Loss of estrogen receptor-alpha (ER-alpha) and promoter hypermethylation in gastric cancer / 대한내과학회지

ABSTRACT

BACKGROUND: The significance of ER expression and hormone manipulation in gastric cancer is not established. There have been several reports supporting the role of the ER gene as tumor suppressor gene in carcinogenesis. The ER-alpha gene is located on chromosome 6q25.1. Deletions of the long arm of chromosome 6 are common in gastric carcinoma, suggesting the presence of tumor suppressor genes in this region. The proportion of ER-positive gastric cancers ranges between 0% and 67% depending on the method of detection. Epigenetic inactivation might explain the loss of ER-alpha gene expression in gastric cancer. There is no information available regarding the methylation status of the ER-alpha gene promoter region in gastric cancer so far. The aim of this study was to assess the expression of ER-alpha in gastric cancer cell lines and determine whether methylation of the 5' promoter region is associated with loss of ER-alpha expression in gastric cancer. METHODS: We investigated such methylation in 13 gastric cancer cell lines. Western blot analysis, reverse transcription-polymerase chain reaction (PCR), methylation-specific PCR (MS-PCR) and bisulfite sequencing analyses were used. Immunohistochemical staining for the ER-alpha gene was dome for forty-two paraffin embedded tissues from gastric cancer patients. RESULTS: ER-alpha protein was not detected in any cell line, ER-alpha mRNA was expressed in only Kato III cell line. MS-PCR and bisulfite sequencing showed all thirteen gastric cancer cell lines had methylated CpG regions in their ER-alpha gene promoters. Immunohistochemical staining of ER-alpha showed no positivity in any of examined samples. CONCLUSION: Inactivation of ER-alpha gene expression in gastric cancer cell lines appears associated with CpG island methylation near the TGA initiation codon of the ER-alpha gene.