Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland.
Mol Cancer Res. 2022 Mar 1;20(3):446-455. doi: 10.1158/1541-7786.MCR-21-0444.
AXL, a receptor tyrosine kinase from the TAM (TYRO3 AXL and MER) subfamily, and its ligand growth arrest-specific 6 (GAS6) are implicated in pathogenesis of a wide array of cancers, acquisition of resistance to diverse anticancer therapies and cellular entry of viruses. The continuous development of AXL inhibitors for treatment of patients with cancer and COVID-19 underscores the need to better characterize the cellular effects of AXL targeting. In the present study, we compared the cellular phenotypes of CRISPR-Cas9-induced depletion of AXL and its pharmacological inhibition with bemcentinib, LDC1267 and gilteritinib. Specifically, we evaluated GAS6-AXL signaling, cell viability and invasion, the endo-lysosomal system and autophagy in glioblastoma cells. We showed that depletion of AXL but not of TYRO3 inhibited GAS6-induced phosphorylation of downstream signaling effectors, AKT and ERK1/2, indicating that AXL is a primary receptor for GAS6. AXL was also specifically required for GAS6-dependent increase in cell viability but was dispensable for viability of cells grown without exogenous addition of GAS6. Furthermore, we revealed that LDC1267 is the most potent and specific inhibitor of AXL activation among the tested compounds. Finally, we found that, in contrast to AXL depletion and its inhibition with LDC1267, cell treatment with bemcentinib and gilteritinib impaired the endo-lysosomal and autophagy systems in an AXL-independent manner.
Altogether, our findings are of high clinical importance as we discovered that two clinically advanced AXL inhibitors, bemcentinib and gilteritinib, may display AXL-independent cellular effects and toxicity.
AXL 是 TAM(TYRO3 AXL 和 MER)亚家族的受体酪氨酸激酶,其配体生长停滞特异性 6(GAS6)参与多种癌症的发病机制,对多种抗癌治疗的耐药性的获得以及病毒进入细胞。不断开发用于治疗癌症和 COVID-19 患者的 AXL 抑制剂突显了更好地描述 AXL 靶向的细胞效应的必要性。在本研究中,我们比较了 CRISPR-Cas9 诱导的 AXL 耗竭及其与 bemcentinib、LDC1267 和 gilteritinib 的药理学抑制的细胞表型。具体而言,我们评估了 GAS6-AXL 信号转导、细胞活力和侵袭、内溶酶体系统和自噬在神经胶质瘤细胞中的作用。我们表明,AXL 的耗竭而不是 TYRO3 的耗竭抑制了 GAS6 诱导的下游信号效应子 AKT 和 ERK1/2 的磷酸化,表明 AXL 是 GAS6 的主要受体。AXL 也是 GAS6 依赖性增加细胞活力所必需的,但对于没有外源性添加 GAS6 的细胞生长的活力是可有可无的。此外,我们揭示了 LDC1267 是测试化合物中最有效和最特异的 AXL 激活抑制剂。最后,我们发现,与 AXL 耗竭及其与 LDC1267 的抑制作用相反,用 bemcentinib 和 gilteritinib 处理细胞会以 AXL 非依赖性方式损害内溶酶体和自噬系统。
总之,我们的发现具有很高的临床重要性,因为我们发现两种临床先进的 AXL 抑制剂 bemcentinib 和 gilteritinib 可能表现出 AXL 非依赖性的细胞效应和毒性。