Upregulation of Galectin-9 and PD-L1 Immune Checkpoints Molecules in Patients with Chronic Lymphocytic Leukemia

BACKGROUND: Deviation of host immune response by engagement of inhibitory receptors is one of the well-known mechanisms of tumor cells for immune evasion and survival. PD-1/PD-L1 and Tim-3/Gal-9 axes are two major pathways in this area which their contribution has been documented in a variety of malignancies. In this study, Gal-9 and PD-L1 expression was investigated in leukemic cells from patients with Chronic Lymphocytic Leukemia (CLL). METHODS: Peripheral blood mononuclear cells (PBMCs) were obtained from 25 untreated CLL patients and 15 sex- and age-matched healthy controls. CLL patients were classified into different clinical stages based on the Rai staging system. Total RNA was extracted from all samples and applied for cDNA synthesis. Relative expression of Gal-9 and PD-L1 mRNA was determined by Real-Time PCR using β-actin as a housekeeping gene. RESULTS: Gal-9 and PD-L1 mRNA was significantly more expressed in CLL patients compared to healthy controls (p<0.0001 and p=0.005, respectively). CLL patients in advanced clinical stages showed higher expression of Gal-9 and PD-L1 in comparison to patients in early clinical stages (p<0.0001 and p=0.004, respectively). CONCLUSION: Our promising results regarding over-expression of Gal-9 and PD-L1 in CLL patients call future complementary studies to more evaluate and confirm these pathways for immunotherapy approaches of this malignancy. Upregulation of both Gal-9 and PD-L1 in CLL patients with advanced clinical stages introduces them as useful prognostic biomarkers for disease progression.