Cytotoxicity of Metoprolol on Leukemic Cells in Vitro

β-Blockers have shown considerable cytotoxic, anti-tumor and anti-angiogenic effects. Metoprolol, a β-Blocker with anti-inflammation, antitumor and anti-angiogenic properties has been widely used for treatment of some cardiovascular diseases such as angina, hypertension, heart failure and myocardial infraction. Limited data exist about the cytotoxic effects of metoprolol on human cancer cells. The aim of this study was to investigate the cytotoxic effect of metoprolol on U937 and MOLT-4 cells in vitro. Methods: Human leukemic T cell (MOLT-4) and monocyte (U937) were cultured in Roswell Park Memorial Institute (RPMI) 1640 complete medium. Then, the cultured U937 and MOLT-4 cells were treated with different concentration of metoprolol (1, 10, 50, 100, 500 and 1000 μg/ml) for 24, 48 and 72 hours. The cytotoxicity of metoprolol was determined by using MTT (3-[4, 5 dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide) assay. Results: Metoprolol significantly decreased the viability of U937 and MOLT-4 cells at 1000μg/ml (3740.14μM) concentration after 48 hours incubation time (P<0.01). In addition, metoprolol significantly reduced the viability of U937 cells at ≥500 μg/ml (≥1870.07μM) concentrations after 72 hours incubation time (P<0.001). Moreover, metoprolol significantly decreased the viability of MOLT- 4 cells at ≥100 μg/ml (≥374.01μM) concentrations after 72 hours incubation (P<0.001). Conclusion: According to the results of this study, metoprolol showed cytotoxic effect on U937 and MOLT-4 cells dose and time dependently. Therefore, metoprolol might have potential implication in therapy of leukemia as well as other malignancies.