The Role of ABC Transporters in Stem Cells

描述（由申请人提供）：本研究提案的总体目标是进一步确定Abcg2转运蛋白在造血干细胞（HSC）、其他非造血器官干细胞和癌症干细胞中的作用。上一个供资期间的工作表明：1）Abcg2表达是HSC中侧群（SP）表型所需的，并用作分离HSC的前瞻性分子标记，2）表达Abcg2的SP细胞存在于骨骼肌中，并且如其他实验室所证明的，存在于许多其他非造血器官中，3）大多数人AML样品含有表达ABCG 2的细胞的小亚群，其可以代表白血病干细胞群体，以及4）Abcg 2的表达保护HSC免受米托蒽醌（一种异生素药物）的影响。现在计划进行的实验将明确确定表达Abcg2的细胞是否在骨骼肌和其他器官系统中具有干细胞活性。通过使用一种新的遗传方法，我们将在不同的发育阶段跟踪小鼠中表达Abcg2的细胞的后代，以评估候选器官系统中是否存在表达Abcg2的干细胞。第二个目标是使用单克隆抗体从人类和非人类灵长类动物中分离造血干细胞。使用一组识别存在于活细胞上的ABCG 2外部表位的单克隆抗体，我们将分离表达ABCG 2的细胞并测试它们的造血干细胞功能，最终目标是定义用于移植方案的新干细胞群体。最后，我们将评估Abcg2表达是否可以识别骨髓性白血病和神经母细胞瘤中的癌症干细胞。两种肿瘤都含有表达侧群表型和ABCG 2的细胞亚群，因此可能代表癌症干细胞群。我们已经并将开发新的遗传小鼠模型，使我们能够以明确的方式测试这一假设。这不仅可以为癌症干细胞提供新的标记，而且对这些人类癌症具有预后和治疗意义。总之，这些研究应进一步阐明的作用，Abcg2转运蛋白在正常和恶性干细胞，并应进一步增加我们的理解ABC转运蛋白在干细胞中的作用。

DESCRIPTION (provided by applicant): The overall goal of this research proposal is to further define the role of the Abcg2 transporter in hematopoietic stem cells (HSCs), in stem cells from other non-hematopoietic organs, and in cancer stem cells. Work in the prior funding period has shown that: 1) Abcg2 expression is required for the side population (SP) phenotype in HSCs and serves as a prospective molecular marker for isolating HSCs, 2) Abcg2-expressing SP cells exist in skeletal muscle, and as demonstrated by other labs, in many other non-hematopoietic organs, 3) a majority of human AML samples contain a small subpopulation of ABCG2-expressing cells that could represent a leukemia stem cell population, and 4) expression of Abcg2 protects HSCs from mitoxantrone, a xenobiotic drug. Experiments are now planned that will unequivocally determine whether Abcg2-expressing cells have stem cell activity in skeletal muscle and in other organ systems. By using a novel genetic approach, we will track the progeny of Abcg2-expressing cells in mice at different stages of development in order to evaluate candidate organ systems for the presence of Abcg2-expressing stem cells. A second aim is to use monoclonal antibodies to isolate hematopoietic stem cells from human and non-human primates. Using a panel of monoclonal antibodies that recognize external epitopes on ABCG2 that are present on living cells, we will isolate cells expressing ABCG2 and test them for hematopoietic stem cell function, with the ultimate goal defining a new stem cell population for use in transplantation protocols. Lastly, we will evaluate whether Abcg2 expression can identify cancer stem cells in myelogenous leukemia and in neuroblastoma. Both tumors contain a subpopulation of cells that express the side population phenotype and ABCG2, and therefore may represent a cancer stem cell population. We have and will develop novel genetic mouse models that should allow us to test this hypothesis in an unequivocal fashion. Not only could this provide a new marker for cancer stem cells, but it would have prognostic and therapeutic significance for these human cancers. Altogether, these studies should further elucidate the role of the Abcg2 transporter in normal and malignant stem cells, and should further increase our understanding of the role of ABC transporters in stem cells.