Effects of ibrutinib and venetoclax on the expression of immune checkpoint molecules in leukemic blasts of patients with acute lymphoblastic leukemia.

Background: In recent decades, targeted therapy using small molecule inhibitors (SMI) have been shown very promising results in the treatment of a variety of solid and hematopoietic malignancies. However, their exact mechanisms, especiallay on the evasion strategies of tumor cells from the host immune system are not fully understood. The current study investigates the effects of two SMIs, ibrutinib and venetoclax, on the expression of inhibitory immune checkpoint molecules in patients with acute lymphoblastic leukemia (ALL). Methods: Leukemic cells were isolated from 20 patients with ALL by magnetic activated cell sorting (MACS) technique. Isolated leukemic cells were cultured and treated by ibrutinib and venetoclax for 48 h. Cell viability and apoptosis were monitored through MTT and flow cytometry assays, respectively. The mRNA expression levels of checkpoint molecules PD-L1, galectin-9, CD200, CD155, CD47, and anti-inflammatory cytokine TGF-β were determined by Real-Time PCR method. Results: The purity of MACS-isolated ALL leukemic cells was >98% as determined by flow cytometry. Following treatment, the proliferation of leukemic cells was significantly decreased and the apoptosis rate was significantly increased, which was more remarkable for venetoclax. Moreover, treatment of leukemic cells with ibrutinib and venetoclax showed alterations in the mRNA expression of immune checkpoint inhibitory ligands and TGF-β. Conclusion: Our results indicated that small molecule inhibitors not only hinder proliferation and enhance apoptosis, but also affect the expression of inhibitory immune checkpoint ligands. By elucidating the precise underlying mechanisms, these drugs could emerge as promising therapeutic options, particularly in the context of combination therapy for ALL.