KRAS and pancreatic intraductal papillary-mucinous neoplasm: Next, it was interrogated, in this model, whether the IPMN lesions were of ductal or acinar origin by using Cre-lines that allow specific recombination of the Brg1 and mutant Kras alleles in adult acinar (Ptf1aCreER) or ductal (Hnf1β-CreERT2) cells [4].