Anti tumor activity of cord blood stem cell derived CD16 positive NK cells as an immune cell therapy for acute lymphoblastic leukemia (ALL)

Abstract

Acute lymphoblastic leukemia (ALL) is an aggressive cancer in children and adults which possess higher CD47 expression than normal cells. ALL chemotherapy has a lot of side effects and in most cases is ineffective. However arrival of Natural killer (NK) cell immunotherapy raised hopes for successful treatment of cancers, tailoring NK cells to meet clinical requirements is still under investigation. Of note, CD16+ (FCγIIIa) NK cells eliminate tumor cells with antibody dependent cell cytotoxicity (ADCC) mechanism. On the other hand decrease in CD16 expression happens in caseof coculture with tumor cells by the effect of ADAM17. In this study, we evaluated the ADCC effect of CD16 positive NK cells by using of anti-CD47 antibody and ADAM17 inhibitor. Material and Methods: The mononuclear cells were isolated from umbilical cord blood by Ficoll-Paque density gradient and CD34 positive cells were enriched with MACS LS column using CD34 microbeads. Then cells were cultured for 21 days in the presence of different cytokines. Flow cytometry was performed on days 7, 14 and 21. Expression of CD47 and ADAM17 evaluated using westernblot and Flow cytometry. NK cell cytotoxicity was evaluated by measuring expression of CD107a and secretion of IFN-γ in combination of ALL cell line in the presence and absence of ADAM17 inhinitor⸲ anti-CD 47 antibody and Macrophages. Result: Therefore, we evaluated ADCC effect of cord blood stem cell derived CD16+ NK cells with using anti CD47 blocking antibody. CD16+ NK cells generated efficiently from CD34 positive cord blood cells in vitro using IL-2, IL-15 and IL-21 cytokines, although it was not dose dependent. CD16+ cells derived from CD34+ cells in day 14 of culture efficiently increased apoptosis in ALL cells, produced INFγ and increased CD107-a expression when used anti CD47 antibody (increased around 30-40%). Interestingly, CD16+ NK cell cytotoxicity slightly increased in combination with macrophages against ALL cells (around 10%).