Induction of apoptosis in BPH stromal cells by adenoviral-mediated overexpression of caspase-7

Purpose: We hypothesized that expression/activity of critical components of the apoptotic pathway can be used to induce apoptosis of a human prostate cell line derived from benign prostatic hyperplasia (BPH) tissue. Materials and Methods: We analyzed the apoptotic pathway in BPH, cells trea ted with the powerful inducer of apoptosis, staurosporine (STS), and adenov iruses overexpressing caspase-3, -7, or the control gene lacZ. Results: Twelve hours post-STS, most BPH cells were floating in the culture medium, TUNEL staining was widespread, and DEVDase activity (the catalytic activity of type II caspases) was increased. The pan-caspase inhibitor, Z- VAD-FMK, prevented STS-induced apoptosis, Based on these observations, we p erformed immunoblot analysis for the three known group II caspases (that is caspase-2, -3 and -7), but none of them was detected with three commercial ly available antibodies. Nevertheless, in view of the presence of increased DEVDase activity, we reasoned that a group II caspase must be a critical m ediator of apoptosis in this model. If correct, we postulated that overexpr ession and activation of a type II caspase should cause apoptosis. To test this hypothesis, we coupled the cDNAs encoding caspase-3 and caspase-7 to a denoviral vectors and obtained constructs AvC3 and AvC7. Cells infected wit h AvC3 or AVC7 overexpressed the protein for caspase-3 or -7 within 24 to 4 8 hours. Caspase-3 overexpression did not cause apoptosis above that observ ed in cells receiving the control adenovirus expressing the lacZ cDNA (AvLa c-Z). In contrast, caspase-7 overexpression induced massive apoptosis, BPH cells were then infected with increasing multiplicity of infection (MOI) of AvC7 and AvlacZ. A positive correlation was found between the amount of ca spase-7 expressed and the level of DEVDase activity measured. AVC7 at MOIs of 25:1 and 50:1 induced apoptosis in about 50% of BPH cells at; 72 hours p ost-infection. This effect was AVC7 specific, because the same MOIs of Avla cZ were not apoptogenic. Conclusions: Adenoviral-mediated overexpression of caspase-7 induces apopto sis of BPH-derived cells.