Chemosensitization of Androgen-Independent Prostate Cancer with Neutral Endopeptidase

• Published in: Clinical cancer research Vol. 10; no. 1; pp. 260 - 266
• Main Authors: SUMITOMO, Makoto, ASANO, Tomohiko, ASAKUMA, Junichi, ASANO, Takako, NANUS, David M, HAYAKAWA, Masamichi
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.01.2004
• Subjects: Androgens - pharmacology; Annexin A5 - metabolism; Antineoplastic agents; Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis - drug effects; Biological and medical sciences; Cells, Cultured - drug effects; Drug Resistance, Neoplasm; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Etoposide - pharmacology; Humans; Male; Medical sciences; Mitochondria - drug effects; Mitochondria - metabolism; Neoplasms, Hormone-Dependent - enzymology; Neoplasms, Hormone-Dependent - pathology; Neprilysin - antagonists & inhibitors; Neprilysin - metabolism; Organophosphonates - pharmacology; Pharmacology. Drug treatments; Phenylalanine - analogs & derivatives; Phenylalanine - pharmacology; Prostate - metabolism; Prostate - pathology; Prostatic Neoplasms - enzymology; Prostatic Neoplasms - pathology; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Protein Kinase C-delta; Recombinant Proteins - pharmacology; Tumors; Peptidases; Androgen; Enzyme; Hydrolases; Metalloendopeptidases; Neprilysin; Malignant tumor; Sex steroid hormone; Urogenital system; Prostate
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-0798-3

Purpose: We investigated whether neutral endopeptidase (NEP) could augment chemosensitivity to anticancer drugs by promoting protein kinase C (PKC)δ-mediated mitochondrial apoptosis in prostate cancer (PC) cells. Experimental Design: Human PC cell lines LNCaP and PC-3, and a normal prostate epithelial cell line (PrEC) were used. The protein expression was detected by Western blot analysis, and the protein turnover was determined by pulse-chase assay. Apoptotic ratio was measured by annexin V staining. Results: Western blot analyses and pulse-chase assays showed that the specific NEP inhibitor CGS24592 decreased PKCδ protein expression by promoting PKCδ protein degradation in NEP-expressing LNCaP cells. Conversely, recombinant NEP (rNEP) increased PKCδ protein expression by delaying PKCδ protein degradation in NEP-negative PC-3 cells. Apoptosis assays showed that rNEP promoted anticancer drug-induced apoptosis in PC-3 cells specifically through PKCδ activity that mediated anticancer drug-induced mitochondrial change such as cytochrome- c release and caspase-9 activation. Of note, rNEP was able to increase PKCδ protein expression predominantly in PC-3 cells rather than in PrEC cells. Treatment with rNEP before subtoxic concentrations of etoposide (0.1 μ m ) significantly promoted mitochondrial apoptosis compared with only etoposide in PC-3 cells ( P < 0.01) but not in PrEC cells. Conclusions: These results suggest that NEP enzyme activity contributes to anticancer drug-induced PC cell apoptosis dependent on PKCδ-mediated mitochondrial events. More importantly, the combination of NEP with anticancer drugs may be a promising therapeutic modality because rNEP is able to augment chemosensitivity in androgen-independent PC with minimal toxicity in normal tissues.