To evaluate whether the antitumor effects of niclosamide combined with DDP were synergistic, additive or antagonistic, combination index (CI) value for drug synergy was calculated using the CompuSyn software (Version 2.1, ComboSyn, Inc., Paramus, NJ, USA) as previously described (14 (link)). Using data obtained from CCK-8 assays and CompuSyn software, the dose-effect curves for single agents and their combinations were generated, and the CI values for each dose and the corresponding effect level, referred to as the fraction affected (Fa; the fraction of cells inhibited following drug exposure, for example 0.5 when cell growth is inhibited by 50%), were calculated. CI values <1 indicated a synergistic effect, values equal to 1 indicated an additive effect and values >1 indicated an antagonistic effect. Then, to provide a visual illustration of drug interactions, the Fa-CI plot was constructed by simulating CI values over a range of Fa levels from 0.1 to 0.95 (18 (link),19 (link)).