title: ECRG4 acts as a tumor suppressor and as a determinant of chemotherapy resistance in human nasopharyngeal carcinoma.
abstract: BACKGROUND
  Human nasopharyngeal carcinoma (NPC) is a malignant type of cancer with an increasing incidence. As yet, however, molecular biomarkers with a strong diagnostic impact and a major therapeutic promise have remained elusive. Here, we identified the esophageal carcinoma related gene 4 (ECRG4) as a novel candidate tumor suppressor gene and a promising therapeutic target for NPC.
  
  
  METHODS
  RT-PCR, Western blotting, methylation-specific PCR and bisulfite sequencing were performed to assess the expression and methylation status of the ECRG4 gene in primary NPC samples, NPC-derived cell lines and patient-derived peripheral blood samples. The NPC-derived cell line CNE1 was selected for treatment with a methylation inhibitor to restore ECRG4 expression. In addition, cell proliferation, invasion and colony formation assays were performed to assess the inhibitory effects of exogenous ECRG4 expression in CNE1 cells.
  
  
  RESULTS
  Down-regulated ECRG4 expression was found to occur in 82.5% (33/40) of the primary NPC biopsies tested. This down-regulation was significantly correlated with its tumor-specific promoter methylation status (72.5%, 29/40) and was also observed in the matching peripheral blood samples from the NPC patients (57.5%, 23/40). Pharmacologic demethylation through 5-aza-dC treatment led to gene reactivation in ECRG4 methylated and silenced NPC cell lines. Moreover, exogenous expression of ECRG4 in the CNE1 cell line strongly inhibited its growth and invasive capacities, as well as its enhanced chemosensitivity to cisplatin through autophagy induction.
  
  
  CONCLUSIONS
  Our data suggest that methylation-mediated suppression of the ECRG4 gene occurs frequently in NPC and that restoration of its expression may have therapeutic benefits.
authors.affiliation: Department of Pharmacy, Luohe Medical College, 148 Daxue-Road, Luohe, 462002, China, youyanjie@163.com.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: You
authors.forename: Wenjun
authors.initials: W
authors.lastname: Yang
authors.forename: Xin
authors.initials: X
authors.lastname: Qin
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Haijun
authors.initials: H
authors.lastname: Li
authors.forename: Canfeng
authors.initials: C
authors.lastname: Lin
authors.forename: Wenmei
authors.initials: W
authors.lastname: Li
authors.forename: Cunguo
authors.initials: C
authors.lastname: Gu
authors.forename: Yinpo
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Ran
mesh_terms: D015153:Blotting, Western; D002277:Carcinoma; D019175:DNA Methylation; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D016147:Genes, Tumor Suppressor; D006801:Humans; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D025521:Tumor Suppressor Proteins
chemical_list: C476999:ECRG4 protein, human; D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins