Promoter methylation of heat shock protein B2 in human esophageal squamous cell carcinoma

Hypermethylation of gene promoters and the corresponding loss of gene expression are recognized as a hallmark of human cancer, and DNA methylation has emerged as a promising biomarker for the detection of human esophageal squamous cell carcinoma (ESCC). To identify novel genes methylated in ESCC, we screened 35 candidate genes identified from an oligonucleotide microarray. Among them, the heat shock protein B2 (HSPB2) was methylated in 95.7% (67/70) of primary ESCCs, whereas no methylation was found in normal esophageal tissues from ESCC patients (0%, 0/20). RT-PCR analysis revealed that HSPB2 expression was silenced or weakly expressed in most ESCC cell lines, and re-activated by the demethylating agent 5-aza-2'-deoxy-cytidine. These results indicate that promoter methylation of HSPB2 is one of the causal factors for loss or down-regulation of HSPB2 expression. mRNA expression of HSPB2 in ESCC tissues was significantly down-regulated compared to normal tissues. Our data suggest that promoter methylation of HSPB2 deserves further attention as a novel molecular biomarker in human ESCC.