Thiazolidinones as Potential Inhibitors to Target RPB12 for Treatment of Colorectal Cancer Growth

Colorectal cancer (CRC) remains a major cause of cancer-related mortality worldwide, and selective molecular targets and corresponding inhibitors remain insufficiently developed. Starting from a phenotypic screening hit, we performed systematic structural optimization guided by metabolism-guided modification, leading to the discovery of B9. B9 selectively inhibited HCT116 CRC cells and showed much weaker inhibition of normal colonic epithelial NCM460 cells (IC50 = 0.052 vs 1.114 μM). B9 also suppressed CRC clonogenic growth, 3D spheroid formation, and migration- and invasion-associated phenotypes in vitro. B9 achieved significant tumor growth inhibition (TGI = 80.1%) in vivo without obvious toxicity. RPB12 was identified as a candidate cellular target of B9 by activity-based protein profiling (ABPP) and validated by shRNA knockdown, CETSA, DARTS, SPR, and molecular docking. These findings support RPB12 as a novel promising target for the treatment of CRC and B9 as the first RPB12-targeting inhibitor for further development in CRC therapy.