Abstract 1297: Increases in the numbers of myeloid-derived suppressor cells in Egyptian children with acute lymphoid leukemia

Abstract Background: Acute lymphoblastic leukemia (ALL) or acute lymphoid leukemia is an acute form of leukemia. Although the mechanism behind the relapse in ALL is not clearly known, one possible mechanism could be the accumulation of immune regulatory cells, in particular myeloid-derived suppressor cells (MDSCs). We and others have reported that MDSCs cause suppression of host immune responses through several mechanisms. Aim: The main goal of this study was to determine whether these cells accumulate in ALL patients and whether they are affected by chemotherapy. Materials and Methods: Upon informed consent, patients with B-Linage Acute Lymphoblastic Leukemia “B-ALL” (n = 20) were recruited in this study along with healthy volunteers (n = 20). Patients included in this study were risk stratified according to risk classification system and treated according to treatment protocols including high risk pre B-ALL protocol, standard risk pre B-ALL. MDSCs were characterized as HLA-DR-Lin-CD33+CD11b+ cells. Results: Our preliminary results showed significant increases in the numbers of myeloid population with MDSC-like phenotype in B-ALL patients at different stages of chemotherapy treatment when compared with healthy control volunteers (Mean = 1.01%). The increases in the numbers of these cells were higher after treatment of the patients with induction chemotherapy. Further, the increased numbers of MDSCs associated with high numbers of circulating leukemic stem cells (LSCs). Conclusion: Our preliminary data suggest that cells with MDSCs like-phenotype emerge in ALL patients and possibly play a critical role in establishing an immune suppressive environment in children with ALL. Further research is needed to determine if circulating MDSCs like-phenotype populations are a immunosuppressive and whether they can be modulated. Acknowledgment: This work has been supported by a grant (ID# 5245) funded from the Science and Technology Development Fund (STDF), Ministry of Scientific Research and Technology, Egypt to Mohamed L. Salem, the Principal investigator of this project. Note: This abstract was not presented at the meeting. Citation Format: Mohamed L. Salem. Increases in the numbers of myeloid-derived suppressor cells in Egyptian children with acute lymphoid leukemia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1297. doi:10.1158/1538-7445.AM2015-1297