INFLUENCE OF 5-LIPOXYGENASE ON IN-VITRO GROWTH OF HUMAN MAMMARY-CARCINOMA CELL-LINE MCF-7

The aim of this study was to investigate the direct effect of 5-lipoxy genase (5-LO) on the growth of human mammary cancer cells MCF-7 in vit ro. Cell growth was measured according to the level of H-3-thymidine i ncorporation. 5-LO was shown to inhibit H-3-thymidine incorporation. T he inhibitory effect was 19, 42 and 78% when administered at concentra tions of 0.1, 0.2 or 0.5 U/ml, respectively. Its effect was time- and dose-dependent and was statistically significant at concentrations of 0.2 and 0.5 U/ml. We have also shown that the specific 5-LO inhibitor MK-886 (1 mu M) lifts the inhibitory effect of 5-LO (0.2 U/ml). Moreov er, when treated with an activator of 5-lipoxygenase calcium ionophore A23187 (10 mu M) MCF-7 cells synthesize LTB4. The results of this stu dy are evidence of the role of 5-lipoxygenase in the regulation of hum an mammary cancer cells growth in vitro.