Regulation of MDR1 Expression and Drug Resistance by CD44

描述(申请人提供)：转移和耐药性是癌症治疗失败的主要原因。癌症生物学中这两个重要但没有明确关联的方面已经得到了广泛的研究，但只有间接证据表明，表型可能在功能上有联系。P-糖蛋白(P-gp)和CD44分别是已知的多药耐药和转移的决定因素。P-gp是MDR1(ABCB1)基因的产物，是一种依赖于ATP的跨膜转运蛋白，对肿瘤细胞具有耐药性。CD44是一种与细胞黏附、运动和转移有关的膜蛋白，是透明质酸的主要受体，透明质酸是存在于所有类型的哺乳动物细胞外基质中的主要糖胺聚糖，如卵巢癌转移的最重要部位腹膜。在研究CD44在肿瘤转移中的作用时，我们意外地发现了CD44和P-gp在耐药中的两个独立但可能相互关联的机制：CD44与P-gp物理上相互作用，CD44激活MDR1和P-gp的表达，这种诱导依赖于CD44 Ser291的磷酸化。这一机制似乎是转录的，因为初步数据显示，将CD44导入零细胞可以激活MDR1启动子的构建。然而，确切的机制尚不清楚。目前还不清楚通过这种蛋白质-蛋白质相互作用增加耐药性的机制是什么。我们的总体目标是调查耐药的发生机制。具体地说，我们将解决以下目标：1)研究CD44调节MDR1表达和P-gp功能的机制。1A.验证CD44与P-gp相互作用的生理学/药理学意义。1B.目的：探讨CD44调控MDR1转录的机制。2)研究CD44表达对体内化疗耐药的影响。1A.目的：探讨CD44在卵巢癌小鼠移植瘤耐药中的作用。2B。目的：探讨CD44和P-gp双重表达是否是卵巢癌耐药的预测指标。

DESCRIPTION (provided by applicant): Metastases and drug resistance are the major causes of treatment failure in cancer. These two important but not clearly related aspects in the biology of cancer have been extensively studied, but there is only indirect evidence that the phenotypes may be functionally linked. Two proteins, P-glycoprotein (P-gp) and CD44, are well known determinants of multidrug resistance and metastases, respectively. P-gp, the product of the MDR1 (ABCB1)-gene, is a transmembrane ATP-dependent transporter that confers drug resistance to cancer cells. CD44 is a membrane protein implicated in cell adhesion, motility and metastases and is the major receptor for hyaluronan, the principal glycosaminoglycan found in all types of mammalian extracellular matrices, such as the peritoneum, the most important site for ovarian cancer metastases. When studying the role of CD44 in cancer metastases, we unexpectedly uncovered two separate but possibly interrelated mechanisms linking CD44 and P-gp in drug resistance: CD44 physically interacts with P-gp and CD44 activates MDR1 and P-gp expression and this induction is dependent of CD44 Ser 291 phosphorylation. The mechanism appears to be transcriptional, since preliminary data shows that introduction of CD44 into null cells activates an MDR1 promoter construct. However the exact mechanism is not known. It is also unclear what is the mechanism that leads to increase drug resistance through this protein-protein interaction. Our overall goal is to investigate the mechanisms responsible for the development of drug resistance. Specifically, we will address the following aims: 1) To investigate mechanisms by which CD44 regulates MDR1 expression and P-gp function. 1A. To verify the physiological/pharmacological significance of the interactions between CD44 and P-gp. 1B. To determine the mechanism by which CD44 regulates MDR1 transcription. 2) To study the impact of CD44 expression on in vivo chemoresistance. 1A. To test the effect of CD44 in drug resistance in an ovarian cancer mouse xenograft model. 2B. To determine whether the dual expression of CD44 and P-gp is a predictive marker for drug resistance in women with ovarian cancer.