The fms-related tyrosine kinase 3 (FLT3) receptor has been extensively studied over the past two decades with regard to oncogenic alterations that do not only serve as prognostic markers but also as therapeutic targets in acute myeloid leukemia (AML). Internal tandem duplications (ITDs) became of special interest in this setting as they are associated with unfavorable prognosis. Because of sequence-dependent protein conformational changes FLT3-ITD tends to autophosphorylate and displays a constitutive intracellular localization. Here, we analyzed the effect of tyrosine kinase inhibitors (TKIs) on the localization of the FLT3 receptor and its mutants. TKI treatment increased the surface expression through upregulation of FLT3 and glycosylation of FLT3-ITD and FLT3-D835Y mutants. In T cell-mediated cytotoxicity (TCMC) assays, using a bispecific FLT3 × CD3 antibody construct, the combination with TKI treatment increased TCMC in the FLT3-ITD-positive AML cell lines MOLM-13 and MV4-11, patient-derived xenograft cells and primary patient samples. Our findings provide the basis for rational combination of TKI and FLT3-directed immunotherapy with potential benefit for FLT3-ITD-positive AML patients.

中文翻译：

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酪氨酸激酶抑制增加了 FLT3-ITD 的细胞表面定位，并增强了 FLT3 定向的急性髓系白血病免疫治疗。


过去二十年来，fms 相关酪氨酸激酶 3 (FLT3) 受体在致癌改变方面得到了广泛研究，这些改变不仅可以作为预后标志物，还可以作为急性髓系白血病 (AML) 的治疗靶点。内部串联重复（ITD）在这种情况下变得特别有趣，因为它们与不良预后相关。由于序列依赖性蛋白质构象变化，FLT3-ITD 倾向于自磷酸化并显示出组成型细胞内定位。在这里，我们分析了酪氨酸激酶抑制剂（TKI）对 FLT3 受体及其突变体定位的影响。 TKI 处理通过上调 FLT3 以及 FLT3-ITD 和 FLT3-D835Y 突变体的糖基化来增加表面表达。在 T 细胞介导的细胞毒性 (TCMC) 测定中，使用双特异性 FLT3 × CD3 抗体构建体，与 TKI 治疗组合可增加 FLT3-ITD 阳性 AML 细胞系 MOLM-13 和 MV4-11（患者来源的异种移植细胞）中的 TCMC和主要患者样本。我们的研究结果为 TKI 和 FLT3 定向免疫治疗的合理组合提供了基础，对 FLT3-ITD 阳性 AML 患者具有潜在益处。