Effect of IL-6 pretreatment on anti-Fas MoAb-induced SAPK and p38 MAPK activation, as well as DNA fragmentation, in RPMI 8226 MM cells. Cells were cultured in media alone or pretreated with IL-6 as indicated before anti-Fas MoAb treatment. Cell lysates were immunoprecipitated with anti-SAPK Ab (A) or anti-p38 MAPK Ab (B). The resulting protein complexes were washed and then incubated in kinase buffer containing GST-Jun and [γ-³²P]ATP for 15 minutes at 30°C. The phosphorylated proteins were resolved by 10% SDS-PAGE, stained with Coomassie blue, dried, and analyzed by autoradiography. (C) Cells were cultured in either media alone or treated with 100 ng/mL of IL-6 for 3 to 4 hours before stimulation with anti-Fas MoAb for 6 hours. Genomic DNA was isolated, end-labeled with [γ³²P]ATP, and analyzed by 1.8% agarose gel electrophoresis. MW, molecular weight markers (123-bp ladders and HindIII digest of l-DNA).