FasL:Fas ratio--a prognostic factor in breast carcinomas

Programmed cell death (apoptosis) is primarily mediated by Fas ligand (FasL; CD95L) and the Fas receptor (Fas; CD95). In this study, FasL was detected by immunohistochemical analysis in 85% of breast carcinomas and 14% of fibroadenomas randomly chosen, indicating that high expression of FasL might play a role in tumor pathology. FasL and Fas levels as well as FasL:Fas ratios were further ascertained in 215 human breast tumors, including 199 invasive ductal carcinomas, by real-time quantitative reverse transcription-PCR and compared with expression levels and ratios found in 25 normal human tissues, in 37 fibroadenomas, and in 5 normal breast tissues. Among breast carcinomas, high FasL mRNA expression seems to be positively correlated with histological grading (n = 212; P<0.0001). A ratio of FasL:Fas mRNA transcripts >1 is found to be significantly associated with decreased patient's disease-free survival (n = 211; P<0.03) and increased mortality (n = 211; P = 0.19). A FasL:Fas ratio >1 is related to tumor progression scored by histological grading (n = 212; P<0.02). The selection process leading to highly aggressive breast tumor variants might be enhanced by FasL-mediated tumor fratricide, eventually a possible target for novel therapeutic strategies.