Effect of promegestone, tamoxifen, 4-hydroxytamoxifen and ICI 164,384 on the oestrone sulphatase activity of human breast cancer cells.

In the present study, we explored the effects on sulphatase activity by Promegestone (R-5020), Tamoxifen (TAM), 4-hydroxytamoxifen (4-OH-TAM) and ICI 164,384 in the T-47D hormone-dependent and MDA-MB-231 hormone-independent mammary cancer cell lines. Using homogenates of these cells it was observed that Promegestone has a significant effect on the inhibition of oestrone (E 1 ) sulphatase activity. As this effect is competitive, it is suggested that there is a direct action of this compound on the enzyme. Tamoxifen has very little or no effect, 4-hydroxytamoxifen has an intermediate effect and ICI 164,384 is active in the enzyme inhibition, particularly with MDA-MB-231 cells