EFFECTS OF LYMPHOCYTES AND FIBROBLASTS ON THE GROWTH OF HUMAN MAMMARY-CARCINOMA CELLS STUDIED IN SHORT-TERM PRIMARY CULTURES

Breast carcinomas commonly contain varying amounts of fibrous stroma a nd infiltrates of lymphoid cells. Dickson and Lippman (Endocrine Rev., 8,29, 1987) have proposed a model of growth regulation in breast canc er involving interactions between stroma and carcinoma cells. This mod el is based on results obtained with established cell lines. In an eff ort to bring experimentation closer to the clinical situation we have used short-term primary cultures from human breast cancer in co-cultur es with lymphocytes and fibroblasts. Cultures were established in a ch emically defined serum-free medium (CDM3). Cell types were characteriz ed on the basis of live morphology and expression of vimentin and kera tin 18. A semi-quantitative system was developed for measuring growth of epithelial cells, thus defining two indices: maximal growth index ( GI-max) and growth rate (GR). Moderate-to-good growth was obtained fro m 34 out of 46 carcinoma samples (74%) and 30 out of 38 parallel sampl es of non-cancerous tissue (79%). Success in culture was negatively co rrelated with the amount of hard stroma but unrelated to age of patien t or clinical status. Malignant epithelium was clearly identified in 1 2 out of 34 (35%) carcinoma samples. For the evaluation of responses o f epithelial cells in co-cultures, the cultures from each sample were ranked according to GI-max. From 20 co-culture experiments using carci noma samples, the following results were obtained: the highest GI-max was found in 11 of the co-cultures with lymphocytes; in six of the co- cultures with fibroblasts; in one case in the control culture without partner cells; and in two experiments there was no difference between controls and co-cultures. The corresponding values for non-cancerous s amples were: 5 out of 17, 2/17, 2/17, and 8/17. Control experiments pe rformed without partner cells confirmed that these differences in GI-m ax between cultures were beyond random variations. Four samples displa yed particularly vigorous responses to lymphocytes, and two samples re sponded extensively to fibroblasts. In four of these six samples cance r cells proliferated. We conclude that it is feasible to use primary c ultures of breast carcinomas for experimentation. Fibroblasts did not have very marked effects on epithelial cell growth, but, contrary to e xpectation, there was a clear tendency for lymphocytes to stimulate gr owth.