A transgene consisting of a chicken beta actin promoter, followed by a GFP (green fluorescence protein) expression cassette flanked by two lox sites and preceding a human K-RasV12 cDNA combined with an ALPP (PLAP; human placenta-like alkaline phosphatase) expression construct. Expression of oncogenic K-RasV12 is dependent on Cre-mediated deletion of the GFP fragment.