Participation of tenascin and transforming growth factor-beta in reciprocal epithelial-mesenchymal interactions of MCF7 cells and fibroblasts.

The tumor stroma is essential for the development of the tumor epithelium. Tenascin is an extracellular matrix protein highly expressed in the stroma of malignant mammary tumors. We therefore tested whether in vitro MCF7 cells were able to induce fibroblasts to synthesize tenascin. Indeed MCF7 cell-conditioned medium contained tenascin-inducing activity. This activity was shown to be transforming growth factor-beta. The morphology of the MCF7 cells was in turn affected by the addition of tenascin to the culture medium. The cells partially detached from the substratum and lost their cell-cell contracts.