407008

MIR223

MIRN223|miRNA223|mir-223;microRNA 223;MIR223;microRNA 223

hsa-mir-223

Xq12

ncRNA

BACKGROUND/AIMS: Over the past decade, heat shock protein 90 (Hsp90) has emerged as a potential therapeutic target for cancer. However, the molecular mechanisms of down-regulation Hsp90 expression in osteosarcoma are incompletely understood. To develop potential therapy targeting Heat shock protein 90B1 (Hsp90B1), we studied the roles of miR- 223 in the proliferation and apoptosis of human osteosarcoma. METHODS: pcDNA3.1(+)- miR-223 plasmid vectors were constructed and transfected into MG63 cells. Co-transfection of miR-223 expression vector with pMIR-Hsp90B1 (The recombined vector of pMIR-GLOTM luciferase vector containing Hsp90B1-3UTR) led to the reduced activity of luciferase in a dual-luciferase reporter gene assay, suggesting that Hsp90B1 is a target gene of miR-223. expression of HSP90B1 was detected by RT-PCR and western blotting analysis. Cell proliferation was determined using the MTT assay. Cell-cycle distribution and apoptosis were examined by flow cytometry. PI3K, p-Akt, Akt, mTOR, Bcl-2 and Bid were also detected by western blotting analysis. After a mouse xenograft model of human MG63 tumors was constructed, tumor growth, microvessel density and proliferation in each group was determined. RESULTS: The pcDNA3.1(+)-miR-223 vector efficiently suppressed the expression of HSP90B1, while silencing miR-223 increased expression of Hsp90B1. Furthermore, overexpression of miR-223 results in significant inhibition of cell growth on culture plates. Moreover, cancer cells showed significant G0/G1 arrest and increased apoptosis due to gene silencing. Protein levels of PI3k, p-Akt, mTOR, and Bcl-2 were decreased, whereas Bid levels were increased. Microvessel density as assessed by CD34 levels and cell growth by PCNA levels decreased according to immunohistochemical analysis. CONCLUSION: Hsp90B1 is a direct target of miR-223 and miR- 223 may have a tumor suppressor function in osteosarcoma through the PI3K/Akt/mTOR pathway and could be used in anticancer therapies in osteosarcoma.

Osteosarcoma is one of the most common tumors. The mechanisms of formation and development of osteosarcoma have been studied for a long time. Recently, more and more evidence showed that miRNAs play important roles in regulating tumor growth. In this study we found that miRNA-223 was downregulated in both osteosarcoma patients tumor tissues and osteosarcoma cell lines. Overexpression of miRNA-233 greatly inhibited the proliferation of Saos-2 cells. Cell cycle analysis by flow cytometry showed the arrest of cell cycle progression at the G1 phase. Further mechanistic study indicated that Ect2 was directly targeted by miR-223. Downregulation of Ect2 by miR-223 induces the expression of p21, p27 and the phospharylation of retinoblastoma, which are involved in the G1 block. We concluded that miR-223 functions as a tumor suppresser in osteosarcoma and miR-223/Ect2/p21 signaling is an important pathway that regulates the osteosarcoma cell cycle progression and proliferaion.