Subacute Megakaryocytopoietic Toxicity of Maleimide Derivative with Antitumor Activity

Maleimide derivative (MI-1, 1-(4-Cl-benzyl)-3-Cl-4-(CF₃-phenylamino)-1Н-pyrrole-2,5-dione, synthesized in Taras Shevchenko National University of Kyiv, Ukraine), is a competitive inhibitor of PDK1, VEGF-R1,2,3, Src(h), Syk(h) and other protein kinases. MI-1 inhibits the proliferation of the tumor cells (HCT-116, SW-620, etc.). Histological studies revealed that MD decreases the number of colon tumors, monocytes, and platelets in the blood of rats with 1,2-dimethylhydrazine-induced colon carcinogenesis.

The aim of this work was to analyze the effects of МІ-1 on the state of megakaryocytopoiesis of healthy rats in the doses, exceeding the effective antitumor dose 5- and 10-fold.

Method: The white outbred male rats with the initial weight of 140 - 160 g were randomly divided into four groups (5-8 rats per group) and treated per os daily for 14 days with: I (control) - 0.1 ml sunflower oil containing 15% of DMSO; II - 2.7 mg/kg of MI-1 (effective antitumor); III - 13.5 mg/kg (5 times); IV - 27 mg/kg (10 times dose) dissolved in 0.1 ml of the sunflower oil containing 15% DMSO. Blood cells and myelograms were determined by conventional methods. The difference between the parameters was evaluated by nonparametric Mann-Whitney test.

Results: The platelet count in blood after the effect of MI-1 in 5-fold and 10-fold doses is decreased (p=0.012; p=0.027 respectively) vs. control group. The number of megakaryocytes does not change in bone marrow. The morphofunctional state of megakaryocytes testified to the redistribution of cells by the differentiation degree and the number of segments in the nucleus. MI-1 in the dose of 27 mg/kg causes an increase in the content of immature promegakaryocytes (p=0.035) on the background of the decrease in the total content of mature polychromatophilic and oxyphilic cells (р=0.031). There is an increase in the number of hyposegmented megakaryocytes (with 1-5 segments of the nucleus) not only at the expense of immature cells, but also of mature polychromatophils and cells with 11 and more segments of the nucleus (hypersegmented). The control group predominantly has cells with a great number of segments in the nucleus (6 and more) at all the stages of differentiation: promegakaryocytes, basophilic, polychromatophilic and oxyphilic megakaryocytes. The increase in the amount of immature megakaryocytes with increase in the number of hyposegmented and micro-megakaryocytes after the 10-fold dose of MI-1 testifies to the delay in differentiation of the mentioned cells which may condition the decrease in the production of platelets.

Conclusion: The MI-1 is a compound with low toxic effect in the dose, 10 times exceeding the effective one, compared to 5-fluorouracil which is hematotoxic in the effective dose, and fatal - in the dose, five times exceeding the effective one (data do no shown). This is evidence that MI-1 is a promising substance with antitumor activity and low toxicity which is advantageous for its application.