Department of Breast and Endocrine Surgery, Graduate School of Medicine, Juntendo University, Tokyo, Japan.
Breast Cancer Res Treat. 2012 Jun;133(2):427-36. doi: 10.1007/s10549-011-1758-x. Epub 2011 Sep 11.
Neoadjuvant chemotherapy (NAC) has become the standard treatment for advanced breast cancer. Several prognostic markers, including estrogen receptor-α (ERα), are used to predict the response to NAC. However, the molecular significance of ERα expression in the efficacy of chemotherapy is not yet fully understood. To examine this issue, we first evaluated ERα transcriptional activity in breast cancer cells derived from pre-NAC specimens using estrogen response element-green fluorescent protein (ERE-GFP) as a reporter gene, and found that, in the cases for which ERα activities determined by GFP expression were not detected or low, pCR (pathological complete response) could be achieved even though ERα protein was expressed. Next, we examined the effects of alterations in ERα expression levels on sensitivity to paclitaxel, a key drug in NAC, by stable expression of ERα in ER-negative SKBR3 cells and by siRNA-mediated down-regulation of ERα in ER-positive MCF-7 cells, and showed that ERα expression and sensitivity to paclitaxel showed an inverse correlation. We also established paclitaxel-resistant MCF-7 cell clones and found that they have higher estrogen-induced ER activity than parent cells. Paclitaxel is a microtubule-stabilizing agent, while HDAC6 (histone deacetylase 6), which we previously identified as an estrogen-regulated gene, enhances cell motility by destabilizing microtubules via deacetylation of α-tubulin. Finally, we demonstrate herein that ERα knockdown in MCF-7 cells prevents deacetylation of α-tubulin, thereby increasing sensitivity to paclitaxel. Taken together, these results suggest that ERα expression directly regulates sensitivity to paclitaxel in NAC for breast cancer via the effect on microtubule stability.
新辅助化疗 (NAC) 已成为晚期乳腺癌的标准治疗方法。几种预后标志物，包括雌激素受体-α (ERα)，用于预测对 NAC 的反应。然而，ERα 表达在化疗疗效中的分子意义尚未完全了解。为了研究这个问题，我们首先使用雌激素反应元件-绿色荧光蛋白 (ERE-GFP) 作为报告基因，评估了来自新辅助化疗前标本的乳腺癌细胞中 ERα 的转录活性，发现尽管 ERα 蛋白表达，但在 GFP 表达未检测到或低的情况下，仍可达到 pCR（病理完全缓解）。接下来，我们通过 ER 阴性 SKBR3 细胞中 ERα 的稳定表达和 ER 阳性 MCF-7 细胞中 ERα 的 siRNA 下调，研究了 ERα 表达水平的变化对 NAC 中关键药物紫杉醇敏感性的影响，并表明 ERα 表达和紫杉醇敏感性呈负相关。我们还建立了紫杉醇耐药 MCF-7 细胞克隆，并发现它们比亲本细胞具有更高的雌激素诱导的 ER 活性。紫杉醇是一种微管稳定剂，而我们之前鉴定为雌激素调节基因的 HDAC6（组蛋白去乙酰化酶 6）通过去乙酰化 α-微管蛋白来破坏微管，从而增强细胞迁移。最后，我们在此证明 MCF-7 细胞中 ERα 的敲低可防止 α-微管蛋白的去乙酰化，从而增加对紫杉醇的敏感性。总之，这些结果表明，ERα 表达通过对微管稳定性的影响直接调节 NAC 中乳腺癌对紫杉醇的敏感性。
