Fig. 7. Cancer-derived myoepithelial cells share many characteristics of normal myoepithelial cells but fail to reorient inside-out acini. (A) Isolation of cancer-derived myoepithelial cells expressing typical myoepithelial markers. Purified cancer-derived myoepithelial cells (a,b) stained with -smooth muscle actin (green) and keratins (red) to document the concurrent myo- and epithelial phenotypes (bar, 50 µm). (B) Lack of reversal of inside-out acini by cancer-derived myoepithelial cells. Sections of (a) the acinus assay embedded with the cancer-derived myoepithelial cell line and (b) an immortalized, normal-derived myoepithelial cell line. The sections are double stained for the apical marker sialomucin (green) and the nuclear stain propidium iodide (red). Note the lack of polarization with the cancer myoepithelial cells (C-MEP) and the correctly polarized lumina (encircled) with the immortalized myoepithelial cells (N-MEP) (bar, 25 µm).