The Role Of Folate And P16 Gene Promoter Region CpG Island Methylation And MeCP2 Protein Expression In Cervical Lesions

ObjectiveCervical cancer is a serious malignancy affecting women's health, HR-HPV is now known to be a necessary cause of cervical cancer but not be the sole cause. Folic acid as one donor of the SAM participates in DNA synthesis and methylation, and it is closely related with the incidence of cervical cancer. Methylation of promoter region CpG island of p16 gene is a frequent event in a variety of primary tumors. MeCP2 protein may reflect the state of DNA CpG island methylation and its abnormal expression related to the occurrence with a variety of tumors. There is a certain correlation between the above incident,and the relevant reports have yet to be seen eabout its exact role in the course of cervical lesions. This study aimed to explore the relations of folic acid, methylation of p16 gene promoter region CpG island, MeCP2 protein expression and cervical lesions,under the premise of HPV16 infection.MethodsA case-control study was used.85 cases of cervical squamous cell carcinoma (SCC),60 cases of cervical intraepithelial neoplasia (CIN2/3) and 85 cases of chronic cervicitis, diagnosed by pathology and without the systematic treatment in the same period, selected from Shanxi Tumor Hospital and The Second Hospital Affiliated to Shanxi Medical University during the October 2008～July 2009,were chosen as the case group. Tissue and vein blood in elbow of the three group were collected. Age, ethnicity, place of residence conditions and other factors were similar or identical between the case group and the control group. All of the subjects were excluded from the blood system, digestive system diseases, B vitamins use within the past three months, and tumors of other system. Serum folate levels were measured by RIA; HPV16 infections of surgical biopsy specimens were detected by PCR; methylation of P16ink4a gene were detected by MSP; MeCP2 protein expression was dected by Western-blotting method. Using SPSS13.0, normally distributed measurement data was analyzed by the F test and T-test and the skewed distributed data by Kruskal-wallis test; count data was analyzed by x2 test and x2 trend test; interactions was analyzed by stratify analysis.Results1.Univariate analysis of cervical lesions:for the first time having sex with younger age, number of pregnancies, productive times, the history of abortion as cancer risk factors change; menopause as protective factors; found no smoking, drinking,, gynecological history, family history of cancer and relationship with cervical change, for the first time a small child-bearing age a risk factor for the SCC, the incidence of CIN was not found with the relationship.2. The relationship between serum folate, HPV16 and cervical lesions:Serum folate levels of SCC group and CIN group were lower than the control group and the difference was statistically significant (H=12.08, P<0.001). A dose-response relationship of serum folic acid and SCC and CIN existed(x2 trend 1=14.842, P1=0.000;x2 trend 2=12.301, P2=0.000);HPV16-positive rate of SCC group and CIN group was significantly higher than the control group(27.18%),and the difference was statistically significant (x2=17.87, P=0.000; x2=4.46, P=0.035). Adose-response relationship existed(x2 trend=17.81, P=0.000); The deficiency of serum folic acid and HPV16-positive may exist in synergy in the course of SCC and CIN.The rate of P16 methylation in SCC and CIN group were higher than the control group and the difference was statistically significant (x2=36.62, P=0.000;x2=12.74, P=0.000). Serum folic acid deficiency with P16 methylation exist in synergy while SCC and CIN occur; HPV16-positive with P16 methylation exist in antagonism while SCC and CIN occur.3. The relationship of MeCP2 protein expression, p16 methylation and cervical lesions:The protein expression of SCC and CIN group were higher than the control group and the difference was statistically significant (F=69.62, P=0.000). SCC group, CIN group and control group was statistically significant difference between each other by pairwise comparison (P= 0.000). The difference of SCC and CIN group was not statistically significant (P= 0.405). The risk of SCC and CIN with MeCP2 protein high expression and p16 methylation was higher than the role of either a single factor. MeCP2 protein high expression and the P16 methylation existed in synergy in the course of SCC and CIN.4. Multivariate analysis of cervical lesions:a little age of first sexual intercourse, HPV16 infection, p16 methylation and MeCP2 is highly expressed in cervical cancer risk factors change; menopause, and high serum folate level is a protective factor for Cervical Cancer; productive times are risk factors for SCC, no found that the relationship with CIN.Conclusion1. A young age to have sex the first time, rising the risk factors of cervical cancer; menopause is the protective factors of cervical cancer; productive time was SCC risk factors, the relationship was not found with CIN.2.The deficiency of serum folic acid and HPV16-positive are risk factors of cervical lesions, they may exist in synergy in cervical lesions.3.P16 promoter CpG island methylation can increase the risk of cervical lesions. Serum folic acid deficiency with P16 hypermethylation may exist in synergy while cervical lesions occur; HPV16-positive with P16 methylation may exist in antagonism while cervical lesions occur.4. MeCP2 protein high expression may be related to cervical lesions.MeCP2 protein high expression and P16 methylation may exist in synergy in cervical lesions.