MiR-223/Ect2/p21 signaling regulates osteosarcoma cell cycle progression and proliferation.

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.