Objective: To investigate the effect of methylation status of breast cancer metastasis suppressor gene 1 (BRMS1) on the expression of breast cancer and the biological behavior of cancer cells in triple-negative breast cancer (TNBC). Methods: The expression of BRMS1 in TNBC tissues and corresponding non-malignant tissues and its relationship with clinicopathological parameters were detected by immunohistochemistry. The mRNA and protein expression of BRMS1 in normal breast epithelial cells and TNBC cells were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. The methylation specific polymerase chain reaction (MSP) was used to detect the methylation status of BRMS1 in each cell. These cells were treated with demethylated preparations (5-Aza-dC) to re-activate BRMS1 expression. Using tumor cell invasion assay to detect influence of BRMS1 demethylation on the invasion capacity of cancer cells. The data were statistically analyzed. Results: The positive expression rate of BRMS1 protein in TNBC tissues was significantly lower than that in corresponding non-malignant tissues (χ(2)= 6.635, P<0.05). The mRNA expression level of BRMS1 in patients with lymph node metastasis was significantly lower than those with no lymph node metastasis (P=0.018). The down-regulation of BRMS1 expression was related to the methylation of DNA promoter, which was statistically significant (χ(2)=14.68, P<0.05). The mRNA and protein expression of BRMS1 was also correlated with tumor size and TNM staging (P=0.000-0.003). After using 5-Aza-dC, the number of cells with invasive capacity was significantly lower than those of the control group (t=3.262-10.72, P<0.05). Conclusions: The decrease of BRMS1 expression in TNBC cells is related to the methylation of DNA. Demethylation can inhibit the invasion of breast cancer cells.
目的： 探讨三阴性乳腺癌(TNBC)中乳腺癌转移抑制基因1(BRMS1)DNA启动子甲基化修饰及其表达对癌细胞生物学行为的影响。 方法： 采用免疫组织化学法检测BRMS1在TNBC及癌旁组织标本中的表达情况。通过反转录PCR(reverse transcription－PCR，RT－PCR)和Western印迹法检测TNBC细胞及正常乳腺上皮细胞中BRMS1 mRNA及蛋白表达情况，应用甲基化特异性聚合酶链反应(MSP)检测各细胞中BRMS1的甲基化状态，去甲基化制剂5－Aza－dC处理使BRMS1表达再活化，侵袭实验检测BRMS1去甲基化对癌细胞侵袭能力的影响，将数据进行统计学分析。 结果： BRMS1蛋白在TNBC组织中的阳性表达率为29.9%(20/67)明显低于其在癌旁组织中的阳性表达率61.2%(41/67)，差异具有统计学意义(χ(2)＝6.635，P<0.05)，有淋巴结转移者BRMS1 mRNA的表达水平低于无淋巴结转移者(P＝0.018<0.05)，BRMS1表达下调与DNA启动子甲基化有关，差异有统计学意义(χ(2)＝14.68，P<0.05)。BRMS1 mRNA及蛋白表达与肿瘤大小及TNM分期亦有相关性(P＝0.000～0.003<0.05)。经5－Aza－dC处理后，侵袭细胞数目较对照组显著减低，差异有统计学意义(t＝3.262～10.72，P<0.05)。 结论： TNBC中存在BRMS1表达下调，并与该基因DNA启动子甲基化修饰有关，去甲基化可使BRMS1表达再活化从而抑制细胞侵袭能力。.
Keywords: Breast cancer metastasis suppressor gene 1; Metastasis; Methylation; Triple-negative breast cancer.