Molecular Cancer, 2013, 12(1):1-17.

Epigenetic reactivation of estrogen receptor-α (ERα) by genistein enhances hormonal therapy sensitivity in ERα-negative breast cancer

Yuanyuan Li, Syed M Meeran, Shweta N Patel, et al

Department of Biology University of Alabama at Birmingham, Birmingham, USA; et al

Estrogen receptor-α (ERα)-negative breast cancer is clinically aggressive and normally does not respond to conventional estrogen target-directed therapies. The soybean isoflavone, genistein (GE), has been shown to prevent and inhibit breast cancer and recent studies have suggested that GE can enhance the anticancer capacity of an estrogen antagonist, tamoxifen (TAM), especially in ERα-positive breast cancer cells. However, the role of GE in ERα-negative breast cancer remains unknown.

METHODS:

We have evaluated the in vitro and in vivo epigenetic effects of GE on ERα reactivation by using MTT assay, real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, western-blot assay, immunoprecipitation (ChIP) assay, immunohistochemistry and epigenetic enzymatic activity analysis. Preclinical mouse models including xenograft and spontaneous breast cancer mouse models were used to test the efficacy of GE in vivo.

RESULTS:

We found that GE can reactivate ERα expression and this effect was synergistically enhanced when combined with a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), in ERα-negative MDA-MB-231 breast cancer cells. GE treatment also re-sensitized ERα-dependent cellular responses to activator 17β-estradiol (E2) and antagonist TAM. Further studies revealed that GE can lead to remodeling of the chromatin structure in the ERα promoter thereby contributing to ERα reactivation. Consistently, dietary GE significantly prevented cancer development and reduced the growth of ERα-negative mouse breast tumors. Dietary GE further enhanced TAM-induced anti-cancer efficacy due at least in part to epigenetic ERα reactivation.

CONCLUSIONS:

Our studies suggest that soybean genistein can epigenetically restore ERα expression, which in turn increases TAM-dependent anti-estrogen therapeutic sensitivity in vitro and in vivo. The results from our studies reveal a novel therapeutic combination approach using bioactive soybean product and anti-hormone therapy in refractory ERα-negative breast cancer which will provide more effective options in breast cancer therapy.

英国《肿瘤分子》，2013年2月

雌激素受体 α （ERα）由于金雀异黄素的表观遗传活化增强了 ERα-阴性乳腺癌对内分泌疗法的敏感性

李媛媛，赛义德  M 米尔让，维塔 N 帕特尔，等

美国阿拉巴马大学伯明翰分校生物学院等

背景︰

雌激素受体 α （ERα）-阴性乳腺癌在临床上具侵略性并且不响应常规的雌激素靶向疗法。大豆异黄酮，金雀异黄素 (GE)，已被证明可以预防和抑制乳腺癌，最近的研究表明 GE 可以提高雌激素拮抗剂，三苯氧胺 (TAM) 的抗癌能力，特别是对ERα 阳性乳腺癌细胞。然而，GE 在ERα-阴性乳腺癌中的作用仍然是未知的。

方法︰

我们采用MTT比色法测定，实时逆转录-聚合酶链反应 (RT-PCR) 检测、 免疫印迹测定、 免疫沉淀 （芯片） 技术、 免疫组化和表观遗传酶活性分析测试了GE 对ERα 活化在体内和体外表观遗传的影响。临床前小鼠模型包括异种移植和自发性乳腺癌小鼠模型被用于测试 GE 在体内的疗效。

结果︰

我们发现在ERα 阴性 MDA-MB-231 乳腺癌细胞中，GE 可以重新激活ERα 的表达，并且当与一种组蛋白去乙酰化酶 (HDAC) 抑制剂曲古霉素 (TSA)共同使用时，这种效应协同增强。GE 治疗也会使重新致敏 ERα 依赖性细胞对活化剂 17 β-雌二醇 (E2) 和拮抗剂TAM的反应更加敏感。进一步研究发现，GE 可以导致 ERα 启动子染色质结构的重塑，从而有助于 ERα的活化。总之，膳食 GE 明显阻止了癌症的发展并减缓了 ERα-阴性小鼠乳腺肿瘤的生长。至少部分由于表观遗传ERα 的活化，膳食 GE 进一步增强了TAM诱导的抗癌功效。

结论︰