Department of Molecular Genetics, Tohoku University, Sendai, Japan.
Cytometry A. 2011 Feb;79(2):107-17. doi: 10.1002/cyto.a.21014. Epub 2011 Jan 18.
Circulating tumor cells (CTC) are an important biomarker for several solid cancers. Most of the commercially available systems for enumeration of CTC are based on immunomagnetic enrichment of epithelial cell adhesion molecule (EpCAM/CD326)-expressing CTC before microscopic cell imaging or reverse-transcription PCR (RT-PCR). The aim of this study was to establish a practical method for enumeration of CTC using a novel flow cytometer that has a disposable microfluidic chip, which is designed to realize absolute cross contamination-free measurements and to collect the analyzed cell sample. Although the process of enumeration and labeling of CTC was optimized for this device, the simplified protocol described here could be applied to other flow cytometers. Cultured cancer cells spiked into normal blood were enriched using MACS® EpCAM-MicroBeads following cell labeling with an allophycocyanin (APC)-conjugated EpCAM mAb, instead of by intracellular staining of cytokeratins (CK). The EpCAM double-positive selection/labeling method allows enumeration of intact CTC, maintenance of cellular integrity, and the concomitant performance of a CTC viability test. The combination of the fine-tuned CTC enrichment process and the cytometric multicolor analysis resulted in a linear relationship between the output cell count and the input cell number from zero to hundreds of cells. In particular, a satisfactory signal/noise ratio was obtained by gate-exclusion of leukocyte signals using an anti-CD45 mAb. The entire process had little influence on the viability of the spiked lung cancer cell PC-9. Measured PC-9 and breast cancer MCF-7 cells bearing EpCAM-MicroBeads, APC-conjugated EpCAM mAb, and the DNA staining dye SYTO9 grew normally, demonstrating the potential usefulness of the collected samples for further studies. This intact CTC enumeration and analysis procedure (iCeap) would be of great benefit to clinicians by providing them with rapid stratification of antitumor therapy, and to basic researchers by permitting further molecular and cellular characterization of CTC.
循环肿瘤细胞(CTC)是几种实体瘤的重要生物标志物。目前大多数商业化的 CTC 计数系统都是基于免疫磁珠富集上皮细胞黏附分子(EpCAM/CD326)阳性的 CTC,然后进行细胞成像或逆转录聚合酶链反应(RT-PCR)分析。本研究旨在建立一种实用的方法,使用一种新型的流式细胞仪来计数 CTC,该流式细胞仪具有一次性微流控芯片,旨在实现绝对无交叉污染的测量,并收集分析的细胞样本。虽然为该设备优化了 CTC 的计数和标记过程,但这里描述的简化方案也可以应用于其他流式细胞仪。使用 MACS®EpCAM-MicroBeads 对培养的癌细胞进行富集,然后用 APC 标记的 EpCAM mAb 对其进行细胞标记,而不是通过细胞角蛋白(CK)的细胞内染色。EpCAM 双阳性选择/标记方法允许对完整的 CTC 进行计数,保持细胞完整性,并同时进行 CTC 活力测试。精细调整的 CTC 富集过程与细胞计数多色分析相结合,使得输出细胞计数与从零到数百个细胞的输入细胞数量之间呈线性关系。特别是,通过使用抗 CD45 mAb 排除白细胞信号,获得了令人满意的信号/噪声比。整个过程对肺癌细胞 PC-9 的活力几乎没有影响。经过 EpCAM-MicroBeads、APC 标记的 EpCAM mAb 和 DNA 染色染料 SYTO9 标记的测量 PC-9 和乳腺癌 MCF-7 细胞正常生长,表明收集的样本可用于进一步研究,具有潜在的应用价值。这种完整的 CTC 计数和分析程序(iCeap)将为临床医生提供快速的抗肿瘤治疗分层,为基础研究人员提供进一步的 CTC 分子和细胞特征分析,带来极大的益处。
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