目的 探讨内皮素受体B（EDNRB）基因在4株乳腺癌细胞中的表达、甲基化状态以及恢复EDNRB表达对MCF-7细胞增殖的影响。 方法 采用甲基化特异性PCR（MS-PCR）和亚硫酸盐测序法（BSP）分析4株乳腺癌细胞中EDNRB的甲基化状态；反转录聚合酶链反应（RT-PCR）检测EDNRB mRNA的表达水平；采用四甲基偶氮唑蓝（MTT）法和集落形成实验检测EDNRB表达恢复对MCF-7细胞增殖的影响。 结果 EDNRB在乳腺癌细胞MCF-7和ZR-75-1中表达缺失，并呈高甲基化状态；而在EDNRB表达最高的MDA-MB-231细胞中其启动子呈低甲基化，表明乳腺癌细胞中EDNRB基因启动子甲基化状态与其表达成负相关。5-氮杂胞苷（5-Aza-CR）能够反转EDNRB基因的表达，EDNRB表达恢复后MCF-7细胞的增殖受到抑制。 结论 EDNRB基因启动子区CpG岛频繁甲基化可能在乳腺癌发生发展中发挥重要作用，EDNRB有望成为乳腺癌早期诊断的新的分子标志物。

Objective To investigate the expression level and methylation status of endothelin receptor B (EDNRB) gene in four breast cancer cell lines and the effect of re-expression of methylated EDNRB on MCF-7 cell proliferation. Methods Methylation-specific PCR (MS-PCR) and bisulfite sequencing PCR (BSP) were used to detect methylation status of EDNRB in breast cancer cell lines. EDNRB gene expression level was measured by reverse transcription-PCR (RT-PCR). The colorimetric MTT assay and colony formation were used to investigate the effect of re-expression of methylated EDNRB on MCF-7 cell proliferation. Results No gene expression and promoter hypermethylation of EDNRB were detected in MCF-7 and ZR-75-1 cell lines. While the low frequency of methylation event happened in MDA-MB-231 cells which had the highest expression level of EDNRB. These results suggested that, in 4 breast cancer cell lines, the negative correlation existed between methylation status in the promoter region and expression of EDNRB gene. The expression of EDNRB gene in MCF-7 cells could be recovered by 5-azacytidine (5-Aza-CR) in a dose-dependent manner from 5 μmol/L to 10 μmol/L. Re-expression of EDNRB gene significantly inhibited cell proliferation. Conclusion Methylation of CpG islands in the promoter region of EDNRB gene may play important roles in the carcinogenesis and development of breast cancer. EDNRB gene may be a new molecular marker in the early diagnosis of breast cancer.