NGALR is overexpressed and regulated by hypomethylation in esophageal squamous cell carcinoma

Neutrophil gelatinase-associated lipocalin receptor (NGALR) mRNA level is reduced in isolated chronic myelogenous leukemia blasts but up-regulated in esophageal squamous cell carcinoma (ESCC). The mechanism of NGALR regulation is unknown. Here, we show the expression pattern of NGALR and examine the aberrant methylation of its gene in ESCC and esophageal carcinoma cell lines.

The expression pattern of NGALR was analyzed by immunohistochemistry in 59 ESCCs and compared with noncancerous tissues. The DNA methylation status was investigated by methylation-specific PCR and by bisulfite genomic sequencing in esophageal carcinoma cell lines and surgically resected samples. Methylated cell lines were treated with a methylation inhibitor to restore NGALR expression.

The expression of NGALR in ESCC was significantly higher in tumor cell membrane and cytoplasm than in normal esophageal epithelium (P < 0.01). Methylated alleles were detected in three NGALR-nonexpressing cell lines but were not detected in three NGALR-expressing cell lines. Treatment of methylated cell lines with 5-aza-2'-deoxycytidine, a methylation inhibitor, restored NGALR expression. In surgically resected samples, 31 of 77 (40.3%) primary esophageal carcinomas and 46 of 77 (59.7%) paired normal tissues contained methylated NGALR alleles (P < 0.05).

Our results suggest that NGALR hypomethylation contributes to its expression in esophageal carcinomas and that this overexpression may play a role in the pathogenesis of esophageal carcinomas.