Inhibition of a new AXL isoform (AXL3) induces apoptosis of mantle cell lymphoma cells

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma having a poor overall survival that is in need for the development of new therapeutics. In this study, we report the identification and expression of a new isoform splice variant of the tyrosine kinase receptor AXL in MCL cells. This new AXL isoform, called AXL3, lacks the ligand-binding domain of the commonly described AXL splice variants and is constitutively activated in MCL cells. Interestingly, functional characterization of AXL3, using CRISPRi, revealed that only the knockdown of this isoform leads to apoptosis of MCL cells. Importantly, pharmacological inhibition of AXL activity resulted in a significant decrease in the activation of well-known pro-proliferative and survival pathways activated in MCL cells (i.e.b-catenin, AKT, and NF-kB). Therapeutically, pre-clinical studies using a xenograft mouse model of MCL indicated that bemcentinib is more effective than ibrutinib in reducing the tumour burden and to increase the overall survival. Our study highlights the importance of a previously unidentified AXL splice variant in cancer and the potential of bemcentinib as a targeted therapy for MCL