Lineberger Comprehensive Cancer Center , University of North Carolina at Chapel Hill , NC , USA ; Division of Hematology/Oncology , University of North Carolina at Chapel Hill , NC , USA ; UNC Institute for Pharmacogenomics and Individualized Therapy , University of North Carolina at Chapel Hill , NC , USA.
PeerJ. 2013 Feb 12;1:e31. doi: 10.7717/peerj.31. Print 2013.
The anti-CD20 monoclonal antibody, rituximab, provides a significant therapeutic benefit for patients with B-cell disorders. However, response to therapy varies and relapses are common, so an understanding of both inherited and acquired rituximab resistance is needed. In order to identify mechanisms of inherited resistance, sensitive versus resistant individuals were selected from a survey of 92 immortalized lymphoblastoid B-cell lines from normal individuals. Levels of CD20 protein and surface expression were lower in the resistant group. In contrast, CD20 mRNA levels were not correlated with susceptibility, suggesting regulation at a post-transcriptional level. To examine acquired resistance, resistant sublines were selected from both lymphoblastoid as well as lymphoma cell lines. Confirming previous findings, there was significant down-regulation of CD20 protein expression in all the resistant sublines. CD20 mRNA splice variants are reported to be associated with development of resistance. Three splice variants were observed in our cell lines, each lacking the binding epitope for rituximab, but none were associated with rituximab resistance. The second generation anti-CD20 mAb, ofatumumab, was more active compared with rituximab in vitro in the survey of all B-cell lines, mirroring results that have been reported previously with malignant B-cells. These studies show that normal B-lymphoblastoid cell lines can be used to model both innate and acquired mechanisms of resistance. They validate the important role of CD20 expression and enable future genetic studies to identify additional mediators of anti-CD20 mAb resistance.
抗 CD20 单克隆抗体利妥昔单抗为 B 细胞疾病患者提供了显著的治疗益处。然而，治疗反应各不相同，复发很常见，因此需要了解遗传和获得性利妥昔单抗耐药性。为了确定遗传耐药性的机制，从正常个体的 92 个永生淋巴母细胞系的调查中选择了敏感和耐药个体。耐药组的 CD20 蛋白和表面表达水平较低。相比之下，CD20 mRNA 水平与易感性无关，表明在转录后水平受到调节。为了研究获得性耐药性，从淋巴母细胞系和淋巴瘤细胞系中选择了耐药亚系。与之前的发现一致，所有耐药亚系中 CD20 蛋白表达均显著下调。报道称 CD20 mRNA 剪接变体与耐药的发展有关。在我们的细胞系中观察到三种剪接变体，每种都缺乏与利妥昔单抗结合的表位，但没有一种与利妥昔单抗耐药性相关。第二代抗 CD20 mAb，奥法妥珠单抗，在所有 B 细胞系的调查中比利妥昔单抗在体外更活跃，反映了先前在恶性 B 细胞中报道的结果。这些研究表明，正常 B 淋巴母细胞系可用于模拟先天和获得性耐药机制。它们验证了 CD20 表达的重要作用，并使未来的遗传研究能够确定抗 CD20 mAb 耐药性的其他介质。
