Department of Oncology, the First Affiliated Hospital of Zhengzhou University, ErQi District, Zhengzhou 450052, PR China.
Oncol Rep. 2011 Sep;26(3):621-8. doi: 10.3892/or.2011.1352. Epub 2011 Jun 17.
Approximately one-third of breast cancers lack estrogen receptor α (ERα) because of the hypermethylation of the CpG island in the receptor's promoter. These tumors are associated with poorer histological differentiation, a higher growth fraction, are rarely responsive to endocrine therapy and have a worse clinical outcome. Thus, re-expression of ERα in ERα-negative breast cancers may restore the sensitivity of antiestrogen therapy. The ERα-negative breast cancer cell line MDA-MB-435s was treated with different concentrations of arsenic trioxide (As2O3). MS-PCR was used to detect the change in the methylation status of ERα. RT-PCR, immunohistochemistry and Western blot analyses were used to detect changes in the mRNA and protein expression of DNA methyl-transferase-1 (DNMT1) and ERα. Cell proliferation was examined using the MTT assay. A xenograft model in nude mice was used to further examine the results we observed in vitro. The ERα gene was demethylated after As2O3 treatment of MDA-MB-435s cells. RT-PCR, immunohistochemistry and Western blot analyses revealed that DNMT1 expression was inhibited and ERα was re-expressed in a concentration-dependent manner after As2O3 treatment. The MTT assay showed that cell proliferation was significantly suppressed after exposure to different concentrations of As2O3. Addition of tamoxifen (TAM) further suppressed levels of cell proliferation. In vivo, the xenograft tumor volumes of As2O3-treated mice were smaller than those observed in untreated and TAM-treated mice. Treatment with a combination of As2O3+TAM resulted in further suppression. As2O3 can act as a demethylation agent to restore ERα expression in ERα-negative breast cancer cells and re-sensitize these cells to endocrine therapy in vitro and in vivo.
大约三分之一的乳腺癌由于受体启动子中的 CpG 岛高甲基化而缺乏雌激素受体 α (ERα)。这些肿瘤与组织学分化较差、生长分数较高、对内分泌治疗反应性差且临床预后较差有关。因此，在 ERα 阴性乳腺癌中重新表达 ERα 可能恢复抗雌激素治疗的敏感性。用不同浓度的三氧化二砷 (As2O3) 处理 ERα 阴性乳腺癌细胞系 MDA-MB-435s。MS-PCR 用于检测 ERα 甲基化状态的变化。RT-PCR、免疫组化和 Western blot 分析用于检测 DNA 甲基转移酶-1 (DNMT1) 和 ERα 的 mRNA 和蛋白表达变化。使用 MTT 测定法检查细胞增殖情况。在裸鼠异种移植模型中进一步研究我们在体外观察到的结果。As2O3 处理 MDA-MB-435s 细胞后，ERα 基因去甲基化。RT-PCR、免疫组化和 Western blot 分析显示，As2O3 处理后 DNMT1 表达受到抑制，ERα 呈浓度依赖性重新表达。MTT 测定表明，不同浓度的 As2O3 暴露后细胞增殖明显受到抑制。添加他莫昔芬 (TAM) 进一步抑制细胞增殖水平。在体内，As2O3 处理组的异种移植肿瘤体积小于未处理组和 TAM 处理组。联合使用 As2O3+TAM 导致进一步抑制。As2O3 可作为一种去甲基化剂，在体外和体内恢复 ERα 阴性乳腺癌细胞中 ERα 的表达，并使这些细胞重新对内分泌治疗敏感。
