Blockade of the epidermal growth factor receptor tyrosine kinase suppresses tumorigenesis in MMTV/Neu + MMTV/TGF-α bigenic mice

A. E G Lenferink, Jean F. Simpson, Laura K. Shawver, Robert J. Coffey, James T. Forbes, Carlos L. Arteaga

Research output: Contribution to journalArticle

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Abstract

Overexpression of ErbB-2/Neu has been causally associated with mammary epithelial transformation. Here we report that blockade of the epidermal growth factor receptor (EGFR) kinase with AG-1478 markedly delays breast tumor formation in mouse mammary tumor virus (MMTV)/Neu + MMTV/transforming growth factor α bigenic mice. This delay was associated with inhibition of EGFR and Neu signaling, reduction of cyclin-dependent kinase 2 (Cdk2) and mitogen-activated protein kinase (MAPK) activities and cyclin D1, and an increase in the levels of the Cdk inhibitor p27(Kip)1. In addition, BrdUrd incorporation into tumor cell nuclei was prevented with no signs of tumor cell apoptosis. These observations prompted us to investigate the stability of p27. Recombinant p27 was degraded rapidly in vitro by untreated but not by AG-1478-treated tumor lysates. Proteasome depletion of the tumor lysates, addition of the specific MEK1/2 inhibitor U-0126, or a T187A mutation in recombinant p27 all prevented p27 degradation. Cdk2 and MAPK precipitates from untreated tumor lysates phosphorylated recombinant wild-type p27 but not the T187A mutant in vitro. Cdk2 and MAPK precipitates from AG-1478-treated tumors were unable to phosphorylate p27 in vitro. These data suggest that increased signaling by ErbB receptors up-regulates MAPK activity, which, in turn, phosphorylates and destabilizes p27, thus contributing to dysregulated cell cycle progression.

Original languageEnglish (US)
Pages (from-to)9609-9614
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume97
Issue number17
StatePublished - Aug 15 2000

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Mouse mammary tumor virus
Epidermal Growth Factor Receptor
Protein-Tyrosine Kinases
Carcinogenesis
Cyclin-Dependent Kinase 2
Mitogen-Activated Protein Kinases
Neoplasms
Cyclin D1
Transforming Growth Factors
Proteasome Endopeptidase Complex
Cell Nucleus
Cell Cycle
Breast
Up-Regulation
Apoptosis
Breast Neoplasms
Mutation
tyrphostin AG 1478
In Vitro Techniques

ASJC Scopus subject areas

  • General
  • Genetics

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Blockade of the epidermal growth factor receptor tyrosine kinase suppresses tumorigenesis in MMTV/Neu + MMTV/TGF-α bigenic mice. / Lenferink, A. E G; Simpson, Jean F.; Shawver, Laura K.; Coffey, Robert J.; Forbes, James T.; Arteaga, Carlos L.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 97, No. 17, 15.08.2000, p. 9609-9614.

Research output: Contribution to journalArticle

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abstract = "Overexpression of ErbB-2/Neu has been causally associated with mammary epithelial transformation. Here we report that blockade of the epidermal growth factor receptor (EGFR) kinase with AG-1478 markedly delays breast tumor formation in mouse mammary tumor virus (MMTV)/Neu + MMTV/transforming growth factor α bigenic mice. This delay was associated with inhibition of EGFR and Neu signaling, reduction of cyclin-dependent kinase 2 (Cdk2) and mitogen-activated protein kinase (MAPK) activities and cyclin D1, and an increase in the levels of the Cdk inhibitor p27(Kip)1. In addition, BrdUrd incorporation into tumor cell nuclei was prevented with no signs of tumor cell apoptosis. These observations prompted us to investigate the stability of p27. Recombinant p27 was degraded rapidly in vitro by untreated but not by AG-1478-treated tumor lysates. Proteasome depletion of the tumor lysates, addition of the specific MEK1/2 inhibitor U-0126, or a T187A mutation in recombinant p27 all prevented p27 degradation. Cdk2 and MAPK precipitates from untreated tumor lysates phosphorylated recombinant wild-type p27 but not the T187A mutant in vitro. Cdk2 and MAPK precipitates from AG-1478-treated tumors were unable to phosphorylate p27 in vitro. These data suggest that increased signaling by ErbB receptors up-regulates MAPK activity, which, in turn, phosphorylates and destabilizes p27, thus contributing to dysregulated cell cycle progression.",
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