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MOLECULAR PHARMACOLOGY 52:437-444 (1997).

Inhibition of Mitosis and Microtubule Function through Direct Tubulin Binding by a Novel Antiproliferative Naphthopyran LY290181

Dan L. Wood, Dulal Panda, Todd R. Wiernicki, Leslie Wilson, Mary Ann Jordan, and Jai Pal Singh

Cardiovascular Research, Lilly Research Laboratories, Indianapolis, Indiana 46285 (D.L.W., T.R.W., J.P.S.), and Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, California 93106 (D.P., L.W., M.A.J.)

The mechanism of action of a novel antiproliferative compound LY290181 [2-amino-4-(3-pyridyl)-4H-naphtho(1,2-b)pyran-3-carbonitrile] was characterized. LY290181 is a potent inhibitor of cell proliferation, producing 50% inhibition of vascular smooth muscle, endothelial, Chinese hamster ovary, HeLa, and human erythroleukemia cells at concentrations of 8-40 nM. Cell cycle analysis showed that LY290181 caused accumulation of smooth muscle cells at the G₂/M phase and induced mitotic arrest in Chinese hamster ovary cells and HeLa cells. At low concentrations (3-30 nM), LY290181 blocked transition of cells from metaphase to anaphase and disrupted mitotic spindle organization. At high concentrations (100 nM), LY290181 produced a concentration-dependent loss of cytoplasmic and spindle microtubules. LY290181 inhibited the polymerization of purified bovine brain microtubule protein into microtubules, and it depolymerized preformed microtubules. Using tubulin-1-anilino-8-naphthalene sulfonate complex fluorescence, we have shown that LY290181 directly interacted with tubulin in a unique manner. These studies show that LY290181 induces cell growth arrest in prometaphase/metaphase, and tubulin appears to be its molecular target.