Kute Timothy E, Savage Lori, Stehle John R, Kim-Shapiro Jung W, Blanks Michael J, Wood James, Vaughn James P
Department of Pathology, Wake Forest University, Winston-Salem, NC, USA.
Cancer Immunol Immunother. 2009 Nov;58(11):1887-96. doi: 10.1007/s00262-009-0700-0. Epub 2009 Apr 2.
An understanding of model systems of trastuzumab (Herceptin) resistance is of great importance since the humanized monoclonal antibody is now used as first line therapy with paclitaxel in patients with metastatic Her2 overexpressing breast cancer, and the majority of their tumors has innate resistance or develops acquired resistance to the treatment. Previously, we selected trastuzumab-resistant clonal cell lines in vitro from trastuzumab-sensitive parental BT-474 cells and showed that cloned trastuzumab-resistant cell lines maintain similar levels of the extracellular Her2 receptor, bind trastuzumab as efficiently as the parental cells, but continue to grow in the presence of trastuzumab and display cell cycle profiles and growth rates comparable to parental cells grown in the absence of trastuzumab (Kute et al. in Cytometry A 57:86-93, 2004). We now show that trastuzumab-resistant and trastuzumab-sensitive cells both surprisingly display trastuzumab-mediated growth inhibition in athymic nude mice. This demonstrates that resistance developed in vitro is not predictive of resistance in vivo. The observation that in vitro resistant cells are sensitive to trastuzumab in vivo could be explained by antibody dependent cellular cytotoxicity (ADCC). Therefore, both parental and trastuzumab-resistant cells were assayed for ADCC in real time on electroplates with and without trastuzumab in the presence of a natural killer cell line (NK-92), and granulocyte or mononuclear cellular fractions isolated from human peripheral blood. Mononuclear cells and NK-92 cells were more effective in killing both parental and trastuzumab-resistant cells in the presence of trastuzumab. Both trastuzumab-resistant cells and trastuzumab-sensitive cells showed similar susceptibility to ADCC despite displaying divergent growth responses to trastuzumab. The granulocyte fraction was able to kill these cells with equal efficacy in the presence or absence of trastuzumab. These results support a model of trastuzumab tumor cell killing in vivo mediated primarily by ADCC from the mononuclear fraction of innate immune cells and suggest that in the clinical setting not only should changes in signaling transduction pathways be studied in acquired tumor resistance to trastuzumab, but also mechanisms by which tumors impede immune function should be evaluated.
了解曲妥珠单抗（赫赛汀）耐药的模型系统非常重要，因为这种人源化单克隆抗体目前在转移性HER2过表达乳腺癌患者中与紫杉醇联合用作一线治疗，而大多数患者的肿瘤对该治疗具有先天性耐药或产生获得性耐药。此前，我们从对曲妥珠单抗敏感的亲本BT-474细胞中体外筛选出曲妥珠单抗耐药的克隆细胞系，并表明克隆的曲妥珠单抗耐药细胞系维持相似水平的细胞外HER2受体，与亲本细胞一样有效地结合曲妥珠单抗，但在曲妥珠单抗存在的情况下继续生长，并且显示出与在无曲妥珠单抗条件下生长的亲本细胞相当的细胞周期谱和生长速率（Kute等人，《细胞分析A》57:86-93，2004年）。我们现在表明，曲妥珠单抗耐药细胞和曲妥珠单抗敏感细胞在无胸腺裸鼠中均令人惊讶地表现出曲妥珠单抗介导的生长抑制。这表明体外产生的耐药性并不能预测体内的耐药性。体外耐药细胞在体内对曲妥珠单抗敏感这一观察结果可以用抗体依赖性细胞毒性（ADCC）来解释。因此，在有或无曲妥珠单抗存在的情况下，使用自然杀伤细胞系（NK-92）以及从人外周血中分离的粒细胞或单核细胞组分，在电板上实时检测亲本细胞和曲妥珠单抗耐药细胞的ADCC。在曲妥珠单抗存在的情况下，单核细胞和NK-92细胞在杀死亲本细胞和曲妥珠单抗耐药细胞方面更有效。尽管曲妥珠单抗耐药细胞和曲妥珠单抗敏感细胞对曲妥珠单抗表现出不同的生长反应，但它们对ADCC的敏感性相似。粒细胞组分在有或无曲妥珠单抗存在的情况下能够以相同的效力杀死这些细胞。这些结果支持了一种模型，即曲妥珠单抗在体内杀死肿瘤细胞主要是由天然免疫细胞单核细胞组分介导的ADCC所致，并表明在临床环境中，不仅应研究获得性肿瘤对曲妥珠单抗耐药时信号转导途径的变化，还应评估肿瘤阻碍免疫功能的机制。
