Retinoic acid, CRABP, and cancer

描述（由申请人提供）：视黄酸（RA）在许多癌症（包括乳腺癌）中表现出化疗和化学预防活性。然而，RA治疗被药理学剂量下该药剂的显著毒性和肿瘤中RA耐药性的发展所混淆。RA的生物学活性由核激素受体视黄酸-和类视黄酸X-受体（RAR和RXR）介导。此外，RA在细胞中结合两种细胞内蛋白，细胞RA结合蛋白I和II（CRABP-I和CRABP-II）。我们以前发现，CRABP-II（而不是CRABP-I）促进RA的交付，由它激活的受体，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的生物活性敏感。我们最近的数据确实表明，CRABP-II表达增强了培养的乳腺癌细胞的反应性RA诱导的生长抑制，并抑制肿瘤的发展，在两个小鼠模型的乳腺癌。因此，CRABP-II可能包含用于治疗和预防某些癌症的新靶标。为了更好地理解RA和CRABP-II在乳腺癌中的活性的潜在机制，本申请具有以下具体目的：（1）鉴定MCF-7乳腺癌细胞中由RA和CRABP-II调节的靶基因。将使用亲和素表达阵列来比较表达不同水平的CRABP-II的MCF-7细胞的基因表达谱，在不存在RA的情况下或在用RA处理后。(2)研究CRABP-Ⅱ和RA对转基因乳腺癌小鼠肿瘤生长的影响。将使用小鼠模型MMTV-neu/Erb-B2，其中乳腺肿瘤自发产生并在免疫监视下进展。将生成两种小鼠模型：CRABP-II表达破坏的MMTV-neu小鼠和乳腺组织中过表达CRABP-II的MMTV-neu小鼠。表征在表达不同水平的CRABP-II的小鼠中发展的肿瘤将使我们能够评估蛋白质抑制肿瘤发生和使乳腺肿瘤对RA诱导的体内生长抑制敏感的能力。此外，将使用Affymble阵列分析参与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.