The Role of ABC Transporters in Stem Cells

描述(由申请人提供)：这项研究提案的总体目标是进一步确定ABCG2转运体在造血干细胞(HSCs)、来自其他非造血器官的干细胞和癌症干细胞中的作用。上一个资助期的工作表明：1)ABCG2的表达是造血干细胞侧面群(SP)表型所必需的，并且可作为分离HSCs的潜在分子标志物；2)ABCG2表达的SP细胞存在于骨骼肌中，并且正如其他实验室所证明的那样，在许多其他非造血器官中，3)大多数人类AML样本包含一小部分ABCG2表达的细胞亚群，可以代表白血病干细胞群；以及4)ABCG2的表达可以保护HSCs免受异种药物米托蒽酮的伤害。现在正在计划进行实验，明确确定ABCG2表达细胞在骨骼肌和其他器官系统中是否具有干细胞活性。通过使用一种新的遗传学方法，我们将跟踪小鼠不同发育阶段表达ABCG2的细胞的后代，以便评估候选器官系统中是否存在表达ABCG2的干细胞。第二个目标是使用克隆抗体从人类和非人类灵长类动物中分离出造血干细胞。使用一组识别ABCG2上存在于活细胞上的外部表位的单抗，我们将分离表达ABCG2的细胞并测试它们的造血干细胞功能，最终目标是确定一个新的干细胞群体，用于移植方案。最后，我们将评估ABCG2的表达是否能够识别髓系白血病和神经母细胞瘤中的肿瘤干细胞。这两种肿瘤都含有表达副群体表型和ABCG2的细胞亚群，因此可能代表癌症干细胞群体。我们已经并将开发新的遗传小鼠模型，这将使我们能够以一种明确的方式测试这一假设。这不仅可以为癌症干细胞提供一个新的标记物，而且对这些人类癌症具有预后和治疗意义。总之，这些研究应该进一步阐明ABCG2转运蛋白在正常和恶性干细胞中的作用，并进一步加深我们对ABC转运蛋白在干细胞中的作用的理解。

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.