[Hormonal regulation in breast cancer from cell lines to patients]

Culture of human breast cancer cell lines has made it possible to better understand how oestrogens and anti-oestrogens interact with oestrogen receptors and thus regulate breast cancer cell growth. In addition, since human cell lines are cultured, immunologic and genetic probes can be used to compare in vitro cell behaviour with in vivo tumour development. The discovery of certain proteins, specifically induced by oestrogens 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 under study as a prognostic marker for metastasis. For patients, the implications of such fundamental results are great since clinicians could adapt management on the basis of a more specific prognosis. Nevertheless, it must be kept in mind that although in vitro cell cultures can provides an extremely fruitful model of cancer cell growth, in vivo breast cancer is not equivalent to a mono-layer of epithelial cancer cells 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 new tumour markers.