When tamoxifen was systemically administered to Fzd9WT/WT;MycER;BclXL and Fzd9KO/KO;MycER;BclXL animals for 3-wk to activate MycER, control Fzd9WT/WT;MycER;BclXL transgenic mice rapidly developed grossly hyperplastic insulinomas (Fig 1A and C), whereas Fzd9KO/KO;MycER;BclXL mice exhibited no detectable β-cell tumor hyperplasia and pancreatic islets preserved their normal size (Fig 1B and C). The gene discussed is BCL2L1; the disease is pancreatic insulinoma.