KLF1 Activates RAC3 to Mediate Fatty Acid Synthesis and Enhance Cisplatin Resistance in Bladder Cancer Cells.

While cisplatin remains a frontline treatment for bladder cancer (BCa), the onset of resistance greatly hampers its effectiveness. RAC3 is closely linked to chemoresistance in cancer cells, but its specific role in cisplatin resistance within BCa is still elusive. RAC3 expression in BCa was analyzed using bioinformatics and quantitative polymerase chain reaction (qPCR). The gene set enrichment analysis (GSEA) identified RAC3-enriched pathways and the correlation between RAC3 and fatty acid synthase (FASN), a gene involved in fatty acid synthesis. Potential upstream transcription factors of RAC3 were predicted and their interaction with RAC3 was confirmed via dual-luciferase and chromatin immunoprecipitation (ChIP) assays. T24/DDP, a cisplatin-resistant BCa cell line, was established to probe into the regulatory role of RAC3 in cisplatin resistance. Cell proliferation was evaluated by colony formation and the IC values after cisplatin treatment were determined using cell counting kit-8 (CCK-8). The levels of free fatty acids and triglycerides (TGs), as well as the expression of DGAT2 and FASN proteins, were measured to gauge the extent of fatty acid synthesis in cells. Elevated expression of RAC3 was observed in BCa and the cisplatin-resistant BCa cells (T24/DDP). The knockdown of RAC3 within T24/DDP cells was demonstrated to counteract cisplatin resistance. Subsequent analyses identified RAC3 as being notably enriched in the fatty acid synthesis pathway, with Kruppel-like factor 1 (KLF1) emerging as a key upstream regulator. The overexpression of RAC3 was correlated with increased cisplatin resistance in T24/DDP cells, an effect that was mitigated by the addition of the FASN inhibitor, Orlistat. Furthermore, the downregulation of KLF1 suppressed RAC3 expression, disrupted fatty acid synthesis, and attenuated cisplatin resistance in T24/DDP cells. Conversely, the co-overexpression of RAC3 counteracted the effects conferred by KLF1 knockdown. Our study has validated that KLF1 activates RAC3 to mediate fatty acid synthesis and promote cisplatin resistance in BCa, suggesting the KLF1/RAC3 axis as a potential target for combating cisplatin-resistant BCa.