Molecular targets of soy isoflavones in breast cancer progression

描述（由申请人提供）：该提案的广泛，长期目标是阐明大豆食品对转移性癌症的影响。原发性肿瘤或循环中的转移性癌细胞可能通过过多的触发因素（包括饮食和环境因素）在远处部位建立继发性转移。人们对食用大豆预防癌症做了大量的研究，但对已确定的癌症转移没有研究。因此，该提案解决了关于主要大豆异黄酮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SC 3授予期间生成的数据。我们报道了在小鼠模型中，大豆苷元或大豆异黄酮、大豆苷元和黄豆黄素（5：4：1）的混合饮食给药增加了乳腺肿瘤的生长和转移。膳食大豆黄酮或大豆异黄酮上调真核蛋白质合成起始因子eIF 4 E和eIF 4G的基因表达，以及对升高的eIF 4 E和eIF 4G水平敏感的促癌分子的蛋白质表达。随后，我们发表了牛尿酚，一种由肠道细菌产生的大豆苷元代谢产物，是一种关键的大豆苷元，通过增加控制转移的蛋白质的表达而导致癌症恶性肿瘤。该提案将建立在前一个奖项的结果，通过测试大豆异黄酮通过调节蛋白质合成起始来调节癌症进展的假设。代表各种乳腺癌类型（雌激素受体阳性、三阴性和HER 2型）的人转移性乳腺癌细胞系将用于以下特定目的。具体目标1将描述单独或组合的大豆异黄酮、染料木素、大豆苷元、雌马酚和黄豆黄素对调节细胞凋亡的作用。 蛋白质合成起始和与体外癌症进展相关的细胞功能。本研究还将通过检测eIF 4G或eIF 4 E敲低或雷帕霉素抑制eIF 4 E的作用来确定大豆介导的eIF 4G和eIF 4 E上调对癌症进展的贡献。由于雌马酚增加了中心转录因子c-Myc的表达，因此还将测试c-Myc在响应于大豆异黄酮的蛋白质合成起始因子上调中的作用。具体目标2将验证大豆苷元代谢物雌马酚作为大豆异黄酮的关键促癌成分的作用。将在患有由转移性人乳腺癌细胞建立的乳腺肿瘤的免疫受损小鼠中测定雌马酚单独或与染料木黄酮和黄豆黄素组合对转移的作用。还将用对照或针对eIF 4G的小干扰RNA（siRNA）处理小鼠，以研究eIF 4G在雌马酚介导的肿瘤生长和转移中的作用。还将检测从该目的中提取的肿瘤和肺转移瘤的促癌分子表达。这种综合性的实验策略有望描绘出大豆消费对乳腺癌患者和幸存者潜在有害影响的分子基础。因此，拟议的研究与国家普通医学科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.