Astragali Radix - Curcumae Rhizoma synergistically potentiates 5-fluorouracil antitumor efficacy in colorectal cancer by disrupt DNA repair–cell cycle coordination

Background The herb pair Astragali Radix (HQ) and Curcumae Rhizoma (EZ), collectively termed AC, represents a classical combination in Traditional Chinese Medicine (TCM) frequently prescribed for colorectal cancer (CRC). Although AC is commonly administered as an adjuvant to chemotherapy, the molecular basis underlying its synergistic antitumor activity remains insufficiently defined. Methods The combinatorial efficacy of AC with 5-fluorouracil (5-FU) was evaluated in a CRC xenograft mouse model. Bioavailable plasma constituents following oral administration were characterized using UPLC-QTOF-MS. Transcriptomic alterations induced by AC in HCT116 cells were profiled by RNA sequencing. Mechanistic pathways were identified through integrative analysis combining differential gene expression, network pharmacology prediction, and clinical relevance assessment using TCGA CRC datasets. Putative compound–target interactions were predicted by molecular docking and subsequently examined using cellular thermal shift assays (CETSA). Functional validation was performed by flow cytometry and Western blotting in both human (HCT116) and murine (CT26) CRC models. Results AC significantly suppressed tumor growth in vivo and potentiated the antitumor efficacy of 5-FU. Gene set enrichment analysis demonstrated coordinated downregulation of pathways governing cell cycle progression, DNA replication, and mismatch repair. AC treatment dose-dependently reduced the expression of key regulatory hubs, including PLK1, CDK1, CCNB1, CDC25A, and c-JUN. Among the bioavailable constituents, demethoxycurcumin and kumatakenin partially recapitulated the synergistic inhibitory effect with 5-FU on CRC cell viability. Target engagement analyses suggested direct interactions of these compounds with CDK1 and CCNB1, supporting their role as functional mediators of AC activity. Conclusion The aqueous extract of AC enhances the therapeutic efficacy of 5-FU in CRC by disrupting the coordination between DNA repair and cell-cycle progression, thereby increasing tumor vulnerability to replication stress. Rather than acting on a single oncogenic node, AC appears to destabilize an integrated proliferative regulatory network. These findings provide mechanistic support for the traditional use of AC as a chemotherapeutic adjuvant and offer a rational foundation for its further translational development in CRC therapy.