Expression of the apoptosis-inducing ligands FasL and TRAIL in malignant and benign human breast tumors

Apoptosis-inducing ligands such as Fas ligand (FasL) and tumor necrosis fac tor-related apoptosis-inducing ligand (TRAIL) have been found to play an im portant role in cell regulation. Different malignant tumors show an altered expression of these ligands and their respective receptors compared to nor mal tissues. The purpose of this study was therefore to investigate express ion of TRAIL, Fast, and its receptor Fas on protein and mRNA levels in brea st carcinomas (n=40), fibroadenomas (n=7), and normal breast tissues (n=5). Immunohistochemical reaction demonstrated that Fast was strongly expressed in breast cancer tissues (34/40) while only one fibroadenoma and one norma l breast tissue reacted weakly positive for Fast. All fibroadenomas and nor mal breast tissues as well as the majority of breast cancer tissues express ed Fas on protein level. Quantitative RT-PCR analysis detected high express ion of Fast mRNA in breast cancer tissues and fibroadenomas, whereas fibroa denomas showed the highest Fas mRNA copy numbers, followed by breast cancer tissues and normal breast tissues (P<0.05). Compared to Fast expression, T RAIL could be detected in less breast cancer tissues on protein level (21/4 0) and was found in only one fibroadenoma and none of the normal breast tis sues. Thus, it can be concluded that malignant breast tumors show an altere d expression of the two apoptosis-inducing ligands Fast and TRAIL.