Expression of mutant K-Ras with Lkb1 inhibition or p16p19 loss in embryonic pancreas cultured ex vivo. (A) Pancreatic explants were harvested from E14.5 Lkb1^MG/MG embryos that were heterozygous for lox.stop.lox KrasG12D, infected in vitro with AAV.Cre.IRES.GFP, and then cultured for two additional days with 1NMPP1. GFP-positive and -negative cells show similar morphology and pattern of E-cadherin and ZO-1 staining. GFP was detected with an anti-GFP antibody. (B) E14.5 p16p19^−/− and Kras^G12D/WTp16p19^−/−(Pdx1-Cre) pancreatic explants were cultured for 5 d, fixed, and stained with Muc-1 antibody. Explants with Kras^G12D/WT exhibit regions with irregular branching and luminal dilations. (C) E14.5 p16p19^−/− and Kras^G12D/WTp16p19^−/−(Pdx1-Cre) pancreatic explants were cultured for 8 d, fixed, and stained with Muc-1, ZO-1, and E-cadherin antibodies. Explants with Kras^G12D/WT exhibit regions of progressively disrupted tissue architecture and occasional cells with mislocalized E-cadherin (arrows). (Note: Muc-1 and ZO-1 are shown as maximum projections across a 10-µM z-stack; E-cadherin is a single section from the middle of the z-stack.) Bars: (A) 75 µM; (B) 200 µm; (C) 50 µm.