title: Rapamycin inhibits multiple stages of c-Neu/ErbB2 induced tumor progression in a transgenic mouse model of HER2-positive breast cancer.
abstract: Amplification of the HER2 (ErbB2, c-Neu) proto-oncogene in breast cancer is associated with poor prognosis and high relapse rates. HER2/ErbB2, in conjunction with ErbB3, signals through the Akt/phosphatidylinositol 3-kinase pathway and leads to the activation of mammalian target of rapamycin (mTOR), a critical mRNA translation regulator that controls cell growth. Gene expression analysis of mammary tumors collected from mouse mammary tumor virus-c-Neu transgenic mice revealed that mRNA levels of several mTOR pathway members were either up-regulated (p85/phosphatidylinositol 3-kinase and p70S6 kinase) or down-regulated (eIF-4E-BP1) in a manner expected to enhance signaling through this pathway. Treatment of these mice with the mTOR inhibitor rapamycin caused growth arrest and regression of primary tumors with no evidence of weight loss or generalized toxicity. The treatment effects were due to decreased proliferation, associated with reduced cyclin D1 expression, and increased cell death in primary tumors. Whereas many of the dead epithelial cells had the histopathologic characteristics of ischemic necrosis, rapamycin treatment was not associated with changes in microvascular density or apoptosis. Rapamycin also inhibited cellular proliferation in lung metastases. In summary, data from this preclinical model of ErbB2/Neu-induced breast cancer show that inhibition of the mTOR pathway with rapamycin blocks multiple stages of ErbB2/Neu-induced tumorigenic progression.
authors: Department of Pharmacology, CWRU School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4965, USA.
authors: Jonathan D
authors: JD
authors: Mosley
authors: John T
authors: JT
authors: Poirier
authors: Darcie D
authors: DD
authors: Seachrist
authors: Melissa D
authors: MD
authors: Landis
authors: Ruth A
authors: RA
authors: Keri
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D004848:Epithelium / Q000473:pathology; D006965:Hyperplasia; D008175:Lung Neoplasms / Q000556:secondary; D008325:Mammary Neoplasms, Experimental / Q000098:blood supply / Q000201:enzymology / Q000473:pathology*; D008324:Mammary Tumor Virus, Mouse; D051379:Mice; D008822:Mice, Transgenic; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases
chemical_list: D000903:Antibiotics, Antineoplastic; D011494:Protein Kinases; D018719:Erb-b2 Receptor Tyrosine Kinases; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; C546843:mTOR protein, mouse
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