title: Synergistic effect of oncogenic RET and loss of p18 on medullary thyroid carcinoma development.
abstract: Activating mutations in the RET proto-oncogene are associated with both familial and sporadic medullary thyroid carcinoma (MTC) development; however, the genetic mechanisms underlying MTC tumorigenesis remain largely unknown. Recently, we have identified somatic inactivating mutations in the cell cycle inhibitor gene P18 in human MTC, which coincided with activating RET mutations, suggesting a role for loss of P18 in combination with oncogenic RET in the multistep process of MTC development. Therefore, we crossed transgenic mice expressing oncogenic RET (RET2B) with mice lacking p18 (and p27, another cell cycle inhibitor) and monitored MTC development. RET2B;p18(+/-) mice and RET2B;p18(-/-) mice developed MTC with a highly increased incidence compared with their corresponding single mutant littermates. In addition, expression of oncogenic RET causes an earlier age of onset and larger MTCs in p18(-/-);p27(+/-) mice. In a subset of MTCs of RET2B;p18(+/-)(;p27(+/-)) mice, p18(Ink4c) expression was completely lost. This loss of p18(Ink4c) expression correlated with higher proliferation rates as well as with larger MTCs, indicating that loss of p18 in combination with oncogenic RET not only increases the risk for MTC development but also enhances MTC progression. Our data strongly indicate that oncogenic RET and loss of p18 cooperate in the multistep tumorigenesis of MTC.
authors.affiliation: Department of Metabolic and Endocrine Diseases, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Wendy
authors.initials: W
authors.lastname: van Veelen
authors.forename: Carola J R
authors.initials: CJ
authors.lastname: van Gasteren
authors.forename: Dennis S
authors.initials: DS
authors.lastname: Acton
authors.forename: David S
authors.initials: DS
authors.lastname: Franklin
authors.forename: Ruud
authors.initials: R
authors.lastname: Berger
authors.forename: Cornelis J M
authors.initials: CJ
authors.lastname: Lips
authors.forename: Jo W M
authors.initials: JW
authors.lastname: Höppener
mesh_terms: D000818:Animals; D002116:Calcitonin / Q000378:metabolism; D018276:Carcinoma, Medullary / Q000235:genetics* / Q000473:pathology*; D002453:Cell Cycle; D002471:Cell Transformation, Neoplastic; D050763:Cyclin-Dependent Kinase Inhibitor p18 / Q000378:metabolism*; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D000090063:Proto-Oncogene Mas; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000473:pathology*
chemical_list: D050763:Cyclin-Dependent Kinase Inhibitor p18; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D002116:Calcitonin; D051096:Proto-Oncogene Proteins c-ret