title: Prognostic significance of aberrantly silenced ANPEP expression in prostate cancer.
abstract: BACKGROUND
  Novel biomarkers for prostate cancer (PC) are urgently needed. This study investigates the expression, epigenetic regulation, and prognostic potential of ANPEP in PC.
  
  
  METHODS
  Aminopeptidase N (APN; encoded by ANPEP) expression was analysed by immunohistochemistry using tissue microarrays representing 267 radical prostatectomy (RP) and 111 conservatively treated (CT) PC patients. Clinical end points were recurrence-free survival (RFS) and cancer-specific survival (CSS), respectively. The ANPEP promoter methylation levels were determined by bisulphite sequencing or MethyLight analysis in 278 nonmalignant and PC tissue samples, and in cell lines.
  
  
  RESULTS
  The APN expression was significantly downregulated in PC compared with nonmalignant prostate tissue samples. Aberrant promoter hypermethylation was frequently observed in PC tissue samples, and 5-aza-2'-deoxycytidine induced ANPEP expression in three hypermethylated prostate cell lines, suggesting epigenetic silencing. Negative APN immunoreactivity was significantly associated with short RFS and short CSS in the RP and CT cohort, respectively, independently of routine clinicopathological predictors. Combining APN with a known angiogenesis marker (vascular endothelial growth factor or microvessel density) improved risk prediction significantly in both cohorts.
  
  
  CONCLUSIONS
  Our results suggest negative APN immunoreactivity as a new independent adverse prognostic factor for patients with clinically localised PC and, furthermore, that epigenetic mechanisms are involved in silencing of ANPEP in PC.
authors: Department of Molecular Medicine, Aarhus University Hospital, Brendstrupgaardsvej 100, DK-8200 Aarhus N, Aarhus, Denmark. orntoft@ki.au.dk
authors: K D
authors: KD
authors: Sørensen
authors: M O
authors: MO
authors: Abildgaard
authors: C
authors: C
authors: Haldrup
authors: B P
authors: BP
authors: Ulhøi
authors: H
authors: H
authors: Kristensen
authors: S
authors: S
authors: Strand
authors: C
authors: C
authors: Parker
authors: S
authors: S
authors: Høyer
authors: M
authors: M
authors: Borre
authors: T F
authors: TF
authors: Ørntoft
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D018826:CD13 Antigens / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation; D000077209:Decitabine; D018572:Disease-Free Survival; D044127:Epigenesis, Genetic; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000235:genetics; D011401:Promoter Regions, Genetic; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000601:surgery; D017422:Sequence Analysis, DNA
chemical_list: D014408:Biomarkers, Tumor; D000077209:Decitabine; D018826:CD13 Antigens; D001374:Azacitidine