In our study, Pdx1-Cre;Kras;N1ko but not Pdx1-Cre;Kras;N2ko or Pdx1-Cre;Kras developed skin lesions (Fig. 1A and B) which points to the importance of Notch1 but not Notch2 for skin tumor development. This evidence concerns the gene PDX1 and skin neoplasm.