Cyclin D as a Retinoid Differentiation Molecular Target

描述（申请人提供）：NIH RO 1-CA 111422的修订版竞争性延续申请：“细胞周期蛋白D作为维甲酸分化的分子靶点”继续深入研究细胞周期蛋白D1作为全反式维甲酸的主要靶点的重要作用（RA，维甲酸）反应，现在检查这也是刺猬（Hh）途径的目标，也是维甲酸调节，但以前未认识到的方式对生殖细胞肿瘤（GCT）（人类胚胎干细胞（ES）的恶性对应物）的分化和自我更新至关重要。有趣的是，我们的研究揭示了一种独特的类维生素A反应：诱导Patched-1（Ptch 1）受体，该受体驱动自我更新的丧失并调节分化。Ptch 1是Hh途径的靶基因，并用作Hh活化的读出。探索的假设是RA通过一种新的机制抑制Hh信号传导，Ptch 1诱导，独立于Smoothened（Smo），Hh抑制剂（如环巴胺）的唯一公认靶点。认识到这一点的重要性来自于我们团队成功使用的挖掘基因谱研究，以确定胚胎癌（EC）中独特的类维生素A靶点。该提案探索了一种独特的药理学机制，调节EC和可能的其他肿瘤的自我更新。我们的具体目标是：（1）发现RA诱导Ptch 1表达是否是EC细胞不依赖于Smo的一种普遍机制，以及这是否是多能EC细胞终末分化的一种共同途径;（2）通过影响Hh靶点和调节细胞凋亡的Ptch 1表达的获得和丧失研究来探测该途径的功能重要性，自我更新或分化反应;以及（3）通过了解RA是否诱导ES细胞中的Ptch 1来阐明体内和临床相关性通过证实Ptch 1及其靶标在独特的肿瘤库中差异表达，从而能够全面分析分化的肿瘤细胞（或其他癌症或干细胞）以及Ptch 1报告小鼠，（成熟畸胎瘤）与未分化（EC）GCT。这已经成功地揭示了D型细胞周期蛋白作为人类EC生长、化疗反应和分化的关键调节因子。这些独特的体外，体内和临床资源与药理学，细胞和分子生物学方法将提供关键的见解Hh途径在调节细胞凋亡，自我更新或分化的GCT或其他肿瘤。 公共卫生相关性：该项目研究了FDA批准的维生素A衍生物全反式维甲酸如何通过一种以前未被认识到的诱导其受体Patched的机制来抑制hedgehog途径。这种机制在胚胎癌和干细胞中是活跃的。该项目与胚胎癌细胞有关，胚胎癌细胞是正常干细胞的恶性对应物，该项目的成功完成将为靶向癌症中的hedgehog通路以抑制这些细胞的自我更新或生长并诱导凋亡或分化的维甲酸作用提供见解。

DESCRIPTION (provided by applicant): This revised competing renewal application of NIH RO1-CA111422: "Cyclin D as a Retinoid Differentiation Molecular Target" continues in depth studies of the important role of cyclin D1 as a major target of all-trans- retinoic acid (RA, retinoid) response by now examining how this is also a target of the hedgehog (Hh) pathway, also retinoid regulated, but in a previously unrecognized manner critical for differentiation and self- renewal of germ cell tumors (GCTs), the malignant counterparts of human embryonal stem (ES) cells. Intriguingly, our studies uncovered a unique retinoid response: induction of the Patched-1 (Ptch1) receptor which drives loss of self-renewal and regulates differentiation. Ptch1 is a target gene of the Hh pathway and is used as a read-out of Hh activation. The hypothesis explored is RA represses Hh signaling by a novel mechanism, Ptch1 induction, independent of smoothened (Smo), the only recognized target of Hh inhibitors, such as cyclopamine. Recognizing importance of this came from mining gene profiling studies successfully used by our team to identify unique retinoid targets in embryonal cancers (ECs). This proposal explores a distinct pharmacologic mechanism regulating self-renewal of ECs and likely other tumors. We are eager to pursue the Specific Aims that: (1) discover whether RA induction of Ptch1 is a general mechanism engaged by EC cells independent of Smo and if this is a common pathway of agents that trigger terminal differentiation of pluripotent EC cells; (2) probe the functional importance of this pathway by gain and loss of Ptch1 expression studies that affect Hh targets and regulate apoptosis, self-renewal or differentiation response; and (3) elucidate in vivo and clinical relevancy by learning whether RA induces Ptch1 in ES cells (or other cancer or stem cells) as well as in Ptch1 reporter mice and by confirming Ptch1 and its targets are differentially expressed in a unique tumor bank enabling comprehensive analyses of differentiated (mature teratoma) versus undifferentiated (EC) GCTs. This has successfully uncovered D-type cyclins as key regulators of human EC growth, chemotherapy response and differentiation. These unique in vitro, in vivo, and clinical resources with pharmacologic, cell and molecular biologic approaches will provide critical insights into the Hh pathway in regulating apoptosis, self-renewal or differentiation of GCT or other tumors. PUBLIC HEALTH RELEVANCE: This project studies how all-trans-retinoic acid, an FDA approved Vitamin A derivative, causes repression of the hedgehog pathway through a previously unrecognized mechanism that induces its receptor, Patched. This mechanism is active in embryonal cancers and stem cells. This project is relevant to embryonal cancer cells, the malignant counterpart of normal stem cells and successful conclusion of this project will provide insights into the retinoid role of targeting the hedgehog pathway in cancer to suppress self-renewal or growth and induce apoptosis or differentiation in these cells.