Long non-coding RNA SOX2OT promotes the stemness phenotype of bladder cancer cells by modulating SOX2

Background Accumulating evidence indicates that long non-coding RNAs (lncRNAs) are potential biomarkers and key regulators of tumour development and progression. SOX2 overlapping transcript (SOX2OT) is a novel lncRNA that acts as a potential biomarker and is involved in the development of cancer and cancer stem cells. However, the clinical significance and molecular mechanism of SOX2OT in bladder cancer are still unknown. Methods The expression level of SOX2OT was determined by RT-qPCR in a total of 106 patients with urothelial bladder cancer and in different bladder cancer cell (BCC) lines. Bladder cancer stem cells (BCSCs) were isolated from BCCs using flow cytometry based on the stem cell markers CD44 and ALDH1. Loss-of-function experiments were performed to investigate the biological roles of SOX2OT in the stemness phenotype of BCSCs. Comprehensive transcriptional analysis, RNA FISH, dual-luciferase reporter assays and western blots were performed to explore the molecular mechanisms underlying the functions of SOX2OT. Results SOX2OT was highly expressed in bladder cancer, and increased SOX2OT expression was positively correlated with a high histological grade, advanced TNM stage and poor prognosis. Further experiments demonstrated that knockdown of SOX2OT inhibited the stemness phenotype of BCSCs. Moreover, inhibition of SOX2OT delayed xenograft tumour growth and decreased metastases in vivo. Mechanistically, we found that SOX2OT was mainly distributed in the cytoplasm and positively regulated SOX2 expression by sponging miR-200c. Furthermore, SOX2 overexpression reversed the SOX2OT silencing-induced inhibition of the BCSC stemness phenotype. Conclusion This study is the first to demonstrate that SOX2OT plays an important regulatory role in BCSCs and that SOX2OT may serve as a potential diagnostic biomarker and therapeutic target in bladder cancer.

背景 越来越多的证据表明，长链非编码RNA（lncRNAs）是肿瘤发生和发展的潜在生物标志物以及关键调节因子。SOX2重叠转录本（SOX2OT）是一种新型的lncRNA，可作为潜在的生物标志物，并参与癌症和癌症干细胞的发展。然而，SOX2OT在膀胱癌中的临床意义和分子机制仍然未知。 方法 通过实时定量聚合酶链反应（RT - qPCR）测定了总共106例尿路上皮膀胱癌患者以及不同膀胱癌细胞（BCC）系中SOX2OT的表达水平。利用基于干细胞标志物CD44和乙醛脱氢酶1（ALDH1）的流式细胞术从膀胱癌细胞中分离出膀胱癌干细胞（BCSCs）。进行功能缺失实验以研究SOX2OT在膀胱癌干细胞干性表型中的生物学作用。进行综合转录分析、RNA荧光原位杂交（RNA FISH）、双荧光素酶报告基因检测和蛋白质印迹（western blots）以探索SOX2OT功能的潜在分子机制。 结果 SOX2OT在膀胱癌中高表达，并且SOX2OT表达增加与高组织学分级、晚期TNM分期以及不良预后呈正相关。进一步的实验表明，敲低SOX2OT可抑制膀胱癌干细胞的干性表型。此外，抑制SOX2OT可延缓体内移植瘤的生长并减少转移。从机制上讲，我们发现SOX2OT主要分布在细胞质中，并且通过吸附miR - 200c正向调节SOX2的表达。此外，SOX2的过表达逆转了由SOX2OT沉默诱导的膀胱癌干细胞干性表型的抑制。 结论 本研究首次证明SOX2OT在膀胱癌干细胞中起重要的调节作用，并且SOX2OT可能作为膀胱癌的潜在诊断生物标志物和治疗靶点。