Cellular analysis of the mode of action of methyl-3,5-diiodo-4-(4'-methoxyphenoxy) benzoate (DIME) on tumor cells.

The hormonally inactive methyl-3,5-diiodo-4-(4'-methoxyphenoxy) benzoate (DIME) at 1-4 mu M concentration induces morphologic changes in E-ras 20 and MDA-MB-231 and other human cancer cells such as multinucleation and enlargement and arrests the cell cycle in the M phase without affecting interphase. Time-lapse videomicroscopy allowed us to follow individual cells. Cells exposed to DIME divided in an abnormal manner, leading to 20% cell fusion and multinucleation. Chromosome painting demonstrated a large accumulation of chromosomes after 5 days of treatment with DIME, consistent with the failure of cells to divide normally. Chromosome breakage was not observed. On the other hand, highly abnormal tubulin-containing structures ensue upon exposure to DIME (1 mu M for 18 h) treatment, indicating an early biochemical action of DIME on the spindle assembly system.