Circular RNAs (circRNAs) regulate gene expression by acting as a 'sponge' for microRNAs (miRs) and play crucial roles in tumorigenesis, including in bladder cancer (BC). circRNA‑baculoviral IAP repeat‑containing 6 (circ‑BIRC6) has been reported to participate in the pathogenesis of several cancer types. The present study aimed to elucidate the roles and potential mechanisms of circ‑BIRC6 in the progression of BC. circ‑BIRC6 expression levels in BC cell lines were determined using reverse transcription‑quantitative PCR. Following circ‑BIRC6 knockdown, cell proliferation, invasion and migration were detected using Cell Counting Kit‑8, colony formation, Transwell and wound healing assays, respectively. Western blotting was also conducted to evaluate the expression levels of X‑box binding protein 1 (XBP1) and epithelial‑mesenchymal transition (EMT)‑associated proteins. In addition, rescue experiments were performed using by transfecting a miR‑495‑3p inhibitor into T24 cells following circ‑BIRC6 knockdown. The interactions between circ‑BIRC6, miR‑495‑3p and XBP1 was verified using dual luciferase reporter assays. Moreover, T24 cells with circ‑BIRC6 knockdown and miR‑495‑3p inhibitor transfection were used for the tumor‑bearing experiment. Tumor growth was observed and Ki‑67 expression was determined using immunohistochemistry. The results demonstrated that circ‑BIRC6 expression was upregulated in BC cell lines. Moreover, circ‑BIRC6 knockdown notably attenuated the proliferation, invasion, migration and EMT of BC cells, which was blocked by the miR‑495‑3p inhibitor. It was also identified that circ‑BIRC6 sponged miR‑495‑3p to regulate XBP1 expression. In addition, results from the xenograft experiments indicated that the knockdown of circ‑BIRC6 and miR‑495‑3p expression significantly inhibited tumor growth. It was also found that the expression levels of XBP1, Ki‑67 and EMT‑associated proteins in tumor tissues of the co‑transfection group were markedly restored compared with the circ‑BIRC6 knockdown group. In conclusion, these findings demonstrated that circ‑BIRC6 knockdown suppressed BC tumorigenesis and progression via regulation of the miR‑495‑3p/XBP1 signaling axis, offering a promising therapeutic target for the treatment of BC.

中文翻译：

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沉默 circ-BIRC6 通过靶向 miR-495-3p/XBP1 信号轴抑制膀胱癌细胞的增殖、侵袭、迁移和上皮间质转化。

环状 RNA (circRNA) 通过充当 microRNA (miR) 的“海绵”来调节基因表达，并在包括膀胱癌 (BC) 在内的肿瘤发生中发挥关键作用。据报道，circRNA-杆状病毒 IAP 重复序列 6 (circ-BIRC6) 参与了几种癌症类型的发病机制。本研究旨在阐明 circ-BIRC6 在 BC 进展中的作用和潜在机制。使用逆转录定量 PCR 测定 BC 细胞系中的 circ-BIRC6 表达水平。在 circ-BIRC6 敲低后，分别使用 Cell Counting Kit-8、集落形成、Transwell 和伤口愈合试验检测细胞增殖、侵袭和迁移。还进行了蛋白质印迹以评估 X-box 结合蛋白 1 (XBP1) 和上皮间质转化 (EMT) 相关蛋白的表达水平。此外，通过在 circ-BIRC6 敲低后将 miR-495-3p 抑制剂转染到 T24 细胞中来进行拯救实验。circ-BIRC6、miR-495-3p 和 XBP1 之间的相互作用通过双荧光素酶报告基因分析得到验证。此外，将具有 circ-BIRC6 敲低和 miR-495-3p 抑制剂转染的 T24 细胞用于荷瘤实验。观察到肿瘤生长并使用免疫组织化学测定 Ki-67 表达。结果表明，circ-BIRC6 表达在 BC 细胞系中上调。此外，circ-BIRC6 敲低显着减弱了 BC 细胞的增殖、侵袭、迁移和 EMT，被 miR-495-3p 抑制剂阻断。还发现 circ-BIRC6 吸收 miR-495-3p 来调节 XBP1 的表达。此外，异种移植实验的结果表明，circ-BIRC6 和 miR-495-3p 表达的敲低显着抑制了肿瘤的生长。还发现与circ-BIRC6敲低组相比，共转染组肿瘤组织中XBP1、Ki-67和EMT相关蛋白的表达水平明显恢复。总之，这些发现表明，circ-BIRC6 敲低通过调节 miR-495-3p/XBP1 信号轴抑制了 BC 肿瘤的发生和进展，为治疗 BC 提供了有希望的治疗靶点。异种移植实验的结果表明，circ-BIRC6 和 miR-495-3p 表达的敲低显着抑制了肿瘤的生长。还发现与circ-BIRC6敲低组相比，共转染组肿瘤组织中XBP1、Ki-67和EMT相关蛋白的表达水平明显恢复。总之，这些发现表明，circ-BIRC6 敲低通过调节 miR-495-3p/XBP1 信号轴抑制了 BC 肿瘤的发生和进展，为治疗 BC 提供了有希望的治疗靶点。异种移植实验的结果表明，circ-BIRC6 和 miR-495-3p 表达的敲低显着抑制了肿瘤的生长。还发现与circ-BIRC6敲低组相比，共转染组肿瘤组织中XBP1、Ki-67和EMT相关蛋白的表达水平明显恢复。总之，这些发现表明，circ-BIRC6 敲低通过调节 miR-495-3p/XBP1 信号轴抑制了 BC 肿瘤的发生和进展，为治疗 BC 提供了有希望的治疗靶点。与 circ-BIRC6 敲低组相比，共转染组肿瘤组织中的 Ki-67 和 EMT 相关蛋白显着恢复。总之，这些发现表明，circ-BIRC6 敲低通过调节 miR-495-3p/XBP1 信号轴抑制了 BC 肿瘤的发生和进展，为治疗 BC 提供了有希望的治疗靶点。与 circ-BIRC6 敲低组相比，共转染组肿瘤组织中的 Ki-67 和 EMT 相关蛋白显着恢复。总之，这些发现表明，circ-BIRC6 敲低通过调节 miR-495-3p/XBP1 信号轴抑制了 BC 肿瘤的发生和进展，为治疗 BC 提供了有希望的治疗靶点。