Sebejova Ludmila, Borsky Marek, Jaskova Zuzana, Potesil David, Navrkalova Veronika, Malcikova Jitka, Sramek Martin, Doubek Michael, Loja Tomas, Pospisilova Sarka, Mayer Jiri, Trbusek Martin
Center of Molecular Medicine, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic; Department of Internal Medicine-Hematology and Oncology, University Hospital Brno and Faculty of Medicine, Masaryk University, Brno, Czech Republic.
Department of Internal Medicine-Hematology and Oncology, University Hospital Brno and Faculty of Medicine, Masaryk University, Brno, Czech Republic.
Exp Hematol. 2014 Oct;42(10):867-74.e1. doi: 10.1016/j.exphem.2014.06.003. Epub 2014 Jun 23.
Abnormalities in ATM and TP53 genes represent important predictive factors in chronic lymphocytic leukemia (CLL); however, the efficacy of CD20 targeting immunotherapy is only poorly defined in the affected patients. Therefore, we tested the in vitro response to ofatumumab (OFA) and rituximab (RTX) in 75 CLL samples with clearly defined p53 or ATM inactivation. Using standard conditions allowing complement-dependent cytotoxicity, i.e., 10 μg/mL of antibodies and 20% active human serum, we observed clear differences among the tested genetic categories: ATM-mutated samples (n = 17) represented the most sensitive, wild-type samples (n = 31) intermediate, and TP53-mutated samples (n = 27) the most resistant group (ATM-mut vs. TP53-mut: P = 0.0005 for OFA and P = 0.01 for RTX). The response correlated with distinct levels of CD20 and critical complement inhibitors CD55 and CD59; CD20 level median was the highest in ATM-mutated and the lowest in TP53-mutated samples (difference between the groups P < 0.01), while the total level of complement inhibitors (CD55 plus CD59) was distributed in the opposite manner (P < 0.01). Negligible response to both OFA and RTX was noted in all cultures (n = 10) tested in the absence of active serum, which strongly indicated that complement-dependent cytotoxicity was a principal cell death mechanism. Our study shows that (1) common genetic defects in CLL cells significantly impact a primary response to anti-CD20 monoclonal antibodies and (2) ATM-mutated patients with currently poor prognosis may potentially benefit from immunotherapy targeting CD20.
ATM和TP53基因异常是慢性淋巴细胞白血病（CLL）的重要预测因素；然而，CD20靶向免疫疗法在受影响患者中的疗效尚不清楚。因此，我们检测了75份明确存在p53或ATM失活的CLL样本对奥法木单抗（OFA）和利妥昔单抗（RTX）的体外反应。在允许补体依赖性细胞毒性的标准条件下，即10μg/mL抗体和20%活性人血清，我们观察到测试的基因类别之间存在明显差异：ATM突变样本（n = 17）最敏感，野生型样本（n = 31）中等敏感，TP53突变样本（n = 27）最耐药（OFA：ATM突变组与TP53突变组比较，P = 0.0005；RTX：P = 0.01）。反应与CD20以及关键补体抑制剂CD55和CD59的不同水平相关；CD20水平中位数在ATM突变样本中最高，在TP53突变样本中最低（两组间差异P < 0.01），而补体抑制剂（CD55加CD59）的总水平分布则相反（P < 0.01）。在无活性血清的所有测试培养物（n = 10）中，对OFA和RTX的反应均微不足道，这强烈表明补体依赖性细胞毒性是主要的细胞死亡机制。我们的研究表明：（1）CLL细胞中的常见基因缺陷显著影响对抗CD20单克隆抗体的初始反应；（2）目前预后较差的ATM突变患者可能从靶向CD20的免疫疗法中获益。
