MICE DEFICIENT IN BOTH P53 AND RB DEVELOP TUMORS PRIMARILY OF ENDOCRINE ORIGIN

To examine whether a cooperative role exists between inherited Rb and p53 deficiency in tumorigenesis, crosses were made between p53- and Rb -deficient mice and were monitored for subsequent tumor incidence and spectrum. Parental mice containing either Rb or p53 mutant alleles sho wed a predisposition for pituitary adenomas or lymphomas and sarcomas, respectively. Mice heterozygous for both Rb and p53 mutant alleles de veloped tumors of endocrine origin (medullary thyroid carcinomas, panc reatic islet cell carcinomas, and pituitary adenomas) in addition to l ymphomas and sarcomas. Except for pituitary adenomas, these endocrine tumors were rarely seen in the parental p53 or Rb mutant mice. Mice de ficient for both Rb and p53 showed a faster rate of tumor development than mice deficient only in Rb or p53. These results indicate that p53 and Rb do cooperate in the acceleration of tumorigenesis and in the d evelopment of endocrine tumor types.