Estrone sulfatase activity and effect of antiestrogens on transformation of estrone sulfate in hormone-dependent vs. independent human breast cancer cell lines.

The effect of the anti-estrogens ICI 164,384 and tamoxifen on the estradiol (E2) concentration after incubation of estrone sulfate (E1-S) with different hormone-dependent (MCF-7 and T-47D) and hormone-independent (MDA-MD-231 and MDA-MB-436) mammary cancer cells, as well as the estrone sulfatase activity in these various cell lines, are presented. The anti-estrogen ICI 164,384 decreased very significantly the concentration of E2 after incubation of E1-S with MCF-7 (control, mean +/- SE: 100 +/- 24 pg/mg DNA; + ICI 164,384 [10(-6)M]: 7 +/- 2 pg/mg DNA). This effect was much more intense than with tamoxifen. A similar effect was observed with T-47D cells. However, no significant effect was observed in the hormone-independent cells. In the intact cell, estrone sulfatase activity was very intense in the hormone-dependent cells, but very small in the hormone-independent cells. However, this activity became very strong after homogenization in the hormone-independent cells. The data suggest that estrone sulfate can play an important role on the bioavailability of E2 in hormone-dependent breast cancer, and that understanding the control of estrone sulfatase activity can open new knowledge of the estrogen responses and new possibilities of therapeutic application in breast cancer.