NK-CELLS TRAFFIC TO THE BONE MARROW AS A POTENTIAL IMMUNOLOGICAL MECHANISM OF ACTION OF HYPOMETHYLATING AGENTS FOR HIGH-RISK MDS AND AML

Abstract

Introduction: In addition to direct cytotoxic effect of hypomethylaging agents (HMAs) on myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) cells, HMA upregulates effector T-cell function by demethylating T-cell exhaustion-associated genes (Hazem, Cell 2017) or trafficking effector T-cells to bone marrow (BM) by Th1-type chemokines activation (Peng, Nature 2019). We tried to elucidate dynamic changes of immune cells profile and gene expression after HMA treatment in patients with MDS or AML. Methods: We performed scRNAseq on consecutive BM samples from an high-risk MDS (HR-MDS) patient treated with azacitidine: we categorized cell clusters based on immune-cell types, assessed changes in immune-cell proportions following treatment, and conducted a differentially expressed genes (DEG) analysis. In addition, changes in immune-cells proportions before vs. after HMA treatment in HR-MDS patients were evaluated, and the association between the immune-cell proportions changes and response to HMA were analyzed from seuqential BM aspirates from HR-MDS/AML patients. Results: In the scRNAseq data, the NK-cell cluster exhibited the most significant increase in the relative proportion up to response, whereas the effector T-cells clusters showed only a modest increase of proportion upon HMA response. DEG revealed an overexpression of CXCR4 in the NK-cell cluster at the timepoint of response, suggesting the recruitment of NK cells to BM. The trafficking of NK cells to BM after HMA response were reproduced in serial BM aspirates from patients with HR-MDS/AML. Conclusions: NK-cells recruited into BM through CXCR4 overexpression and anti-leukemic cytotoxicity exerted by NK cells may represent a crucial immunological mechanism of action for HMAs in patients with HR-MDS/AML.