VESNARINONE EXHIBITS ANTITUMOR EFFECT AGAINST MYELOID-LEUKEMIA CELLS VIA APOPTOSIS

Vesnarinone is a positive inotropic agent used for treating congestive heart failure. We evaluated its ex vivo effects on myeloid leukemia c ell lines and primary acute myelogenous leukemia cells. Vesnarinone in hibited the incorporation of radiolabeled thymidine by a myeloid cell line, HL60, in a dose-dependent manner at concentrations ranging from 0.1 to 30 mu g/mL. A maximum 40%, suppression was seen at a concentrat ion of 10 mu g/mL. Determination of viable cell counts by trypan blue dye exclusion method demonstrated vesnarinone to be-cytocidal fur HL60 cells. Vesnarinone induced DNA fragmentation as detected by electroph resis in HL60 cells after 72-hour culture; this effect was not inhibit ed by GCSF. The apoptosis induced by vesnarinone was also detected by the in situ end-labeling method. Northern blot analysis showed a reduc tion of c-myc mRNA expression in HL60 cells by vesnarinone. However, i mmunostaining assay showed no change in the expression of Fas and Bcl- 2 proteins. We next examined the effect of vesnarinone on primary myel oid leukemia cells derived from 10 patients: 3 cases of MI, 2 of M2, 3 of M3, 1 of M4, and 1 of M6, by the French-American-British classific ation. Vesnarinone inhibited the incorporation of thymidine in all cel ls, with a mean suppression of 58.1%. DNA electrophoresis showed induc tion of DNA fragmentation in cultured cells with vesnarinone for 72 ho urs in 8 of Me 10 patients with primary leukemia. However, bone marrow munonuclear cells from healthy controls showed no growth suppression or DNA fragmentation in response to vesnarinone. These results suggest that vesnarinone may be useful in treating myeloid leukemia.