THE EFFECT OF ACTIVATION OF TOLL-LIKE RECEPTORS ON THE CD150 EXPRESSION LEVEL IN MALIGNANT B-LYMPHOCYTES OF PATIENTS WITH CHRONIC LYMPHOCYTIC LEUKEMIA

Shcherbina V.M., Gordiienko I.M.

• RE Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology, NAS of Ukraine, Kyiv, Ukraine

Chronic lymphocytic leukemia (CLL) is the most common nosological form of lymphoproliferative diseases diagnosed in the adult population. The molecular variability of malignant B-lymphocytes, due to both genetic alterations and the state of intracellular signaling networks, underlies the formation of heterogeneity in the biological properties of cells, which is directly related to the features of the clinical course of the disease and the patients` response to chemotherapy. Major attention in CLL studying is paid to the characterization of the expression pattern of signaling molecules and the state of the corresponding receptor-mediated signaling pathways. It has been proven that the expression of the CD150 receptor on the plasma membrane of CLL B-lymphocytes may indicate a difference in the sensitivity of cells to the cytotoxic effect of drugs. Moreover, activation of the CD150 receptor using monoclonal demonstrated that the CD150-mediated signaling pathway is directly involved in regulating the sensitivity of CLL B-lymphocytes to drugs. Aim: to determine the possibility of regulating the CD150 expression in malignant B-lymphocytes of CLL patients by activating the TLR2/6 and TLR4-mediated signaling pathways. Object and methods­: the study was conducted on B-lymphocytes isolated from the peripheral blood of patients with CLL. The level of CD150 expression on the plasma membrane of B-lymphocytes was assessed by an indirect variant of the immunofluorescence method for immunophenotyping of cells using flow cytometry. Quantitative real-time PCR and western blot analysis were used to determine the level of CD150 mRNA and protein expression in B-lymphocytes after TLR2/6 and TLR4 stimulation. The number of viable B-lymphocytes was determined using resazurin in order to analyze changes in the cell sensitivity to chemotherapeutic drugs under the conditions of prior activation of the studied TLRs. Results: It was demonstrated that activation of TLR4 and TLR2/6-mediated signaling pathways leads to an increase in mRNA expression levels of mCD150, nCD150 and sCD150 isoforms of the CD150 receptor. In addition to the effect on the mRNA level, the activation of TLR4 and TLR2/6 also positively regulates the expression of the CD150 protein in CLL B-lymphocytes. However, translocation of the CD150 receptor to the plasma membrane of cells was not observed. The sensitivity of malignant B-lymphocytes depends on the state of activation of signaling pathways, mediated by the binding of TLR4 and TLR2/6 with the corresponding agonists. Conclusion: the obtained results indicate that the expression of the CD150 receptor in CLL B-lymphocytes, as well as cell sensitivity to the cytotoxic effect of chemotherapeutic drugs, depends on the state of activation of TLR4- and TLR2/6-mediated signaling pathways.