Vanadium complexes are a heterogeneous class of compounds exhibiting interesting biological properties. Herein, we report the effect of a vanadium-salen complex (VO-salen) on proliferative behavior of K562 cell line. The results revealed that VO-salen at 6–32 μM inhibited K562 proliferation with no distinct alteration in cell morphology, extent of apoptosis and/or differentiation. Our results indicated that VO-salen complex has just a cytostatic effect and capable of arresting the affected cells in G2/M phase of cell cycle. In addition, we evaluated the combined effects of VO-salen complex and taxol. The cell cycle analyses showed that VO-salen complex enhanced taxol-induced G2/M arrest and also increased taxol-induced apoptosis through a decrease in the ratio of Bcl-2/Bax which might account for the decrease in the apoptosis threshold among the affected cells. These findings support that combination of VO-salen, as a chemosensitizer, and taxol might constitute an affective new strategy for leukemia therapy.

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