The present invention is based, at least in part, on the generation of an animal model of pancreatic adenocarcinoma which recapitulates the genetic and histological features of human pancreatic adenocarcinoma, including the initiation, maintenance, and progression of the disease. Accordingly, the present invention provides animal models of cancer, e.g., pancreatic adenocarcinoma, wherein an activating mutation of Kras has been introduced, and any one or more known or unknown tumor suppressor genes or loci, e.g., Ink4a/Arf, Ink4a, Arf, p53, Smad4/Dpc, Lkb1, Brca2, or Mlh1, have been misexpressed, e.g., have been misexpressed leading to decreased expression or non-expression. The animal models of the invention may be used, for example, to identify biomarkers of pancreatic cancer, to identify agents for the treatment or prevention of pancreatic cancer, and to evaluate the effectiveness of potential therapeutic agents.