(A) RT-PCR analysis of HB-EGF mRNA expression in a number of leukemic, Hodgkin-, and NK-derived cell lines. HB-EGF: 605 bp; vimentin: 266 bp; marker: 100-bp DNA ladder. (B) 48-hour DT dose-sensitivity curve as evaluated by the MTT method. Only HB-EGF mRNA-positive cell lines were sensitive to DT (ie, >50% death in the range of tested concentrations), indicating membrane expression of the HB-EGF molecule.