FLICE-Like Inhibitory Protein (c-FLIP) suppression does not induce cell death in non-tumourigenic mammary cells. A, Haematoxylin/eosin-stained sections of mouse mammary glands excised from virgin or 14-day gestating β-lactoglobulin(BLG)-Cre/c-FLIP+/+ or BLG-Cre/c-FLIPfl/fl animals. Pictures are representative of four animals per group. B, Mammary epithelial cells isolated from BLG-Cre/c-FLIPfl/fl (Flip-floxed) and c-FLIP+/+ (WT) animals were grown in primary cell culture and incubated in the presence or absence of 100 ng/ml of soluble (mouse) Tumour Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL) for 18 hours. Cell viability was analysed using cellTiter blue viability assay. C, EPH4 (non-tumourgenic) and N202.1A (tumourgenic) cells were transfected with FLIP siRNA (FLIPi) or control siRNA (SCi) for 48 hours, media was then removed and fresh media with or without 100 ng/ml of mouse TRAIL was added for 18 hours and cell death assessed by flow cytometry as described in methods. D, MCF10A (non-tumourgenic) cells were treated and assayed according to C using 20 ng/ml human TRAIL.