Subpopulation profile of CD34<sup>+</sup> pluripotent hematopoietic stem cells in blood malignancies

The incidence of malignant blood diseases has been steadily increasing over past decades. Unlike many other types of malignant neoplasms, blood cancers often occur at a young age, being also the main cause of death among all hematopoietic disorders in pediatric patients. Mutation events in hematopoietic stem cells are the cause of blood cancers which subsequently lead to increasimg number of tumor clones and displacement of healthy cells in the niches they occupy thus leading to a number of changes in blood and bone marrow, including irreversible ones. The aim of this study was to assess the subpopulation composition of pluripotent hematopoietic stem cells in patients with blood cancers and healthy donors. The study included patients with blood cancers (n = 13), including acute lymphoblastic leukemia (ALL; n = 3), acute myeloid leukemia (AML; n = 3), and multiple myeloma (MM; n = 7), as well as healthy donors (n = 4). The phenotypic composition of hematopoietic CD34+CD38- pluripotent cells was assessed by flow cytometry using the following monoclonal antibodies: CD34 APC (BioLegend, USA), CD38 PE-Cy7 (ElabScience, China), CD45RA PerCP (ElabScience, China), CD90 APC-Cy7 (Cloud-Clone Corp., USA), Lin- (cocktail CD3/14/16/19/20/56) FITC (BioLegend, USA). The following populations were assessed: hematopoietic stem cells (Lin-CD34+CD38-CD45RA-CD90+) and pluripotent progenitors (Lin-CD34+CD38-CD45RA-CD90-). In patients with hemoblastoses, the relative number of cells with Lin-CD34+CD38-CD45RA-CD90+ phenotype proved to be increased, thus corresponding to hematopoietic stem cells, but not pluripotent progenitor cells. At the same time, the number of pluripotent progenitor cells tended to decrease in acute myeloid leukemia. We have observed some changes in the subpopulation composition of pluripotent hematopoietic stem cells in patients with blood cancers, when compared with healthy donors.