Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens 15771, Greece.
Mol Cancer Res. 2013 Oct;11(10):1248-57. doi: 10.1158/1541-7786.MCR-13-0096. Epub 2013 Jun 6.
Breast cancer metastasis suppressor-1 (BRMS1) differentially regulates the expression of multiple genes, leading to metastasis suppression without affecting orthotopic tumor growth. For the first time, BRMS1 promoter methylation was evaluated as a prognostic biomarker in primary breast tumors and a subset of corresponding circulating tumor cells (CTC). Formalin-fixed paraffin embedded samples were analyzed for BRMS1 methylation status using methylation-specific PCR in a human specimen cohort consisting of noncancerous tissues, benign fibroadenomas, and primary breast tumors, including some with adjacent noncancerous tissues. Peripheral blood mononuclear cells from a large subset of these patients were fixed in cytospins and analyzed. In addition, BRMS1 expression in cytospins was examined by double-immunofluorescence using anti-BRMS1 and pan-cytokeratin antibodies. BRMS1 promoter methylation was not detected in noncancerous breast tissues or benign fibroadenomas; however, methylation was observed in more than a third of primary breast tumors. Critically, BRMS1 promoter methylation in primary tumors was significantly associated with reduced disease-free survival with a trend toward reduced overall survival. Similarly, a third of cytospin samples were positive for the presence of CTCs, and the total number of detected CTCs was 41. Although a large fraction of CTCs were negative or maintained low expression of BRSM1, promoter methylation was observed in a small fraction of samples, implying that BRSM1 expression in CTCs was either downregulated or heterogeneous. In summary, these data define BRMS1 promoter methylation in primary breast tumors and associated CTCs.
This study indicates that BRSM1 promoter methylation status has biomarker potential in breast cancer.
乳腺癌转移抑制因子 1（BRMS1）通过调控多个基因的表达来抑制肿瘤转移，而不会影响原位肿瘤的生长。BRMS1 启动子甲基化首次被评估为原发性乳腺癌肿瘤及部分相应循环肿瘤细胞（CTC）的预后生物标志物。采用甲基化特异性 PCR 法，对由非癌组织、良性纤维腺瘤和原发性乳腺癌组成的人类标本队列中 BRMS1 甲基化状态进行了分析，包括一些伴有相邻非癌组织的原发性乳腺癌肿瘤。对这些患者的大部分外周血单个核细胞进行了细胞旋涂固定，并进行了分析。此外，还通过使用抗 BRMS1 和泛细胞角蛋白抗体的双重免疫荧光法，对细胞旋涂物中的 BRMS1 表达进行了检测。非癌乳腺组织或良性纤维腺瘤中未检测到 BRMS1 启动子甲基化；然而，超过三分之一的原发性乳腺癌肿瘤中观察到甲基化。关键的是，原发性肿瘤中 BRMS1 启动子甲基化与无病生存时间缩短显著相关，且总生存时间也有缩短趋势。同样，三分之一的细胞旋涂样本中存在 CTCs，共检测到 41 个 CTC。尽管大多数 CTCs 呈阴性或维持 BRSM1 低表达，但在一小部分样本中观察到启动子甲基化，这意味着 CTCs 中 BRSM1 表达要么下调，要么存在异质性。总之，这些数据定义了原发性乳腺癌肿瘤及其相关 CTC 中的 BRMS1 启动子甲基化。
本研究表明 BRMS1 启动子甲基化状态在乳腺癌中具有潜在的生物标志物。
