In Vitro Schedule-Dependent Interaction Between Melphalan and Oxaliplatin in Human Colorectal Cancer Cell Lines

ObjectiveIn order to determine the applicability of oxaliplatin in isolated liver perfusion, we identified the interaction between combinations of oxaliplatin and melphalan in 13 human colorectal cancer cell lines.MethodsCytotoxic activity was determined by the MTT-assay. Three different administration schedules of the two drugs were compared and median effect isobologram analysis was applied to the results, to determine the presence of synergism, additive effects, or antagonism as described by Chou and Talalay [30].ResultsResistance to melphalan did not correspond to resistance to oxaliplatin. All combinations of melphalan and oxaliplatin showed synergistic or additive interaction in the majority of the cell lines. One hour of oxaliplatin followed by 1h of melphalan showed the lowest percentage of cell viability, with synergy in 10 out of 13 cell lines at 50% cell viability. Simultaneous treatment showed the highest cell viability, with antagonism in six cell lines, additivity in two cell lines, synergism in five cell lines at 50% cell viability. One hour of melphalan followed by 1h of oxaliplatin showed synergy in six cell lines, antagonism in another six, and additivity in one cell line.ConclusionsOur findings suggest a schedule-dependent synergistic interaction between melphalan and oxaliplatin. Therefore, oxaliplatin should be considered as a new, potentially valuable additional agent to the currently commonly used melphalan in isolated hepatic perfusion in colorectal cancer patients.