Identification of Oestrone Sulphatase Inhibitors in Breast Cyst Fluid: a New Treatment for Breast Cancer

Introduction Oestrogens play an important role in the development of breast cancer. Oestrone sulphate is a major source of active oestrogens in the breast, being converted to oestrone by oestrone sulphatase. Oestrone is then converted to oestradiol, a potent oestrogen strongly implicated in the development of breast cancer, by the enzyme 1713-hydroxysteroiddehydrogenase. In vitro oestrone sulphatase activity in breast tissue has been shown to be at least 1.000 times as high as aromatase activity, which converts androgens to oestrogens. Hence, local production of active oestrogens from oestrone sulphate is a very important source of oestrogens in breast tumours. I have previously found that breast cyst fluid is a potent inhibitor of oestrone sulphatase activity in certain breast cancer cell lines. Oestrone sulphatase inhibition is potentially of great importance in the treatment of women with hormonedependent breast cancers. The aim of this study was to identify the substances present in breast cyst fluid which are responsible for the oestrone sulphatase inhibitory property of breast cyst fluid.