Calculation of the combination index

To determine the combined effects of DMC and 5‐Fu on colon cancer cells, the combination index was calculated. Cells were treated with 5‐Fu and/or DMC at the indicated concentrations for 48 h before performing a CCK‐8 assay. Calculation of the combination index was performed using the following formula: Q = E_a+b/(E _a + E _b −E _a × E _b), where Q is the combination index; E _a + b represents the rate of cell proliferation inhibition induced by the combination drug; E _a and E _b represent the rate of cell proliferation inhibition of each drug ⁵. Resulting values of Q < 0.85, Q > 1.15, and 0.85 < Q < 1.15 indicate antagonism, synergy, and an additive effect, respectively.