In view of our findings with PyMT-induced β-cell hyperplasia, we determined whether the survival or proliferation of PyMT-induced acinar cell carcinoma cells depended on continued expression of PyMT. To do this, we identified 8 Pdx1-tTA; tet-o-PyMT-IRES-Luc bitransgenic mice with strong luciferase activity (>108 photons/sec) and palpable pancreatic acinar cell carcinomas, and placed them on a doxycycline-containing diet to turn off the expression of the PyMT-IRES-Luc transgene. The gene discussed is PDX1; the disease is acinar cell carcinoma.