The results indicate that CLCA4 is also induced by stress and by conditions that promote epithelial differentiation such as growth on permeable membranes or suspension in extracellular matrix; that CLCA4 is required to maintain differentiation, as its attenuation caused EMT; and that ectopic expression of CLCA4 similarly inhibits proliferation of breast cancer cells, as transduction of either CLCA2 or CLCA4 into MCF7 resulted in microcolonies of enlarged cells. This evidence concerns the gene CLCA4 and breast cancer.