Study On The Correlation Between Insulin/PI3K/Akt Signaling Pathway And Endometrial Carcinogenesis

Endometrial carcinoma is one of the most common gynecologic malignancy, andthe carcinogenesis mechanism remains unclear. The incidence rate shows a continuouselevation tendency worldwidely. Study on etiology about this cancer is of particularimportance.It is accepted that the risk factors for endometrial carcinoma include obesity,hypertension and diabetes mellitus. Polycystic ovary syndrome is a commonendocrinology disorder in young endometrial cancer patients. The samepathophysiological basis of these risk factors is insulin-resistance. Endometrialcarcinoma may be an insulin-related cancer. It is well known that insulin mediates themetabolic effect in target tissue. As a multi-functional hormone, insulin also plays animportant role in the growth and differentiation of some normal or neoplasm cellsthrough insulin receptor (INSR) and its downstream signaling pathway, such asphosphatidylinositol 3-kinase (PI3K) /Akt and Ras /MAPK. It is reported that theoverexpression or abnormal activation of insulin signaling pathway may be associatedwith some tumors. The study on the assocaition between insulin signaling pathway andthe endometrial carcinogenesis is very few. In this study, using endometrial cancer cellline and human endometrial carcinoma tissue, we want to investigate the role of Inslin/PI3K/Akt signaling pathway in the endometrial carcinogenesis from four parts.Sectionâ… . Expression and activation of insulin receptor inendometrial carcinomaObjective: To explore the role of insulin receptor (INSR)expression and activationin endometrial carcinogenesis. Study the correlation between INSR activation and the circular insulin level.Methods: 63 endometrial carcinoma cases (EC), 21 endometrial atypical hyperplasis(AHE) and 22 normal control (NE) were all from General Hospital of TianJin MedicalUniversity. Collected clinical information, measured body indices. Fasting serumC-peptide and insulin concentration were all measured. Expression of INSR inend0metrium was examined by RT-PCR and Western blot (WB). Immunoprecipitation/WB was used to measure the tyrosine phosphorylation of INSRβ-subunit.Result: The serum C-peptide and insulin level in EC group were all higher than that inNE group. INSR was expressed not only in the normal endometrium but also in theatypical hyperplasia endometrium and endometrial carcinoma. Tyrosinephosphorylation of INSR was positively correlate with fasting serum C peptide andinsulin concentration (r=0.496, 0.334). Compared with AHE and NE group, theexpression and activation of INSR in endomerial carcinoma were significantly higher.There was no siginificant difference in INSR expression between AHE and NE group.However, INSR activation in AHE group was higher than normal control. INSRexpression and activation in endometrioid carcinoma were higher than that in otherhistologic types. Patients in FIGOâ…¢stage or with poor differentiation tumor had higherINSR expression and activation. Abnormal activation of INSR was also carrelate withpelvic lypmphonode metastasis in endomatrial carcinoma.Conclusions: Insulin receptor which expressed frequently in endometrium is thebasis of insulin signaling transduction. INSR activation in endometrium is correlatewith circular insulin level positively. Overexpression and abnormal activation of theinsulin receptor in endometrium are two characters in endometrial carcinoma patients,and which are correlate with poor clinical-pathologic features. Sectionâ…¡. Expression and activation of insulin receptor substrate-1in endometrial carcinomaObjective: To explore the role of insulin receptor substrate-1 (IRS-1) expression andactivation in endometrial carcinogenesis. Study the correlation bwteen insulin receptor'sfunction and that of insulin receptor substrate-1.Methods: 63 endometrial carcinoma cases (EC), 21 atypical hyperplasis (AHE) and22 normal control (NE) were all from General Hospital of TianJin Medical University.IRS-1 expression in endometrium was examined by RT-PCR and Western blot (WB).Immunoprecipitation/WB was used to measure the phosphorylation of IRS-1.Result: IRS-1 mRNA and protein were often expressed in the endometrium.Tyrosine phosphorylation of IRS-1 was correlate with fasting serum C peptide