Department of Medicine, Dalhousie University, Halifax, NS, Canada.
Departments of Pediatrics & Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada.
Breast Cancer Res. 2020 Oct 6;22(1):105. doi: 10.1186/s13058-020-01342-2.
ErbB2/HER2 oncoprotein often drives breast cancers (BCs) which are treated with the anti-ErbB2 antibody trastuzumab. The efficacy of trastuzumab-based metastatic BC therapies is routinely assessed by imaging studies. Trastuzumab typically becomes ineffective in the case of this disease and is then replaced by other drugs. Biomarkers of BC trastuzumab response could allow imaging studies and the switch to other drugs to occur earlier than is now possible. Moreover, bone-only BC metastases can be hard to measure, and biomarkers of their trastuzumab response could facilitate further treatment decisions. Such biomarkers are presently unavailable. In this study, we searched for proteins whose levels in BC cell-emitted extracellular vesicles (EVs) potentially correlate with BC trastuzumab sensitivity.
We isolated EVs from cultured trastuzumab-sensitive and trastuzumab-resistant human BC cells before and after trastuzumab treatment and characterized these EVs by nanoparticle tracking analysis and electron microscopy. We found previously that ErbB2 drives BC by downregulating a pro-apoptotic protein PERP. We now tested whether trastuzumab-induced PERP upregulation in EVs emitted by cultured human BC cells correlates with their trastuzumab sensitivity. We also used mass spectrometry to search for additional proteins whose levels in such EVs reflect BC cell trastuzumab sensitivity. Once we identified proteins whose EV levels correlate with this sensitivity in culture, we explored the feasibility of testing whether their levels in the blood EVs of trastuzumab-treated metastatic BC patients correlate with patients' response to trastuzumab-based treatments.
We found that neither trastuzumab nor acquisition of trastuzumab resistance by BC cells affects the size or morphology of EVs emitted by cultured BC cells. We established that EV levels of proteins PERP, GNAS2, GNA13, ITB1, and RAB10 correlate with BC cell trastuzumab response. Moreover, these proteins were upregulated during trastuzumab-based therapies in the blood EVs of a pilot cohort of metastatic BC patients that benefited from these therapies but not in those derived from patients that failed such treatments.
Upregulation of a protein set in EVs derived from cultured breast tumor cells correlates with tumor cell trastuzumab sensitivity. It is feasible to further evaluate these proteins as biomarkers of metastatic BC trastuzumab response.
ErbB2/HER2 癌蛋白常驱动乳腺癌（BC）的发生，而抗 ErbB2 抗体曲妥珠单抗可用于治疗此类癌症。目前，临床上常通过影像学研究来评估基于曲妥珠单抗的转移性 BC 治疗的疗效。然而，曲妥珠单抗在治疗此类疾病时通常会失效，之后会被其他药物所取代。如果能找到 BC 曲妥珠单抗应答的生物标志物，就有可能更早地进行影像学研究并换用其他药物。此外，骨-only BC 转移瘤较难测量，如果能找到其曲妥珠单抗应答的生物标志物，就有可能进一步改善治疗决策。然而，目前尚无此类生物标志物。在本研究中，我们通过检测培养的曲妥珠单抗敏感型和耐药型人 BC 细胞在曲妥珠单抗治疗前后分泌的细胞外囊泡（EVs）中的蛋白水平，来寻找与 BC 曲妥珠单抗敏感性相关的蛋白。
我们在曲妥珠单抗治疗前后分别从培养的曲妥珠单抗敏感型和耐药型人 BC 细胞中分离 EVs，并通过纳米颗粒跟踪分析和电子显微镜对这些 EVs 进行了表征。我们之前发现，ErbB2 通过下调促凋亡蛋白 PERP 来驱动 BC 的发生。本研究检测了培养的人 BC 细胞分泌的 EVs 中，曲妥珠单抗诱导的 PERP 上调是否与细胞的曲妥珠单抗敏感性相关。此外，我们还使用质谱法来寻找 EVs 中其他蛋白水平反映 BC 细胞对曲妥珠单抗敏感性的情况。在鉴定出与培养中 BC 细胞的敏感性相关的 EV 蛋白后，我们又进一步研究了检测这些蛋白在接受曲妥珠单抗治疗的转移性 BC 患者血液 EVs 中的水平是否与患者对曲妥珠单抗治疗的应答相关的可行性。
我们发现，曲妥珠单抗或 BC 细胞对曲妥珠单抗的耐药性均不影响培养的 BC 细胞分泌的 EVs 的大小或形态。我们确定，PERP、GNAS2、GNA13、ITB1 和 RAB10 等蛋白的 EV 水平与 BC 细胞对曲妥珠单抗的应答相关。此外，在接受基于曲妥珠单抗的治疗的转移性 BC 患者的血液 EVs 中，这些蛋白在治疗期间上调，而在对治疗无效的患者的血液 EVs 中则未上调。
培养的乳腺癌肿瘤细胞衍生的 EVs 中一组蛋白的上调与肿瘤细胞对曲妥珠单抗的敏感性相关。进一步评估这些蛋白作为转移性 BC 曲妥珠单抗应答的生物标志物是可行的。
