FLLL31 Induces Apoptosis via the FOXO4/BCL6 Axis to Inhibit Bladder Cancer Progression

Bladder cancer represents one of the most common malignancies globally, posing a severe threat to human health. Through compound library screening, we identified tetramethylcurcumin (FLLL31), a diketone analog of curcumin, as exhibiting significant inhibitory effects on the malignant biological behaviors of bladder cancer cells. Although possessing diverse biological activities, the application of FLLL31 in bladder cancer has not been reported previously. To investigate the function and mechanism of FLLL31, we assessed its impact on the proliferation, migration, and invasion of T24 and 5637 cells using CCK-8, EdU, colony formation, and Transwell. The in vivo efficacy of FLLL31 was evaluated by intraperitoneal injection in BALB/c-nu mice bearing subcutaneous xenografts. Utilizing RNA-seq, qRT-PCR, Western blotting, electron microscopy, flow cytometry, and JC-1 staining, we further explored the mechanism underlying FLLL31's inhibition of malignant behaviors in bladder cancer cells. The results demonstrate that FLLL31 inhibits malignant bladder cancer behaviors by inducing apoptosis via the FOXO4/BCL6 axis. This pathway was further confirmed by the observation that lentiviral knockdown of either FOXO4 or BCL6 attenuated FLLL31-induced apoptosis. Mechanistically, FLLL31 upregulates FOXO4, leading to increased BCL6 expression. This subsequently suppresses the antiapoptotic protein Bcl-xL, thereby triggering apoptosis. These findings highlight the therapeutic potential of FLLL31 for bladder cancer and identify the FOXO4/BCL6 pathway as a promising novel target.