Abstract 2376: AXL receptor tyrosine kinase stimulates cell softening and cancer progression via Rac signaling pathway

Abstract

Abstract Cancer cells exhibit different biophysical properties, such as cell stiffness and elasticity, compared with normal cells. It is now well accepted that cell stiffness measured by atomic force microscope (AFM) is a quantitative indicator of cancer progression and metastasis. To study the role of cell softening in malignant progression, Using Transwell assays and AFM, six human non-small cell lung cancer cell lines were classified into two groups: a high motility-low stiffness (HMLS) group and a low motility-high stiffness (LMHS) group. We found a significant difference in expression 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 and phosphorylated AXL levels than LMHS cells. Exogenous AXL gene expression in H1703 LMHS cells exhibited increased motility and decreased stiffness, along with lower 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 gene stimulated both actin stress fibre formation and focal adhesion kinase phosphorylation, which inhibited tumour formation in a mouse xenograft model. Treatment with Ras/Rac inhibitor SCH 51344, which blocks disruption of actin stress fibres, exerted similar effects to AXL inactivation in H1299 and H1703-AXL cells, but not in H1703 cells (no AXL expression). Furthermore, treatment with an ROCK inhibitor, Y27632, did not show any effect in two AXL expressing cells, while it stimulated motility in H1703 cells. Considering all these results, we propose that the Ras/Rac pathway operates downstream of AXL and suppresses the Rho/ROCK pathway. Cell softening induced by AXL activation is a key biophysical property of cancer cells, and AXL is thus a new target for inhibition of malignant progression in non-small cell lung cancer. Citation Format: Masami Suganuma, Keisuke Iida, Shota Yokoyama, Anchalee Rawangkan, Kozue Namiki, Pattama Wongsirisin. AXL receptor tyrosine kinase stimulates cell softening and cancer progression via Rac signaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2376.