Cold Plasma-Activated Medium Reverses Chemoresistance in Colorectal Cancer via ROS-Mediated Suppression of ABC Transporters and Redox Homeostasis Disruption

Chemotherapy resistance mediated by multidrug resistance (MDR) remains a significant challenge in the treatment of colorectal cancer (CRC). Limited studies suggested that reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated by cold atmospheric plasma-activated medium (PAM) may reverse chemotherapy resistance in drug-resistant tumors, however, the underlying mechanisms are not fully understood. This study investigates the efficacy and molecular mechanisms of PAM in reversing Adriamycin (ADR) resistance in CRC cell lines (HCT8/ADR, HCT15/ADR) compared to their parental counterparts (HCT8, HCT15). Resistant cells exhibited significantly elevated mRNA and protein expression of multidrug resistance protein 1 (MDR1) and ATP-binding cassette subfamily G member 2 (ABCG2). PAM, enriched with ROS/RNS, effectively reversed chemotherapy resistance by increasing intracellular ROS levels, inducing apoptosis, and disrupting cytoskeletal integrity. Notably, PAM downregulated the transcription of MDR1 and ABCG2 and enhanced ADR accumulation in HCT8/ADR cells. RNA sequencing revealed that PAM modulates membrane ion channel activity, potentially restoring drug retention. Furthermore, PAM suppressed antioxidant enzyme expression, exacerbating oxidative stress and inducing selective death of resistant cells. These findings highlight PAM as a promising adjunctive strategy to overcome chemotherapy resistance in CRC, warranting further preclinical and clinical investigation.