Studies of clonal cell lines developed from primary breast cancers indicate that the ability to undergo morphogenesis in vitro is lost early in malignancy.

In an attempt to obtain cell lines from the different components found in primary breast cancers, we used a low-calcium medium to culture epithelial cells of mixed phenotype and a recombinant T antigen containing retrovirus to immortalize cells found in these cultures. In each case, the histology of the sample used for culture was examined in detail and the best growth was obtained from samples associated with a substantial in situ or benign component and from lobular rather than ductal carcinomas. Clonal cell lines were developed from each of 4 tumours: 1 infiltrating ductal (tumour number 2), 2 infiltrating lobular (tumours 3 and 5) and 1 mucoid (tumour 6). To try to identify the phenotype and origin of the cell lines, immunohistochemical markers, histological analysis of tissue sections and behavioural markers were used. All the cell lines expressed mainly luminal epithelial cell markers, but the basal epithelial keratin, keratin 14, was also expressed homogeneously or heterogeneously. Growth in agar was seen with some but not all cell lines derived from only 1 tumour (tumour 5) and tumour development in nude mice was observed (with low efficiency) with cell lines from only 1 tumour (tumour 6). The data suggest that the cell lines obtained from the infiltrating ductal carcinoma (tumour 2) developed from cells cultured from the associated benign component, while the cell lines from tumours 3, 5 and 6 may each have developed from a cell in an early stage of malignancy. When tested for their ability to undergo morphogenesis on extracellular matrix components, cell lines from tumour 2 made well-developed ductal-alveolar-like structures, while those from the other tumours did not.