Department of Chemical Engineering, University of Michigan, 2300 Hayward St, Ann Arbor, MI 48109, USA.
Department of Cell and Developmental Biology, University of Michigan, 109 Zina Pitcher Pl, Ann Arbor, MI 48109, USA.
Lab Chip. 2017 Mar 29;17(7):1349-1358. doi: 10.1039/c6lc01496h.
The extent of inter- and intra-tumor cell heterogeneity observed in patient tumors appears to be directly associated with patient prognosis. Moreover, studies indicate that targeting distinct subpopulations of tumor cells may be more relevant to successfully managing cancer metastasis. The ability to distinguish and characterize unique tumor cell subpopulations within a given sample is thus exigent. Existing platforms separate cells binarily, based on some threshold level of phenotypic characteristics without consideration of the continuum levels of biomarker expression and the associated implications. Herein we describe how specific tumor cell groups have been immunomagnetically enriched according to a continuum of EpCAM surface marker expression levels. Even among a relatively homogenous group of cells such as the PANC-1 cell line, cells could be separated according to their EpCAM levels into low, moderate and high expression. To physiologically assess each subpopulation, a wound healing assay was performed which revealed distinct invasive potentials among each subset. Furthermore, the clinical relevance of the approach was demonstrated by isolating pancreatic cancer CTCs from the same patient sample based on their EpCAM levels. We demonstrate a robust method of isolating CTCs according to their varying protein levels, which enables extensive studies on tumor cell heterogeneity. Interestingly, 5 of 6 samples had CTCs that could be recovered at all three levels of EpCAM expression though the majority of CTCs were recovered as low expression events. Preliminary studies that compare tumor cell subpopulations in this continuum manner can potentially increase our understanding of the dynamic nature of cell heterogeneity and how it relates to patient outcomes. Ultimately further investigation may yield therapeutic targets against virulent cell subpopulations.
在患者肿瘤中观察到的肿瘤细胞内和肿瘤细胞间异质性的程度似乎与患者的预后直接相关。此外，研究表明，针对肿瘤细胞的不同亚群进行靶向治疗可能更有助于成功管理癌症转移。因此，能够区分和表征给定样本中独特的肿瘤细胞亚群是非常必要的。现有的平台根据表型特征的某个阈值水平对细胞进行二进制分离，而不考虑生物标志物表达的连续水平及其相关影响。本文描述了如何根据 EpCAM 表面标志物表达水平的连续变化，免疫磁性富集特定的肿瘤细胞群体。即使在像 PANC-1 细胞系这样相对同质的细胞群中，也可以根据 EpCAM 水平将细胞分为低表达、中表达和高表达。为了在生理上评估每个亚群，进行了划痕愈合实验，结果显示每个亚群之间存在不同的侵袭潜力。此外，通过根据 EpCAM 水平从同一患者样本中分离胰腺癌 CTCs，证明了该方法的临床相关性。我们展示了一种根据其不同蛋白水平分离 CTCs 的强大方法，这使我们能够对肿瘤细胞异质性进行广泛研究。有趣的是，尽管大多数 CTCs 作为低表达事件被回收，但在 6 个样本中有 5 个样本能够在 EpCAM 表达的所有三个水平上回收 CTCs。以这种连续方式比较肿瘤细胞亚群的初步研究可能会增加我们对细胞异质性动态性质及其与患者预后关系的理解。最终，进一步的研究可能会针对致命的细胞亚群产生治疗靶点。
