In melanoma, a variety of genetically engineered mouse models (GEMMs) have been reported to recapitulate main genetic alterations in this disease, including, but not limited to, the activation of the Braf oncogene and the loss of the Pten tumor suppressor (Dankort et al, 2009; Dhomen et al, 2010). The gene discussed is PTEN; the disease is melanoma.