Liu Yi, Wei Jing, Liu Jiaxin, Ma Weina, Duan Yanting, Liu Daihong
Department of Hematology, Chinese PLA Medical School, Beijing 100853, P.R. China.
Department of Hematology, The Sixth Medical Center of PLA General Hospital, Beijing 100048, P.R. China.
Oncol Lett. 2021 May;21(5):397. doi: 10.3892/ol.2021.12658. Epub 2021 Mar 18.
AXL receptor tyrosine kinase (AXL) upregulation mediates drug resistance in several types of human cancer and has become a therapeutic target worthy of exploration. The present study investigated AXL antigen expression and the effects of novel AXL-targeted agents in acute myeloid leukemia (AML) cells. AXL antigen expression in drug-sensitive and drug-resistant human AML cell lines, and AML blast cells from 57 patients with different clinical characteristics, was analyzed by flow cytometry and compared. Furthermore, the effects of the novel AXL antibody DAXL-88, antibody-drug conjugate DAXL-88-monomethyl auristatin E (MMAE), AXL small molecule inhibitor R428 and their combination with FMS-like tyrosine kinase 3 (FLT3) inhibitor quizartinib (AC220) in AML cells were analyzed by Cell Counting Kit-8 assay, flow cytometry and western blotting. The present study revealed that AXL antigen expression was upregulated in FLT3-internal tandem duplication (ITD)/tyrosine kinase domain mutation-positive (TKD) AML blast cells compared with FLT3-ITD/TKD AML cells. Additionally, AXL antigen expression was markedly upregulated in the AC220-resistant FLT3-ITD MV4-11 cell line (MV4-11/AC220) and in FLT3 inhibitor-resistant blast cells from a patient with FLT3-ITD AML compared with parental sensitive cells. The AXL-targeted agents DAXL-88, DAXL-88-MMAE and R428 exhibited dose-dependent cytotoxic effects on FLT3-mutant AML cell lines (THP-1, MV4-11 and MV4-11/AC220) and blast cells from patients with FLT3-ITD AML. Combinations of AXL-targeted agents with AC220 exerted synergistic cytotoxic effects and induced apoptosis in MV4-11/AC220 cells and FLT3 inhibitor-resistant blast cells. The antileukemic effect of DAXL-88 and DAXL-88-MMAE may rely on their ability to block AXL, FLT3 and their downstream signaling pathways. The present study demonstrated the association between AXL antigen expression upregulation and drug resistance in FLT3-ITD AML, and proposed a method for overcoming FLT3 inhibitor resistance of FLT3-ITD AML using novel AXL-targeted agents.
AXL受体酪氨酸激酶（AXL）的上调介导了多种人类癌症的耐药性，已成为一个值得探索的治疗靶点。本研究调查了AXL抗原表达以及新型AXL靶向药物对急性髓系白血病（AML）细胞的影响。通过流式细胞术分析并比较了药物敏感和耐药的人类AML细胞系以及57例具有不同临床特征患者的AML原始细胞中的AXL抗原表达。此外，通过细胞计数试剂盒-8检测、流式细胞术和蛋白质免疫印迹法分析了新型AXL抗体DAXL-88、抗体-药物偶联物DAXL-88-单甲基奥瑞他汀E（MMAE）、AXL小分子抑制剂R428以及它们与FMS样酪氨酸激酶3（FLT3）抑制剂quizartinib（AC220）联合使用对AML细胞的影响。本研究表明，与FLT3-ITD/TKD AML细胞相比，FLT3内部串联重复（ITD）/酪氨酸激酶结构域突变阳性（TKD）的AML原始细胞中AXL抗原表达上调。此外，与亲本敏感细胞相比，AC220耐药的FLT3-ITD MV4-11细胞系（MV4-11/AC220）以及一名FLT3-ITD AML患者的FLT3抑制剂耐药原始细胞中AXL抗原表达明显上调。AXL靶向药物DAXL-88、DAXL-88-MMAE和R428对FLT3突变的AML细胞系（THP-1、MV4-11和MV4-11/AC220）以及FLT3-ITD AML患者的原始细胞表现出剂量依赖性的细胞毒性作用。AXL靶向药物与AC220联合使用对MV4-11/AC220细胞和FLT3抑制剂耐药原始细胞发挥协同细胞毒性作用并诱导细胞凋亡。DAXL-88和DAXL-88-MMAE的抗白血病作用可能依赖于它们阻断AXL、FLT3及其下游信号通路的能力。本研究证明了AXL抗原表达上调与FLT3-ITD AML耐药之间的关联，并提出了一种使用新型AXL靶向药物克服FLT3-ITD AML对FLT3抑制剂耐药的方法。
