CAR-NK cells derived from cord blood predominantly originated from CD56-CD7+CD34-HLA-DR- lineage markers- NK progenitor cells

Cord blood (CB)-derived chimeric antigen receptor (CAR)-natural killer (NK) cells targeting CD19 has been shown to be effective against B cell malignancies. While human CD56+ NK cells can be expanded in vitro, it is also known that NK cells can be differentiated from hematopoietic progenitor cells. It is still unclear whether CAR-NK cells are originated from mature NK cells or NK progenitor cells in CB. Here we found that CAR-NK cells are predominantly derived from the CD56- NK progenitor cells. We first found that substantial numbers of CD19 CAR-NK cells were produced from the CD56- CB mononuclear cells after in vitro culture for two weeks. Single cell RNAseq analysis of CD56-CD3-CD14-CD19- CB mononuclear cells revealed that those cells were subdivided into three subpopulations based on the expression of CD34 and HLA-DR. NK cells were predominantly produced from the CD34-HLA-DR- cells. In addition, in the CD34-HLA-DR- cells, only CD7+ cells could differentiate into NK cells. These results indicate that CD56-CD7+CD34- HLA-DR-lineage marker (Lin)- cells are the major origin of human CB-derived CAR-NK cells, indicating that we need to develop methods to enhance the quality and quantity of NK cells produced from these NK cell progenitor cells. CD56-CD3-CD14-CD19- cord blood mononuclear cells from three independent donors were FACS-sorted and subjected to the analysis