Retinoic acid, CRABP, and cancer

描述(由申请人提供)：维甲酸(RA)在包括乳腺癌在内的许多癌症中显示出化学治疗和化学预防活性。然而，RA治疗被这种药物在药理剂量下的显着毒性和肿瘤中RA耐药性的发展所混淆。RA的生物学活性是由核激素受体维甲酸和维甲酸X受体(RARs和RXRs)介导的。此外，RA在细胞内与两种细胞内蛋白结合，细胞内RA结合蛋白I和II(CRABP-I和CRABP-II)。我们先前发现CRABP-II(但不是CRABP-I)促进RA递送到由其激活的受体，即RAR。我们进一步发现CRABP-II的这种活性增强了RAR的转录活性，这表明结合蛋白的存在可以使细胞对RA的生物学活性敏感。我们最近的数据确实表明，CRABP-II的表达增强了培养的乳腺癌细胞对RA诱导的生长抑制的反应性，并抑制了两种乳腺癌小鼠模型的肿瘤发展。因此，CRABP-II可能包含治疗和预防某些癌症的新靶点。为了更好地了解RA和CRABP-II在乳腺癌中的作用机制，该应用具有以下特定目的：(1)在MCF-7乳腺癌细胞中寻找受RA和CRABP-II调控的靶基因。Affymetrix表达阵列将用于比较在没有RA或经RA治疗后表达不同水平CRABP-II的MCF-7细胞的基因表达谱。(2)研究CRABP-II和RA对转基因乳腺癌小鼠肿瘤生长的影响。将使用MMTV-neu/Erb-B2小鼠模型，在该模型中，乳腺肿瘤自发发生并在免疫监视下进展。将产生两种小鼠模型：CRABP-II表达中断的MMTV-neu小鼠和在乳腺组织中过度表达CRABP-II的MMTV-neu小鼠。在小鼠体内表达不同水平的CRABP-II的肿瘤的特征将使我们能够评估该蛋白在体内抑制肿瘤形成和使乳腺肿瘤对RA诱导的生长抑制敏感的能力。此外，Affymetrix阵列将用于分析参与CRABP-II表达和RA给药对MMTV-neu小鼠肿瘤生长影响的基因。

DESCRIPTION (provided by applicant): Retinoic acid (RA) exhibits chemotherapeutic and chemopreventive activities in a number of cancers, including breast cancer. RA therapy is however confounded by a marked toxicity of this agent at pharmacological doses and by development of RA-resistance in tumors. The biological activities of RA are mediated by the nuclear hormone receptors retinoic acid- and retinoid X- receptors (RARs and RXRs). In addition, RA binds in cells to two intracellular proteins, cellular RA binding proteins I and II (CRABP-I and CRABP-II). We previously found that CRABP-II (but not CRABP-I) facilitates the delivery of RA to the receptor that is activated by it, namely RAR. We found further that this activity of CRABP-II enhances the transcriptional activity of RAR, suggesting that the presence of the binding protein could sensitize cells to the biological activities of RA. Our recent data indeed indicate that CRABP-II expression enhances the responsiveness of cultured mammary carcinoma cells to RA-induced growth inhibition, and suppresses tumor development in two mouse models of breast cancer. Hence, CRABP-II may comprise a novel target for therapy and prevention of some cancers. To better understand the mechanisms underlying the activities of RA and CRABP-II in mammary carcinomas, this application has the following specific aims: (1) To identify target genes that are regulated by RA and CRABP-II in MCF-7 mammary carcinoma cells. Affymetrix expression arrays will be utilized to compare gene expression profiles of MCF-7 cells that express different levels of CRABP-II, in the absence of or upon treatment with RA. (2) To study the effects of CRABP-II and RA on tumor growth in transgenic breast cancer mouse models. The mouse model MMTV-neu/Erb-B2, in which breast tumors arise spontaneously and progress under immune surveillance, will be used. Two mouse models will be generated: MMTV-neu mice with disrupted expression of CRABP-II, and MMTV-neu mice that over-express CRABP-II in mammary tissue. Characterization of tumors that develop in mice expressing different levels of CRABP-II will allow us to assess the ability of the protein to inhibit tumorigenesis and to sensitize breast tumors to RA-induced growth inhibition in vivo. In addition, Affymetrix arrays will be used to analyze genes that are involved in the effects of CRABP-II expression and RA administration on tumor growth in MMTV-neu mice.