Drug interaction analysis

Drug interaction analysis between 5-FdU-ECyd and cisplatin was based on cell viability data, obtained by the fluorometric Cell Titer Blue^®-Assay (Promega, Fitchburg, USA), according to the manufacturer's instructions. Statistical analysis was performed by the combination index method [43], which is based on the combination of drugs at a broad range of equipotent molar concentrations or, as our modification, with standard cisplatin dose-response curves with a fixed 5-FdU-ECyd concentrations at each reading point. Additional information to this method is provided in Supplementary Materials.