Fig. 2  Pancreatic islet tumorigenesis in Men1+/− mice is inhibited in the Cdk4−/− background, but not in the Cdk2−/− background. (A) Histological examinations of pancreatic islets and tumors after hematoxylin-eosin staining. Pancreas samples were obtained from 15-month-old mice with the indicated genotypes. (B) Immunofluorescence microscopy for insulin. Green, insulin; Blue, DAPI. (C) Incidences of pancreatic islet tumors at 15 months. The total numbers of Men1+/+mice, Men1+/− mice, Men1+/−;Cdk4−/− mice and Men1+/−;Cdk2−/− mice examined for tumorigenesis were 12, 29, 30 and 34, respectively (see Results for details). *, p=0.0003; **, p<0.0001; N.S., not significant.