Inflammation perturbs NK cell phenotype and function in chronic myeloid leukemia (CML)

Abstract Natural killer (NK) cells have the capacity to recognize and clear cancer cells by releasing cytotoxic granules. In fact, NK cells’ mature phenotype and abundance are associated with prolonged treatment-free remission in chronic myeloid leukemia (CML). However, NK cell anti-leukemic activity is suppressed during the disease, and the environmental triggers of this impairment are not fully characterized. Given the role of inflammatory cytokines in the progression of myeloid malignancies, we define their impact on NK cell function in a BCR-ABL1 +CML chimeric mouse model. Consistent with clinical observations, NK cells are reduced in counts in leukemic mice, display immature phenotype, low degranulation rate, and altered expression of activating and inhibitory receptors. Single-cell RNAseq analysis confirmed these observations at the transcriptional level, and revealed enrichment in genes and pathways associated with inflammatory cytokine response (e.g., GM-CSF, LTα/β, XCL1, IL-6st, IL-2Ra, SOCS1/2/3, CIS; IL-6/STAT3 and TNFa/NF-kB pathways) in CML-exposed NK cells. To validate the clinical relevance of our findings, we characterized NK cells from CML patients. As expected, NK cell frequencies are reduced in our cohort and display diminished K562-targeted degranulation. Mirroring mouse scRNAseq data, patient NK cells possess a pro-inflammatory gene signature with the activation of JAK-STAT, TNFa/NF-kB, and PI3K-Akt signaling pathways. As this is likely triggered by leukemic cytokines, we found that leukemic serum dampens ex vivo NK cell degranulation capacity. Thus, we speculate that NK cells are sensitive to CML-associated cytokines and that inflammation represents an optimal target for NK-boosting immunotherapies.