Using the mouse mammary tumor virus LTR-driven polyoma middle T antigen (MMTV-PyMT) mouse model of tumor progression, Kouros-Mehr et al. demonstrated that GATA3 is downregulated in carcinomas compared to adenomas, and that GATA3 is the only member of the GATA family of transcription factors which is differentially expressed between these two subsets [13]. Here, GATA3 is linked to carcinoma.