Inhibition of oestrone sulphatase activity in the MDA-MB-231 breast cancercell line by breast cyst fluid from Malaysian women

oestrone sulphate is a major source of active oestrogens in the breast. It is converted to oestrone by oestrone sulphatase. Breast cyst fluid (BCF) is a rich source of sex hormones and growth factors. BCF obtained from Britis h women has been shown to inhibit oestrone sulphatase activity in the MCF-7 oestrogen-receptor-positive breast cancer cell line. The aim of the presen t study was to assess whether BCF obtained from Malaysian women inhibited o estrone sulphatase activity in the MCF-7 and MDA-MB-231 breast cancer cell lines. The cell lines were grown in supplemented Dulbecco's Modified Eagle Medium for 3 days, following which a 3-day incubation with sterilised BCF w as carried out. At the end of the treatment period the cell monolayers were assayed for oestrone sulphatase activity and the number of cell nuclei cou nted on a Coulter Counter. BCF was also fractionated on a Bio-Sil SEC 125-5 column by HPLC and the effects of the fractions collected on oestrone sulp hatase activity in the MDA-MB-231 cell line were assessed. All 18 samples o f BCF tested inhibited cell growth in the MDA-MB-231 cell line while 8 out of 10 samples inhibited MCF-7 cell growth; 15 out of 18 BCF samples inhibit ed oestrone sulphatase activity in the MDA-MB-231 cell line whereas 5 out o f 10 samples stimulated oestrone sulphatase activity in the MCF-7 cell line . HPLC fractions corresponding to molecular weights of > 158 kDa and 28 kDa were found to inhibit oestrone sulphatase activity in the MDA-MB-231 cell line. Further work is required to fully characterise these substances as th ey may have roles to play in the prevention of breast cancer.