A Study On The Role And Mechanism Of Notch1 As Signal In Ovarian Tumorigenesis

Background Ovarian carcinoma is a sort of malignant tumors which happen in ovarian tissue. Its incidence is in the second place of gynecology malignant tumor about 15%,but its mortality rate is in the first place.It has characteristics of delitescence,difficult to discover in the early state,easy to metastasize and develop quickly.So,it's very important to find a new path for tumorous gene therapy.The Notch signaling cascade is remarkably conserved from Drosophila to man,and the complexity of this cascade is higher in mammals.Receptor-ligand interaction between two neighbouring cells leads to successive proteolytic cleavages of Notch,resulting in the release of the intracellular domain(ICN) of the receptor.ICN translocates to the nucleus where it converts the transcription factor CBF1/Su(H)/LAG1(CSL) from a repressor to a transcriptional activator.The target gene of ICN- CBF1/Su(H)/LAG1(CSL) is HES1.HES1 is a transcription factor of basic helix-loop-helix,and it's very important in cell differentiation and genic transcription.Notch signaling is involved in a variety of cell differentiation, proliferation and apootosis that affect the development and functions of many organs.The past study show that pathophysiologic alterations in Notch signaling have been associated with tumorigenesis.Expression and localization of Notch receptors and their ligands have been observed in the adult human ovarial tussue and altered during ovarial pathogenesis.So this pathway may be critical both for normal ovarial formation and the abnormal tumorigenesis,and the relationship between Notch siganling and ovarial carcinoma is a new field of dtudy,and it also may be a new gene therapy for ovarial carcinoma.Purpose (1) To study the significance of Notch1 expression in tumor transformation and progression and its relationship with clinical pathology characteristics. (2)To determine the expression of Notch1 gene in ovarian carcinoma cell lines and to screen target cells for further study at Notch1 in ovarian carcinomas.(3)To determine the expression of HES1 as Notch1's downstream gene in ovarian carcinoma cell lines and to provide experiment data for further study.Methods (1) using immunohistochemistry SP staining method examine the expressions of Notch1 in 34 cases of ovarian cancers,18cases of borderline and malignant tumors,23 cases of ovarian benign tumors and 26 cases of normal ovaries. They are analyzed by Chi-square test of SPSS12.0.(2)using immunofluorescence staining,RT-polymerase chain reaction and western blotting examine the expressions of Notch1 in ovarian carcinoma cell line SKOV3,HO-8910,HO-8910PM and 3AO.(3)using RT-polymerase chain reaction and western blotting examine the expressions of Notch1's downstream gene HES1.Results:(1) The positive rate of Notch1 expression in ovarian cancers(25/34, 74%)was significantly higher than that in borderline and malignant tumors(12/18, 67%),ovarian benign tumors(7/23, 30%)and normal ovaries(6/26, 23%), (P〈0.01).There was no significant difference between the latter three groups(P >0.05).(2) The expression of Notch1 in ovarian cancers was correlated with histological typing(P〈0.01),not with operative pathology staging,tissue infiltration,lymph node metastasis and pathology typing(P)0.05).The lower histological typing is ,the lower the expression of Notch1.(3) The expression of Notch1 mRNA and protein could be examined in all four ovarian carcinoma cell lines by immunofluorescence staining,RT-polymerase chain reaction and western blotting. The expression of Notch1 is strong positive expression in HO-8910-PM cell line,positive expression in SKOV3 and 3AO cell lines and weak positive expression in HO-8910 cell line.(4) The expression of HES1 mRNA and protein could be examined in all four ovarian carcinoma cell lines by RT-polymerase chain reaction and western blotting,but they donot have significant deviation in every ovarian carcinoma cell.Conclusion: (1) The expression of Notch1 is becoming higher in the stage of canceration.It is related to carcinogenesis of ovarian cancer.(2) The expression of Notch1 in ovarian cancers was correlated with histological typing,The lower histological typing is ,the lower the expression of Notch1.(3) Notch1 gene expressed in SKOV3,HO-8910,HO-8910-PM and 3AO cell lines and strong positive expression in HO-8910-PM cell line.So HO-8910-PM cell line could be used as a screen target cell for further study at Notch1 in ovarian carcinomas.(4)HES1 as Notch1'S downstream gene expressed in SKOV3,HO-8910,HO-8910-PM and 3AO cell lines.The experimental result show that Notch1 and its downstream gene HES1 expressed in ovarian cancer and ovarian carcinoma cells and it maybe one of the mechanisms in tumorigenesis.So, it can provid a new path for tumorous gene therapy.