Identification of an Early Unipotent Neutrophil Progenitor with Pro-tumoral Activity in Mouse and Human Bone Marrow

Abstract

Neutrophils are short-lived cells that play important roles in both health and disease. Neutrophils and monocytes originate from the granulocyte monocyte progenitor (GMP) in bone marrow; however, unipotent neutrophil progenitors are not well defined. Here, we use cytometry by time of flight (CyTOF) and single-cell RNA sequencing (scRNA-seq) methodologies to identify a committed unipotent early-stage neutrophil progenitor (NeP) in adult mouse bone marrow. Importantly, we found a similar unipotent NeP (hNeP) in human bone marrow. Both NeP and hNeP generate only neutrophils. NeP and hNeP both significantly increase tumor growth when transferred into murine cancer models, including a humanized mouse model. hNeP are present in the blood of treatment-naive melanoma patients but not of healthy subjects. hNeP can be readily identified by flow cytometry and could be used as a biomarker for early cancer discovery. Understanding the biology of hNeP should allow the development of new therapeutic targets for neutrophil-related diseases, including cancer.

Neutrophil Diversity in Health and Disease

“…Although the latter process has been better characterized in mice (see below), there is also evidence for neutrophil recycling and destruction within the human BM [32]. Currently, there is renewed interest in better understanding the sequential steps of neutrophil maturation [33,34], as well as the transcriptomic and epigenomic programs they carry [35], and through which these granulocytes progressively acquire specific functional abilities. Further complicating our understanding of neutrophil identities, the phenotype of circulating mature neutrophils appears to vary over the course of their lifespan [3,6,8,9].…”

“…Developmental analysis of neutrophil populations within the mouse BM has instead revealed the existence of subpopulations of proliferative precursors as well as immature and mature neutrophils (similar to their circulating counterparts), and these have also been proposed to be present in humans (see above) ( Figure 1); these subpopulations display different expansion and effector activities under microbial and tumoral stress [33,34]. Indeed, although mature neutrophils were found to be essential for antimicrobial host defense in a mouse model of cecal ligation and puncture (CLP)-induced sepsis [33], neutrophil precursors were able to expand and support granulopoiesis in CLP [33], as well as in pancreatic [33] and melanoma [34] tumor mouse models; in the latter models, neutrophil precursors could also promote tumor growth by exerting T cell-mediated immunosuppression via programmed death ligand 1 (PD-L1/CD274)-dependent mechanisms [34]. Similarly, the neutrophil 'aging' process is better documented in mice than in humans.…”

Chromosome Transplantation: Correction of the Chronic Granulomatous Disease Defect in Mouse Induced Pluripotent Stem Cells

“…By a time‐course flow cytometry analysis, we identified the day within step 2 when the highest yield of granulocyte precursors were achieved. To do this, we focused on the recently characterized early proliferative neutrophil progenitors that are able to generate colony‐forming unit granulocyte (CFU‐G) in methylcellulose‐based medium . Flow cytometry analysis using anti‐CD45, cKit, CD11b, CD115, Ly6G antibodies revealed that the highest frequency of CD45 + cKit int CD11b + CD115 − Ly6G − neutrophil progenitors, was obtained at 14–18 days (Supporting Information Fig.…”

CyTOF reveals phenotypically-distinct human blood neutrophil populations differentially correlated with melanoma stage

“…11 Our group has also identified a CD117 + CD66b + CD38 + neutrophil progenitor (NeP), which was found in the blood of tumor-bearing animals. 12 Additional work in this area is summarized in two excellent review articles. 13,14 Nevertheless, a lack of widely-accepted subpopulation markers has impeded our understanding of neutrophil heterogeneity.…”

“…These endeavors demonstrate that neutrophil-lineage cells comprise a heterogeneous pool in mouse and human BM. 11,12 Additionally, recent scRNA-seq analyses reveal 6 neutrophil clusters with distinct transcriptional signatures in human lung tumors but the surface markers needed to classify these populations were not identified. 16 Interestingly, work in this field has also suggested differential involvement of neutrophil subpopulations in cancer.…”