Figure 3: Results of combination treatment. ras-NIH3T3 cells were added with 5-FU (50 ng/ml), PEP (500 ng/ml) or MTX (50 ng/ml). Immediately after the addition, cells were plated in the presence of varying concentrations of MIT (A), PEP (B) and VP-16 (C). After culture for three days, the viabilities were measured by the MTT assay. The abscissa and ordinate represent the concentration of the latter drugs and the relative viability versus that in the absence of the latter drugs, respectively.