miRNAs (miRs) play an important role in cancer cell growth and migration; however, the potential roles of miRs in osteosarcoma remain largely uncharacterized. By applying a miR microarray platform and unsupervised hierarchical clustering analysis, we found that several miRs have altered expression levels in osteosarcoma cell lines and tumor tissues when compared to normal human osteoblasts. Three miRs, miR-199a-3p, miR-127-3p, and miR-376c were significantly decreased in osteosarcoma cell lines, while miR-151-3p and miR-191 were increased in osteosarcoma cell lines in comparison to osteoblasts. Transfection of precursor miR-199a-3p into osteosarcoma cell lines significantly decreased cell growth and migration, thus indicating that the inhibition effect is associated with an increase in the G1-phase and a decrease of the S-phase cell population. Additionally, we observed decreased mTOR and Stat3 expression in miR-199a-3p transfected cells. This study provides new insights for miRs in osteosarcoma and suggests that miR-199a-3p may play a functional role in osteosarcoma cell growth and proliferation. Restoring miR-199a-3p’s function may provide therapeutic benefits in osteosarcoma.

Recent studies have revealed that long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays an important role in the development of several solid tumors. However, the function of MALAT1 in the tumorigenesis of osteosarcoma remains unknown. In the present study, levels of MALAT1 in human osteosarcoma cell lines and tissues were detected by quantitative real-time polymerase chain reaction (RT-PCR). The roles of MALAT1 in osteosarcoma were investigated by using in vitro and in vivo assays. We observed that MALAT1 expression was up-regulated in human osteosarcoma cell lines and tissues. In vitro knockdown of MALAT1 by siRNA significantly inhibited cell proliferation and migration, and induced cell cycle arrest and apoptosis in osteosarcoma cells. In addition, MALAT1 knockdown markedly suppressed the formation of tubular network structures and caused breakage of stress fibers in osteosarcoma cell lines U2OS and MNNG/HOS. Furthermore, MALAT1 knockdown delayed tumor growth in an osteosarcoma xenograft model. Specifically, we found that administration of MALAT1 siRNA decreased the protein levels of RhoA and its downstream effectors Rho-associated coiled-coil containing protein kinases (ROCKs). Taken together, these findings suggest that MALAT1 plays an oncogenic role in osteosarcoma and may be a promising therapeutic target for the treatment of osteosarcoma patients. ß

Osteosarcoma is the most common human primary malignant bone tumor in children and young adults. Sensitive and non-invasive biomarkers that can facilitate disease detection at early stage are highly desirable to improve survival rate and help to determine optimized treatment for osteosarcoma. The small non-coding RNAs, microRNAs (miRNAs), have recently been identified as critical regulators for various diseases including cancer and may represent a novel class of cancer biomarkers. In this study, we aimed to detect the potential of circulating miRNAs as biomarkers for osteosarcoma. Levels of six candidate miRNAs (miR-21, miR-199a-3p, miR-143, miR-34, miR-140, and miR-132) that were previously demonstrated to be regulated in osteosarcoma were examined in plasma of 40 osteosarcoma patients and 40 matched healthy controls by quantitative reverse-transcription polymerase chain reaction assays. The results showed that circulating levels of miR-21 were significantly higher in osteosarcoma patients than controls, while miR-199a-3p and miR-143 were decreased in osteosarcoma patients. We replicated the findings in an independent study of 40 osteosarcoma patients and 40 matched controls and confirmed the results. Receiver operating characteristics curve analysis of the combined populations demonstrated that the three-miRNA signature could discriminate cases from controls with an area under the curve of 0.953 (95 % CI 0.924-0.984). In addition, circulating miR-21 and miR-143 were correlated with both metastasis status and histological subtype of the patients, while miR-199a-3p only correlated with histological subtype. Our data suggest that altered levels of circulating miRNAs might have great potential to serve as novel, non-invasive biomarkers for osteosarcoma.