Retention of wild-type p53 in tumors from p53 heterozygous mice: reduction of p53 dosage can promote cancer formation

EMBO J. 1998 Aug 17;17(16):4657-67. doi: 10.1093/emboj/17.16.4657.


Tumor suppressor genes are generally viewed as being recessive at the cellular level, so that mutation or loss of both tumor suppressor alleles is a prerequisite for tumor formation. The tumor suppressor gene, p53, is mutated in approximately 50% of human sporadic cancers and in an inherited cancer predisposition (Li-Fraumeni syndrome). We have analyzed the status of the wild-type p53 allele in tumors taken from p53-deficient heterozygous (p53+/-) mice. These mice inherit a single null p53 allele and develop tumors much earlier than those mice with two functional copies of wild-type p53. We present evidence that a high proportion of the tumors from the p53+/- mice retain an intact, functional, wild-type p53 allele. Unlike p53+/- tumors which lose their wild-type allele, the tumors which retain an intact p53 allele express p53 protein that induces apoptosis following gamma-irradiation, activates p21(WAF1/CIP1) and Mdm2 expression, represses PCNA expression (a negatively regulated target of wild-type p53), shows high levels of binding to oligonucleotides containing a wild-type p53 response element and prevents chromosomal instability as measured by comparative genomic hybridization. These results indicate that loss of both p53 alleles is not a prerequisite for tumor formation and that mere reduction in p53 levels may be sufficient to promote tumorigenesis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Chromosome Mapping
  • DNA Primers
  • Gene Dosage*
  • Genes, p53*
  • Heterozygote*
  • Loss of Heterozygosity
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neoplasms, Experimental / genetics*
  • Neoplasms, Experimental / pathology
  • Tumor Suppressor Protein p53 / genetics


  • DNA Primers
  • Tumor Suppressor Protein p53