Petersen O W, Hansen S H, Laursen I, van Deurs B
Department of Anatomy, Panum Institute, University of Copenhagen, Denmark.
Eur J Cell Biol. 1989 Dec;50(2):500-9.
Myoepithelial cells express both epithelial and stromal (smooth muscle) cell characters. Moreover, while separating the luminal (secretory) epithelial cells from the connective tissue in normal breast glands, myoepithelial cells apparently disappear in invasive carcinomas, or their phenotypic characteristics become down-regulated. In the present study we have used a chemically defined culture model system to study how expression of smooth muscle isoforms of actin in myoepithelial cells is influenced by insulin by using immunoblotting, immunofluorescence and electron microscopy. We show that in the absence of insulin, myoepithelial cells do not proliferate but exhibit a differentiated phenotype. Hence, they contain distinct bundles of actin filaments and also numerous caveolae at the cell surface. In contrast, with insulin in the medium, cell proliferation increases dramatically. Concomitantly the smooth muscle actin expression and the associated caveolae disappear within a week. However, other cytoskeletal proteins such as keratins and vimentin are expressed no matter whether insulin is absent or present.
肌上皮细胞同时表达上皮细胞和基质（平滑肌）细胞的特征。此外，在正常乳腺中将管腔（分泌性）上皮细胞与结缔组织分离时，肌上皮细胞在浸润性癌中明显消失，或者其表型特征下调。在本研究中，我们使用了化学定义的培养模型系统，通过免疫印迹、免疫荧光和电子显微镜研究胰岛素如何影响肌上皮细胞中肌动蛋白平滑肌异构体的表达。我们发现，在没有胰岛素的情况下，肌上皮细胞不增殖，但表现出分化的表型。因此，它们含有明显的肌动蛋白丝束，并且在细胞表面也有许多小窝。相反，培养基中加入胰岛素后，细胞增殖显著增加。与此同时，平滑肌肌动蛋白表达和相关小窝在一周内消失。然而，无论有无胰岛素，其他细胞骨架蛋白如角蛋白和波形蛋白都会表达。
