The cytotoxicity of TRAIL and DR4-4 Fab at various concentrations was compared in TRAIL-resistant human leukemia cell lines (THP-1 and Molt-4) and in mildly resistant and sensitive human lymphoma/leukemia cell lines (U-937, Jurkat, and HL60) using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (Figure 3A,B). Here, TNFRSF10A is linked to leukemia.