title: Adiponectin as a potential tumor suppressor inhibiting epithelial-to-mesenchymal transition but frequently silenced in prostate cancer by promoter methylation.
abstract: BACKGROUND
  Recent evidence suggests a particular role for obesity in prostate cancer (PCa) progression. Adiponectin (ADN) is a hormone secreted by adipose tissue and has a variety of functions including the inhibition of PCa cell proliferation. Although serum ADN levels have been identified to be related with carcinogenesis in a tissue-specific context, the exact role of endogenous ADN in PCa cells remains largely unknown.
  
  
  METHODS
  Two tissue microarrays were constructed and immunohistochemistry (IHC) was utilized to detect ADN's expression in a cohort of 96 Chinese PCa patients with radical prostatectomy as well as 15 cases with Benign Prostatic Hyperplasia (BPH). MTS and transwell assays were applied to validate the effects of ADN on proliferation and invasive capacity of PCa cells. Real-time PCR and Western blot were performed to evaluate the expression at transcript and protein levels. Epigenetic modifications of ADN's promoter after TGF-β1 treatment in 22RV1 cells was monitored by chromatin immunoprecipitation (ChIP). Methylation-Specific PCR (MSP) was performed to determine the methylation status of ADN's promoter.
  
  
  RESULTS
  IHC showed decreased levels of ADN in 1 of 15 (6.7%) BPH cases, 6 of 27 (22.2%) PCa cases with low Gleason score (<7), 18 of 26 (69.2%) cases with Gleason score 7, but 32 of 43 (74.4%) cases with high Gleason score (>7). Silencing endogenous ADN could promote proliferation and invasion of 22RV1 cells via orchestrating Epithelial-to-mesenchymal Transition (EMT) process. TGF-β1, a potent EMT inducer, could decrease levels of chromatin markers associated with active genes (H3K4me3, H4acetylK16), and increase levels of repressive marker (H3K27me3) at ADN promoter in 22RV1 cells. Additionally, 5-aza and TSA treatment restored ADN expression in LNCaP cells in which the ADN expression was almost absent. MSP analysis revealed that methylation in the promoter might be involved in decreased expression of ADN in PCa tissues.
  
  
  CONCLUSIONS
  Our findings indicated that endogenous ADN may function as a tumor suppressor gene through inhibiting EMT of PCa cells but is down-regulated in PCa via promoter hypermethylation.
authors: Department of Pathology, Shandong University Medical School, Jinan, China.
authors: Weiwei
authors: W
authors: Tan
authors: Department of Pathology, Shandong University Medical School, Jinan, China.|Research Center for Medicinal Biotechnology, Key Laboratory for Rare & Uncommon Diseases of Shandong Province, Shandong Academy of Medicinal Sciences, Jinan, China.
authors: Lin
authors: L
authors: Wang
authors: Department of Clinical Laboratory, The Fourth People's Hospital of Jinan, Jinan, China.
authors: Quanping
authors: Q
authors: Ma
authors: Department of Pathology, Shandong University Medical School, Jinan, China.
authors: Mei
authors: M
authors: Qi
authors: Department of Pathology, Shandong University Medical School, Jinan, China.
authors: Ning
authors: N
authors: Lu
authors: Department of Pathology, Shandong University Medical School, Jinan, China.
authors: Lili
authors: L
authors: Zhang
authors: Department of Pathology, Shandong University Medical School, Jinan, China.|Department of Pathology, Shandong University Qilu Hospital, Jinan, China.
authors: Bo
authors: B
authors: Han
mesh_terms: D052242:Adiponectin / Q000235:genetics / Q000378:metabolism; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002681:China; D019175:DNA Methylation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008297:Male; D060787:Neoplasm Grading; D011401:Promoter Regions, Genetic; D011467:Prostate / Q000378:metabolism / Q000473:pathology; D011468:Prostatectomy / Q000379:methods; D011470:Prostatic Hyperplasia / Q000378:metabolism / Q000473:pathology; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D052242:Adiponectin; D000964:Antimetabolites, Antineoplastic; D001374:Azacitidine
keywords: EMT; adiponectin; methylation; prostate cancer