The Expression, Biological Function And Clinical Significance Of IGF2 Gene In Human Ovarian Cancer

Objective:Ovarian cancer is the most common gynecological malignancies represented by difficult diagnosis, high degree of malignancy, rapid progression and poor prognosis. Currently due to the lack of effective early detection methods, the majority of patients are diagnosed at advanced stages. As clinical stage is one of the most important factors affecting tumor prognosis, discovery of early and accurate screening and prognosis biomarkers is vital to improve the survival of ovarian cancer patients.Recently we found a prominent different expression of IGF2 between ovarian cancer tissue and adjacent normal tissue. Followed by investigating large body of literatures, we found no reports on the function of IGF2 gene in ovarian cancer progression and clinical significance.To further investigate the vital role played by IGF2 in the clinical classification and progression of ovarian cancer, we analyzed the relevance between IGF2 expression and clinical pathology and prognosis. Furthermore, knockdown of ovarian cancer cell models was constructed to study the function of IGF2 in cell cycle, proliferation, apoptosis, metastasis and invasion.Methods:1. RT-PCR, RT-qPCR and western-blot were applied to analyze IGF2 expression in ovarian cancer tissues and normal ovarian tissues.2. Tissue microarray and immunohistochemistry methods were used to study IGF2 expression in ovarian cancer tissues and adjacent tissues.3. By analyzing the positive rate and staining intensity of the tumor cells in tissue microarray samples, we used SPSS 13.0 software to investigate the relationship between IGF2 expression and patients clinical data.4. The online database Kaplan-Meier plotter was used to analyze the relationship between the survival of ovarian cancer patients and IGF2 expression.5. The role of IGF2 in tumor cell cycle and cell proliferation was analyzed by flow cytometry and MTS methods.6. The role of IGF2 in tumor cell apoptosis and invasion was analyzed by flow cytometry and Transwell methods.Results:1. Using RT-PCR, RT-q PCR and Western-blot to analyze the expression of IGF2 in 10 cases of normal ovarian tissues and 35 cases of ovarian cancer tissues, the results showed that the expression of IGF2 gene in ovarian cancer tissues was significantly higher than that in normal ovarian tissue(P=0.000).2. The expression of IGF2 in ovarian cancer tissue and adjacent cancer tissue were analyzed in tissue microarray containing 72 cases of ovarian cancer and 15 cases in adjacent tissues by immunohistochemistry, and the results showed that IGF2 expression was significantly higher than that in adjacent tissues(P=0.000).3. The relationship between IGF2 expression and patients clinical data was investigated by analyzing the positive rate and staining intensity of the tumor cells in tissue microarray samples. We found that IGF2 expression in ovarian cancer patients was closely related to tumor grade(p=0.047), but not to age, histological type, tumor location and tumor size.4. The online database Kaplan-Meier plotter was used to analyze the relationship between the survival of ovarian cancer patients and IGF2 expression. The results showed that expression of IGF2 was negatively correlated with both OS and PFS of ovarian cancer patients(HR=1.44, P=0.000) and(HR=1.35, P=0.000) respectively. These results indicate that, IGF2 expression is closely associated with poor prognosis of ovarian cancer patients.5. By analyzing the relationship between IGF2 expression and survival of different sub-groups of patients, we found a varied prognostic significance of IGF2 expression in different clinical stages, pathological type and mode of chemotherapy. IGF2 expression is closely related to a poor prognosis of clinical Phase I + II(HR=2.60, P=0.014) and III(HR =1.30, P=0.003) patients. For patients with pathological grade 2(HR=1.59, P=0.004) and 3(HR=1.31, P=0.002), higher IGF2 expression demonstrated a shorter survival time than that of low expression. For patients received a single platinum drugs(HR=1.48, P=0.000), a single class of drugs paclitaxel(HR=1.46, P=0.00024) or joint action of two drugs(HR= 1.46, P=0.0000), higher IGF2 expression demonstrate a shorter survival time than that of low expression.6. The function of IGF2 in cell cycle, apoptosis, cell proliferation and cell invasion were studied in IGF2 knockdown cell model by flow cytometry, MTS methods and Transwell methods, respectively. The results showed that knockdown of IGF2 gene significantly suppressed ovarian cancer cells proliferation and caused cell cycle arrest in G1 phase. In additon, knockdown of IGF2 gene can significantly promote apoptosis in ovarian cancer cells and inhibited cell invasion.Conclusion:1. IGF2 is overexpressed in ovarian cancer tissues compared with normal ovarian tissue and adjacent tissues, and its expression is significantly correlated with pathological grading of patients.2. IGF2 expression is closely related to the survival time of patients with ovarian cancer, it is an important poor prognostic factor and it is an important biomarker for prognosis.3. IGF2 gene is an important oncogene in ovarian cancer and it is widely involved in the process of ovarian cancer occurrence and development.