Abstract
BackgroundOsteosarcoma is one of the most common malignant bone tumors with the annual global incidence of approximately four per million. Upregulated gene 4 (URG4) expression in the osteosarcoma tissue is closely associated with recurrence, metastasis, and poor prognosis of osteosarcoma. However, the biological function and underlying mechanisms of URG4 in osteosarcoma have not been elucidated. This study aimed to explore the expression and underlying mechanism of URG4 in osteosarcoma.MethodsThe expression level of URG4 in osteosarcoma and normal tissues was compared using immunohistochemistry (IHC). PCR and western blotting (WB) techniques are used to detect URG4 mRNA and protein levels. Wound healing and Transwell analysis to assess the effect of URG4 on osteosarcoma cell migration and invasion. Cell Counting Kit-8 assay and colony proliferation assay were performed to evaluate the effects of silencing URG4 on the inhibition of cell proliferation. The cell cycle distribution was detected by flow cytometry, and a xenograft mouse model was used to verify the function of URG4 in vivo.ResultsURG4 was found to be highly expressed in osteosarcoma tissues and cells, and its high expression was correlated with advanced Enneking stage, large tumor size, and tumor metastasis in osteosarcoma patients. The proliferation in osteosarcoma cell lines and cell cycle in the S phase was suppressed when siRNA was used to downregulate URG4. URG4 promoted cell proliferation and tumorigenesis in vitro and in vivo. WB verified that URG4 promotes cell proliferation in osteosarcoma via pGSK3β/β-catenin/cyclinD1 signaling.ConclusionURG4, which is high-expressed in osteosarcoma, promotes cell cycle progression via GSK3β/β-catenin/cyclin D1 signaling pathway and may be a novel biomarker and potential target for the treatment of osteosarcoma.
Highlights
Osteosarcoma is one of the most common malignant bone tumors with the highest incidence in children and teenagers [1]
Cell cycle analysis showed that HOS and MG63 cells processed with siRNA1-Upregulated gene 4 (URG4) or siRNA2-URG4 had a significant increase of cells in the G1 phase and a decrease of cells in S phase (Fig. 3c). These findings demonstrated that silenced URG4 increased the percentage of cells in the G1 phase and reduced that of cells in the S phase, representing that downregulating URG4 might be responsible for influences in the osteosarcoma cell cycle
Since the transcription of cyclin D1 protein can be upregulated by β-catenin signaling, β-catenin is crucial for cell proliferation [41, 42], and our current study has demonstrated that URG4 enhanced the stability of cyclin D1 by inducing the phosphorylation of Glycogen Synthase Kinase-3β (GSK-3β) resulting in the accumulation of β-catenin and its nuclear translocation
Summary
Osteosarcoma is one of the most common malignant bone tumors with the highest incidence in children and teenagers [1]. URG4, a novel oncogene located on the short arm of chromosome 7p13, promotes cell proliferation via the MAPK, PI3K, Akt, and NF-kappa B pathways. Huang et al suggested that URG4 expression in osteosarcoma tissue is closely associated with recurrence, metastasis, and poor prognosis of osteosarcoma [14]. It is worth noting that URG4 plays an important role in regulating the biological function of malignant tumors through a variety of signaling pathways (MAPK, PI3K, Akt, and NF-κB pathways). Osteosarcoma is one of the most common malignant bone tumors with the annual global incidence of approximately four per million. Upregulated gene 4 (URG4) expression in the osteosarcoma tissue is closely associated with recurrence, metastasis, and poor prognosis of osteosarcoma. This study aimed to explore the expression and underlying mechanism of URG4 in osteosarcoma
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