Gap junction transmembrane channels allow the transfer of small molecules between the cytoplasm of adjacent cells. They are formed by proteins named connexins (Cxs) that have long been considered as a tumor suppressor. This widespread view has been challenged by recent studies suggesting that the role of Connexin 43 (Cx43) in cancer is tissue- and stage-specific and can even promote tumor progression. High throughput profiling of invasive breast cancer has allowed for the construction of subtyping schemes that partition patients into at least four distinct intrinsic subtypes. This study characterizes Cx43 expression during cancer progression with each of the tumor subtypes using a compendium of publicly available gene expression data. In particular, we show that Cx43 expression depends greatly on intrinsic subtype. Tumor grade also co-varies with patient subtype, resulting in Cx43 co-expression with grade in a subtype-dependent manner. Better survival was associated with a high expression of Cx43 in unstratified and luminal tumors but with a low expression in Her2e subtype. A better understanding of Cx43 regulation in a subtype-dependent manner is needed to clarify the context in which Cx43 is associated with tumor suppression or cancer progression.

The epithelium's functional unit is the bilayered acinus, made of a layer of luminal cells, surrounded by a layer of basal cells mainly composed of myoepithelial cells.Aim:The aim of this study was to develop a reproducible and manipulable 3D co-culture model of the bilayered acinus in vitro to study the interactions between the two layers.Materials & methods:Two different combinations of cell lines were co-cultured in Matrigel: SCp2 and SCg6 mice cells, or MCF-12A and Hs 578Bst human cell lines.Results:Confocal microscopy analysis showed that only MCF-12A and Hs 578Bst cells could form some bilayered acini. This in vitro bilayered acini model will allow us to understand the role of interactions between luminal and myoepithelial cells in the normal breast development.

The mammary gland is a complex organ, structured in a ramified epithelium supported by the stroma. The epithelium's functional unit is the bilayered acinus, made of a layer of luminal cells surrounded by a layer of basal cells mainly composed of myoepithelial cells. The aim of this study was to develop a reproducible and manipulable three-dimensional co-culture model of the bilayered acinus in vitro to study the interactions between the two layers. Two different combinations of cell lines were co-cultured in Matrigel: SCp2 and SCg6 mice cells, or MCF-12A and Hs 578Bst human cell lines. Cell ratios and Matrigel concentration were optimized. The resulting acini were analysed by confocal microscopy using epithelial (E-cadherin) and myoepithelial (-smooth muscle actin) markers. SCp2 and SCg6 cells formed distinct threedimensional structures, whereas MCF-12A and Hs 578Bst cells formed some bilayered acini. This in vitro bilayered acini model will allow us to understand the role of interactions between luminal and myoepithelial cells in the normal breast development.