ANALYSIS OF CATHEPSIN-D FORMS AND THEIR CLINICAL IMPLICATIONS IN HUMAN PROSTATE-CANCER

Purpose: To assess cathepsin D (Cat.D) status in the prostate, we anal yzed the different Cat.D forms in human prostate tissues using Western immunoblots. Materials and Methods: Cell extracts were prepared from prostate tissues (n = 42) obtained from radical prostatectomy, adoptin g the tissue homogenization method. Expression of the different Cat.D forms was analyzed using Western blots, The catalytic activity of Cat. D was assayed by acid treatment, in which cell extracts were incubated in acidic buffer (pH 3 to 4) at 37C for 1 hour. Results: Pathological ly confirmed normal (NML), benign prostatic hyperplasia (BPH) and canc er (CAP) specimens all expressed Cat.D, but as two distinct forms. Bot h NML and BPH predominantly expressed an inactive procathepsin D(Pro.C at.D), while CAP notably exhibited an active mature Cat.D. The assessm ent of Cat.D activity, using PSA (prostate specific antigen) as a phys iological substrate, showed that such activity was consistently higher in CAP than in NML/BPH specimens. Further studies revealed that the m ode of Cat.D activation in CAP specimens appeared to be primarily due to acid-induced autoproteolysis (self-degradation) of mature Cat.D. Co nclusion: This study demonstrates that expression and activity of Cat. D varies among prostate specimens. A greater expression of mature Cat. D with a higher catalytic activity in CAP specimens is the most notabl e difference from NML/BPH. Therefore, the differential expression/acti vity of Cat.D forms may be a useful indicator for assessing prostate c ancer status.