PB1888 FEATURES OF CYSTEIN-RICH PROTEIN METALLOTHIONEIN FUNCTIONING IN CHRONIC B-LYMPHOCYTIC LEUKEMIA CELLS

Abstract

Background: The main approach to the hematological cancers treatment is an intensive chemotherapy. However, often its ineffectiveness could be result of the phenomenon of multiple drug resistance (MDR) – immunity of cancer cells to cytostatic drugs. The most important MDR pathways are increased drug efflux resulting in reduced its accumulation, activation of detoxification mechanisms in tumor cells, altered activities of certain enzymes and level of intracellular thiols such as metallothioneins or reduced glutathione which bind compounds toxic for cells. Study and comprehension of these mechanisms will enable the design of suitable techniques and procedures for malignant tumor treatment. Aims: To investigate the level of expression of cystein-rich proteins metallothioneins in lymphocytes of patients with chronic B-lymphocytic leukemia (B-CLL) and to find out their role in the maintenance of redox state under this pathological state. Methods: Lymphocytes were separated from the B-CLL patient's and healthy donor's peripheral blood by density gradient centrifugation on histopaque. Monoclonal antibodies UC1MT (Abcam), UIC2 (Immunotech), MRP1 (R&D) were used to evaluate MTs I-II types, ABCB1, ABCC1 expression, respectively. Reactive oxygen species (ROS) level was assessed using fluorescent probe CM-H2DCFDA (Invitrogen). All investigations were carried out on the FACScanto II (BD). Results: A significant reduction (1.5–2.0-fold) of the MT expression level in B-CLL lymphocytes in comparison to the last one in healthy donors was reveled, despite the proven role of this protein in the detoxification processes from drugs. Additionally a comparative evaluation of expression of the membrane protein-transporters ABC family associated with MDR – ABCB1/P-gp and ABCC1/MRP1 was conducted. Theirs significant rise was found in tested group of B-CLL patients. Moreover, the rise of the ABCC1/ABCB1 expression ratio in leukemia cells reveled under enhanced ROS level compare to normal cells. Summary/Conclusion: Thus, in B-CLL cells the role of MT in the maintaining of redox state (ROS sequestration) is decreased under the rise of ABCC1 function. It is clear that the potential of MT as the scavengers of ROS is not fully understood, but the present data show that this protein could be selected as a target for novel treatment strategies for patients with leukemia.