Tumor-induced activation of caspase-8.

Fas-sensitive or Fas-resistant Jurkat cells were treated with agonistic anti-Fas Ab (CH-11, 200 ng/mL) or coincubated with tumor cells for 16 hours. At the end of the incubation period, Jurkat cells were negatively selected by removal of tumor cells, lysed, and assessed by Western blotting for loss in expression of caspase-8. Equal loading was confirmed by equivalent detection of nonspecific bands on the same membrane when stripped and probed for the presence of other caspases (not shown).