miR-142 suppresses proliferation and induces apoptosis of osteosarcoma cells by upregulating Rb

It has been reported that microRNA-142 (miR-142) is a tumor suppressor gene. The present study primarily investigated whether the overexpression of miR-142 was able to inhibit the proliferation, apoptosis and expression of apoptosis-associated proteins in osteosarcoma (OS) cells. Different concentrations of miR-142 were transfected into the OS MG-63 cell line using Lipofectamine 2000. The cell lines were divided into three groups: Normal group (non-transfected group), miR-142 transfected group, and negative group, which were transfected with random miR-142 fragment. The proliferation of cells was detected by MTT assay. The expression of miR-142 was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). DAPI staining was performed to investigate the influence of miR-142 on the morphology of MG-63c ells. The apoptotic cell percentages were determined by flow cytometry with Annexin V-fluorescein isothiocyanate/propidium iodide double staining. Expression of tumor suppressors, phosphatase and tensin homolog (PTEN) and Retinoblastoma-associated protein (Rb), and apoptosis-associated proteins were evaluated by western blotting. RT-qPCR indicated a higher expression of miR-142 in the transfected group (miR-142 was transfected into the MG-63 cell line) compared with that in the normal (non-transfected group) and negative control groups. The proliferation of miR-142 transfected cells was significantly lower compared with that in the normal and negative groups. Furthermore, an increased apoptosis rate accompanied by a statistically significant upregulation of PTEN, Rb phosphorylation, cleaved caspase-3 and cytochrome c protein levels were detected in the transfected group, indicating an internal apoptosis pathway was involved in this process. Furthermore, no significant changes were identified between the normal and negative groups (P>0.05). The present study demonstrated that miR-142 overexpression by liposomal transfection resulted in an inhibitory effect on MG-63 cell proliferation. The underlying mechanisms may relate to the upregulation of tumor suppressor and activation of caspase signaling pathway, which may provide a novel horizon in short nucleotide drugs on the management of OS.