Ram Sripad, Kim Dongyoung, Ober Raimund J, Ward E Sally
a Department of Immunology ; University of Texas Southwestern Medical Center ; Dallas , TX USA.
MAbs. 2014;6(5):1211-9. doi: 10.4161/mabs.29865.
The receptor tyrosine kinase HER2 is known to play a central role in mitogenic signaling, motivating the development of targeted, HER2-specific therapies. However, despite the longstanding use of antibodies to target HER2, controversies remain concerning antibody/HER2 trafficking behavior in cancer cells. Understanding this behavior has direct relevance to the mechanism of action and effective design of such antibodies. In the current study, we analyzed the intracellular dynamics of trastuzumab, a marketed HER2-targeting antibody, in a panel of breast and prostate cancer cell lines that have a wide range of HER2 expression levels. Our results reveal distinct post-endocytic trafficking behavior of antibody-HER2 complexes in cells with different HER2 expression levels. In particular, HER2-overexpressing cells exhibit efficient HER2 recycling and limited reductions in HER2 levels upon antibody treatment, and consequently display a high level of antibody persistence on their plasma membrane. By contrast, in cells with low HER2 expression, trastuzumab treatment results in rapid antibody clearance from the plasma membrane combined with substantial decreases in HER2 levels and undetectable levels of recycling. A cell line with intermediate levels of HER2 expression exhibits both antibody recycling and clearance from the cell surface. Significantly, these analyses demonstrate that HER2 expression levels, rather than cell origin (breast or prostate), is a determinant of subcellular trafficking properties. Such studies have relevance to optimizing the design of antibodies to target HER2.
受体酪氨酸激酶HER2在促有丝分裂信号传导中发挥核心作用，这推动了靶向HER2特异性疗法的发展。然而，尽管长期以来一直使用抗体来靶向HER2，但关于癌细胞中抗体/HER2的转运行为仍存在争议。了解这种行为与这类抗体的作用机制和有效设计直接相关。在本研究中，我们分析了曲妥珠单抗（一种已上市的靶向HER2的抗体）在一系列HER2表达水平广泛的乳腺癌和前列腺癌细胞系中的细胞内动态变化。我们的结果揭示了抗体-HER2复合物在不同HER2表达水平的细胞中不同的内吞后转运行为。特别是，HER2过表达的细胞在抗体处理后表现出高效的HER2再循环和HER2水平的有限降低，因此在其质膜上显示出高水平的抗体持久性。相比之下，在HER2表达低的细胞中，曲妥珠单抗处理导致抗体从质膜快速清除，同时HER2水平大幅下降且未检测到再循环水平。HER2表达水平中等的细胞系既表现出抗体再循环又表现出抗体从细胞表面清除。重要的是，这些分析表明HER2表达水平而非细胞来源（乳腺或前列腺）是亚细胞转运特性的决定因素。此类研究与优化靶向HER2抗体的设计相关。
