KRAS and neoplasm: There was no significant difference in tumor size observed between the mutated Kras driven tumors with wild type Notch1 alleles (R+ N1w/w), the mutated Kras driven tumors with heterozygous Notch1 knock-out (R+ N1f/w) and the mutated Kras driven tumors with homozygous Notch1 knock-out (R+ N1f/f).