ABCB5 P-Glycoprotein in Cancer Multidrug Resistance

描述(申请人提供)：由MDR1(ABCB1)P-糖蛋白和相关的ATP结合盒(ABC)转运体介导的多药耐药(MDR)是成功治疗癌症的障碍。ABCB5 P-糖蛋白是一种新的ABC转运蛋白，它介导肿瘤细胞的药物外流，调节生理组织中细胞融合和祖细胞的分化。假设ABCB5在癌症中具有双重功能，通过其作为药物外排转运体的功能来赋予MDR，并作为涉及肿瘤干细胞的细胞融合的决定因素来调节肿瘤的更新。本研究的目的是(1)系统地鉴定ABCB5药物外排底物并检测ABCB5在此类化合物耐药中的作用；(2)确定表达ABCB5的癌细胞是否具有肿瘤干细胞的功能；(3)研究ABCB5在肿瘤多药耐药和体内肿瘤形成中的作用，并检查ABCB5是否可以作为肿瘤的特异性靶点。首先，ABCB5基因和蛋白的表达将在具有100,000种化合物耐药性的NCI-60癌细胞系中进行分析，并将通过以下方法建立耐药性相关性。比较分析。候选的ABCB5转运底物将在ABCB5基因转染的细胞系中使用竞争性药物外排分析进行实验验证，并在ABCB5阻断的人类癌细胞系和小鼠ABCB5/-基因敲除细胞中进行化疗敏感性分析。其次，将通过肿瘤克隆形成和细胞融合检测ABCB5阳性肿瘤细胞相对于ABCB5阴性肿瘤群体的自我更新能力，以及ABCB5阳性前体细胞对肿瘤细胞生长和分化的作用机制。第三，将在人-鼠肿瘤异种移植模型中研究ABCB5在对已确定的药物底物耐药中的体内作用以及ABCB5阳性的肿瘤细胞与肿瘤形成和生长的体内相关性。这些结果将确定ABCB5在癌症多药耐药中的作用，并将确定化疗耐药的ABCB5阳性细胞是否在表达癌症时发挥肿瘤干细胞的作用。因此，这些发现将确定ABCB5是否代表了临床肿瘤学的一个新的治疗靶点。

DESCRIPTION (provided by applicant): Multidrug resistance (MDR) mediated by MDR1 (ABCB1) P-glycoprotein and related ATP-binding cassette (ABC) transporters is an impediment to successful cancer therapy. ABCB5 P-glycoprotein is a novel ABC transporter, which mediates drug efflux in cancer cells and regulates cell fusion and resultant differentiation of progenitor cells in physiological tissues. It is hypothesized that ABCB5 mediates dual functions in cancer, conferring MDR via its function as a drug efflux transporter, and regulating tumor renewal as a determinant of cell fusion involving tumor stem cells. This study aims to (1) identify systematically ABCB5 drug efflux substrates and examine the role of ABCB5 in the chemoresistance to such compounds, (2) determine whether ABCB5-expressing cancer cells function as tumor stem cells, and (3) investigate the role of ABCB5 in cancer MDR and tumor formation in vivo and examine whether ABCB5 can be specifically targeted for tumor eradication. First, ABCB5 gene and protein expression will be assayed across the NCI-60 cancer cell lines with resistance profiles for >100,000 compounds and drug resistance correlations will be established by. COMPARE analysis. Candidate ABCB5 transport substrates will be validated experimentally using competitive drug efflux analysis in ABCB5 gene-transfected cell lines, and chemosensitivity assays performed in ABCB5-blocked human cancer cell lines and murine ABCB5 -/- knockout cells. Second, the capacity of ABCB5-positive tumor cells vis-a-vis ABCB5-negative tumor bulk populations for self-renewal and the mechanistic contribution of ABCB5-positive progenitor cells to tumor culture growth and differentiation will be examined in vitro using tumor clonogenicity and cell fusion assays. Third, the in vivo role of ABCB5 in chemoresistance to identified drug substrates and the in vivo relevance of ABCB5-positive tumor cells for tumor formation and growth will be studied in human to mouse tumor xenograft models. The results will define the role of ABCB5 in cancer MDR and will establish whether chemoresistant ABCB5- positive cells function as tumor stem cells in expressing cancers. Thus, the findings will identify whether ABCB5 represents a novel therapeutic target in clinical oncology.