title: Up-regulation of PI3K/Akt signaling by 17beta-estradiol through activation of estrogen receptor-alpha, but not estrogen receptor-beta, and stimulates cell growth in breast cancer cells.
abstract: Estrogen stimulates cell proliferation in breast cancer. The biological effects of estrogen are mediated through two intracellular receptors, estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta). However, the role of ERs in the proliferative action of estrogen is not well established. Recently, it has been known that ER activates phosphatidylinositol-3-OH kinase (PI3K) through binding with the p85 regulatory subunit of PI3K. Therefore, possible mechanisms may include ER-mediated phosphoinositide metabolism with subsequent formation of phosphatidylinositol-3,4,5-trisphosphate (PIP(3)), which is generated from phosphatidylinositol 4,5-bisphosphate via PI3K activation. The present study demonstrates that 17beta-estradiol (E2) up-regulates PI3K in an ERalpha-dependent manner, but not ERbeta, and stimulates cell growth in breast cancer cells. In order to study this phenomenon, we have treated ERalpha-positive MCF-7 cells and ERalpha-negative MDA-MB-231 cells with 10nM E2. Treatment of MCF-7 cells with E2 resulted in a marked increase in PI3K (p85) expression, which paralleled an increase in phospho-Akt (Ser-473) and PIP(3) level. These observations also correlated with an increased activity to E2-induced cell proliferation. However, these effects of E2 on breast cancer cells were not observed in the MDA-MB-231 cell line, indicating that the E2-mediated up-regulation of PI3K/Akt pathway is ERalpha-dependent. These results suggest that estrogen activates PI3K/Akt signaling through ERalpha-dependent mechanism in MCF-7 cells.
authors.affiliation: Department of Biochemistry, Center for Healthcare Technology Development, Chonbuk National University Medical School, Jeonju, Republic of Korea.
authors.forename: Young-Rae
authors.initials: YR
authors.lastname: Lee
authors.forename: Jinny
authors.initials: J
authors.lastname: Park
authors.forename: Hong-Nu
authors.initials: HN
authors.lastname: Yu
authors.forename: Jong-Suk
authors.initials: JS
authors.lastname: Kim
authors.forename: Hyun Jo
authors.initials: HJ
authors.lastname: Youn
authors.forename: Sung Hoo
authors.initials: SH
authors.lastname: Jung
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004958:Estradiol / Q000494:pharmacology / Q000502:physiology*; D047628:Estrogen Receptor alpha / Q000819:agonists*; D047629:Estrogen Receptor beta / Q000819:agonists*; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis / Q000502:physiology*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis / Q000502:physiology*; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate; D004958:Estradiol; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt