Abstract
The Axl receptor tyrosine kinase belongs to the TAM (Tyro3, Axl, Mer) family of proteins and is upregulated in multiple types of cancers, including non-small cell lung cancer. In normal tissues, TAM receptor tyrosine kinases contribute to immune regulation. In cancer, Axl expression is associated with poor outcomes and is controlled through various transcriptional and epigenetic mechanisms. Preclinical studies have shown that Axl is involved in cancer cell migration, growth, survival and resistance to chemotherapy through activation of multiple downstream signaling pathways, such as Ras/MAPK, PI3K and Rac1. Axl is also expressed on endothelial cells and plays a role in angiogenesis. In preclinical models, Axl inhibition decreases cancer growth and impedes lung cancer metastases. Small molecule Axl inhibitors have been developed and are currently being used as monotherapy or in combination with cytotoxic chemotherapy or anti-EGFR therapy in early clinical trials. Here, we review Axl structure, functions, regulation, and preclinical and clinical studies in lung cancer.