Background and purpose: MicroRNAs are endogenous small RNAs and involved in target gene regulation in post-transcription level. As a tumor suppressor

microRNA-335 (miR-335) was participated in the occurrence and progression in many types of human tumors. This study aimed at investigating whether miR-335 can regulate cell migration and invasion by negative targeting Rho associated coiled-coil forming protein kinase (ROCK1) in human osteosarcoma cell line MG-63. Methods: The specific binding ability of miR-335 to ROCK1 3’-untranslated region (UTR) was theoretically predicted and detected by the luciferase reporter gene assay. Western blot and realtime PCR were used to evaluate the effect of miR-335 on the expression of ROCK1 at protein and mRNA levels. Cell migration and invasion assays were performed by transwell chambers in MG-63 cells intervened by over-expression of miR-335 and knockdown of ROCK1. Results: Luciferase reporter gene assay showed that miR-335 could target ROCK1 3’-UTR. Lower miR-335 but higher ROCK1 was expressed in MG-63 cells. The results of Western blot showed that ROCK1 protein expression was decreased by transfection of miR-335 mimic or siROCK1. Transwell chambers results showed decreased cells invading through the substrate membrane after over-expression of miR-335 or knockdown of ROCK1 gene. Conclusion: miR-335 inhibits the migration and invasion ability of MG-63 human osteosarcoma cell line

which may through targeting ROCK1 3’-UTR and subsequent down-regulating ROCK1 expression.