Curcumin reverses irinotecan-acquired resistance in DLD1 colorectal cancer cells: Insights from whole transcriptomic data

Acquired resistance to chemotherapy, including irinotecan, remains a major challenge in treating metastatic colorectal cancer (CRC). Natural compounds such as curcumin have demonstrated potential in resensitizing chemoresistant cancer cells to existing therapies. This study investigates curcumin's ability to reverse irinotecan resistance in CRC cells and the underlying molecular mechanisms. An irinotecan-resistant CRC cell line (DLD1_IRI-R) was established by gradually increasing irinotecan exposure. The DLD1 cell line was selected for its intermediate sensitivity to irinotecan among CRC cell lines. Cell sensitivity to irinotecan and curcumin was assessed using the MTT assay, with drug interactions evaluated via the Chou-Talalay method. Apoptosis and cell cycle progression were analyzed by flow cytometry, proliferation by clonogenic assays, and migration in 3D microfluidic systems. Whole-genome transcription profiling was conducted using microarrays, with functional analysis performed in Ingenuity Pathway Analysis. DLD1_IRI-R cells exhibited a 7.17-fold increase in irinotecan resistance, accompanied by reduced proliferation and migration. Resistance acquisition led to dysregulation of genes involved in irinotecan metabolism (CYPs, UGTs, AKRs), efflux transport (ABCs), and ER stress adaptation. The gene coding for the drug target, TOP1, was also inhibited. Curcumin, combined with irinotecan at IC₁₀, reduced irinotecan's IC₅₀ by 3.74-fold, exhibiting strong synergy. Curcumin significantly modulated 3,901 genes (FC > |±2|), inducing apoptosis, disrupting ER stress adaptation, reducing proliferation, and inhibiting migration. It also upregulated TOP1 while suppressing key resistance-associated genes, including 18 CYPs, 4 UGTs, 4 AKRs, and 20 ABCs. These findings suggest that low-dose curcumin effectively reverses irinotecan resistance in CRC cells, enhancing chemotherapy sensitivity and inhibiting metastasis-associated traits.