SOX4 is a member of the SOX (SRY-related HMG-box) family of transcription factors with a critical role in embryonic development and in cell-fate determination during organogenesis of the heart, pancreas, brain, and in B and T lymphocyte differentiation. SOX4 gene expression is upregulated in many cancer types, and increased SOX4 activity contributes to cellular transformation, cell survival, and metastasis. Gene expression profiling has uncovered SOX4 with upregulated activity during TGF--induced epithelial-mesenchymal transition (EMT) in normal and cancerous breast epithelial cells. SOX4 is indispensable for EMT and cell survival invitro and for primary tumor growth and metastasis invivo. SOX4 is identified as a master regulator of EMT by governing the expression of the epigenetic modifier Ezh2.