Herman Netskar

Abstract The functional diversity of natural killer (NK) cell repertoires stems from differentiation, homeostatic, receptor–ligand interactions and adaptive-like responses to viral infections. In the present study, we generated a single-cell transcriptional reference map of healthy human blood- and tissue-derived NK cells, with temporal resolution and fate-specific expression of gene-regulatory networks defining NK cell differentiation. Transfer learning facilitated incorporation of tumor-infiltrating NK cell transcriptomes (39 datasets, 7 solid tumors, 427 patients) into the reference map to analyze tumor microenvironment (TME)-induced perturbations. Of the six functionally distinct NK cell states identified, a dysfunctional stressed CD56 bright state susceptible to TME-induced immunosuppression and a cytotoxic TME-resistant effector CD56 dim state were commonly enriched across tumor types, the ratio of which was predictive of patient outcome in malignant melanoma and osteosarcoma. This resource may inform the design of new NK cell therapies and can be extended through transfer learning to interrogate new datasets from experimental perturbations or disease conditions.

NK cells, resulting in missing self-recognition.

Background Natural killer (NK) cells hold great promise as a source for allogeneic cell therapy against hematological malignancies, including acute myeloid leukemia (AML). Current treatments are hampered by variability in NK cell subset responses, a limitation which could be circumvented by specific expansion of highly potent single killer immunoglobulin-like receptor (KIR) + NKG2C + adaptive NK cells to maximize missing-self reactivity. Methods We developed a GMP-compliant protocol to expand adaptive NK cells from cryopreserved cells derived from select third-party superdonors, that is, donors harboring large adaptive NK cell subsets with desired KIR specificities at baseline. We studied the adaptive state of the cell product (ADAPT-NK) by flow cytometry and mass cytometry as well as cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq). We investigated the functional responses of ADAPT-NK cells against a wide range of tumor target cell lines and primary AML samples using flow cytometry and IncuCyte as well as in a mouse model of AML. Results ADAPT-NK cells were >90% pure with a homogeneous expression of a single self-HLA specific KIR and expanded a median of 470-fold. The ADAPT-NK cells largely retained their adaptive transcriptional signature with activation of effector programs without signs of exhaustion. ADAPT-NK cells showed high degranulation capacity and efficient killing of HLA-C/KIR mismatched tumor cell lines as well as primary leukemic blasts from AML patients. Finally, the expanded adaptive NK cells had preserved robust antibody-dependent cellular cytotoxicity potential and combination of ADAPT-NK cells with an anti-CD16/IL-15/anti-CD33 tri-specific engager led to near-complete killing of resistant CD45 dim blast subtypes. Conclusions These preclinical data demonstrate the feasibility of off-the-shelf therapy with a non-engineered, yet highly specific, NK cell population with full missing-self recognition capability.

NK cells with an induced CD57 phenotype display increased functional potential associated with increased transcription of genes involved in adhesion and immune synapse formation. Rapidly cycling cells upregulate NKG2A, display a general loss of functionality, and a transcriptional signature associated with increased apoptosis/cellular stress, actin-remodeling, and nuclear factor κB (NF-κB) activation. These results shed light on the role of intra-lineage plasticity during NK cell homeostasis and suggest that the functional fate of the cell is tightly linked to the acquired phenotype and transcriptional reprogramming.

Abstract Natural killer cell repertoires are functionally diversified as a result of differentiation, homeostatic receptor-ligand interactions and adaptive responses to viral infections. However, the regulatory gene-circuits that define the manifold cell states and drive NK cell differentiation have not been clearly resolved. Here, we performed single-cell RNA sequencing of 26,506 cells derived from sorted phenotypically-defined human NK cell subsets to delineate a tightly coordinated differentiation process from a small population of CD56 bright precursors to adaptive NKG2C + CD56 dim NK cells. RNA velocity analysis identified a clear directionality in the transition from CD56 bright to CD56 dim NK cells, which was dominated by genes involved in transcription and translation as well as acquisition of NK cell effector function. Gene expression trends mapped to pseudotime, defined by increasing entropy, identified three distinct transcriptional checkpoints, reflecting important changes in regulatory gene-circuits. The CD56 bright NK cell population dominated pseudotime with two distinct checkpoints separating precursors from intermediate states that gradually took on transcriptional signatures similar to CD56 dim NK cells. The final checkpoint occurred during late terminal differentiation of CD56 dim NK cells and was associated with unique divergent gene-expression trends. Furthermore, we utilized this single-cell RNA sequencing resource to decipher the regulation of genes involved in lysosomal biogenesis and found a coordinated gradual increase in the RAB4 and BLOC1S gene families with differentiation into CD56 dim NK cells. These results identify important gene programs driving functional diversification and specialization during NK cell differentiation and hold potential to guide new strategies for NK cell-based cancer immunotherapy.