Breast gross cystic disease protein 15 in human breast cancer in culture.

Media from explants of 120 human breast cancers cultured for 24 h were analysed for breast gross cystic disease protein 15 (GCDFP-15). The protein was detected in media from 94 tumours (73%) in concentrations varying from 1.5 to 2100 ng/ml. Levels were not related to menopausal status of the patient, disease stage, tumour oestrogen receptors or the derivation of tumour material. However, concentrations were significantly related to the degree of apocrine differentiation of the tumour and, in a subset of the cancers, capacity to release GCDFP-15 was positively correlated with incidence of progestogen and androgen receptors. There was also a negative quantitative correlation between production of GCDFP-15 and glycoprotein hormone alpha subunit (but no relationship with CEA). In 10 tumours culture was continued for 48 h. Values for GCDFP-15 were always considerably lower in the 24-48 h media compared with those from 0-24 h and cytosols from post-culture explants contained no detectable GCDFP-15. In contrast, CEA levels were often comparable in 0-24 and 24-48 h media and explants after culture frequently contained substantial amounts of CEA. The high proportion of breast carcinomas producing GCDF-15 in relatively large amounts and its rapid release make it an interesting marker by which the in vitro activity of human breast cancers may be monitored.