Mladenov Radoslav, Hristodorov Dmitrij, Cremer Christian, Hein Lea, Kreutzer Fabian, Stroisch Tim, Niesen Judith, Brehm Hannes, Blume Tobias, Brümmendorf Tim Henrik, Jost Edgar, Thepen Theophilus, Fischer Rainer, Stockmeyer Bernhard, Barth Stefan, Stein Christoph
Department of Experimental Medicine and Immunotherapy, Institute for Applied Medical Engineering, RWTH Aachen University Clinic, Aachen, Germany.
Department of Pharmaceutical Product Development, Fraunhofer Institute for Molecular Biology and Applied Ecology, Aachen, Germany.
Int J Cancer. 2015 Dec 1;137(11):2729-38. doi: 10.1002/ijc.29628. Epub 2015 Jun 12.
Antibody-based immunotherapy of leukemia requires the targeting of specific antigens on the surface of blasts. The Fc gamma receptor (CD64) has been investigated in detail, and CD64-targeting immunotherapy has shown promising efficacy in the targeted ablation of acute myeloid leukemia (AML), acute myelomonocytic leukemia (AMML) and chronic myeloid leukemia cells (CML). Here we investigate for the first time the potential of FcαRI (CD89) as a new target antigen expressed by different myeloid leukemic cell populations. For specific targeting and killing, we generated a recombinant fusion protein comprising an anti-human CD89 single-chain Fragment variable and the well-characterized truncated version of the potent Pseudomonas aeruginosa exotoxin A (ETA'). Our novel therapeutic approach achieved in vitro EC50 values in range 0.2-3 nM depending on the applied stimuli, that is, interferon gamma or tumor necrosis factor alpha. We also observed a dose-dependent apoptosis-mediated cytotoxicity, which resulted in the elimination of up to 90% of the target cells within 72 hr. These findings were also confirmed ex vivo using leukemic primary cells from peripheral blood samples of three previously untreated patients. We conclude that CD89-specific targeting of leukemia cell lines can be achieved in vitro and that the efficient elimination of leukemic primary cells supports the potential of CD89-ETA' as a potent, novel immunotherapeutic agent.
基于抗体的白血病免疫疗法需要靶向原始细胞表面的特定抗原。Fcγ受体（CD64）已得到详细研究，靶向CD64的免疫疗法在急性髓系白血病（AML）、急性粒单核细胞白血病（AMML）和慢性髓系白血病细胞（CML）的靶向消融中显示出有前景的疗效。在此，我们首次研究FcαRI（CD89）作为不同髓系白血病细胞群体表达的新靶抗原的潜力。为了实现特异性靶向和杀伤，我们构建了一种重组融合蛋白，其包含抗人CD89单链可变片段和特征明确的铜绿假单胞菌外毒素A（ETA'）的截短版本。根据所施加的刺激，即干扰素γ或肿瘤坏死因子α，我们的新型治疗方法在体外实现了0.2 - 3 nM范围内的半数有效浓度（EC50）值。我们还观察到剂量依赖性的凋亡介导的细胞毒性，这导致在72小时内高达90%的靶细胞被清除。使用来自三名先前未经治疗患者外周血样本的白血病原代细胞进行的体外实验也证实了这些发现。我们得出结论，体外可实现对白血病细胞系的CD89特异性靶向，并且白血病原代细胞的有效清除支持CD89 - ETA'作为一种有效的新型免疫治疗剂的潜力。
