Cancer therapy often results in heterogeneous responses in different metastatic lesions in the same patient. Inter- and intra-tumor heterogeneity in proteomic signaling within the various tumor compartments and its impact on therapy are not well characterized due to the limited sensitivity of single cell proteomic approaches. To overcome this barrier, we applied single cell mass cytometry with a customized 29-antibody panel [against cell states, receptor tyrosine kinases (RTK) and phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR)-, mitogen-activated protein kinase (MAPK)-, and cytokine- signaling] to PTEN-deleted orthotopic prostate cancer xenograft models to measure the evolution of kinase activities in different tumor compartments during metastasis and upon drug treatment. Compared with primary tumors and circulating tumor cells (CTCs), bone metastases but not lung and liver metastases exhibited elevated PI3K/mTOR signaling and RTKs including c-Met protein, which, when suppressed, impaired tumor growth in the bone. Intra-tumoral heterogeneity within tumor compartments also arises from highly proliferative EpCAM-high epithelial cells with increased PI3K and mTOR kinase activities co-existing with poorly proliferating EpCAM-low mesenchymal populations with reduced kinase activities, findings recapitulated in epithelial and mesenchymal CTC populations in metastatic prostate and breast cancer patients. Increased kinase activity in EpCAM-high cells rendered them more sensitive to PI3K/mTOR inhibition and drug resistant EpCAM-low populations with reduced kinase activity emerged over time. Taken together, single cell proteomics identified microenvironment- and cell state-dependent activation of kinase networks creating heterogeneity and differential drug sensitivity among and within tumor populations across different sites, defining a new paradigm of drug responses to kinase inhibitors.

中文翻译：

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肿瘤区室的单细胞蛋白质组学可识别差异激酶活性，从而定义对mTOR-PI3-激酶抑制的敏感性

癌症疗法通常会导致同一患者不同转移灶的异质性反应。由于单细胞蛋白质组学方法的敏感性有限，无法很好地表征各种肿瘤区室中蛋白质组信号传导的肿瘤间和肿瘤内异质性。为克服这一障碍，我们采用了定制的29抗体面板[针对细胞状态，受体酪氨酸激酶（RTK）和雷帕霉素磷酸肌醇3激酶/哺乳动物靶标（PI3K / mTOR）-，促分裂原活化蛋白）进行单细胞大规模细胞计数激酶（MAPK）和细胞因子信号转导]到PTEN缺失的原位前列腺癌异种移植模型中，以测量转移过程中和药物治疗后不同肿瘤区室中激酶活性的演变。与原发性肿瘤和循环肿瘤细胞（CTC）相比，骨转移而非肺和肝转移显示出升高的PI3K / mTOR信号传导和包括c-Met蛋白的RTK，这在被抑制时会损害骨骼中的肿瘤生长。肿瘤区室中的肿瘤内异质性也源于具有高增殖PI3K和mTOR激酶活性的高增殖EpCAM高上皮细胞与具有低激酶活性的低增殖EpCAM低间充质人群共存，在转移性上皮和间充质CTC群体中概括了发现前列腺癌和乳腺癌患者。EpCAM高细胞中激酶活性的增强使它们对PI3K / mTOR抑制更加敏感，并且随着时间的推移出现了耐药性降低的激酶活性低的EpCAM低人群。在一起