This Article Full Text Full Text (PDF) Supplementary Data Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by García-Morales, P. Articles by Martínez-Lacaci, I. Search for Related Content PubMed PubMed Citation Articles by García-Morales, P. Articles by Martínez-Lacaci, I.

Research Articles: Therapeutics

Cyclin D3 is down-regulated by rapamycin in HER-2-overexpressing breast cancer cells

¹ Instituto de Biología Molecular y Celular, Universidad Miguel Hernández; ² Unidad de Investigación, Hospital General Universitario de Elche, Elche, Spain and ³ Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York

Requests for reprints: Isabel Martínez-Lacaci, Instituto de Biología Molecular y Celular, Edificio Torregaitán, Universidad Miguel Hernández, 03202 Elche, Spain. Phone: 34-96-6658744; Fax: 34-96-6658758. E-mail: imlacaci{at}umh.es

Rapamycin and its analogues are being tested as new antitumor agents. Rapamycin binds to FKBP-12 and this complex inhibits the activity of FRAP/mammalian target of rapamycin, which leads to dephosphorylation of 4EBP1 and p70 S6 kinase, resulting in blockade of translation initiation. We have found that RAP inhibits the growth of HER-2-overexpressing breast cancer cells. The phosphorylation of mammalian target of rapamycin, p70 S6 kinase, and 4EBP1 is inhibited by rapamycin and cells are arrested in the G₁ phase, as determined by growth assays, fluorescence-activated cell sorting analysis, and bromodeoxyuridine incorporation studies. Rapamycin causes down-regulation of cyclin D3 protein, retinoblastoma hypophosphorylation, loss of cyclin-dependent kinase (cdk) 4, cdk6, and cdk2 activity. The half-life of cyclin D3 protein decreases after rapamycin treatment, but not its synthesis, whereas the synthesis or half-life of cyclin D1 protein is not affected by the drug. Additionally, rapamycin caused accumulation of ubiquitinated forms of cyclin D3 protein, proteasome inhibitors blocked the effect of rapamycin on cyclin D3, and rapamycin stimulated the activity of the proteasome, showing that the effect of rapamycin on cyclin D3 is proteasome proteolysis dependent. This effect depends on the activity of HER-2 because Herceptin, a neutralizing antibody against HER-2, is able to block both the induction of proteasome activity and the cyclin D3 down-regulation due to rapamycin. Furthermore, inhibition of HER-2 gene expression by using small interfering RNA blocked the rapamycin effects on cyclin D3. These data indicate that rapamycin causes a G₁ arrest in HER-2-overexpressing breast cancer cells that is associated with a differential destabilization and subsequent down-regulation of cyclin D3 protein. [Mol Cancer Ther 2006;5(9):2172–81]

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

⁴ Supplementary materials for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

Received 9/ 9/05; revised 6/23/06; accepted 7/12/06.

This article has been cited by other articles:

				S. Oliere, M. Arguello, T. Mesplede, V. Tumilasci, P. Nakhaei, D. Stojdl, N. Sonenberg, J. Bell, and J. Hiscott Vesicular Stomatitis Virus Oncolysis of T Lymphocytes Requires Cell Cycle Entry and Translation Initiation J. Virol., June 15, 2008; 82(12): 5735 - 5749. [Abstract] [Full Text] [PDF]

				L. M. Petti, E. C. Ricciardi, H. J. Page, and K. A. Porter Transforming signals resulting from sustained activation of the PDGF{beta} receptor in mortal human fibroblasts J. Cell Sci., April 15, 2008; 121(8): 1172 - 1182. [Abstract] [Full Text] [PDF]