title: Mitogenic and anti-apoptotic effects of insulin in endometrial cancer are phosphatidylinositol 3-kinase/Akt dependent.
abstract: OBJECTIVE
  To determine serum insulin levels, expression and phosphorylation of InsR, IRS-1 and Akt in endometrial cancer (EC) tissues, and to explore the correlation between them. To investigate if insulin-induced mitogenic and anti-apoptotic effects are PI3K-dependent in EC cells.
  
  
  METHODS
  Serum insulin levels were measured by radioimmunoassay. We performed RT-PCR and western blotting to evaluate the expression and activation of key proteins of PI3K/Akt pathway in 63 EC tissues. The proliferation and apoptosis rates were determined with MTT, BrdU and annexin V/PI assays.
  
  
  RESULTS
  Serum insulin levels and InsR, IRS-1 and Akt expression and phosphorylation were significantly elevated in patients with EC compared to those without EC. Additionally, levels of p-InsR, p-IRS-1, and p-Akt were significantly higher in patients with high-grade, advanced stage, deep myometrial invasion, and lymph-node metastasis. The expression and activation of InsR, IRS-1, and p-Akt were positively related with the levels of serum insulin. The insulin-induced mitogenic and anti-apoptotic effects in EC cells were blocked when cells were pre-incubated with LY294002. Ishikawa 3-H-12 cells showed increased p-Akt levels after treatment with insulin at 10(-8)M for 15min. The insulin-induced Akt activation was inhibited by LY294002 in a dose-dependent manner.
  
  
  CONCLUSIONS
  Insulin played an essential role in EC tumorigenesis. Activation of InsR, IRS-1, and Akt was associated with features of aggressive EC. Insulin was a mitogenic and anti-apoptotic agent for EC cells, and these effects were dependent on PI3K/Akt pathway. Decreasing insulin level and blocking the InsR-IRS-PI3K-Akt pathway could be viable preventive and therapeutic strategies for EC.
authors.affiliation: Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China.
authors.forename: Yingmei
authors.initials: Y
authors.lastname: Wang
authors.forename: Shaofang
authors.initials: S
authors.lastname: Hua
authors.forename: Wenyan
authors.initials: W
authors.lastname: Tian
authors.forename: Lizhi
authors.initials: L
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.forename: Huiying
authors.initials: H
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Fengxia
authors.initials: F
authors.lastname: Xue
mesh_terms: D017209:Apoptosis / Q000502:physiology; D045744:Cell Line, Tumor; D004714:Endometrial Hyperplasia / Q000097:blood; D016889:Endometrial Neoplasms / Q000097:blood* / Q000201:enzymology* / Q000473:pathology; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism
chemical_list: C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt