ABCB5 P-Glycoprotein in Cancer Multidrug Resistance

MDR1(ABCB1)P-糖蛋白及其相关ATP结合盒介导的多药耐药(MDR) (ABC)转运蛋白是癌症治疗成功的障碍。ABCB5 P-糖蛋白是一种新的ABC 转运蛋白，介导癌细胞的药物外流，调节细胞融合和由此产生的分化 生理组织中的祖细胞。推测ABCB5在癌症中具有双重功能， 通过药物外排转运体的功能赋予MDR，并作为决定因素调节肿瘤的更新 涉及肿瘤干细胞的细胞融合。本研究的目的是(1)系统地鉴定ABCB5药物外排 底物和检测ABCB5在对这种化合物的抗药性中的作用，(2)确定 ABCBS表达的癌细胞是否具有肿瘤干细胞的功能；(3)研究ABCB5的作用 在癌症多药耐药和体内肿瘤形成中的作用，并检测ABCB5是否可以特异性靶向于 肿瘤根除。首先，将在NCI-60癌细胞中检测ABCB5基因和蛋白的表达 将建立具有100,000种化合物的抗药性概况和抗药性相关性的品系。 比较分析。候选的ABCB5传输底物将在实验中得到验证 ABCB5基因转导细胞的竞争性药物外排分析及药敏试验 在ABCBS阻断的人类癌细胞系和小鼠ABCB5/-基因敲除细胞中进行。第二， ABCBS阳性肿瘤细胞相对于ABCBS阴性肿瘤群体的自我更新能力 ABCBS阳性祖细胞在肿瘤培养、生长和分化中的作用 分化将通过肿瘤克隆形成和细胞融合试验进行体外检测。第三，活体内 ABCB5在已鉴定药物底物耐药中的作用及ABCBS阳性的体内相关性 肿瘤细胞对肿瘤形成和生长的影响将在人-鼠肿瘤异种移植模型中进行研究。这个 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- 阳性细胞在表达癌症时起到肿瘤干细胞的作用。因此，这些发现将确定是否 ABCB5代表了临床肿瘤学治疗的新靶点。

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.