Western blot analysis of caspase-3 and caspase-9 in total cell lysates. OHS cells were left untreated (-) or treated with 100 u/ml IFN-γ (+) for 24, 48 and 72 hours, and lysates subjected to Western blot analysis as described in "Materials and Methods". As a positive control for caspase activation, an immunotoxin-treated breast cancer cell line was included. α-tubulin serves as a loading control. The results shown are representative of three independent experiments.