Correlation Of IEX-1 Hypermethylation With Tumorigenesis And The Development Of Ovarian Cancer

Background and ObjectiveOvarian malignant tumor is one of the three major malignant tumor in department of gynaecology. The mortality of ovarian cancer ranks first in women’s cancer of the world. Ovarian cancer is a serious threat to people’s lives and health, with a high incidence, especially in developing countries. Early diagnosis and treatment of ovarian cancer become an urgent problem for human. Gene expression is regulated mainly by two sorts of mechanisms, genetics and epigenetics. The mechanism of genetic change is involved in nucleotide sequence, but now can only explain part of the mechanism of tumorigenesis. Epigenetics is a kind of mechanism which does not involve DNA sequence changes, but includes heritable changes in gene expression. Now epigenetics is considered more common than genetics in the mechanism of gene expression regulation and control.Many gene with important function participate in the occurrence and development of tumor through Epigenetics. DNA methylation is the main way of Epigenetics and is studied thoroughly.It’s related to the expression of tumor suppressor gene, their role in the tumorigenesis is a research hotspot in recent years.And the data showed that gene methylation is associated with different pathological type of breast cancer.Immediate early response gene X-1,IEX-1, plays a key role in cell apoptosis, proliferation and differentiation. It has confirmed that, in a variety of human tumors the abnormal expression of IEX- 1 is closely related to the prognosis of tumor according to the different tumor type and stage of development. Our preliminary study found: The development of ovarian cancer is associated with the lower expression of IEX- 1. Mammals, including human, 90% of DNA methylation happened in second nucleotide cytosine(Cp G) sequence. And the IEX- 1 gene promoter region is rich in the Cp G islands which are methylated easily. In conclusion, IEX- 1 gene DNA methylation may be linked to IEX- 1 gene function inactivation in ovarian cancer tissues.Methylation- specific polymerase chain reaction(MSP)、RT-PCR and Immunohistochemistry was used to detect methylation of the IEX-1 gene、the expression of IEX-1 m RNA and protein respectly in different ovarian tissue and 3 ovarian cancer cells.The aim is to explore the level of DNA methylation of IEX- 1 gene and its relationship with the IEX- 1 m RNA and protein expression in different pathological type of ovarian cancer tissue. Methods1. Methylation- specific polymerase chain reaction(MSP) was used to detect methylation of the IEX-1 gene in different ovarian tissue and 3 ovarian cancer cells;2. RT-PCR was used to detect the expression of IEX-1 m RNA in different ovarian tissue and 3 ovarian cancer cells;3. The expression of IEX-1 protein in different ovarian tissue and 3 ovarian cancer cells was detected by Immunohistochemistry.4. Using SPSS 17.0 statistical software for analysis.The comparison of DNA methylation level of IEX- 1 gene、 m RNA and protein expression level in different pathologic types and surgical pathology points was tested by the Fisher’s exact probability method.The relationship of IEX- 1 gene DNA methylation with its m RNA and protein expression level was tested by χ2, the inspection level, α = 0. 05.Results1.The positive rate of IEX-1 gene methylation was significantly higher in ovarian cancer than in benign control specimens(44.2%; 28.6%;both P<O.05);the IEX-1 gene methylation in 3 ovarian cancer cells are all positive;2. The positive rate of IEX-1 gene expression was significantly lower in ovarian cancer than in benign control specimens(30.2%; 81.0%;both P<O.05);the expression of IEX-1 gene in 3 ovarian cancer cells are all low;3. The positive rate of IEX-1 protein expression in ovarian cancer with IEX-1 gene methylation was significantly lower than that in ovarian cancer without IEX-1 gene methylation(10.5%; 45.8%; P<O.05). Conclusion1. Hypermethylation of Cp G islands in the promoter of the IEX-1 gene exists in ovarian cancer and can downregulate IEX-1 expression;2. The level of hypermethylation of these Cp G islands might be involved in tumorigenesis and the development of ovarian cancer. Key words:IEX-1; DNA methylation; Methylation- specific polymerase chain Results...