Sineoculis homeobox homolog 1 (Six1) is one of the transcription factors that act as master regulators of development and is frequently dysregulated in cancers. However, the biological role of Six1 is not clear in osteosarcoma. To address the expression of Six1 in osteosarcoma cells, three osteosarcoma cell lines (U2OS, SaOS-2, and MG63) and a human osteoblastic cell line (hFOB1.19) were used to detect the expression of Six1 by quantitative real-time polymerase chain reaction and western blotting. The results showed that Six1 was upregulated in osteosarcoma cell lines compared to human osteoblastic cell line hFOB1.19. To investigate the role of Six1 in osteosarcoma cells, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry analysis, and transwell chamber assays were used to determine the effects of Six1 on the cell viability, cycle, apoptosis, and migration properties in U2OS cells. The results showed that Six1 could promote U2OS cell proliferation and migration, and suppress U2OS cell apoptosis. In addition, we investigated the effects of Six1 on the expression of following proteins (cyclin D1, caspase-3, and vascular endothelial growth factor-C (VEGF-C)). Results showed that Six1 could increase the expression of cyclin D1 and VEGF-C, and decrease the expression of caspase-3. All these data suggested that Six1 might be involved in the promotion of growth, proliferation, and migration of U2OS cells, as well as the inhibition of apoptosis of U2OS cells. These data might provide information for the prediction of osteosarcoma prognosis and potential targets for therapy of osteosarcoma.

No abstract

Osteosarcoma (OS) is the most common primary malignant bone tumor and the third most common cancer that occurs during childhood and adolescence. Increasing evidence has suggested that microRNA (miR)-23b-3p has an important role in OS tumorigenesis; however, the underlying molecular mechanisms remain unknown. The aim of the present study was to investigate the expression levels of miR-23b-3p and sine oculis homeobox homolog 1 (SIX1) in OS tissues and cell lines (MG-63, SaOS-2 and U2OS), as well as to observe the effects of miR-23b-3p on U2OS cell viability, cell cycle, apoptosis and invasive ability. The results revealed that the expression levels of miR-23b-3p were significantly decreased in OS tissues and cell lines compared with tumor-adjacent normal tissues and a non-cancerous human fetal osteoblastic cell line (hFOB1.19). To investigate the underlying mechanisms of miR-23b-3p in OS tumorigenesis and progression, human U2OS cell lines over-or under expressing miR-23b-3p were established. The effects of miR-23b-3p on U2OS cell viability, cell cycle, apoptosis and invasion properties were determined by performing Cell Counting Kit-8, flow cytometry and Transwell invasion assays. miR-23b-3p was revealed to suppress cell viability, proliferation and invasion, and to enhance the levels of cell apoptosis. Furthermore, SIX1 mRNA and protein expression levels in OS tissues and cell lines were significantly upregulated when compared with tumor-adjacent normal tissues and hFOB 1.19 cells, which suggested that SIX1 expression levels may be inversely associated with miR-23b-3p levels in OS. Luciferase reporter system analysis demonstrated that miR-23b-3p binds to the SIX1 3'-untranslated region. miR-23b-3p downregulation contributed to SIX1 upregulation, which facilitated the potentiation of cyclin D1 and vascular endothelial growth factor-C expression levels, as well as the inhibition of caspase-3 expression. Collectively, these results suggested that miR-23b-3p is downregulated and SIX1 is upregulated in OS cells, and that miR-23b-3p inhibition may suppress the proliferation and invasion of OS cells, and contribute to cell apoptosis via negative regulation of SIX1. miR-23b-3p/SIX1 may therefore represent a potential target for the treatment of OS.

Background Osteosarcoma is a disease with high mortality in children and adolescents, and metastasis is one of the important clinical features of osteosarcoma. N6-Methyladenosine (m6A) is the most abundant methylation modification in mRNA, which is regulated by m6A regulators. It is reported that it is related to the occurrence and development of tumors. However, the mechanism of its action in osteosarcoma is rarely known. The purpose of this study was to identify the potential role of m6A regulatory factor in osteosarcoma and its clinical prognostic value. Methods Here, we used The Cancer Genome Atlas (TCGA) to comprehensively analyze the relationship between m6A regulatory factors and osteosarcoma (metastasis group and non-metastasis group). We analyzed their survival relationship and analyzed all the m6A regulatory factors in TCGA tumor data set by using the univariate Cox proportional hazard regression model. Finally, we selected two survival-related methylation regulators (FTO and IGF2BP2) as risk gene signature. Results According to the median risk, patients were divided into low-risk group and high-risk group. Multivariate Cox regression analysis showed that these two risk genes were considered to be the key factors independently predicting the prognosis of patients with osteosarcoma. In addition, we verified their characteristics with gene expression omnibus (GEO) DataSets and confirmed that they are related to tumor and immune-related signaling pathways through gene set enrichment analysis (GESA) and immune infiltration analysis. Conclusions In conclusion, m6A regulators might play an important role in the metastasis of osteosarcoma and have potential important value for the prognosis and treatment strategy of osteosarcoma patients.