title: Insulin-like growth factor-II regulates PTEN expression in the mammary gland.
abstract: The tumor suppressor PTEN is altered in many cancers, including breast cancer, but only a handful of factors are known to control its expression. PTEN plays a vital role in cell survival and proliferation by regulating Akt phosphorylation, a key component of the phosphatidylinositol 3 kinase (PI3K) pathway. Here we show that insulin-like growth factor-II (IGF-II), which signals through PI3K, regulates PTEN expression in the mammary gland. IGF-II injection into mouse mammary gland significantly increased PTEN expression. Transgenic IGF-II expression also increased mammary PTEN protein, leading to reductions in Akt phosphorylation, epithelial proliferation, and mammary morphogenesis. IGF-II induced PTEN promoter activity and protein levels and this involved the immediate early gene egr-1. Thus, we have identified a novel negative feedback loop within the PI3K pathway where IGF-II induces PTEN expression to modulate its physiologic effects.
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002455:Cell Division; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1; D004847:Epithelial Cells / Q000378:metabolism; D025461:Feedback, Physiological; D005786:Gene Expression Regulation; D017874:Immediate-Early Proteins; D007335:Insulin-Like Growth Factor II / Q000378:metabolism / Q000502:physiology*; D008156:Luciferases / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D019076:Transgenes; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D007335:Insulin-Like Growth Factor II; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase