CD45 inhibition in myeloid leukaemia cells sensitizes cellular responsiveness to chemotherapy

Abstract

Background Myeloid malignancies are a group of blood disorders characterized by the proliferation of one or more haematopoietic myeloid cell lineages, predominantly in the bone marrow and are often caused by aberrant protein tyrosine kinase activity. The protein tyrosine phosphatase CD45 is a transmembrane molecule expressed on all haemopoietic blood cells except that of platelets and red cells. CD45 regulates various cellular physiological processes including proliferation, apoptosis, and lymphocyte activation. The aim of this study was to investigate the role of CD45 in myeloid malignancies in terms of cellular growth, apoptosis, and response to chemotherapy to investigate alternative therapies with less toxicity and more efficacy. Methods The expression profile of CD45 was established in a panel of myeloid leukaemia cell lines and in peripheral blood cells from normal individuals, AML and MPN patients using western blot, flow cytometry, and PCR. CD45 KD was performed by using siRNA nucleofection and lipofectamine RNAiMAX technology. Bioinformatics study was performed using Partek Genomic Suit and Quadratic software for connectivity mapping. RNA sequencing was performed on CD45 KD cells and CD45 inhibited cells versus control cells. Apoptosis was studied by using Caspase-Glo™ Assay and western blotting. Drug combination studies between CD45 inhibitors and chemotherapy were performed and cytotoxicity was estimated by using Cell Titer-Glo® (CTG). Results The expression of CD45 on myeloid leukaemia primary cells and cell lines was heterogeneous with HEL and OCI-AML3 cells showing the highest level. Knockdown (KD) and/or inhibition of CD45 resulted in increased cellular sensitivity to cytarabine and ruxolitinib. Bioinformatics analysis identified of alendronate, allopurinol, and balsalazide as CD45 inhibitors along with genes whose expression was correlated with CD45 expression such as JAK2, ACTR2, THAP3 Serglycin and PBX-1 genes. Conclusions CD45 inhibition could be explored as a potential therapeutic partner for treatment of myeloid malignancies in combination with chemotherapy such as cytarabine. Identification of alendronate, allopurinol, and balsalazide, licensed drugs, could be repurposed as CD45 inhibitors at non-toxic concentrations which effectively increases sensitivity to cytarabine and ruxolitinib at low doses. Therefore, combining CD45 inhibitor drugs with low dose chemotherapy can be beneficial in treating myeloid leukaemia and can provide an alternative therapy characterized by less toxicity and more efficiency especially for elderly patients and those showing chemotherapy resistance.