Huber Stefan, Wege Anja K, Bernhardt Günther, Buschauer Armin, Brockhoff Gero
Department of Pharmaceutical and Medicinal Chemistry II, University of Regensburg, Regensburg, Germany.
Department of Gynecology and Obstetrics, University of Regensburg, Regensburg, Germany.
Cytometry A. 2015 Aug;87(8):707-16. doi: 10.1002/cyto.a.22675. Epub 2015 Apr 17.
Human breast cancer shows a considerable heterogeneity regarding the expression of CD24, CD44, EpCAM, and HER2. These markers are involved in cell adhesion, migration, and proliferation, and thus affect metastasis and, in turn, patient's outcome. The ATP-driven efflux pump (ABC transporter) breast cancer resistance protein (BCRP, ABCG2) is known to confer resistance to a wide variety of structurally unrelated cytostatics and defines subpopulations with enhanced tumor-initiating capacity. The expression of ABCG2 can be induced by treatment with different cytostatic drugs. Concurrent effects of such treatments on the expression of the aforementioned marker proteins and cellular properties related to cancer-initiating cells have not been examined thoroughly. Here, we investigated the effect of the ABCG2 substrate topotecan on the MCF-7 breast cancer cell line and analyzed CD24, CD44, EpCAM, and HER2 expression by flow cytometry. Moreover, we examined the impact of topotecan treatment on the sphere-forming ability in vitro and the tumorigenicity in immunodeficient NMRI-nu/nu and NSG mice. We found an elevated ABCG2 expression in MCF-7 cells in the presence of 500 nM topotecan. Compared with untreated MCF-7 cells, the application of topotecan induced a subpopulation with decreased CD24/EpCAM expression, whereas CD44 expression remained largely unchanged. Topotecan-treated cells showed an impaired mammosphere formation capacity in vitro and reduced tumorigenicity in immunodeficient mice. The data indicate that ABCG2 induction is not necessarily linked to increased tumorigenicity and suggest a major role of CD24 and EpCAM for the preservation of self-renewal capacity in MCF-7 cells and tumor outgrowth in vivo.
人类乳腺癌在CD24、CD44、EpCAM和HER2的表达方面表现出相当大的异质性。这些标志物参与细胞黏附、迁移和增殖，从而影响转移，进而影响患者的预后。已知ATP驱动的外排泵（ABC转运蛋白）乳腺癌耐药蛋白（BCRP，ABCG2）可赋予对多种结构不相关的细胞毒性药物的耐药性，并定义具有增强肿瘤起始能力的亚群。ABCG2的表达可通过用不同的细胞毒性药物处理来诱导。此类处理对上述标志物蛋白表达以及与癌症起始细胞相关的细胞特性的协同作用尚未得到充分研究。在此，我们研究了ABCG2底物拓扑替康对MCF-7乳腺癌细胞系的影响，并通过流式细胞术分析了CD24、CD44、EpCAM和HER2的表达。此外，我们研究了拓扑替康处理对体外成球能力以及在免疫缺陷的NMRI-nu/nu和NSG小鼠体内致瘤性的影响。我们发现，在存在500 nM拓扑替康的情况下，MCF-7细胞中ABCG2表达升高。与未处理的MCF-7细胞相比，应用拓扑替康诱导出一个CD24/EpCAM表达降低的亚群，而CD44表达基本保持不变。经拓扑替康处理的细胞在体外显示出受损的乳腺球形成能力，在免疫缺陷小鼠中致瘤性降低。数据表明，ABCG2的诱导不一定与致瘤性增加相关，并提示CD24和EpCAM在维持MCF-7细胞的自我更新能力和体内肿瘤生长方面起主要作用。
