DHCR24+ Tumor Epithelial Cells Drive Cisplatin Resistance in Bladder Cancer by Enhancing Cholesterol Metabolism to Activate Lipid Raft-Associated MAPK Signaling

Cisplatin-based combination therapy remains the primary treatment modality for patients with advanced bladder cancer (BCa); however, the emergence of drug resistance severely restricts clinical benefits. The molecular mechanisms underlying chemoresistance remain incompletely understood. By integrating single-cell transcriptomics with in vitro and in vivo experiments, we revealed that cholesterol metabolism was significantly hyperactivated in cisplatin-resistant BCa tissues. Further subpopulation re-clustering identified a specific chemoresistant epithelial cell subset (C3) characterized by robust cholesterol metabolism, in which the cholesterol metabolic enzyme DHCR24 was significantly upregulated and played a pivotal role in mediating cisplatin resistance in BCa. Mechanistically, the elevated expression of TFDP1 in cisplatin-resistant BCa epithelial cells upregulated DHCR24 via the formation of the TFDP1-E2F1 transcriptional complex, thereby promoting cholesterol biosynthesis. The enriched intracellular cholesterol facilitated the formation of cell membrane lipid rafts and enhanced the phosphorylation of Src, which in turn hyperactivated the downstream MAPK signaling pathway, ultimately conferring cisplatin resistance. Furthermore, the accumulated cholesterol enhanced PD-L1 protein stability, thereby impairing the efficacy of immunotherapy in BCa. Taken together, our study characterizes a specific DHCR24+ tumor epithelial subpopulation that orchestrates cisplatin resistance via the “cholesterol-lipid raft-MAPK” axis. These findings establish a clear mechanistic link between cholesterol metabolism and cisplatin sensitivity.