Graduate School of Science and Engineering, Saitama University, Sakura-ku, Saitama, 338-8570, Japan.
Research Institute for Clinical Oncology, Saitama Cancer Center, Kitaadachi-gun, Saitama, 362-0806, Japan.
Sci Rep. 2017 Dec 19;7(1):17770. doi: 10.1038/s41598-017-18120-4.
To study the role of cell softening in malignant progression, Transwell assay and atomic force microscope were used to classify six human non-small cell lung cancer cell lines into two groups: a high motility-low stiffness (HMLS) group and a low motility-high stiffness (LMHS) group. We found a significant role of activity of the AXL receptor tyrosine kinase, which belongs to the TAM (Tyro3, AXL, Mer) family, in the stimulation of motility and cell softening. HMLS cells expressed higher AXL levels than LMHS cells and contained phosphorylated AXL. H1703 LMHS cells transfected with exogenous AXL exhibited increased motility and decreased stiffness, with low levels of actin stress fibre formation. Conversely, the AXL-specific inhibitor R428 and AXL-targeting siRNA reduced motility and increased stiffness in H1299 HMLS cells. Knockdown of AXL stimulated actin stress fibre formation, which inhibited tumour formation in a mouse xenograft model. The Ras/Rac inhibitor SCH 51344, which blocks disruption of actin stress fibres, exerted similar effects to AXL inactivation. We therefore propose that the Ras/Rac pathway operates downstream of AXL. Thus, AXL activation-induced cell softening promotes malignant progression in non-small cell lung cancer and represents a key biophysical property of cancer cells.
为了研究细胞软化在恶性进展中的作用，我们使用 Transwell 测定法和原子力显微镜将六种人非小细胞肺癌细胞系分为两组：高迁移率-低硬度（HMLS）组和低迁移率-高硬度（LMHS）组。我们发现，AXL 受体酪氨酸激酶（属于 TAM（Tyro3、AXL、Mer）家族）的活性在刺激运动和细胞软化方面起着重要作用。HMLS 细胞表达的 AXL 水平高于 LMHS 细胞，并含有磷酸化的 AXL。用外源性 AXL 转染的 H1703 LMHS 细胞表现出迁移率增加和硬度降低，肌动蛋白应力纤维形成减少。相反，AXL 特异性抑制剂 R428 和 AXL 靶向 siRNA 降低了 H1299 HMLS 细胞的迁移率并增加了硬度。AXL 的敲低刺激肌动蛋白应力纤维形成，这抑制了小鼠异种移植模型中的肿瘤形成。阻断肌动蛋白应力纤维破坏的 Ras/Rac 抑制剂 SCH 51344 也产生了类似于 AXL 失活的效果。因此，我们提出 Ras/Rac 途径在 AXL 下游起作用。因此，AXL 激活诱导的细胞软化促进了非小细胞肺癌的恶性进展，是癌细胞的一个关键物理特性。
