Expression And Significance Of Lysophosphatidic Acid And Its Receptors, Edg4 And Edg7, In Epithelial Ovarian Tumor

Background and aims:Ovarian carcinoma is one of common gynecology malignant tumors with its high mortality. Because ovarian cancer spot locates in the deep pelvic bottom absencing of early signs and symptoms, about 75-80% patients of all are final diagnosed to be advanced stage. Due to unknown its pathogenesy, the effective therapy to ovarian carcinoma is still absent. Recently the function of lysophosphatidic acid (LPA) and the relationship with ovarian cancer are gradually regarded as a significant focus to ovarian carcinoma gene therapy.LPA is a simplest phospholipids, it can mediate multiple functions ranging from growth promotion and cell cycle progression to cell survival. LPA can increase tumor cell proliferation, survival, invasion, protease production and activation, production of cytokines and resistance to chemotherapeutic agents. LPA participates in the occurrence, development, invasion, metastasis of carcinoma. Activated platelet, lipoidcells, vascular endothelialcells, etc. can secrete LPA. The ovarian cancer cells can also produce LPA and induce autocrine loop formation, which leads to high LPA level in the serum and ascites of ovarian cancer patients. It is suggested that LPA may play an important role in the process of ovarian cancer occurrence and development. The effects of LPA are determined by the LPA receptors expressed on the cell surfaces. The LPA receptors belong to members of the Edg family of G protein-coupled receptors, which have been supposed to mediate LPA signaling transduction pathway for multiple biological effection. LPA can promote apoptosis binding to Edg2, which it takes a role of down-regulation; whereas LPA increases cell DNA synthesis, mitochysis prosperity and induces production of many cytokines. Edg2 expresses highly in the normal cells. Edg4 and Edg7 yet overexpresses in the tumor cells, low expression or non-expession in the normal and immortalized cells, which suggests that high expression of Edg4 and Edg7 maybe relate to the effection of LPA in the tumors.The experiment first planed to detect serum LPA expression level of patients with epithelial ovarian tumor by biochemistry assay and CA125, in order to evaluate it's value in diagnosis of ovarian cancer. Then expressions of Edg4 and Edg7 proteins in epithelial ovarian tumor were detected by immunohistochemical assay (SP) and the relationship between the two receptor proteins and the clinical parameters were investigated, such as clinical stage, pathological grade, ascetic fluid quantity, lymphoid node metastasis, etc. The aim was to investigate the mechanism of tumor growth promoted by LPA, exploring new targets for ovarian cancer therapy and to provide the experiment foundation for gene therapy of ovarian cancer.Material and Methods:1. 70 patients with epithelial ovarian tumor included 50 malignant cases(37 cases of serous cystadenocarcinoma, 13 cases of mucous cystoadenocarcinoma), 20 benign cases(13 cases of serous cystadenoma, 6 cases of mucous cystadenoma and 1 case of endometrioid tumor). Twenty normal women were studied. 50 malignant cases were divided into three groups: primary I stage, primary II—IV stage and relapsed. All cases were confirmed by pathology. Levels of serum LPA were detected by biochemistry assay and compared with tumor relative antigen CA125 levels to evaluate the value of ovarian cancer early period diagnosis through the measurement of serum LPA levels.2. 68 cases of epithelial ovarian tumour paraffin imbedding samples and 12 cases of normal ovarian tissues were collected from department of gynaecology and obstetrics between February of 2000 year and October of 2004 year. All samples were diagnosed by two pathologists and all patients had not accepted the radiotherapy and chemotherapy before operation with complete clinical and pathological information.3. 