Ingthorsson Saevar, Hilmarsdottir Bylgja, Kricker Jennifer, Magnusson Magnus Karl, Gudjonsson Thorarinn
Stem Cell Research Unit, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
Department of Laboratory Hematology, Landspítali-University Hospital, Reykjavik, Iceland.
Curr Mol Biol Rep. 2015;1(4):168-174. doi: 10.1007/s40610-015-0027-x. Epub 2015 Oct 5.
Myoepithelial cells (MEPs) are specialized cells derived from epithelial progenitor cells, yet they also express the contractile machinery of smooth muscle cells. MEPs are prominent in glandular tissues where their function is to help expel secretions generated by the glandular epithelial cells. In the breast, MEPs are part of the bi-layered breast epithelium that line ducts and alveoli positioned perpendicular to the luminal epithelial cells (LEPs), separated from the surrounding stroma by the basement membrane. Researchers have recognized MEPs as important regulators of structural and functional behavior of LEPs, namely having role in polarization of LEPs, and regulating milk production. Furthermore, they have also been proposed to act as tumor suppressors as their presence inhibits invasion of cancer cells into the surrounding stroma. There is, however, accumulating evidence that MEPs in normal breast, carcinoma in situ and in invasive breast cancer differ significantly in terms of marker expression and this may truly interfere with their ability to behave as tumor suppressors. The term myoepithelial cell is often used synonymously with basal cell. While all MEPs, due to their position, can be referred to as basal cells, some basal cells do not fulfill the criteria of being MEPs. Synonymous use of these terms may hold true under normal conditions but careful interpretation of these terms should be used in breast cancer. In recent years, partial myoepithelial differentiation and epithelial to mesenchymal transition (EMT) have been shown to be associated with, and in some cases, necessary for cancer invasion and metastasis. In this review, we will discuss the context-dependent role of MEPs in breast morphogenesis, tumor suppression, and also the appearance of basal or partial myoepithelial differentiation in aggressive forms of breast cancer.
肌上皮细胞（MEPs）是源自上皮祖细胞的特化细胞，但它们也表达平滑肌细胞的收缩机制。肌上皮细胞在腺组织中很突出，其功能是帮助排出腺上皮细胞产生的分泌物。在乳腺中，肌上皮细胞是双层乳腺上皮的一部分，排列在与管腔上皮细胞（LEPs）垂直的导管和腺泡中，通过基底膜与周围的基质分隔开。研究人员已认识到肌上皮细胞是管腔上皮细胞结构和功能行为的重要调节因子，即在管腔上皮细胞的极化中起作用，并调节乳汁分泌。此外，它们还被认为具有肿瘤抑制作用，因为它们的存在会抑制癌细胞侵入周围基质。然而，越来越多的证据表明，正常乳腺、原位癌和浸润性乳腺癌中的肌上皮细胞在标志物表达方面存在显著差异，这可能真的会干扰它们作为肿瘤抑制因子的功能。肌上皮细胞这个术语通常与基底细胞同义使用。虽然所有的肌上皮细胞由于其位置都可被称为基底细胞，但一些基底细胞并不符合肌上皮细胞的标准。在正常情况下，这些术语的同义使用可能是正确的，但在乳腺癌中应谨慎解释这些术语。近年来，部分肌上皮分化和上皮-间质转化（EMT）已被证明与癌症侵袭和转移有关，在某些情况下是癌症侵袭和转移所必需的。在这篇综述中，我们将讨论肌上皮细胞在乳腺形态发生、肿瘤抑制中的上下文依赖性作用，以及在侵袭性乳腺癌中基底或部分肌上皮分化的表现。
