Inhibition of drugs-induced apoptosis by CD40L L cells in carcinoma cell lines. Breast carcinoma cell lines (T47D, BT20) were pre-incubated 24 hours alone or with irradiated (75 Gy) L cells expressing CD40L, then incubated with DOX (0.5 μg/ml), ETO (7.5 μg/ml), CDDP (7.5 μg/ml), VIN (50 nM) and TAX (50 nM) for 24 hours. The intensity of fluorescence, using TUNEL assay, was proportional to the number of fluorescein labeled DNA strand breaks. The threshold level of fluorescence intensity beyond which cells were considered to be in apoptosis was 101. *Apoptosis was significantly decreased (Student t test, p < 0.05) upon co-culture with irradiated CD40L L cells as compared to no L cells This experiment is representative of 7 different experiments.