Caffeine Potentiates Apoptosis Induction at a Lower Dose of Oxaliplatin in HCT-116 and HT-29

Background: Colorectal cancer (CRC) continues to represent a major threat to cancer-related mortality, though advancements in diagnostic modalities and therapeutic strategies have been achieved. Oxaliplatin, a platinum-based chemotherapeutic agent with demonstrated efficacy against CRC, constitutes a cornerstone of standard treatment regimens. Nevertheless, its clinical utility is limited by drug resistance and significant adverse effects. Objective: This study aims to investigate the modulatory effects of caffeine on the therapeutic efficacy of oxaliplatin as an anticancer agent in CRC in vitro . Materials and Methods: 3-[4,5-Dimethylthiazole-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was performed to determine the cytotoxic effects of oxaliplatin and caffeine in monotherapy and combination on human CRC cell lines HCT-116 and HT-29 and healthy human peripheral blood mononuclear cells (PBMCs). Clonogenic assay was performed to evaluate the effect on cell proliferation. Flow cytometry-based Annexin V-FITC/PI dual staining was performed to detect apoptosis induction. The expression level of apoptosis-markers was examined by western blot. Results: The MTT assay demonstrated dose-dependent cytotoxicity of oxaliplatin and caffeine, both as monotherapies and in combination, against HCT-116 and HT-29 cells, while sparing normal PBMCs. Combination therapy lowered oxaliplatin’s IC 50 values through synergistic and additive interactions respectively in HCT-116 and HT-29. Co-treatment suppressed cell proliferation and induced apoptosis to a degree comparable to that of oxaliplatin monotherapy, with a more pronounced effect in HCT-116. Conclusion: These preliminary observations suggest that caffeine may enhance the anticancer efficacy of oxaliplatin and may potentially alleviate its adverse effects by enabling dose reduction in the CRC model in vitro .