andinsulin level positively (r=0.491, 0.259). There was a positive relationship betweenINSR and IRS-1 activation(r=0.691). There were no differences in IRS-1 mRNA andprotein expression among these groups. Tyrosine phosphorylation of IRS-1 in EC washigher than that in AHE and NE group. Activation of IRS-1 in AHE was higher than thenormal control. IRS-1 activation in endometrioid carcinoma was higher than that inother histologic types. IRS-1 tyrosine phophorylation was siginificantly higher inpatients with high stage, high grade, deep myometrial invasion and pelvic lymphonodemetastasis.Conclusions: IRS-1 activation in endometrium is correlate with INSR activation andthe circular insulin level positively. At insulin-resistance state, there is nopost-receptor deficiency in endometrial insulin signaling pathway. There is abnormalactivation of IRS-1 in endometrial carcinoma, which is related with the poor clinical-pathologic features. Sectionâ…¢. Expression and activation of PI3K/Aktin endometrial carcinomaObjective: Examine the expression and activation of PI3K p85 regulatory subunit aswell as Akt in endometrial carcinoma. Study the relationship among INSR, IRS-1 andAkt's activation in endometrial carcinogenesis.Methods: 63 endometrial carcinoma cases (EC), 21 atypical hyperplasis (AHE) and22 normal control (NE) were all from General Hospital of TianJin Medical University.p85 subunit mRNA expression in endometrium was examined by RT-PCR. Western blotwas used to measure Akt expression and activation.Result: p85 and Akt were often expressed in endometrium. Serum C-peptide andinsulin concentration were all positively correlate with Akt activation (r=0.514, 0.490).The activation of Akt in endometrium is positively correlate with the activation ofinsulin recetptor and its substrate (r=0.720, 0.681).The expression of p85 mRNA andAkt protein were not significantly different among these groups. Akt activation in ECgroup was more significant than that in AHE and NE group. Akt activation in AHEgroup was higher than the normal control. Abnormal activation of Akt in endometrialcarcinoma was associated with high stage, high grade, deep myometrial invasion,positive peritoneal cytology, serosal invasion and pelvic lymphonode metastasis.Conclusions: Insulin/PI3K/Akt signaling pathway is exist in endometrium. There isno transduct deficiency in this pathway at insulin-resistance state. Abnormal activationof Akt is an important event in endometrial carcinogenesis and progress, and which iscorrelate with poor clinical-pathologic characteristics of endometrial carcinoma.Sectionâ…£. Mitogenic and anti-apoptotic effects induced by insulin inendometrial cancer cells are via PI3K/Akt signaling pathwayObjective: To explore the role of PI3K/Akt signaling pathway in the insulin- induced regulation of proliferation and apoptosis in endometrial cancer cells in vitro.Methods: Serum-starved human endometrial cancer cell line Ishikawa 3-H-12 cellswere stimulated by insulin with or without LY294002, a specific inhibitor of PI3K. Theexpression of Akt, phospho- Akt (Ser⁴⁷³ p-Akt) was detected with Western blot. The cellproliferation and apoptotic ratio was examined with MTT assay and flow cytometricanalysis, respectively.Result: After 15 min stimulation with 10^-6mol/L insulin, Akt in Ishikawa cells wasactivated significantly. LY294002 blocked the Akt phosphorylation induced by insulinin a dose-depedent manner. In MTT assay, insulin treatment promoted the proliferationof Ishikawa cells significantly, this effect was inhibited by LY294002 in aconcentration-dependent manner. Study with flowcytometery showed that insulininhibited the apoptosis of Ishikawa cells. LY294002 blocked this antiapoptotic effectof insulin.Conclusions: Insulin-induced mitogenic and anti-apoptotic effects in endometrialcancer cells are PI3K/Akt dependent.In summary, the results demonstrate that overexpression of insulin recetor inendometrium, and hyperinsulinemia secondary to the insulin resistance lead to theabnormal activation of insulin receptor and its substrate. As a result of it, PI3K/Aktsignaling pathway is upregulated. This abnormal activation in Insulin/PI3K/Aktsignaling pathway could promote cell proliferation and inhibit apoptosis, which mayplay a vital role in the carcinogenesis and progress of endometrial carcinoma.