title: Increased PADI4 expression in blood and tissues of patients with malignant tumors.
abstract: BACKGROUND
  Peptidylarginine deiminase type 4 (PAD4/PADI4) post-translationally converts peptidylarginine to citrulline. Recent studies suggest that PADI4 represses expression of p53-regulated genes via citrullination of histones at gene promoters.
  
  
  METHODS
  Expression of PADI4 was investigated in various tumors and non-tumor tissues (n = 1673) as well as in A549, SKOV3 and U937 tumor cell lines by immunohistochemistry, real-time PCR, and western blot. Levels of PADI4 and citrullinated antithrombin (cAT) were investigated in the blood of patients with various tumors by ELISA (n = 1121).
  
  
  RESULTS
  Immunohistochemistry detected significant PADI4 expression in various malignancies including breast carcinomas, lung adenocarcinomas, hepatocellular carcinomas, esophageal squamous cancer cells, colorectal adenocarcinomas, renal cancer cells, ovarian adenocarcinomas, endometrial carcinomas, uterine adenocarcinomas, bladder carcinomas, chondromas, as well as other metastatic carcinomas. However, PADI4 expression was not observed in benign leiomyomas of stomach, uterine myomas, endometrial hyperplasias, cervical polyps, teratomas, hydatidiform moles, trophoblastic cell hyperplasias, hyroid adenomas, hemangiomas, lymph hyperplasias, schwannomas, neurofibromas, lipomas, and cavernous hemangiomas of the liver. Additionally, PADI4 expression was not detected in non-tumor tissues including cholecystitis, cervicitis and synovitis of osteoarthritis, except in certain acutely inflamed tissues such as in gastritis and appendicitis. Quantitative PCR and western blot analysis showed higher PADI4 expression in gastric adenocarcinomas, lung adenocarcinomas, hepatocellular carcinomas, esophageal squamous cell cancers and breast cancers (n = 5 for each disease) than in the surrounding healthy tissues. Furthermore, western blot analysis detected PADI4 expression in cultured tumor cell lines. ELISA detected increased PADI4 and cAT levels in the blood of patients with various malignant tumors compared to those in patients with chronic inflammation and benign tumors. This was consistent with immunohistochemical results. Additionally, PADI4 and cAT levels were significantly associated with higher levels of known tumor markers.
  
  
  CONCLUSIONS
  Our results suggest that PADI4 expression is increased in the blood and tissues of many malignant tumors, a finding useful for further understanding of tumorigenesis.
authors.affiliation: Key Laboratory for Bio-drugs of Ministry of Health, Research Center For Medicinal Biotechnology, Shandong Academy of Medical Sciences, Jingshi Road 89, Jinan, Shandong, 250062, PR China. changxt@126.com
authors.forename: Xiaotian
authors.initials: X
authors.lastname: Chang
authors.forename: Jinxiang
authors.initials: J
authors.lastname: Han
authors.forename: Li
authors.initials: L
authors.lastname: Pang
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Zhonglin
authors.initials: Z
authors.lastname: Shen
mesh_terms: D000991:Antithrombins / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002956:Citrulline / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D006867:Hydrolases / Q000097:blood / Q000378:metabolism*; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008297:Male; D009363:Neoplasm Proteins / Q000097:blood / Q000378:metabolism*; D009369:Neoplasms / Q000097:blood / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases
chemical_list: D000991:Antithrombins; D009363:Neoplasm Proteins; D002956:Citrulline; D006867:Hydrolases; C000629235:PADI4 protein, human; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases