Meni, C. | bioRxiv Science

bioRxiv2025

AXL mediates mast cell survival and resistance to tyrosine kinase inhibitors in mastocytosis

Mastocytosis is a clonal disorder driven by KIT mutations, but resistance to tyrosine kinase inhibitors (TKIs) remains a major challenge. Following the discovery of an AXL L197M mutation in a patient with congenital aggressive mastocytosis, we demonstrated unexpected wild-type AXL expression in neoplastic mast cells (MCs) across mastocytosis subtypes, challenging current views concerning mastocytosis pathophysiology. AXL was undetectable in steady-state MCs but several factors, including IFN- and IFN-{beta}, induced its expression, consistent with the inflammatory nature of mastocytosis and the high interferon levels in patient plasma. Ectopic expression of WT or L197M AXL in the ROSA KIT D816V cell line enhanced proliferation and survival by upregulating pSTAT5, pSTAT3, pFAK, p-p38, survivin and BCL2. Both AXL forms conferred resistance to the KIT inhibitor PKC412/midostaurin by sustaining BCL2, MCL1, and BCL-XL expression while reducing caspase-3 activation. L197M AXL induced slightly stronger resistance to apoptosis than WT, but this difference was not significant. Combined KIT and AXL targeting (PKC412+R428) restored TKI sensitivity by downregulating BCL-XL, Livin and cIAP1, and activating caspase-3, highlighting the therapeutic potential of dual KIT/AXL pathway inhibition. Importantly, neoplastic MCs from a mast cell leukemia patient harboring the KIT F522C mutation and unresponsive to PKC412 strongly expressed AXL and displayed marked in vitro sensitivity to R428 alone, highlighting AXL as a potential therapeutic target in aggressive mastocytosis not driven by KIT D816V. These findings identify AXL as a previously unrecognized driver of malignant MC survival and TKI resistance, and support AXL inhibition as a promising therapeutic strategy in aggressive mastocytosis. Key Points- AXL is aberrantly expressed in neoplastic mast cells, driving survival and resistance to KIT inhibition in mastocytosis. - Dual KIT and AXL inhibition restores TKI sensitivity in KIT-mutant mastocytosis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/686205v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1569c9eorg.highwire.dtl.DTLVardef@1445b32org.highwire.dtl.DTLVardef@bf3565org.highwire.dtl.DTLVardef@14a94f0_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

Absence of severe COVID-19 in patients with clonal mast cells activation disorders: effective anti-SARS-CoV-2 immune response.

Mast cells are key actors of innate immunity and Th2 adaptive immune response which counterbalance Th1 response, critical for anti-viral immunity. Clonal Mast Cells Activation Disorders (cMCADs) such as mastocytosis and clonal mast cells activation syndrome are characterized by an abnormal mast cells accumulation and/or activation. No data have been published on the anti-viral immune response of patients with cMCADs. The aims of the study were to collected, in a comprehensive way, outcomes of cMCADs patients who experienced a biologically-proven COVID-19 and to characterize both anti-endemic coronaviruses and specific anti-SARS-CoV-2 immune responses in these patients. Clinical follow-up and outcome data were collected prospectively for one year within the French rare disease network CEREMAST encompassing patients from all over the country. Anti-SARS-CoV-2 and anti-endemic coronaviruses specific T-cells were assessed with an enzyme-linked immunospot assay (EliSpot) and anti-SARS-CoV-2 humoral response with dosage of circulating levels of specific IgG, IgA and neutralizing antibodies. Overall, 32 cMCADs patients were identified. None of them required non-invasive or mechanical ventilation; two patients were hospitalized to receive oxygen and steroid therapy. In 21 patients, a characterization of the SARS-CoV-2-specific immune response has been performed. A majority of patients showed a high proportion of circulating SARS-CoV-2-specific interferon (IFN)-{gamma} producing T-cells and high levels of anti-Spike IgG antibodies with neutralizing activity. In addition, no defects in anti-endemic coronaviruses responses were found in patients with cMCADs compared to non-cMCADs controls. Patients with cMCADs frequently showed a spontaneous IFN-{gamma} T-cell production in absence of any stimulation that correlated with circulating basal tryptase levels, a marker of mast cells burden. These findings underscore that patients with cMCADs might be not at risk of severe COVID-19 and the spontaneous IFN-{gamma} production might explain this observation. Author SummaryMast cells are immune cells involved in many biological processes including the anti-microbial response. However, previous studies suggest that mast cells may have a detrimental role in the response against viruses such as SARS-CoV-2, responsible for COVID-19. When a mutation occurs in mast cells, it can lead to a group of diseases called clonal mast cells activation disorders (cMCADs), characterized by deregulated activation of these cells. Hence, patients with cMCADs might be more susceptible to severe COVID-19 than general population. We therefore conducted a 1-year study in France to collect data from all cMCADs patients included in the CEREMAST rare disease French network and who experienced COVID-19. Interestingly, we did not find any severe COVID-19 (i.e. requiring non-invasive or mechanical ventilation) in spite of well-known risk factors for severe COVID-19 in a part of cMCADs patients. We then have studied the immune response against SARS-CoV-2 and other endemic coronaviruses in these patients. We did not observe any abnormalities in the immune response either at the level of T and B lymphocytes. These findings underscore that these patients might not be at risk of severe COVID-19 as one might have feared.

immunology↗