title: Carboxypeptidase-D is elevated in prostate cancer and its anti-apoptotic activity is abolished by combined androgen and prolactin receptor targeting.
abstract: BACKGROUND
  Carboxypeptidase-D (CPD) cleaves C-terminal arginine for nitric oxide (NO) production. CPD and NO levels are upregulated by testosterone (T) and prolactin (PRL) to promote survival of prostate cancer (pCa) cells. This study evaluated CPD immunostaining and T/PRL regulation of CPD and NO levels in benign and malignant prostate tissues/cells to determine the role of CPD in pCa.
  
  
  METHODS
  Immunohistochemistry (IHC) and tissue microarrays (TMA) were used to determine CPD immunostaining in prostate specimens. QPCR and immunoblotting were used to quantify CPD mRNA/protein expression in prostate cells. NO production was measured using 4,5-diaminofluorescein diacetate assay.
  
  
  RESULTS
  CPD staining increased from 8.9 ± 3.8% (Mean ± SEM, n = 15) of benign epithelial cell area to 30.9 ± 2.9% (n = 30) of tumor cell area in one set of TMAs (P = 0.0008) and from 5.9 ± 0.9% (n = 45) of benign epithelial cell area to 18.8 ± 1.9% (n = 55) of tumor area in another (P < 0.0001). IHC of prostate tissues (≥50 mm(2)) confirmed increased CPD staining, from 13.1 ± 2.9% in benign (n = 16) to 29.5 ± 4.4% in pCa (n = 31, P = 0.0095). T and/or PRL increased CPD expression in several pCa but not benign cell lines. T and PRL acted synergistically to increase NO production, which was abolished only when receptor antagonists flutamide and Δ1-9-G129R-hPRL were used together.
  
  
  CONCLUSIONS
  CPD immunostaining and T/PRL-stimulated CPD expression were higher in pCa than benign tissues/cells. Elevated CPD increased NO production, which was abolished when both AR and PRLR were inhibited. Our study implicates a critical role for the T/PRL-stimulated CPD-Arg-NO pathway in pCa progression, and suggests that AR+PRLR inhibition is a more effective treatment for pCa.
authors.affiliation: Departments of Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada.
authors.forename: Lynn N
authors.initials: LN
authors.lastname: Thomas
authors.forename: Jennifer
authors.initials: J
authors.lastname: Merrimen
authors.forename: David G
authors.initials: DG
authors.lastname: Bell
authors.forename: Ricardo
authors.initials: R
authors.lastname: Rendon
authors.forename: Vincent
authors.initials: V
authors.lastname: Goffin
authors.forename: Catherine K L
authors.initials: CK
authors.lastname: Too
mesh_terms: D000726:Androgen Antagonists / Q000494:pharmacology; D000728:Androgens / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002268:Carboxypeptidases / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D005485:Flutamide / Q000494:pharmacology; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis; D011388:Prolactin / Q000494:pharmacology; D011467:Prostate / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D011981:Receptors, Prolactin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013739:Testosterone / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000726:Androgen Antagonists; D000728:Androgens; D011944:Receptors, Androgen; D011981:Receptors, Prolactin; D009569:Nitric Oxide; D013739:Testosterone; D005485:Flutamide; D011388:Prolactin; D002268:Carboxypeptidases; C078874:carboxypeptidase D
keywords: carboxypeptidase-D; nitric oxide; prolactin; prostate cancer; testosterone