ABCB5 P-Glycoprotein in Cancer Multidrug Resistance

描述（由申请人提供）：由MDR 1（ABCB 1）P-糖蛋白和相关ATP结合盒（ABC）转运蛋白介导的多药耐药（MDR）是成功进行癌症治疗的障碍。ABCB 5 P-糖蛋白是一种新的ABC转运蛋白，它介导肿瘤细胞中的药物外排，并调节生理组织中的细胞融合和由此产生的祖细胞分化。假设ABCB 5在癌症中介导双重功能，通过其作为药物外排转运蛋白的功能赋予MDR，并调节肿瘤更新作为涉及肿瘤干细胞的细胞融合的决定因素。本研究的目的是（1）系统地鉴定ABCB 5药物外排底物，并检查ABCB 5在对此类化合物的化学抗性中的作用，（2）确定表达ABCB 5的癌细胞是否作为肿瘤干细胞发挥作用，（3）研究ABCB 5在体内癌症MDR和肿瘤形成中的作用，并检查ABCB 5是否可以特异性靶向根除肿瘤。首先，将在NCI-60癌细胞系中测定ABCB 5基因和蛋白质表达，所述NCI-60癌细胞系具有对> 100，000种化合物的耐药性谱，并且将通过建立耐药性相关性。比较分析。候选ABCB 5转运底物将在ABCB 5基因转染细胞系中使用竞争性药物外排分析进行实验验证，并在ABCB 5阻断的人癌细胞系和鼠ABCB 5-/-敲除细胞中进行化学敏感性试验。其次，将使用肿瘤克隆形成和细胞融合测定法在体外检查ABCB 5阳性肿瘤细胞相对于ABCB 5阴性肿瘤主体群体的自我更新能力以及ABCB 5阳性祖细胞对肿瘤培养物生长和分化的机制贡献。第三，将在人至小鼠肿瘤异种移植模型中研究ABCB 5在对鉴定的药物底物的化学抗性中的体内作用以及ABCB 5阳性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ABCB 5在癌症MDR中的作用，并将确定化学抗性ABCB 5阳性细胞是否在表达癌症中作为肿瘤干细胞发挥作用。因此，研究结果将确定ABCB 5是否代表临床肿瘤学中的新治疗靶点。

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.