Assessment of tumor necrosis factor receptor and Fas signaling pathways by transcriptional profiling.

Apoptosis, or programmed cell death, is an important mechanism by which cells are eliminated during immune regulation and embryonic development. Aberrations in the signaling pathways leading to apoptosis may result in cancer, autoimmune diseases, or inflammatory disorders. In view of this, an understanding of the signaling capabilities of apoptosis-inducing or death receptors is essential to understanding their roles in biology and disease. We used cDNA microarrays to examine the downstream transcriptional effects of two members of the tumor necrosis factor (TNF) family of death receptor ligands. We compared the transcriptional responses of a model colon cancer cell line, HT29, to TNF-alpha and anti-Fas activating antibody. Both ligands induced a subset of genes characteristic of activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Follow-up analyses demonstrated that, although TNF-alpha activated NF-kappaB through IkappaB-alpha degradation, alpha-Fas treatment led to NF-kappaB activation through a mechanism distinct from IkappaB-alpha degradation.