Introduction: Acquired cancer therapy resistance evolves under selection pressure of immune surveillance and favors mechanisms that promote drug resistance through cell survival and immune evasion. AXL receptor tyrosine kinase is a mediator of cancer cell phenotypic plasticity and suppression of tumor immunity, and AXL expression is associated with drug resistance and diminished long-term survival in a wide range of malignancies, including NSCLC.
Methods: We aimed to investigate the mechanisms underlying AXL-mediated acquired resistance to first- and thirdgeneration small molecule EGFR tyrosine kinase inhibitors (EGFRi) in NSCLC.
Results: We found that EGFRi resistance was mediated by up-regulation of AXL, and targeting AXL reduced
reactivation of the MAPK pathway and blocked onset of acquired resistance to long-term EGFRi treatment
in vivo. AXL-expressing EGFRi-resistant cells revealed phenotypic and cell signaling heterogeneity incompatible with a simple bypass signaling mechanism, and were characterized by an increased autophagic flux. AXL kinase inhibition by the small molecule inhibitor bemcentinib or siRNA mediated AXL gene silencing was reported to inhibit the autophagic flux in vitro, bemcentinib treatment blocked clonogenicity and induced
immunogenic cell death in drug-resistant NSCLC in vitro, and abrogated the transcription of autophagy-associated genes in vivo. Furthermore, we found a positive correlation between AXL expression and autophagy-associated gene signatures in a large cohort of human NSCLC (n ¼ 1018).
Conclusion: Our results indicate that AXL signaling supports a drug-resistant persister cell phenotype through a
novel autophagy-dependent mechanism and reveals a unique immunogenic effect of AXL inhibition on drug-resistant NSCLC cells.
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http://creativecommons.org/licenses/by-nc-nd/4.0/
Funding Info:
This work was partly supported by the Research Council of Norway through its Centres of Excellence funding
scheme, project number 223250 (CCBIO affiliates). Dr. Lotsberg was supported by a PhD fellowship grant from
Helse Vest RHF (the Western Norway Regional Health Authority, grant number 911934). Dr. Minna was supported by National Cancer Institute grant Lung Cancer SPORE (P50CA070907), Cancer Prevention Research Institute of Texas (CPRIT), and Margot Johnson Foundation grants. Dr. Chouaib was supported by la Ligue Contre le Cancer (EL2015.LNCC/SaC). Dr. Lorens was supported by grants from the Norwegian Research Council (grant number 204868) and Norwegian Cancer Society (grant number 190330). Dr. Engelsen was supported by the FRIPRO Mobility Grant Fellowship from the Research Council of Norway co-funded by the EU’s Seventh Framework Programme’s Marie Skłodowska Curie Actions (MSCA COFUND, grant agreement number 608695), Legat for Forskning av Kreftsykdommer fund at University of Bergen (UiB), and Familien Blix fund for this project. Flow cytometry, cell sorting analysis, and mass cytometry were performed at the Flow Cytometry Core Facility, Department of Clinical Science, at UiB. Flow cytometry was also performed at the Imaging and Cytometry Platform (PFIC) at Gustave Roussy Cancer Campus Grand Paris. Gene expression analysis was performed at the genomics core facility (GCF) at UiB. Imaging was performed at the Molecular Imaging Center (MIC) at UiB. The results published here are in part based upon data generated by the TCGA Research Network (https://www.cancer.goc/tcga). We acknowledge the TCGA network and the lung cancer patients that consented to donate tumor tissue for application in cancer research. The authors also thank Sissel Vik Berge, Ingrid Sandven Gavlen, Eline Milde Nævdal, and Anna Boniecka; Endy Spriet, Hege Avsnes Dale and Anne Karin Nyhaug at MIC; Marianne Enger, Brith Bergum and Jørn Skavland at the Flow Cytometry Core Facility/ UiB; and Bendik Nordanger at the Department of Pathology, University of Bergen and Haukeland University Hospital for their skillful technical assistance.