HORMONAL REGULATIONS OF BREAST CANCERS FR OM CELL-LINES TO PATIENTS

Culture of human breast cancer cell lines has made it possible to bett er understand how oestrogens and anti-oestrogens interact with oestrog en receptors and thus regulate breast cancer cell growth. In addition, since human cell lines are cultured, immunologic and genetic probes c an be used to compare in vitro cell behaviour with in vivo tumour deve lopment. The discovery of certain proteins, specifically induced by oe strogens and secreted in cell cultures, led us to the hypothesis that oestrogen might influence cell growth via a relay protein secreted by cancer cells. Results obtain in our laboratory over the last 15 years allowed us to define cathepsin D, an oestrogen-regulated protein now u nder study as a prognostic marker for metastasis. For patients, the im plications of such fundamental results are great since clinicians coul d adapt management on the basis of a more specific prognosis. Neverthe less, it must be kept in mind that although in vitro cell cultures can provides an extremely fruitful model of cancer cell growth, in vivo b reast cancer is not equivalent to a mono layer of epithelial cancer ce lls growing in a Petri dish. Use of co-cultures and simplified in vivo models may be a new route to further developments. Progress, in terms of patient benefit, depends directly on rapid communications between research laboratories and clinical oncologists engaged in developing n ew tumour markers.