CASPASE-7 IS ACTIVATED DURING LOVASTATIN-INDUCED APOPTOSIS OF THE PROSTATE-CANCER CELL-LINE LNCAP

The goals of this work were to establish a reproducible and effective model of apoptosis in a cell line derived from advanced prostate cance r and to study the role of the caspase family of proteases in mediatin g apoptosis in this system. The study involved the use of the prostate cancer cell line LNCaP, Apoptosis was induced using the hydroxymethyl glutaryl CoA reductase inhibitor, Lovastatin, and was evaluated by ag arose gel electrophoresis of genomic DNA, morphological criteria, and terminal deoxynucleotidyl transferase-mediated nick end labeling, Casp ases were studied by catalytic activity, mRNA induction, and protein p rocessing, Lovastatin (30 mu M) was an effective inducer of apoptosis, causing changes that were evident after 48 h and essentially complete after 96-120 h of treatment, These effects were prevented by the simu ltaneous addition of mevalonate (300 mu M) to the culture medium, Lova statin induced a proteolytic activity that was able to cleave the enzy me poly(ADP-ribose) polymerase and the substrate Z-DEVD-AFC, which is modeled after the P-1-P-4 amino acids of the poly(ADP-ribose) polymera se cleavage site. Caspase-7, but not caspase-3, underwent proteolytic activation during lovastatin-induced apoptosis, an effect prevented by mevalonate. Caspase-7 was the only detected interleukin 1 beta conver ting enzyme family protease with DEVD cleavage activity that exhibited lovastatin-induced mRNA up-regulation. Again, mevalonate blocked this effect Lovastatin-induced apoptosis also was prevented when the caspa se inhibitors Z-DEVD-CH2F or Z-VAD-CH2F (100 mu M) where added to the medium, These studies have identified lovastatin as a powerful inducer of apoptosis in the cell line LNCaP. Caspase activation was a necessa ry event for LNCaP cells to undergo apoptosis during treatment with lo vastatin. Of the caspases tested, only caspase-7 underwent proteolytic activation after stimulation with lovastatin, Identification of caspa se-7 as a potential mediator of lovastatin-induced apoptosis broadens our knowledge of the molecular events associated with programmed cell death in a cell line derived from prostatic epithelium.