Dual targeting of topoisomerase I and DNA G-quadruplexes enhances senescence and chemosensitivity in colorectal cancer.

Colorectal cancer (CRC) remains a therapeutic challenge due to chemoresistance that limits conventional treatment efficacy. We developed ZBH-01, a camptothecin derivative engineered to target both topoisomerase I (TOP1) and DNA G-quadruplexes (G4s). Unlike irinotecan (CPT-11), which requires metabolic activation, ZBH-01 directly stabilizes TOP1-DNA covalent complexes and preferentially binds the hTERT promoter G4, a regulator of telomere maintenance and oncogenic transcription. Structural studies reveal that the crescent-shaped scaffold of ZBH-01 π-π stacks onto the external G-tetrad of the hTERT G4, displacing SP1/MYC transcription factors and suppressing hTERT expression. Functionally, ZBH-01 demonstrated improved efficacy in chemoresistant models, exhibiting 14-fold and 7-fold greater efficacy than CPT-11 and SN-38 respectively in cisplatin-resistant cells, and outperforming CPT-11 by 61-fold and SN-38 by 2.4-fold in 5-FU-resistant models. By concurrently disrupting DNA repair through TOP1-trapping and transcriptional adaptation via G4-stabilization, ZBH-01 induced DNA damage, telomere shortening, and cellular senescence. These findings establish TOP1/G4 dual-targeting as a potential therapeutic strategy to enhance CRC chemosensitivity, presenting a new framework for combining DNA damage induction with transcription modulation.