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Bladder cancer is one of the most common and deadly cancer worldwide. Current chemotherapy has shown limited efficacy in improving outcomes for patients. Nitroxoline, an old and widely used oral antibiotic, which was known to treat for urinary tract infection for decades. Recent studies suggested that nitroxoline suppressed the tumor progression and metastasis, especially in bladder cancer. However, the underlying mechanism for anti-tumor activity of nitroxoline remains unclear. Methods: CircRNA microarray was used to explore the nitroxoline-mediated circRNA expression profile of bladder cancer lines. Transwell and wound-healing assay were applied to evaluate the capacity of metastasis. ChIP assay was chosen to prove the binding of promotor and transcription factor. RNA-pulldown assay was performed to explore the sponge of circRNA and microRNA. Results: We first identified the circNDRG1 (has_circ_0085656) as a novel candidate circRNA. Transwell and wound-healing assay demonstrated that circNDRG1 inhibited the metastasis of bladder cancer. ChIP assay showed that circNDRG1 was regulated by the transcription factor EGR1 by binding the promotor of host gene NDRG1. RNA-pulldown assay proved that circNDRG1 sponged miR-520h leading to the overexpression of smad7, which was a negative regulatory protein of EMT. Conclusions: Our research revealed that nitroxoline may suppress metastasis in bladder cancer via EGR1/circNDRG1/miR-520h/smad7/EMT signaling pathway., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

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., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Programmed cell death protein 1 (PD-1) blockade is a promising therapeutic strategy against prostate cancer. Nitroxoline has been found to have effective anticancer properties in several cancer types. We investigated the efficacy of a combination therapy involving nitroxoline and PD-1 blockade in a prostate cancer mouse model. In our in vitro analysis , we found that nitroxoline inhibited the viability and proliferation of the mouse prostate cancer cell line RM9-Luc-PSA. Additionally, nitroxoline downregulated the expressions of phospho-PI3 kinase, phospho-Akt (Thr308), phospho-Akt (Ser473), phospho-GSK-3β, Bcl-2, and Bcl-xL. Nitroxoline also downregulated programmed death-ligand 1 (PD-L1) expression levels in prostate cancer cell line and tumor tissue. In our murine prostate cancer orthotopic model, nitroxoline plus PD-1 blockade synergistically suppressed tumor growth when compared with nitroxoline or PD-1 blockade alone, leading to reductions in tumor weight, bioluminescence tumor signals, and serum prostate-specific antigen levels. Furthermore, fluorescence-activated cell sorting analysis showed that the combination strategy significantly enhanced antitumor immunity by increasing CD44 + CD62L + CD8 + memory T cell numbers and reducing myeloid-derived suppressor cell numbers in peripheral blood. In conclusion, our findings suggest that nitroxoline plus PD-1 blockade may be a promising treatment strategy in patients with prostate cancer., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.

Glaucocalyxin A (GLA), a major component isolated from Rabdosia japonica, has been proven to show anti-bacterial and anti-tumor biological characteristics according to previous studies. However, its potential effect on bladder cancer remains unknown. The present research aims to investigate the underlying mechanism in treating bladder cancer in vivo and in vitro. Cell proliferation was analyzed by CCK-8 assay and colony formation. Flow cytometry was used to measure the cell cycle distribution and apoptosis. The expressions of the cell cycle and apoptosis-related proteins were detected by western blotting and immunofluorescence staining. Meanwhile, the in vivo study was performed to evaluate the anti-tumor effect on a UMUC3 subcutaneous tumor of NOD/SCID mice model. GLA suppressed colony-formation ability, triggered G2/M arrest and promoted apoptosis of UMUC3 cells in a dose-dependent manner. Furthermore, western blotting showed that GLA downregulated the expressions of PI3K p85, p-Akt, Bcl-2, CDK1, Cyclin B1 whereas upregulated the levels of PTEN, Bax, Cleaved Caspase-3. In vivo, GLA at a dosage of 20 mg/kg significantly inhibited tumor growth compared with the control group by intraperitoneal injection. These results suggested that GLA-related G2/M arrest and apoptosis in UMUC3 cells were mediated by a suppressed PI3K/Akt signaling pathway, which regulated p21 Waf1/Cip1 as well as intrinsic caspase cascade. Collectively, our observations could help to develop new drugs targeting the PI3K/Akt pathway for the treatment of bladder cancer., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.