Molecular targets of soy isoflavones in breast cancer progression

描述(由申请人提供)：这项提案的广泛、长期目标是阐明大豆食品对转移性癌症的影响。原发肿瘤中的转移癌细胞或循环中的癌细胞可能通过包括饮食和环境因素在内的过多触发因素在远处部位建立继发性转移。饮食大豆在预防癌症方面已经做了很多工作，但在癌症转移方面还没有做过很多工作。因此，这项建议解决了关于主要大豆异黄酮类化合物在转移性乳腺癌中的作用和分子靶点的知识空白。理由来自上一次SC3奖项期间产生的数据。我们报道，饮食中添加大豆苷元，或大豆异黄素、大豆苷元和大豆黄素的组合(5：4：1)在大豆食品中发现的比例，在小鼠模型中增加了乳腺癌的生长和转移。饮食中的大豆苷元或大豆异黄酮会上调真核蛋白质合成起始因子eIF4E和eIF4G的基因表达，以及对eIF4E和eIF4G水平升高敏感的致癌分子的蛋白质表达。随后，我们发表了Equol，这是肠道细菌产生的大豆苷元的代谢物，是一种关键的大豆异黄酮类化合物，通过增加控制转移的蛋白质的表达而导致癌症恶性肿瘤。这项建议将建立在前一个奖项的结果的基础上，通过测试大豆异黄酮通过调节蛋白质合成启动来调节癌症进展的假设。代表不同类型乳腺癌的人转移性乳腺癌细胞株：雌激素受体阳性、三重阴性和HER2类型，将用于下列特定目的。具体目标1将描述单独或组合的大豆异黄酮类、染料木素、大豆苷元、马酚和大豆黄素在调节 与体外肿瘤进展相关的蛋白质合成启动和细胞功能。这一目的还将通过检测eIF4G或eIF4E基因敲除或雷帕霉素抑制eIF4E的效果来确定大豆异黄酮介导的eIF4G和eIF4E上调在癌症进展中的作用。由于Equol增加了中央转录因子c-Myc的表达，也将测试c-Myc在蛋白质合成启动因子对大豆异黄酮类反应中的上调作用。特定目标2将验证大豆苷元代谢物Equol作为大豆异黄酮类关键促癌成分的作用。马赛克对转移的影响，单独或与染料木素和大豆黄素联合使用，将在免疫受损的小鼠身上确定，这些小鼠的乳腺肿瘤是由转移性的人类乳腺癌细胞建立的。小鼠还将接受对照或eIF4G的小干扰RNA(SiRNA)处理，以研究eIF4G在马匹介导的肿瘤生长和转移中的作用。从这个目标提取的肿瘤和肺转移也将被测试致癌分子的表达。这一全面的实验策略有望描绘出食用大豆对乳腺癌患者和幸存者的潜在有害影响的分子基础。因此，这项拟议的研究与国家普通医学研究所的使命高度相关。

DESCRIPTION (provided by applicant): The broad, long-term objective of this proposal is to elucidate the effects of soy foods on metastatic cancers. Metastatic cancer cells in primary tumors, or in the circulation, may establish secondary metastases at distant sites via a plethora of triggers, including dietary and environmental factors. Much work has been conducted on dietary soy in cancer prevention, but not in metastasis of established cancers. Therefore, this proposal addresses a gap in knowledge concerning the role and molecular targets of the major soy isoflavones in metastatic breast cancer. The rationale comes from data generated during the previous SC3 award. We reported that dietary administration of daidzein, or combined genistein, daidzein, and glycitein (5:4:1) in the ratio found in soy foods, increased mammary tumor growth and metastasis in a mouse model. Dietary daidzein or soy isoflavones upregulated gene expression of eukaryotic protein synthesis initiation factors eIF4E and eIF4G, as well as protein expression of pro-cancer molecules sensitive to elevated eIF4E and eIF4G levels. Subsequently, we published that equol, a metabolite of daidzein produced by intestinal bacteria, is a pivotal soy isoflavone that contributes to cancer malignancy by increasing the expression of proteins that govern metastasis. This proposal will build upon the results of the previous award by testing the hypothesis that soy isoflavones regulate cancer progression via regulation of protein synthesis initiation. Human metastatic breast cancer cell lines that represent various breast cancer types: estrogen receptor positive, triple negative, and HER2 type, will be used for the following Specific Aims. Specific Aim 1 will delineate the effects of individual or combined soy isoflavones, genistein, daidzein, equol, and glycitein, on regulation of protein synthesis initiation and cell functions relevant to cancer progression in vitro. This Aim wll also determine the contribution of soy-isoflavone-mediated upregulation of eIF4G and eIF4E to cancer progression by testing the effects of eIF4G or eIF4E knockdown, or rapamycin to inhibit eIF4E. Since equol increased the expression of the central transcription factor c-Myc, a role for c-Myc in upregulation of protein synthesis initiation factors in response to soy isoflavones will also be tested. Specific Aim 2 will validate the role of the daidzein metabolite equol as the key cancer promoting component of soy isoflavones. The effect of equol on metastasis, individually or in combination with genistein and glycitein, will be determined in immunocompromised mice with mammary tumors established from metastatic human breast cancer cells. Mice will also be treated with control or small interfering RNA (siRNA) to eIF4G to investigate a role for eIF4G in equol-mediated tumor growth and metastasis. Extracted tumors and lung metastases from this Aim will also be tested for expression of pro-cancer molecules. This comprehensive experimental strategy is expected to delineate the molecular basis for potential detrimental effects of soy consumption in breast cancer patients and survivors. Therefore, the proposed research is highly relevant to the mission of the National Institute of General Medical Sciences.