miR-557 suppressed the malignant behaviours of osteosarcoma cells by reducing HOXB9 and deactivating the EMT process.

MicroRNAs (miRNAs) are vital gene regulators, which play a profound role in the process of forming and developing many diseases, especially tumour. The study intends to excavate the potential regulatory mechanisms of miR-557 and its targeting gene Homeobox B9 (HOXB9) in osteosarcoma. GEO dataset on osteosarcoma was applied to detect the expression of miR-557 and HOXB9. Associations between miR-557 and HOXB9 were speculated by prediction software and verified by dual luciferase assay. Cell proliferation, colony formation and mobility were measured by cell counting kit-8, plate clone formation and transwell assays. Expression of mesenchymal transitions (MTs) related proteins was assessed by western blot analysis. Low expression of miR-557 was presented in osteosarcoma tissues and cell lines. Upregulation of miR-557 restrained osteosarcoma cells proliferation, movement and MT process. HOXB9, served as a target gene of miR-557, was highly expressed in osteosarcoma, and its high expression was associated with poor prognosis in patients with osteosarcoma. In addition, overexpression of HOXB9 attenuated the inhibitory effects of miR-557 on tumour progression by MT process. Overexpression of miR-557 suppressed the growth, metastasis and MT process of osteosarcoma cells by targeting HOXB9, affording novel molecular selection for targeted therapy of osteosarcoma.