The Role Of FHIT Gene Methylation Of Promoter Region's CpG Island And Abnormal Expression Of MeCP2 Protein In Cervical Lesions

ObjectiveCervical cancer is one of the malignant tumors serioualy harming women's health worldwide. High Risk HPV (HR-HPV) is the main cause for cervical cancer, but not the only cause. Reseaches in the recent years, showed that methylation of CpG island, promoter region of tumor-suppressor gene FHIT, is the main way to it's silence, and important to the cervical cancer, and abnormal expression of protein MeCP2 which reflects the methylation status of genes, is closely associated with various kinds of tumors. However, relation between CpG island methylation and protein MeCP2 and role played by both are not seen in any report at present. Women with different stages of cervical cancer were selected as subjects. Under the condition that all the subjects were diagnosed as being infected with HPV, methylation status and expression level of gene FHIT, and levels of MeCP2 mRNA and protein MeCP2 which closely related to the gene transcription, were tested. Rsults from above tests may demonstrate the effect of protein MeCP2 on the methylation in gene FHIT promotor region. We will investigate the role played by methylation of gene FHIT and expression of protein MeCR2 in the development of cervical cancer, which may provide a theoretical evidence for the study of etiology and mechanism of cervical cancer, and suggest a different direction and idea for prevention and clinical therapy of cervical neoplasm.Methods74 cases with squamous cervical cancer were selected from Tumor Hospital affiliating to Shanxi medical University from June,2008 to October 2009, and 52 cases with CIN I and 60 cases with CIN II-III from the Second Hopital affiliating to Shanxi Medical University, while 58 cases with cercitis from Health Care Center for Women and Children of Taiyuan. All sujects got a definite diagnosis through pathological exam, did not receive radiotherapy and chemotherapy before we gained biological material from them. Those sujects with megaloblastic anemia , haemolytic diseases, leukemia,local enteritis, live diseases and other types of tumers were excluded . and those taking in Vitamin B within three monthes were also not included.Information about the demograthy, reproductive, life habits et al were colleced through structural questionair. At admission, we get the tissues of cervix. We adopted PCR to test infection status HPV16, MSP-PCR to detect the methylation status, Real-Time PCR to detect expression levels of gene FHIT and gene MeCP, and Western-blot to test protein expression level. We established database and analyzed data by using SPSS16.0. ANOVA was used to analyzed the qualitative data,χ²Test andχ² Trend Test to analyze the categorical data, Pearson correlaton and Spearman Rank Correlation to analyze the interaction and correlation and Logistic Regression to analyze the risk factors of cervical cancer.Results1) The rate of HPV16 infection in cervical cancer (63.5%) and cervical intraepithelial neoplasia (38.3%) were both higher than in cervicitis,and had significant different among each groups(χ²=30.970,P<0.001,χ² _{趋势}=27.066,P<0.001).2) The rate of methylation of CpG island, promoter region of tumor-suppressor gene FHIT (50.0%) in cervical cancer was higher than other groups, and had significant different among each groups(χ²=46.174,P<0.001), methylation occurred more frequently with the further development of cervical cancer (χ² _{趋势}=43.607,P<0.001).3) Relative expression level of FHIT mRNA was significantly lower in cervical cancer group than that in other groups (F=27.012,P<0.001),and the protein's relative expression lever was significantly lower in cervical cancer group than that in other groups (F=16.040,P<0.001).4) Relative expression level of MeCP2 mRNA was significantly higher in cervical cancer group than that in other groups (F=7.804,P<0.001),and the protein's relative expression lever was significantly higher in cervical cancer group than that in other groups (F=21.576,P<0.001).5)There was positive correlation between HPV16 infection and methylation of FHIT(r=0.472,p<0.05), the analysis of biological interaction indicatated that they had positive additive interaction and positive synergism both in cervical cancer and CIN II-III, but not in CINI.6) Result from interaction analysis between expression level of protein MeCP2 and methylation status of FHIT gene demonstrated that the two factor metioned above were interacted with each other.In the CIN I and CINII-III groups, they had positive additive effect and positive synergism, while in the cervical cancer group, only positive additive effect.7) Negative correlation existed between expressional level of protein MeCP2 and expression level of protein FHIT(r=-0.141,p=0.033).8) Those variables enter the regression models, including mathylation of CpG island in the promoter of gene FHIT and expression level of protein FHIT, in the groups of CINII-III and cervical cancer, and expression level of protein MeCP2 in the groups of CIN I and cervical cancer while histories of gynecopathies enter the regression models of all groups.Conclusions1) HPV16 infection, methylation of CpG island in promoter region of FHIT were risk factors in cervical lesions, and there might be a synergy in cervical cancer.2) Along with cervical lesion, the protein and mRNA's expression lever of MeCP2 were increasing with the FHIT's mRNA and protein reducing. The high expression of MeCP2 and methylation of CpG island in promoter region of FHIT may exist synergy in cervical lesions.3) Histories of gynecopathies are the shared risk factors for CIN and cervical cancer,while occupation, less education received, no cleaning after sexual intercourse and parity are risk factors for cervical cancer.