Fig. 9. Only one of four cancer-derived myoepithelial cells can completely reverse acinus polarity in collagen gels. Frequency of correctly polarized acini in sections of collagen-I gels. Addition of cancer-derived myoepithelial cells from four different sources failed completely to revert acini in two instances, had a partial impact on reversion in one instance, and could revert in the fourth case. Inserts show staining for ß4-integrin (green) counterstained with propidium iodide (red). Data represent mean (±s.e.m.) except for the primary cancer-derived MEP, which are means of triplicate determinations (±s.d.). (bar, 20 µm).