Curran Sean, Vantangoli Marguerite M, Boekelheide Kim, Morgan Jeffrey R
Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI, USA.
Cancer Microenviron. 2015 Aug;8(2):101-9. doi: 10.1007/s12307-015-0171-0. Epub 2015 Aug 4.
It is well-established that upregulation of drug efflux pumps leads to multi-drug resistance. Less is known about the role of the architecture of the tumor microenvironment in this process: how the location of pump expressing cells influences drug exposure to cancerous as well as non-cancerous cells. Here, we report a 3D in vitro model of spheroids with mixtures of cells expressing high and low levels of ABCG2, quantifying pump activity by the ability to reject the fluorescent dye Hoechst 33342. With respect to the organization of the mixed spheroids, three different architectures were observed: 1) high-expressing ABCG2 cells located in the spheroid core surrounded by low-expressing cells, 2) high-expressing ABCG2 cells intermixed with low-expressing cells and 3) high-expressing ABCG2 cells surrounding a core of low-expressing cells. When high-expressing ABCG2 cells were in the core or intermixed, Hoechst uptake was directly proportional to the percentage of ABCG2 cells. When high-expressing ABCG2 cell formed an outer coating surrounding spheroids, small numbers of ABCG2 cells were disproportionately effective at inhibiting uptake. Specific inhibitors of the ABCG2 transporter eliminated the effect of this coating. Confocal microscopy of spheroids revealed the location of high- and low-expressing cells, and Hoechst fluorescence revealed that the ABCG2-dependant drug concentration in the cancer microenvironment is influenced by pump expression level and distribution among the cells within a tissue. In addition to providing a 3D model for further investigation into multicellular drug resistance, these data show that the location of ABCG2-expressing cells can control drug exposure within the tumor microenvironment.
众所周知，药物外排泵的上调会导致多药耐药。关于肿瘤微环境结构在这一过程中的作用，人们了解较少：表达泵的细胞位置如何影响癌细胞和非癌细胞的药物暴露。在这里，我们报告了一种3D体外球体模型，该模型由表达高水平和低水平ABCG2的细胞混合物组成，通过排斥荧光染料Hoechst 33342的能力来量化泵活性。关于混合球体的组织，观察到三种不同的结构：1）高表达ABCG2的细胞位于球体核心，周围是低表达细胞；2）高表达ABCG2的细胞与低表达细胞混合；3）高表达ABCG2的细胞围绕低表达细胞的核心。当高表达ABCG2的细胞位于核心或混合时，Hoechst摄取量与ABCG2细胞的百分比成正比。当高表达ABCG2的细胞形成围绕球体的外层时，少量ABCG2细胞在抑制摄取方面具有不成比例的效果。ABCG2转运蛋白的特异性抑制剂消除了这种外层的作用。球体的共聚焦显微镜显示了高表达和低表达细胞的位置，Hoechst荧光显示癌症微环境中ABCG2依赖性药物浓度受泵表达水平和组织内细胞间分布的影响。除了提供一个3D模型用于进一步研究多细胞耐药性外，这些数据还表明表达ABCG2的细胞位置可以控制肿瘤微环境内的药物暴露。
