Tight correlations were found between mRNA and protein expression and relatively coherent links between these and breast cancer prognosis for connexin subtypes which were either localized to the myoepithelial layer only (Cx43) or both to myoepithelial and luminal epithelial cells (Cx46 and Cx30) in normal mammary glands, as opposed to the luminal epithelia related Cx26 and Cx32, which showed partly discordant prognostic links. Here, GJB1 is linked to breast cancer.