Identification of genes responsive to change in apical polarity in the breast epithelium

Differentiation of monolayered epithelia is characterized by the formation of a basoapical polarity axis, except during the early stages of cancer development. Using mammary glandular structures (acini) produced in a three-dimensional cell culture system we have demonstrated that, in order for mammary epithelial cells to exit quiescence and enter the cell cycle, acini have to lose apical polarity. In order to identify the genes dependent on apical polarity that could control cell quiescence, and possibly other aspects of tissue homeostasis, we have used Affymetrix technology microarray analysis of the 22,277 features/genes of the Human Genome U133A 2.0 array Chip in apically polarized and non-polarized breast epithelial acinar cells in three-dimensional culture. Genes commonly down-regulated in two treatments that altered apical polarity compared to control were considered to be dependent on apical polarity status for their transcription. Apically polarized (Control) and two different populations of non-polarized human mammary epithelial cells (18-alpha-glycyrrhetinic acid =AGA, and 5-aza-2'-deoxycytidine =Aza) were used for microarray analysis containing four biological replicates (1-4) for each treatment. The two treatments that cause loss of apical polarity were compared to reference apically polarized control samples using two different statistical analysis methods (FDR and Holm’s).