N6-methyladenosine-modified SRD5A3, identified by IGF2BP3, sustains cisplatin resistance in bladder cancer

Resistance to cisplatin-based chemotherapy limits the clinical benefit to some bladder cancer patients, and understanding the epigenetic regulation mechanism of cisplatin (CDDP) resistance in bladder cancer from the perspective of N6-methyladenosine (m6A) modification may optimize CDDP-based treatments. The study identified SRD5A3 as an oncogene for bladder cancer and stabilized by a m6A reader, IGF2BP3, to sustain CDDP resistance. Our results revealed that the expression of SRD5A3 was elevated in human bladder cancer tissues and cell lines, and this elevation was more evident in CDDP-resistant T24 and 5637 cells. Results of CCK-8 assay, colony formation assay, EdU staining, and flow cytometric analysis revealed that SRD5A3 knockdown and IGF2BP3 knockdown reduced cell proliferation and prevented chemoresistance in CDDP-resistant T24 and 5637 cells. Results of methylated RNA immunoprecipitation-PCR, RNA immunoprecipitation assay, and luciferase reporter assay showed IGF2BP3 recognized the SRD5A3 m6A modification and stabilized its mRNA. Nude mice implanted subcutaneously with CDDP-resistant T24 cells were injected intraperitoneally with CDDP (2 mg/kg) every 3 days for 35 days and the results demonstrated that SRD5A3 knockdown and IGF2BP3 knockdown effectively inhibited the tumor growth in subcutaneous implantation model. Collectively, the study unveils that IGF2BP3-mediated SRD5A3 m6A modification facilitates bladder cancer progression and induces CDDP resistance, providing rational therapeutic targets for bladder cancer patients.