Molecular-level features of tumours can be tracked using single-cell analyses of circulating tumour cells (CTCs). However, single-cell measurements of protein expression for rare CTCs are hampered by the presence of a large number of non-target cells. Here, we show that antibody-mediated labelling of intracellular proteins in the nucleus, mitochondria and cytoplasm of human cells with magnetic nanoparticles enables analysis of target proteins at the single-cell level by sorting the cells according to their nanoparticle content in a microfluidic device with cell-capture zones sandwiched between arrays of magnets. We used the magnetic labelling and cell-sorting approach to track the expression of therapeutic protein targets in CTCs isolated from blood samples of mice with orthotopic prostate xenografts and from patients with metastatic castration-resistant prostate cancer. We also show that mutated proteins that are drug targets or markers of therapeutic response can be directly identified in CTCs, analysed at the single-cell level and used to predict how mice with drug-susceptible and drug-resistant pancreatic tumour xenografts respond to therapy.

可以使用循环肿瘤细胞 (CTC) 的单细胞分析来追踪肿瘤的分子水平特征。然而，稀有 CTC 的蛋白质表达的单细胞测量受到大量非靶细胞的存在的阻碍。在这里，我们展示了抗体介导的细胞内蛋白质标记与磁性纳米粒子在人类细胞的细胞核、线粒体和细胞质中，通过根据细胞在微流体装置中的纳米粒子含量对细胞进行分类，从而能够在单细胞水平上分析目标蛋白质。夹在磁铁阵列之间的细胞捕获区。我们使用磁性标记和细胞分选方法跟踪从原位前列腺异种移植小鼠和转移性去势抵抗性前列腺癌患者的血液样本中分离的 CTC 中治疗性蛋白质靶标的表达。我们还表明，可以在 CTC 中直接识别作为药物靶点或治疗反应标志物的突变蛋白，在单细胞水平上进行分析，并用于预测具有药物敏感性和耐药性胰腺肿瘤异种移植物的小鼠对治疗的反应。