor effects of GANT61 on OS is unclear. To investigate antitumor effects and mechanism of GANT61 in OS cells and xenograft model. Effects of GANT61 on cell viability, clone formation, cell cycle, apoptosis, migration, and invasion ability of OS cells were assessed. Reactive oxygen species (ROS) levels measured by dichlorofluorescein fluorescence were used to evaluate oxidative stress. The Xenograft model was constructed to investigate the antitumor effects of GANT61 in vivo. The microRNA (miRNA)‐1286 was downregulated, while RAB31 upregulated in OS tissues and cells. GANT61 inhibited viability, migration, and invasion ability of OS cells (SaOS‐2 and U2OS), and induced apoptosis and the ROS production, along with miRNA‐1286 upregulation and RAB13 downregulation. After knockdown of miRNA‐1286, GANT6‐induced cell inhibition was attenuated, along with RAB31 upregulation. Inversely, miRNA‐1286 overexpression downregulated RAB31. Dual‐luciferase reporter assay verified that miR‐1286 negatively targeted RAB13. Moreover, the knockdown of RAB31 stimulated apoptosis and ROS production while inhibited viability, migration, and invasion of GANT61‐treated cells. In vivo experiments further confirmed that GANT61 inhibited tumor growth and RAB13 expression, but enhanced miRNA‐1286. The study demonstrated that GANT61 inhibited cell aggressive phenotype and tumor growth by inducing oxidative stress through the miRNA‐1286/RAB31 axis. Our findings provided a potential antitumor agent for the OS clinical treatment.