Oestrogen sulphatase activity in hormone‐dependent and hormone‐independent breast‐cancer cells: Modulation by steroidal and non‐steroidal therapeutic agents

Abstract

Oestrogen sulphatase may play an important role in providing intracellular oestrogens from E1S for the growth and maintenance of breast tumours. In this study, we characterized oestrogen sulphatase in the hormone-dependent (ER/PR+) MCF-7 and in the hormone-independent (ER/PR-) MDA-MB-231 breast-cancer cells and, furthermore, examined its modulation by MPA, 4-OH-A4, tamoxifen, danazol, ethinyloestradiol and DHAS in both these cell types. Our detailed study of oestrogen sulphatase activity as a function of incubation time, E1S concentration and numbers of MCF-7 and MDA-MB-231 cells showed that more E1S was hydrolysed by MDA-MB-231 cells than by MCF-7 cells at all time points and all substrate concentrations. Additionally, although the Km values of E1S for oestrogen sulphatase in both MCF-7 and MDA-MB-231 cells were similar, the Vmax values, and therefore the activity, differed greatly. The effect of various steroidal and non-steroidal compounds also suggested differences in these 2 cell lines with respect to oestrogen sulphatase inhibition or stimulation. MPA significantly increased the hydrolysis of [3H]E1S in both cell lines, possibly through its effect on membrane fluidity. Tamoxifen increased E1S hydrolysis in MDA-MB-231 cells but not in MCF-7 cells, whereas 4-OH-A4 inhibited E1S in MCF-7 cells but not in MDA-MB-231 cells. Danazol (an isoxazol derivative of 17 alpha-ethinyltestosterone), 17 alpha-ethinyloestradiol and DHAS all significantly inhibited oestrogen sulphatase activity in both cell lines. Furthermore, danazol had a growth-inhibitory effect on both MCF-7 and MDA-MB-231 cells, although MCF-7 cells appeared to be more sensitive to growth inhibition by danazol.

Oestrogen producing enzymes and mammary carcinogenesis: a review

“…It has been observed that both basic fibroblast growth factor and IGF-I increase STS activity in a doseand time-dependent manner in MCF-7 and MDAMB-231 breast cancer cell lines [106]. Moreover, both TNFa and IL-6 up-regulate STS enzyme activity in MCF-7 breast cancer cells.…”

“…Interestingly, STS mRNA levels decreased when MCF-7 breast cancer cells were treated with the progestagen, promegestone (R-5020) [108]. In contrast, it was observed that exposure of MCF-7 and MDA-MB-231 breast cancer cells to the progestagen; medroxyprogesterone acetate, stimulated STS activity in these cells [106].…”

Differential effect of hormone therapy on E1S-sulfatase activity in non-malignant and cancerous breast cells in vitro

“…Basal STS activity did not differ significantly between HBL-100 and MCF-7 cells in vitro. While we are to our knowledge the first to study STS activity in non-malignant human breast cells (basal and after treatment), basal STS activity in MCF-7 cells has been measured before [25,35,37,[38][39][40][41][42][43][44][45][46][47] revealing varying results which might be due to different assay protocols. For example, some authors used intact cells [25,37,38,[42][43][44][45][46][47][48][49][50][51], others cell homogenates [39,50].…”

The development of steroid sulphatase inhibitors

“…In a preliminary study the effect of danazol therapy (800 mg/day for 2 weeks) on the conversion ratio (CR) of oestrone sulphate to oestrone was investigated in three menopausal women with breast cancer (Purohit et al 1992). For two of the three women, a 40% decrease in the CR was detected, while no change occurred in the third subject.…”

“…In intact MCF-7 breast cancer cells, using a physio¬ logical substrate concentration (2 nM), danazol (10 µ ) inhibited sulphatase activity by 62% (Purohit & Reed 1992 Santner & Santen (1993), such an effect is likely to be secondary to their ability to bind to the ER and block the action of oestradiol.…”