RRR-ALPHA-TOCOPHERYL SUCCINATE INDUCTION OF PROLONGED ACTIVATION OF C-JUN AMINO-TERMINAL KINASE AND C-JUN DURING INDUCTION OF APOPTOSIS IN HUMAN MDA-MB-435 BREAST-CANCER CELLS

We have demonstrated that RRR-alpha-tocopheryl succinate (10 mu g/mL v itamin E succinate (VES) treatment of estrogen receptor-negative MDA-M B-435 human breast cancer cells induces 9, 19, 51, and 72% apoptotic c ells on days 1-4, respectively, after treatment, which involves transf orming growth factor-beta signaling. Here, we show that VES-triggered apoptosis of MDA-MB-435 cells induced prolonged elevated expression of c-jun mRNA and protein (neither of which was caused by major increase s in stability) and also induced enhanced activator protein-1 (AP-1) b inding to the consensus DNA oligomer. Furthermore, VES treatments resu lted in increased AP-1 transactivation activity, as measured with an A P-1 promoter/luciferase reporter construct and by the measurement of i ncreased mRNA expression of the AP-1-dependent endogenous gene collage nase. Evidence of VES-induced involvement of the c-jun amino-terminal kinase in these AP-1-dependent events was suggested by data showing pr olonged activity of this kinase, as measured by a kinase assay using g lutathione S-transferase-c-jun as the substrate. The c-jun-dependent t ranscriptional activity was verified by cotransfection of a chimeric t ranscription factor having a galactose 4 DNA-binding domain coupled wi th the transactivation domain of c-jun plus the reporter plasmid 5X GA L4-luciferase. MDA-MB-435 cells infected with an adenovirus expression Vector containing the TAM-67 sequence for dominant/negative-acting mu tant c-jun or transiently transfected with c-jun antisense exhibited a 50-77% reduction in VES-mediated apoptosis as compared with control a denovirus-infected or control sense oligomer-transfected cells. Mel. C arcinog. 22:247-257, 1998. (C) 1998 Wiley-Liss. Inc.