Cre-LoxP deletions of a copy of MEN1 and Rb1 were generated independently and crossed to create double-heterozygous mice for MEN1 and Rb1, which generated higher tumor burden of multiple tumor types and islet hyperplasia but did not decrease survival significantly than either MEN1 or Rb1 only heterozygotes [118]. This evidence concerns the gene RB1 and neoplasm.