Berthon, C. | bioRxiv Science

bioRxiv2024

CXCL8 secreted by immature granulocytes inhibits wildtype hematopoiesis in chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is a severe myeloid malignancy with limited therapeutic options. Single-cell analysis of clonal architecture demonstrated early clonal dominance with few residual wildtype hematopoietic stem cells. Circulating myeloid cells of the leukemic clone and the cytokines they produce generate a deleterious inflammatory climate. Our hypothesis is that therapeutic control of the inflammatory component in CMML could contribute to stepping down disease progression. The present study explores the contribution of immature granulocytes (iGRANs) to CMML progression. iGRANs can be detected and quantified in the peripheral blood of patients by spectral and conventional flow cytometry. Their accumulation is a potent and independent poor prognostic factor. These cells belong to the leukemic clone and behave as myeloid-derived suppressor cells. Bulk and single cell RNA sequencing revealed a pro-inflammatory status of iGRAN that secrete multiple cytokines of which CXCL8 at the highest level. This cytokine inhibits the proliferation of wildtype but not CMML hematopoietic stem and progenitor cells (HSPCs) in which CXCL8 receptors are epigenetically downregulated. CXCL8 receptor inhibitors and CXCL8 blockade restore wildtype HSPC proliferation, suggesting that relieving CXCL8 selective pressure on wildtype HSPCs is a potential strategy to slow CMML progression and restore some healthy hematopoiesis.

cancer biology↗

bioRxiv2023

Tetraspanin CD81 promotes leukemia stem cell function and represents a new therapeutic vulnerability in acute myeloid leukemia

Despite important progress over the last decade, acute myeloid leukemia (AML) is still associated with poor clinical outcome. Novel potent therapies ideally effective against AML stem cells (LSC), a major driver of leukemia initiation and progression, are urgently needed. In particular, targeting common AML-associated antigens at the stem and progenitor cell level represents an attractive therapeutic strategy to achieve deep long-term remissions and is currently the subject of intensive research efforts. In this study, we identified the tetraspanin CD81, a cell surface antigen frequently expressed on AML cells including LSC, as a new determinant of relapse and poor prognosis. CD81 expression was higher in AML cells compared to normal bone marrow cells, and more markedly expressed at relapse. We further showed that modulation of CD81 expression using gain- and loss-of-function approaches affected leukemia aggressiveness, tumor burden, LSC-homing and - xenoengraftment as well as mouse survival. Finally, anti-hCD81 monoclonal antibody-treatment combined with standard chemotherapy in mice with pre-established AML not only reduced leukemia burden but also prolonged relapse-free and overall survival. Collectively, these results identified a new efficacious and safe pharmacological strategy for targeting LSC, opening up novel therapeutic avenues to improve AML outcome. Key pointsO_LICD81 expression in AML including LSC is a new determinant of aggressive disease and poor prognosis. C_LIO_LIAnti-hCD81 monoclonal antibody-treatment of AML xenografts reduced leukemia burden and improved survival rates. C_LI

cancer biology↗