Assessment of anti-tumor cell effect of human leukocyte interferon in combination with anticancer agents by a convenient assay system in monolayer cell culture.

Cell growth inhibition by anticancer agents was determined by a simple dye-uptake method. This technique could be performed more easily and rapidly than the cell counting method, the method for measurement of 3H-thymidine incorporation, or other dye-uptake methods. The number of viable cells was linearly correlated with the amount of dye taken by the surviving cells, so that the method described in this article could be applied to the assessment of anti-tumor cell effects of human leukocyte interferon (Hu IFN-alpha) in combination with anticancer agents. In combinations of Hu IFN-alpha with anticancer agents such as bleomycin, mitomycin C, and cytosine arabinoside in certain concentration ranges, antagonism was noticed when Hu IFN-alpha and anticancer agents were added simultaneously to the cell culture. However, outside those ranges of concentration, additive effects were observed. Furthermore, the treatment of the cell with IFN followed by the anticancer agents and vice versa showed additive effects.