We further demonstrated that CUZD1 is recruited along with pSTAT5 to the regulatory regions of key target genes, such as Ereg and Wap. It is plausible that EREG contributes to CUZD1-mediated epithelial proliferation and alveolar expansion during pregnancy and lactation, as Ereg is a direct transcriptional target of STAT5 and has been implicated in promoting growth and survival of breast cancer cells [40–42]. This evidence concerns the gene STAT5A and breast cancer.