Cytotoxicity of the combination on Hep-2 laryngeal carcinoma cells. (a) Cytotoxic effect of 5-FU, NDV, or both, on Hep-2 cells in vitro. Hep-2 cells were treated with 5-FU (5 µg in two-fold serial dilutions up to 0.039 µg/mL), NDV (128 HUA with two-fold serial dilutions), or a combination of the two treatments. The results for the treated groups are expressed as the cell proliferation rate compared with untreated control cells grown at identical conditions. HUA: hemagglutination unit, which is the smallest virus concentration leading to visible erythrocyte agglutination; (b) isobologram analysis showing synergism between NDV and 5-FU as the point of combination is at the lower left of the hypotenuse, indicating the effect is synergistic at a 50% growth inhibition dose for the Hep-2 tumor cell line. In the figure we can see four points that is less than or equal to 1; and (c) table showing the combination index data for each dose.