80 samples of epithelial ovarian tumors included normal(12 cases), benign(10 cases), bord-erline(10 cases) and malignant tumors(48 cases), while 48 malignant cases were dividedinto serous cystadenocarcinoma(30 cases), mucous cystoadenocarcinoma(11 cases) and endometrioid carcinoma(7 cases); FIGO I stage(12 cases), FIGO II stage(16 cases), FIGO III stage(18 cases), FIGO IV stage(2 cases); G₁ grade(14 cases), G₂ grade(16 cases), G₃ grade(18 cases) according to histological grade. The subgroups included lymphoid node metastasis(22 cases) and non-lymphoid node metastasis(26 cases); ascites quantity more than 500ml(30 cases) and ascites quantity less than 500ml(18 cases). The patients' age was from 30 to 60 years old, mean of 42.56±4.67 years.4. Edg4 and Edg7 proteins expression in epithelial ovarian tumor were detected by immunohistochemical assay (streptomycin avidin-biotin-peroxidase complex staining assay). The relationship between expression of Edg4 and Edg7 proteins and the clinical parameters, such as clinical stage, pathological grade, ascites quantity, lymphoid nodemetastasis, etc. were investigated.5. The data were analyzed by statistics software SPSS13.0 package. The measurement datawere expressed with X|-±s and dealed with analysis of variance(ANOVA) and Fisher exact probabilistic method. Multi-sample rate comparison used contingency table chi-square test, rank-sum test and two samples rate comparison used fourfold table chi-square test. Spearman rank correlation analysis was used to analyze the relevance. The test strandard wasα=0.05.Results:1. Levels of serum LPA in patients with malignant cases were higher significantly than those in normal women and benign cases (F=78.386, P<0.05). Serum LPA level of every epithelial carcinoma group had not statistical significance(F=2.278, P>0.05). The same result to the comparison of normal women and benign cases(F=2.563, P>0.05). CA125 levels in primary ovarian cancer with FIGO II～IV stage and relapsed group were higher than that of primary ovarian cancer with FIGO I stage group, benign tumor group and normal women group(F=544.416, P<0.05).2. The sensitivity(94.1%) and the specificity(89.5%) of serum LPA in epithelial ovarian carcinoma were superior to CA125 with its sensitivity(87.8%) and specificity(51.7%). Especially in primary ovarian cancer with FIGO I stage LPA positive rate was 90%, which had significant statistical difference comparing with only 30% of CA125. (x² = 7.50, P<0.05).3. The positive expression of Edg4 and Edg7 proteins was 91.7% and 95.8%(malignant), 80% and 70%(borderline), 20% and 30%(benign), 16.7% and 16.7%(nonnal). Edg4 and Edg7 proteins expression in malignant and borderline epithelial ovarian tumor was markedly higher than that of benign tumor and normal tissues (Edg4:x²=38.873; Edg7:x²=40.449, P<0.05).4. The expression of Edg4 and Edg7 proteins was significantly associated with FIGO stage, pathological grade, ascites quantity and lymphoid node metastasis. The expression of Edg4 and Edg7 proteins in tissues with FIGO III～IV stage was obviously higher than that of FIGO I～II stage(Edg4:x²=17.807; Edg7:x²=15.481, P<0.05). The expression of two proteins in the G₁ grade tissues was lower than that of G₂ ,G₃ grade tissues significantly(Edg4: x²=18.139; Edg7:x²=20.959, P<0.05). The expression of Edg4 and Edg7 proteins in tissues with lymphoid node metastasis was higher than that of without lymphoid node metastasis (Edg4:x²=10.741;Edg7: x²=6.325, P<0.05). While the expression of two receptor proteins in tissues with ascites quantity more than 500ml was higher than that of the ascites quantity less than 500ml (Edg4: x²=5.807;Edg7:x²=4.434, P<0.05).5. The positive expression of Edg7 protein was higher than that of Edg4 protein in epithelial ovarian cancer, but the expression of two proteins was positive correlation.(r_s=0.978, P<0.05).Conclusions1. Serum LPA levels in patients with epithelial ovarian cancer were high significantly. The sensitivity and the specificity of LPA in diagnosis epithelial ovarian cancer were superior to CA125, especially for early stage ovarian cancer. LPA may be a potential biomarker for diagnosis of epithelial ovarian cancer and a potential monitoring target after operation.2. The expression of Edg4 and Edg7 proteins in epithelial ovarian cancer was markedly high. The expression of Edg4 and Edg7 proteins was significantly associated with the clinical stage, pathological grade, ascites quantity and lymphoid node metastasis.3. The expression degree of Edg4 and Edg7 receptor proteins was positive correlation which suggest that the two proteins had synergistic effect in the occurrence and development of epithelial ovarian cancer. LPA and its receptor would become the potential targets to ovarian cancer gene therapy.