Repeated cycles of first-line chemotherapy drugs such as doxorubicin (DOX) and cisplatin (CIS) trigger frequent chemoresistance in recurrent urothelial bladder cancer (UBC). Nitroxoline (NTX), an antibiotic to treat urinary tract infections, has been recently repurposed for cancer treatment. Here we aimed to investigate whether NTX suppresses drug-resistant UBC and its molecular mechanism. The drug-resistant cell lines T24/DOX and T24/CIS were established by continual exposure of parental cell line T24 to DOX and CIS, respectively. T24/DOX and T24/CIS cells were resistant to DOX and CIS, respectively, but they were sensitive to NTX time- and dose-dependently. Overexpressions of STAT3 and P-glycoprotein (P-gp) were identified in T24/DOX and T24/CIS, which could be reversed by NTX. Western blot revealed that NTX downregulated p-STAT3, c-Myc, Cyclin D1, CDK4, CDK6, Bcl-xL, Mcl-1, and Survivin, which were further confirmed by Stattic, a selective STAT3 inhibitor. In vivo, NTX exhibited the significant anti-tumor effect in T24/DOX and T24/CIS tumor-bearing mice. These results suggested that NTX-induced P-gp reversal, G0/G1 arrest, and apoptosis in drug-resistant UBC were mediated by inhibition of STAT3 signaling. Our findings repurpose NTX as a novel STAT3 inhibitor to induce P-gp reversal, G0/G1 arrest, and apoptosis in drug-resistant UBC.

中文翻译：

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发现和验证硝唑啉作为一种新型 STAT3 抑制剂治疗耐药性尿路上皮膀胱癌

一线化疗药物如多柔比星 (DOX) 和顺铂 (CIS) 的重复周期会引发复发性膀胱尿路上皮癌 (UBC) 的频繁化疗耐药。Nitroxoline (NTX) 是一种治疗尿路感染的抗生素，最近已被重新用于癌症治疗。在这里，我们旨在研究 NTX 是否抑制耐药 UBC 及其分子机制。通过将亲代细胞系 T24 分别持续暴露于 DOX 和 CIS 来建立耐药细胞系 T24/DOX 和 T24/CIS。T24/DOX 和 T24/CIS 细胞分别对 DOX 和 CIS 具有抗性，但它们对 NTX 时间和剂量依赖性敏感。在 T24/DOX 和 T24/CIS 中发现了 STAT3 和 P-糖蛋白 (P-gp) 的过表达，这可以被 NTX 逆转。蛋白质印迹显示 NTX 下调 p-STAT3、c-Myc、Cyclin D1、CDK4、CDK6、Bcl-xL、Mcl-1 和 Survivin，通过选择性 STAT3 抑制剂 Stattic 进一步证实。在体内，NTX 在 T24/DOX 和 T24/CIS 荷瘤小鼠中表现出显着的抗肿瘤作用。这些结果表明 NTX 诱导的 P-gp 逆转、G0/G1 停滞和耐药 UBC 中的细胞凋亡是通过抑制 STAT3 信号传导介导的。我们的研究结果将 NTX 重新用作一种新型 STAT3 抑制剂，以诱导耐药 UBC 中的 P-gp 逆转、G0/G1 停滞和细胞凋亡。耐药 UBC 中的细胞凋亡和凋亡是通过抑制 STAT3 信号传导介导的。我们的研究结果将 NTX 重新用作一种新型 STAT3 抑制剂，以诱导耐药 UBC 中的 P-gp 逆转、G0/G1 停滞和细胞凋亡。耐药 UBC 中的细胞凋亡和凋亡是通过抑制 STAT3 信号传导介导的。我们的研究结果将 NTX 重新用作一种新型 STAT3 抑制剂，以诱导耐药 UBC 中的 P-gp 逆转、G0/G1 停滞和细胞凋亡。