Open in a separate window FIG. HIF-1 protein and VEGF mRNA manifestation that is dependent upon activity of PI3K, AKT (also known as protein kinase B), and the downstream kinase FRAP (FKBP-rapamycin-associated protein). In contrast to additional inducers of HIF-1 manifestation, heregulin activation does not affect the MLN120B half-life of HIF-1 but instead stimulates HIF-1 synthesis inside a rapamycin-dependent manner. The 5-untranslated region of HIF-1 mRNA directs heregulin-inducible manifestation of a heterologous protein. These data provide a molecular basis for VEGF induction and tumor angiogenesis by heregulin-HER2 signaling and establish a novel mechanism for the rules of HIF-1 manifestation. MLN120B Angiogenesis is essential for tumorigenesis as well as metastasis (11, 16, 64), and vascular denseness is an important prognostic factor in breast tumor (19, 27, 58, 59). Vascular endothelial growth factor (VEGF) takes on a major part in tumor angiogenesis (10), and its manifestation in breast cancer is definitely inversely correlated with patient survival (29, 30). VEGF manifestation can be induced by exposure of tumor cells to hypoxia or growth factors and, in both cases, this manifestation is due in part to improved gene transcription that is mediated by hypoxia-inducible element 1 (HIF-1) (6, 9, 12, 22, 44, 63, 65). HIF-1 is definitely a heterodimer composed of HIF-1 and HIF-1 subunits (56, 57). Whereas HIF-1 is definitely constitutively indicated, the manifestation and activity of the HIF-1 subunit are induced by exposure of cells to hypoxia or growth factors (examined in research 49). HIF-1 activates the transcription of genes whose products are required for critical aspects of tumor progression including angiogenesis (plasminogen activator inhibitor 1 and VEGF), iron homeostasis (transferrin and transferrin receptor), and metabolic adaptation (glucose transporters and glycolytic enzymes), as well as several factors that impact tumor cell survival or proliferation (endothelin 1, inducible nitric oxide synthase, and insulin-like growth element 2). HIF-1 is definitely overexpressed in main and metastatic human being tumors (1, 4, 5, 53, 62, 66). In breast tumor, HIF-1 overexpression can be recognized in ductal carcinoma in situ but not in benign ductal hyperplasia (5), i.e., in early-stage malignancy prior to invasion but concomitant with increased angiogenesis (15). HIF-1 activity is definitely improved both by intratumoral hypoxia and by genetic alterations, including loss-of-function mutations in the tumor Rabbit Polyclonal to AGBL4 suppressor genes encoding p53, PTEN, and VHL (von Hippel-Lindau protein) as well as gain-of-function mutations in oncogenes that activate the phosphatidylinositol 3-kinase (PI3K), SRC, and mitogen-activated protein (MAP) kinase signal-transduction pathways (24, 34, 40, 41, 47, 48, 65, 66, 68). Loss or gain of HIF-1 activity is definitely negatively and positively correlated, respectively, with tumor growth and angiogenesis in xenograft assays (6, 24, 28, 33, 40, 44, 45). Among the genetic alterations recognized in human breast cancer, probably one of the most important is the improved activity of the HER2 receptor tyrosine kinase encoded from the gene on chromosome 17q21, which happens in approximately one-third of breast tumors and is associated with improved tumor grade, chemotherapy resistance, and decreased rates of patient survival (36, 43, 50, 51). Overexpression of HER2 transforms MLN120B human being mammary epithelial and mouse 3T3 cells and imparts resistance against the chemotherapeutic providers tamoxifen and Taxol (32, 39, 61). Treatment of breast cancer cells having a neutralizing antibody against HER2 results in a dose-dependent inhibition of VEGF manifestation (38). A humanized monoclonal antibody to HER2 inhibits breast cancer growth and has been authorized for treatment of HER2-overexpressing tumors (35). Unlike additional members of the epidermal growth element receptor (EGFR) family, HER2 offers tyrosine kinase activity in.