MCF-7 CELL-CYCLE ARRESTED AT G1 THROUGH URSOLIC ACID, AND INCREASED REDUCTION OF TETRAZOLIUM SALTS

The effect of ursolic acid on the proliferation of MCF-7 human breast tumor cells was studied. During investigations of the anti-proliferati ve effects of this triterpene, we observed a clear difference between MTT colorimetric assay and direct cell counting, particularly 24 h aft er drug treatment. The MTT assay showed a stimulation of formazan prod uction in the first 24 h exposure of cells to drug. The maximum stimul ation was obtained with 15 and 20 mu m of ursolic acid (about 30-40% o f increase with respect to control); however, the number of cells was not increased as revealed by direct cell counting. Ursolic acid is a p otent inhibitor of MCF-7 cell proliferation. This triterpene exhibits cytostatic and cytotoxic activity. Cell cycle analysis is performed by propidium iodide staining and flow cytometry technique. These results suggest that alterations in cell cycle phase redistribution of MCF-7 human breast cancer, by ursolic acid, may significantly influence MTT reduction of formazan.