Investigating the role of AXL in the matrix stiffness-dependent regulation of Golgi organisation in anchorage-independent lung cancer cells

Abstract

Lung cancer is the most common cause of cancer-related death worldwide. One hallmark feature of many malignant tumours, including lung cancer, is the stiffening of the stroma. Mechanical cues from the extracellular matrix (ECM), such as its stiffness, influence cell behaviour through mechanotransduction pathways. This affects cancer progression, development, treatment and recurrence. Studies have also shown that Golgi organisation is altered in many cancers, and these changes can impact Golgi functions such as glycosylation and trafficking, potentially driving cancer progression. In normal cells, integrin-mediated cell-matrix adhesion regulates Golgi organisation and function; however, in many anchorage-independent cancer cell lines, Golgi organisation becomes adhesion-independent. AXL, a receptor tyrosine kinase, has been identified as a regulator of Golgi organisation in both the anchorage-independent lung cancer cell line A549 and the breast cancer cell line MDAMB231. In MDAMB231 cells, the AXL-Arf1 axis regulates Golgi organisation in a matrix stiffness-dependent manner. In contrast, while A549 cells exhibit matrix stiffness-dependent cell spreading, their Golgi organisation is matrix stiffness-independent. In A549 cells, AXL expression and Akt activation (activated downstream of AXL) are regulated by matrix stiffness, and inhibition of AXL with R428 on glass modulates AXL and Akt activation—similar to MDAMB231 cells. While AXL-Arf1 crosstalk exists in A549 cells (Radhika's work), they do not regulate Golgi organisation in a matrix stiffness-dependent manner. Our studies, however, show that AXL regulates cell spreading independent of Golgi organisation at specific stiffness. The functional significance of this regulation remains to be tested.