Modulation of CDDP-induced apoptosis in U87MG.ΔEGFR cells by various tyrphostin-type tyrosine kinase inhibitors. (A) Reduced Bcl-XL expression upon exposure to tyrphostin AG1478. U87MG.ΔEGFR cells were treated with the ΔEGFR-selective tyrphostin AG1478 (15 μM) with or without CDDP (5 μg/ml), and total cell lysates were prepared. For each sample, 20 μg lysate was used. (B) Increased apoptosis induced by combination treatment by using ΔEGFR-selective tyrphostins (AG1478 or AG1517) and CDDP. U87MG.ΔEGFR cells were treated with or without 5 μg/ml CDDP for 2 days in the presence of the ΔEGFR-selective tyrphostins (AG1478 or AG1517) or the nonspecific, less potent tyrphostins (AG1479 or AG1536) at the concentrations indicated. For control, the vehicle (dimethyl sulfoxide) was used. Apoptosis rate was determined by TUNEL assays from triplicate coverslips. Experiments were repeated independently two to three times, with similar results.