MDSCs are expanded in the presence of AML blasts. C57BL/6 mice were inoculated using retro-orbital injections, with 1 × 105 GFP stably transduced murine syngeneic AML TIB-49 cells. At the onset of symptomatic disease at 21 days, mice were analyzed. (A) Bone marrow and splenocytes were analyzed by flow cytometry for the murine MDSC markers mCD11b and mGr-1 (n = 5; *P < .05). (B) PMBCs from healthy donors were cocultured in direct contact with irradiated, fluorescently labeled AML cells at a ratio of 100:1 (PBMCs:AML). After 5 days, cells were analyzed with flow cytometry. Labeled tumor cells were excluded, and total MDSCs were quantified as a percentage of immature CD11b+/HLA-DR− myeloid cells (n = 3; *P < .05 for MOLM-14 and patient AML cells). (C) Healthy donor PBMCs and AML cells were cocultured in direct contact or with 0.4-μM Transwell insert, and MDSCs were quantified as a percentage of immature CD11b+/HLA-DR− myeloid cells (n = 3; *P < .05).
