Revelation of aberrant lipid accumulation in cisplatin-resistant bladder cancer with stimulated Raman scattering microscopy

Cisplatin is a commonly used chemotherapeutic agent for bladder cancer, but drug resistance remains a major challenge. Previous studies have suggested that lipid metabolic reprogramming is closely associated with tumor resistance. However, the relationship between cisplatin resistance and lipid metabolism in bladder cancer remains unclear. To address this, our study performed quantitative lipid analysis leveraging stimulated Raman scattering (SRS) microscopy integrated with Raman probes, which offers high chemical specificity and spatial resolution. This profiling was conducted across cisplatin-sensitive (BIU-87) and resistant (BIU-87-CisR) bladder cancer cell lines, as well as in patient-derived primary cancer cells. Results showed that lipid accumulation, represented by lipid droplets (LDs) area fraction per cell, was significantly higher in BIU-87-CisR cells than in BIU-87 cells, and lipids within the LDs originated primarily from exogenous fatty acid uptake rather than de novo synthesis. Additionally, the lipid unsaturation within the LDs of BIU-87-CisR cells was significantly lower than that of BIU-87 cells. Upon cisplatin stimulation, the LD area fraction per cell increased markedly in BIU-87 cells but remained unchanged in BIU-87-CisR cells. These findings suggest that resistant bladder cancer cells possess higher levels of lipid accumulation, and LD-enriched cells are likely more resistant to chemotherapy. Finally, SRS imaging of patient-derived primary cells showed that the LD area fraction per cell increased with higher tumor stages and grades, and lipid accumulation primarily relied on exogenous fatty acid uptake as well. In conclusion, our findings demonstrate aberrant lipid accumulation in cisplatin-resistant bladder cancer cells, suggesting that LD content could serve as a potential indicator for assessing chemoresistance. This imaging-based approach may offer new avenues for drug sensitivity testing and therapeutic strategy development, although further validation is needed.