The co-expression of epithelial and mesenchymal master regulators may be critical for the aggressive phenotype of 4T1 cells as depleting Esrp1, Twist, Zeppo1, miR-9 or miR-10b all suppress 4T1 metastasis (Yang et al., 2004; Slorach et al., 2011; Yae et al., 2012; Ma et al., 2010a,b), whereas overexpressing miR-200 family members promotes metastasis of 4T07 breast carcinoma cells, which normally fail to form macroscopic colonies in the lung (Korpal et al., 2011; Dykxhoorn et al., 2009). The gene discussed is ESRP1; the disease is breast carcinoma.