Estrogen-induced genes in breast cancers and their medical applications

The study of several human estrogen receptor positive breast cancer cell li nes has allowed characterization of a number of estrogen-induced proteins ( e.g. progesterone receptor, cathepsin D, pS2 and fibulin-1 in ovarian cell lines). In primary tumours, these markers have different prognostic signifi cance for predicting whether the tumour will be hormone responsive (e.g. pS 2, estrogene and progesterone receptors) or will develop metastasis (e.g. c athepsin D). Studies of estrogen-regulated genes should also lead to new th erapeutic approaches for hormone-resistant cancers. The role of estrogens a s mitogens stimulating the growth of breast and ovarian cancer cell lines i s well established. By contrast, their action an metastasis appears more am biguous. Breast cancer cells without estrogen receptor (ERI are generally l ess differentiated and more aggressive than those containing functional ER. Moreover, the reexpression of ER by transfection in ER-negative cell lines inhibit their metastatic and invasive potential. These results suggest a p rotective role of ER in tumor progression. Studies of the underlying mechan isms of this effect may open new therapeutical strategies.