MDM4 promotes chemoresistance in bladder cancer by attenuating P53-mediated EMT

Chemotherapeutic resistance remains a major cause of treatment failure in bladder cancer. While the epithelial-mesenchymal transition (EMT) is a known driver of metastasis and drug resistance, its regulatory mechanisms require further elucidation. This study investigates the role of murine double minute 4 (MDM4), a key p53 suppressor, in mediating cisplatin resistance through the EMT program.

A cisplatin-resistant T24 cell line (T24-CR) was established, with MDM4 overexpression confirmed through reverse-transcription Quantitative Real-time PCR (RT-qPCR). Functional assays including colony formation, transwell migration, apoptosis analysis, and western blot were performed following MDM4 knockdown. In vivo validation was conducted using a subcutaneous xenograft model in male BALB/c nude mice divided into wild-type T24 cell line (T24-WT), T24-CR, and MDM4-deficient cisplatin-resistant T24 cells (T24-CR-shMDM4) groups.

MDM4 expression was substantially elevated in chemoresistant cells T24-CR at both transcriptional and translational levels. MDM4 depletion effectively restored cisplatin sensitivity, as evidenced by significantly reduced cell viability and colony formation capacity. The knockdown also dramatically impaired metastatic potential, with migration and invasion rates decreasing to levels comparable with parental sensitive cells. At the molecular level, MDM4 inhibition activated the p53 pathway and reversed EMT progression, characterized by E-cadherin restoration and Vimentin downregulation. In vivo studies corroborated these observations, with MDM4-targeted tumors exhibiting slower growth kinetics, prolonged survival outcomes, and histopathological features consistent with mesenchymal-to-epithelial reversion.

Our findings identify the MDM4/p53/EMT axis as a pivotal mechanism driving cisplatin resistance in bladder cancer. The study establishes MDM4 as a promising therapeutic target for overcoming chemoresistance, with experimental evidence showing that its inhibition restores p53 activity and reverses the EMT phenotype both in vitro and in vivo.