Authors' Affiliations: Oncology Programme, Institute for Research in Biomedicine (IRB-Barcelona); Institut de Malalties Hemato-Oncològiques, Hospital Clínic de Barcelona; and Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain; and Cancer Biology and Genetics Program, Howard Hughes Medical Institute and Memorial Sloan-Kettering Cancer Center, New York, New York.
Cancer Res. 2010 Nov 23.
Tumor progression requires ablation of suppressor functions mediated by transforming growth factor β (TGFβ) signaling and by oncogene-induced senescence (OIS), but how these functions are canceled in specific subtypes of breast cancer remains unknown. In this study, we show that HER2-overexpressing breast cancer cells avert TGFβ- and OIS-mediated tumor suppression by switching expression of 2 functionally distinct isoforms of the transcription factor C/EBPβ, which has been implicated previously in breast cancer development. HER2 signaling activates the translational regulatory factor CUGBP1, which favors the production of the transcriptionally inhibitory isoform LIP over that of the active isoform LAP. LIP overexpression prevents the assembly of LAP/Smad transcriptional repressor complexes on the MYC promoter in response to TGFβ, and interferes with activation of OIS responses. Treatment of HER2-transformed mammary epithelial cells with the HER2 antibody trastuzumab reduces LIP levels, restoring these suppressor responses. Our findings reveal a novel mechanism through which HER2 silences tumor suppression in a concerted manner, contributing to the potency of this oncogene in breast cancer. Cancer Res; 70(23); 1-10. ©2010 AACR.
PMID: 21098707 [PubMed - as supplied by publisher] Source: National Library of Medicine.
