Interactions between normal mammary epithelial cells and mammary tumour cells in a model system

Normal mammary epithelial (NME) cells and MCF-7 cells aggregate and grow as spheroids when cultured on extracellular matrix derived from Engelbreth/ H olmes/Swarth (EHS) tumour. NME cells stop dividing and differentiate but MC F-7 cells continue to proliferate, although growth is counterbalanced by ce ll death. In mixed cultures of NME cells and MCF-7 cells, the two cell type s form mixed aggregates but then segregate to form well separated domains, often joined by only a narrow neck of cells. In these mixed cultures the gr owth of MCF-7 cells is inhibited by a factor secreted by NME cells into the medium.