Fas antigen and p55 TNF receptor signal apoptosis through distinct pathways.

The Fas Ag and the p55 TNF receptor (TNF-R1) are related molecules that can signal apoptosis. Some tumor cell lines are selectively killed by Fas activation and others by TNF-R1 activation even though both receptors are often co-expressed. TNF-R1-mediated cytotoxicity can be selectively inhibited under conditions in which Fas-mediated cell death is not affected. Activation of both receptors results in synergistic signaling of apoptosis. These results indicate that different biochemical pathways are activated by Fas and TNF-R1. Combination treatment with agonists of Fas and TNF-R1 may have therapeutic potential.