CFLAR and breast cancer: When c-FLIP inhibition (FLIPi) was combined with TRAIL administration, a significant TRAIL-dependent kill was observed for all of the breast cancer cell lines tested (Figure 2B, white bars; Additional file 1 Figure S5), demonstrating a marked sensitization to TRAIL in resistant cell lines, but no more than an additive effect of FLIPi in the TRAIL-sensitive MDA-MB-231 cell line.