THAP9-AS1 Promotes Tumorigenesis and Reduces ROS Generation through the JAK2/STAT3 Signaling Pathway by Increasing SOCS3 Promoter Methylation in Osteosarcoma.

Shuai Yang,Feng Chen,Qizun Wang,Youfu Zhu,Maohua Li,Weiliang Su,Zhaoyang Guo,Chang Liu,Xiaolin Wu,Bing Wang,Ronghuan Wang,Cinzia Signorini

doi:10.1155/2021/5620475

Abstract

Increasing studies have demonstrated that dysfunction of long noncoding RNAs (lncRNAs) plays critical roles in the development of human cancers. THAP9-AS1 has been reported to be dysregulated and associated with tumor progression in some cancers. However, the function and mechanism of THAP9-AS1 in osteosarcoma (OS) remain unclear. In the present study, we found that the expression of THAP9-AS1 was significantly upregulated in OS tissues and associated with the advanced stage of tumors and poor prognosis of patients. Blast comparison results showed that the SOCS3 promoter region and THAP9-AS1 had base complementary pairing binding sites. The interactions between THAP9-AS1, DNA methyltransferases (DNMTs), and SOCS3 were assessed by RIP and ChIP assays. The results of methylation-specific PCR (MSP) and bisulfite sequencing PCR (BSP) validated that THAP9-AS1 enhanced the methylation level of the SOCS3 promoter. The mRNA levels of SOCS3 in OS cells could be reversed by the demethylation agent 5-aza-2′-deoxycytidine. The mRNA expression of SOCS3 was downregulated in OS tissues and negatively correlated with THAP9-AS1 expression in tumors. Moreover, the western blot and immunofluorescence (IF) assay data showed that THAP9-AS1 activated the JAK2/STAT3 signaling pathway by upregulating p-JAK2 and p-STAT3 and the nuclear translocation of p-STAT3. Functionally, ectopic expression of THAP9-AS1 promoted cell proliferation, migration, and invasion and inhibited apoptosis, and this phenomenon could be reversed by SOCS3. Introduction of the JAK/STAT inhibitor AG490 partially abolished the stimulative effect of THAP9-AS1 on cellular processes. In addition, THAP9-AS1 decreased oxidative stress by reducing reactive oxygen species (ROS) and enhancing the mitochondrial membrane potential of OS cells via the SOCS3/JAK2/STAT3 pathway. Stable overexpression of THAP9-AS1 contributed to tumor growth and metastasis in vivo. In total, our findings suggested that upregulation of THAP9-AS1 might recruit DNMTs to epigenetically inhibit SOCS3, thereby activating the JAK2/STAT3 signaling pathway and oncogenesis of OS. These results provide novel insights for the understanding of OS progression.

Highlights

Osteosarcoma (OS) is one of the most common malignant bone tumors and occurs more frequently in long bones in children and adolescents [1]
Considering that pSTAT3 in the nucleus is essential for the transcription of its downstream target genes, we examined whether nuclear p-STAT3 accumulation was altered by THAP9-AS1 and SOCS3
E-cadherin was suppressed in the THAP9-AS1 groups (Figure 5(f)). These results suggested that THAP9-AS1 contributed to cell growth and that movement might be correlated with the SOCS3/JAK2/STAT3 signaling pathway

Summary

Introduction

Osteosarcoma (OS) is one of the most common malignant bone tumors and occurs more frequently in long bones in children and adolescents [1]. Dysregulation of lncRNAs is related to a wide range of tumor cellular processes, such as proliferation, apoptosis, invasion, autophagy, and angiogenesis [4]. Several lncRNAs were identified as potential diagnostic and prognostic markers of OS patients and acted as oncogenes or tumor suppressors in the development of OS. Our previous study revealed that PVT1 contributed to glucose metabolism, cell proliferation, and motility through the miR-497/HK2 pathway in OS cells [7]. Another mechanism by which lncRNAs regulate gene expression and tumor progression is by regulating promoter DNA methylation through recruiting DNA methyltransferases (DNMTs) [8, 9]. The function and mechanism of THAP9-AS1 in the development of OS remain unknown

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