BackgroundMicroRNAs are short regulatory RNAs that negatively modulate protein expression at a post-transcriptional and/or translational level and are deeply involved in the pathogenesis of several types of cancers. Specifically, microRNA-221 (miR-221) is overexpressed in many human cancers, wherein accumulating evidence indicates that it functions as an oncogene. However, the function of miR-221 in human osteosarcoma has not been totally elucidated. In the present study, the effects of miR-221 on osteosarcoma and the possible mechanism by which miR-221 affected the survival, apoptosis, and cisplatin resistance of osteosarcoma were investigated.Methodology/Principal FindingsReal-time quantitative PCR analysis revealed miR-221 was significantly upregulated in osteosarcoma cell lines than in osteoblasts. Both human osteosarcoma cell lines SOSP-9607 and MG63 were transfected with miR-221 mimic or inhibitor to regulate miR-221 expression. The effects of miR-221 were then assessed by cell viability, cell cycle analysis, apoptosis assay, and cisplatin resistance assay. In both cells, upregulation of miR-221 induced cell survival and cisplatin resistance and reduced cell apoptosis. In addition, knockdown of miR-221 inhibited cell growth and cisplatin resistance and induced cell apoptosis. Potential target genes of miR-221 were predicted using bioinformatics. Moreover, luciferase reporter assay and western blot confirmed that PTEN was a direct target of miR-221. Furthermore, introduction of PTEN cDNA lacking 3′-UTR or PI3K inhibitor LY294002 abrogated miR-221-induced cisplatin resistance. Finally, both miR-221 and PTEN expression levels in osteosarcoma samples were examined by using real-time quantitative PCR and immunohistochemistry. High miR-221 expression level and inverse correlation between miR-221 and PTEN levels were revealed in osteosarcoma tissues.Conclusions/SignificanceThese results for the first time demonstrate that upregulation of miR-221 induces the malignant phenotype of human osteosarcoma whereas knockdown of miR-221 reverses this phenotype, suggesting that miR-221 could be a potential target for osteosarcoma treatment.
Osteosarcoma, the most common primary tumor of the bones, causes many deaths due to its rapid proliferation and drug resistance. Recent studies have shown that cyclin D1 plays a key regulatory role during cell proliferation, and non-coding microRNAs (miRNAs) act as crucial modulators of cyclin D1 (CCND1). The aim of the current study was to determine the role of miRNAs in controlling CCND1 expression and inducing cell apoptosis. CCND1 has been found to be a target of miR-15a and miR-16-1 through analysis of complementary sequences between microRNAs and CCND1 mRNA. The upregulation of miR-15a and miR-16-1 in the cell line SOSP-9607 induces apoptosis and cell cycle arrest. Osteosarcoma cells transfected with miR-15a and miR-16-1 show slower proliferation curves. Moreover, the transcription of CCND1 is suppressed by miR-15a and miR-16-1 via direct binding to the CCND1 3'-untranslated region (3'-UTR). The data presented here demonstrate that the CCND1 contributes to osteosarcoma cell proliferation, suggesting that repression of CCND1 by miR-15a and miR-16-1 could be used for osteosarcoma therapy.
Metastasis is a leading cause of mortality for osteosarcoma patients. The molecular pathological mechanism remains to be elucidated. In the previously study, we established two osteosarcoma cell lines with different metastatic potentials. Differential expressed genes and proteins regarding metastatic ability have been identified. MicroRNAs are important regulators in tumorigenesis and tumor progression. In this study, microRNA microarray was used to assess the differential expressed miRNAs level between these two cell lines. One of the top ranked miRNAs-miR-195 was identified highly expressing in lowly metastatic cells. It was showed that over-expression of miR-195 substantially inhibits migration and invasion of osteosarcoma cells in vitro and pulmonary metastasis formation in vivo. Meanwhile, CCND1 was identified as the target gene of miR-195 and further studied. More importantly, Using real-time PCR, we evaluated the expression of miR-195 and CCND1 in osteosarcoma samples from 107 frozen biopsy tissues and 99 formalin- or paraformalin-fixed, paraffin-embedded (FFPE) tissues. Results indicated lowly expressed miR-195 or highly CCND1 correlated with positive overall survival and their expression inverse relate to each other. In summary, our study suggests miR-195 function as a tumor metastasis suppressor gene by down-regulating CCND1 and can be used as a potential target in the treatment of osteosarcoma.
BackgroundCellular adaptation to a hypoxic microenvironment is essential for tumor progression and is largely mediated by HIF-1α through coordinated regulation of hypoxia-responsive genes. The chemokine SDF-1α and its unique receptor CXCR4 have been implicated in organ-specific metastases of many cancers. In this study, we investigated the response of osteosarcoma cells to hypoxia and the expression of CXCR4 and HIF-1α in human osteosarcoma specimens and explored the roles of CXCR4 and HIF-1α in the cell migration process.Methodology/Principal FindingsWe performed immunohistochemistry, immunocytochemistry, quantitative real-time PCR, Western blots and fluorescent reporter assays to evaluate the correlation between CXCR4 and HIF-1α expression in human osteosarcoma specimens or SOSP-9607 cells under normoxic and hypoxic conditions. Transwell assays were used to assess cell migration under different conditions. Exposure of SOSP-9607 cells to hypoxic conditions resulted in significantly increased migration. When SOSP-9607 cells were subjected to hypoxic conditions, the mRNA and protein levels of CXCR4 were significantly increased in a time-dependent manner. Moreover, siHIF-1α significantly decreased the mRNA and protein levels of CXCR4 under hypoxia, whereas pcDNA-HIF-1α significantly increased the mRNA and protein levels of CXCR4 under normoxia. A luciferase reporter gene study showed that siHIF-1α reduced pGL3-CXCR4 luciferase activity. Furthermore, coexpression of HIF-1α and CXCR4 was significantly higher in patients with distant metastasis compared with those without metastasis.Conclusions/SignificanceThe hypoxia-HIF-1α-CXCR4 pathway plays a crucial role during the migration of human osteosarcoma cells, and targeting this pathway might represent a novel therapeutic strategy for patients suffering from osteosarcoma.
Studies have shown that miR-194 functions as a tumor suppressor and is associated with tumor growth and metastasis. We studied the effects of miR-194 in osteosarcoma and the possible mechanism by which miR-194 affected the survival, apoptosis and metastasis of osteosarcoma. Both human osteosarcoma cell lines SOSP-9607 and U2-OS were transfected with recombinant lentiviruses to regulate miR-194 expression. Overexpression of miR-194 partially inhibited the proliferation, migration, and invasion of osteosarcoma cells in vitro, as well as tumor growth and pulmonary metastasis of osteosarcoma cells in vivo. Potential miR-194 target genes were predicted using bioinformatics. Luciferase reporter assay, real-time quantitative PCR and western blotting confirmed that CDH2 (N-cadherin) and IGF1R were targets of miR-194. Using real-time quantitative PCR, we evaluated the expression of miR-194 and two miR-194 target genes, CDH2 and IGF1R in osteosarcoma samples from 107 patients and 99 formalin- or paraformalin-fixed paraffin-embedded tissues. The expressions of the target genes were also examined in osteosarcoma samples using immunohistochemistry. Overexpression of miR-194 inhibited tumor growth and metastasis of osteosarcoma probably by downregulating CDH2 and IGF1R. miR-194 may prove to be a promising therapeutic agent for osteosarcoma.
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