Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 22 5 2023 10 29 495 503 EN Mojdeh Soltani Department of Immunology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Mahshid Vosoughi Department of Immunology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Mazdak Ganjalikhani-Hakemi Department of Immunology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran AND Department of Immunology, Faculty of Medicine, Yedıtepe Unıversıty, Istanbul, Turkey Hoorieh Shapoorian Department of Immunology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Pezhman Beshkar Department of Laboratory Sciences, School of Allied Medical Sciences, Shahrekord University of Medical Sciences, Shahrekord, Iran Nahid Eskandari Department of Immunology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Behrooz Ghezelbash Department of Immunology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran 2023 04 26 2023 09 14 Programmed death ligand‑1 (PD‑L1) is a pivotal inhibitory checkpoint ligand known to induce T-cell exhaustion via interaction with the programmed death‑1 (PD‑1) receptor. Beyond this, PD-L1’s intrinsic signaling pathways within cancer cells warrant further exploration. This study aims to elucidate the effect of PD-L1 stimulation on the proliferation, survival, and apoptosis of acute myeloid leukemia (AML) cell lines. Two human AML cell lines, HL-60 and THP-1 were cultured and treated with phorbol 12-myristate 13-acetate (PMA) to induce PD-L1overexpression. Post-treatment PD-L1 expression was confirmed via flow cytometry. Subsequently, cell surface PD-L1 was stimulated using a recombinant PD-1, 24 hours post-PMA treatment. The expression alterations in pivotal genes including BCL2, MKI67, BAX, and CASP3 were monitored using quantitative real-time polymerase chain reaction 24 and 48 hours post-treatment. Additionally, annexin-V through flow cytometry. Findings reveal that PD-L1 stimulation augments AML cell proliferation and survival by enhancing MKI67 and BCL2 expressions while concurrently inhibiting cell apoptosis due to decreased BAX and CASP3 expression following PD-L1 stimulation. Notably, stimulated cells expressed exhibited reduced annexin-V compared to control cells. This study underscores that PD-L1 stimulation fosters AML cell proliferation and survival while impeding cell apoptosis. The results hold potential implications for targeting PD-L1 in AML treatment strategies. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/3819 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/3819/1991