Expression of Cannabinoid Receptors on the Neoplastic Lymphocytes in Patients with Chronic Lymphocytic Leukemia.

Endocannabinoids take part in the physiology of neural and immune systems. The latest data showed that these compounds and their receptors play an important role in proliferation and apoptosis of various neoplastic cells. Cannabinoids were shown to increase apoptosis in human leukemia and lymphoma cell lines and culture of neoplastic cells obtained from patients with T-cell acute lymphoblastic leukemia. The aim of the study was an assessment of cannabinoid receptors expression on lymphocytes B derived from patients with CLL. The study group contains newly diagnosed, untreated adult patients with B-cell chronic lymphocytic leukemia; 13 male and 7 female, aged from 44 to 65. All of the patients were in B or C stage according to Binet. Peripheral blood samples from 10 healthy adult donors were used as the control group. The patients were hospitalized in the Department of Haematology, Medical University in Bialystok, Poland. Diagnosis of CLL in all cases was confirmed by routine immunophenotyping study. For flow cytometric analysis 1x10⁵ – 1x10⁶ of peripheral blood cells were incubated with 10ul of anty CB1 and anty CB2 polyclonal antibodies (American Diagnostics). Then 10ul of monoclonal antibodies IgG1-FITC and CD19-PE (Becton Dickinson) were added and the samples were incubated for 20 min in dark in 4°C. The samples were lysed, fixed and stabilized using Immuno-Prep (Coulter procedure) and assessed by flaw cytometry (Epics XL, Coulter). Statistical analysis was performed using non parametric U Mann-Whitney and Wilcoxon Tests. The conducted study revealed high expression of CB1 and CB2 receptors on the surface of neoplastic lymphocytes. The percentage of CB1/CD19 and CB2/CD19 positive cells in CLL patients were significantly higher, compared to the control group respectively (81.2±9,8% vs 12.0±9,3% p<0,05; 94,8±11,0 % vs 9,9±4,0%, p<0,05). No difference was noticed between the percentage of lymphocytes with CB1 and CB2 receptors expression in CLL and control group. Fluorescent intensity of CB2 receptors was about ten folds higher than CB1 receptors in both groups. The study demonstrated the presence of both types of cannabinoid receptors (CB1 and CB2) on neoplastic cells derived from patients with chronic lymphocytic leukemia. The higher percentage of B-lymphocytes expressing cannabinoid receptors in CLL patient suggests that the cannabinoid system may take part in CLL development. High intensity of CB2 receptor may be another target in CLL treatment.