title: p53 gene dosage modifies growth and malignant progression of keratinocytes expressing the v-rasHa oncogene.
abstract: Epidermal keratinocyte cultures were established from newborn mice expressing a null mutation in the p53 gene to explore the contribution of p53 to epidermal growth regulation and neoplasia. Keratinocytes were initiated by transduction with a replication-defective retrovirus encoding the v-rasHa oncogene and grafted onto nude mouse hosts. Tumors arising from keratinocytes heterozygous or null for functional p53 in the presence of v-rasHa have growth rates approximately 5-fold higher than those derived from p53(+/+) controls and rapidly form carcinomas, in contrast to the benign phenotype observed in p53(+/+)/v-rasHa grafts. In vitro, p53-deficient keratinocytes with and without v-rasHa expression display decreased responsiveness to the negative growth regulators transforming growth factors beta 1 and beta 2. In combination with v-rasHa, p53-deficient keratinocytes also exhibit decreased responsiveness to elevated Ca2+. These differences between genotypes cannot be attributed to changes in transforming growth factor beta receptor types present or altered levels of epidermal growth factor receptor and are independent of c-myc transcript levels. mRNA expression for the p-53 inducible protein WAF1 correlates with p53 gene dosage, but low levels are still detectable in p53(-/-) keratinocytes. The altered responsiveness of p53 deficient keratinocytes to negative growth regulators may provide a growth advantage to such cells in vivo and render them more susceptible to genetic alterations and malignant conversion.
authors.affiliation: Laboratory of Cellular Carcinogenesis, National Cancer Institute, Bethesda, Maryland 20892.
authors.forename: W C
authors.initials: WC
authors.lastname: Weinberg
authors.forename: C G
authors.initials: CG
authors.lastname: Azzoli
authors.forename: N
authors.initials: N
authors.lastname: Kadiwar
authors.forename: S H
authors.initials: SH
authors.lastname: Yuspa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002118:Calcium / Q000494:pharmacology; D002277:Carcinoma / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000235:genetics; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis; D066246:ErbB Receptors / Q000032:analysis*; D017353:Gene Deletion; D016259:Genes, myc / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics* / Q000502:physiology; D011905:Genes, ras / Q000235:genetics* / Q000502:physiology; D005838:Genotype; D015603:Keratinocytes / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008969:Molecular Sequence Data; D010212:Papilloma / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis; D012878:Skin Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D066246:ErbB Receptors; D002118:Calcium