ABCB5 P-Glycoprotein in Cancer Multidrug Resistance

MDR 1（ABCB 1）P-糖蛋白及其相关ATP结合盒介导的多药耐药 (ABC)转运蛋白是成功治疗癌症的障碍。ABCB 5 P-glycoprotein是一种新的ABC 转运蛋白，介导癌细胞中的药物流出并调节细胞融合和分化 生理组织中的祖细胞。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，并作为决定因素调节肿瘤更新 涉及肿瘤干细胞的细胞融合本研究旨在（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的癌细胞是否具有肿瘤干细胞的功能，以及（3）研究ABCB 5的作用 在体内癌症MDR和肿瘤形成中，并检查ABCB 5是否可以特异性靶向 肿瘤根除首先，将在NCI-60癌细胞中测定ABCB 5基因和蛋白质表达 将建立对> 100，000种化合物具有抗性谱和药物抗性相关性的品系。 比较分析。候选ABCB 5转运底物将通过以下方法进行实验验证： ABCB 5基因转染细胞系中的竞争性药物外排分析和化学敏感性测定 在ABCBS阻断的人癌细胞系和鼠ABCB 5-/-敲除细胞中进行。二是 ABCBS阳性肿瘤细胞相对维斯ABCBS阴性肿瘤块群体的自我更新能力 以及ABCBS阳性祖细胞对肿瘤培养物生长的机制贡献， 将使用肿瘤克隆形成和细胞融合测定在体外检查分化。第三，体内 ABCB 5在对已鉴定的药物底物的化学抗性中的作用以及ABCB 5阳性表达的体内相关性 将在人至小鼠肿瘤异种移植模型中研究肿瘤细胞的肿瘤形成和生长。的 结果将确定ABCB 5在癌症MDR中的作用，并将确定化疗耐药ABCBS- 阳性细胞作为肿瘤干细胞表达癌症。因此，调查结果将确定是否 ABCB 5代表了临床肿瘤学中的新治疗靶点。

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 ABCBS-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 ABCBS-blocked human cancer cell lines and murine ABCB5 -/- knockout cells. Second, the capacity of ABCBS-positive tumor cells vis-a-vis ABCBS-negative tumor bulk populations for self-renewal and the mechanistic contribution of ABCBS-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 ABCBS-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 ABCBS- 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.