Epigenetic and genetic silencing of CHFR in esophageal adenocarcinomas.
BACKGROUND
The checkpoint with forkhead-associated domain and RING-finger domain (CHFR) is a mitotic checkpoint protein with tumor-suppressor functions. In this study, the authors investigated the epigenetic and genetic mechanisms that regulate CHFR expression in esophageal adenocarcinomas (EACs).


METHODS
Quantitative reverse transcriptase polymerase chain reaction analysis demonstrated downregulation of CHFR transcript in 79% of EACs (44 of 56) compared with 41 normal samples (P < .001). Immunohistochemical analysis of CHFR protein expression showed absence or weak immunostaining for CHFR in 75% of EACs (56 of 75) compared with normal tissue samples. The authors next examined the promoter DNA hypermethylation of CHFR by using quantitative bisulfite pyrosequencing technology. They detected significant CHFR promoter DNA hypermethylation in 31% of tumor samples (18 of 58) compared with normal samples (P < .001). Treatment of OE33 cells with 5-Aza-deoxycytidine led to reduction in the promoter DNA methylation levels with restoration of the CHFR mRNA expression, which confirmed promoter DNA methylation as an epigenetic mechanism regulating CHFR expression. However, they identified several EACs where the CHFR mRNA expression was silenced in the absence of notable methylation. Therefore, the authors examined the relative DNA copy number level of CHFR compared with normal samples.


RESULTS
The results confirmed a decrease or absence of the relative CHFR DNA copy number levels in 59% of tumor samples. Nine tumors that showed loss of CHFR mRNA expression, in absence of promoter DNA hypermethylation, demonstrated a significant loss of relative CHFR DNA copy numbers.


CONCLUSIONS
Taken together, their findings demonstrated that both epigenetic and genetic mechanisms were involved in silencing CHFR expression in EACs.
Soutto
Mohammed
M
Department of Surgery, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, TN 37323, USA.
Peng
Dunfa
D
Razvi
Mohammad
M
Ruemmele
Petra
P
Hartmann
Arndt
A
Roessner
Albert
A
Schneider-Stock
Regine
R
El-Rifai
Wael
W
D000230:Adenocarcinoma / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics*; D019175:DNA Methylation; D015536:Down-Regulation; D004938:Esophageal Neoplasms / Q000235:genetics*; D018628:Gene Dosage; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D018816:Genes, cdc; D006801:Humans; D007150:Immunohistochemistry; D009363:Neoplasm Proteins / Q000235:genetics*; D000075223:Poly-ADP-Ribose Binding Proteins; D044767:Ubiquitin-Protein Ligases
D018797:Cell Cycle Proteins; D009363:Neoplasm Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; C412002:CHFR protein, human; D044767:Ubiquitin-Protein Ligases