Fig 3. Vav1 expression enhances pancreatic ductal adenocarcinoma (PDAC) generation in the K-Ras^G12D/Vav1 mouse pancreas and is critical for pancreatic malignant lesions.

(A) Representative K-Ras^G12D (left) and K-Ras^G12D/Vav1 (right) stained with anti–pan-cytokeratin Abs are shown. The presence of PDAC is shown in a representative pancreatic section from a K-Ras^G12D/Vav1 mouse 1 mo after transgene induction (square, right panel). Scale bar represents 20 μm. (B) The extent of PDAC present in K-Ras^G12D and K-Ras^G12D/Vav1 mice at the different time points after transgene induction was assessed. The histogram summarizes the incidence of PDAC development in K-Ras^G12D mice and in K-Ras^G12D/Vav1 mice. Two of 26 K-Ras^G12D mice (7.7%) and 12 of 39 K-Ras^G12D/Vav1 mice (30.8%) had developed PDAC lesions. PDAC developed in K-Ras^G12D/Vav1 ranging from 1 to 12 mo post transgenes induction, whereas PDAC in K-Ras^G12D developed in mice of 3.5 and 5 mo post transgene induction. Significance of the difference between them (P < 0.05) was calculated using a two-tailed chi-squared test (Fisher’s exact test). (C) In some K-Ras^G12D/Vav1 mice (see numbers below), before completion of 3.5 mo of transgene induction, their Vav1 expression was discontinued for 20 d by removal of Dox from their drinking water (−Dox). Hematoxylin and eosin (H&E) staining of the pancreata of K-Ras^G12D and K-Ras^G12D/Vav1 either treated with Dox and tamoxifen (+Dox) or in which Dox was removed from their drinking water for 20 d before completion of 3.5 mo of transgene induction (−Dox) was performed. All the mice were then analyzed for the appearance of malignant lesions. The number of malignant lesions generated in these mice was calculated as APPD%, both for those treated with Dox (+Dox; n = 13 and n = 17, respectively) and for those in which Dox was omitted for 20 d (−Dox; n = 3 and n = 7, respectively). Significant differences between the two analyzed groups (P < 0.05; t test) are indicated. N.S. refers to statistical nonsignificant differences. SEM are shown. (D) Pancreatic sections from K-Ras^G12D/Vav1 mice after 3.5 mo post transgene induction either treated with Dox (+Dox) or in which Dox treatment was discontinued for 20 d (−Dox) were either stained by H&E (upper panel) or anti-GFP Abs (lower panel). Representative pictures are shown. Scale bar represents 200 μm.