Relationship Between Promoter Methylation Of MBD4 Gene And Expression Of HMLH1 In GCA

Objective: Having been deemed as a separated disease, studies on gastric cardiac adenocarcinoma(GCA) became more and more important .In recent years, GCA contains detachment from primarily focus, so it is necessary to conduct a study of its pathogenesis in order to reduce the GCA morbidity and mortality.These years , DNA promoter methylation has been a hot problem which many scientists make focus on .The purpose of this study was to investigate the methylation , mRNA expression of gene MBD4 , HMLH1 expression in GCA and corresponding non-cancerous tissues . We tried to explore the relationship between gene methylation and the carcinogenesis, metastasis and pathological differentiation of GCA, and provide a new theory and experiment evidence for pathogenesy, gene therapy and immunotherapy, clinical prognosis of GCA .Methods:1 Methylation specific PCR (MSP) was used to detect the methylation status of the 5' CpG island of MBD4 gene in 77 GCA tissues and 46 corresponding non-cancerous tissues.2 RT- PCR was used to examine the mRNA expression of MBD4 in 36 GCA tissues and 26 adjacent non-cancerous tissues.3 Immunohistochemistry (IHC) was used to examine the expression of HMLH1 gene in 30 GCA tissues and 25 corresponding non-cancerous tissues.4 SPSS 13.0 was applied to analyze the results of experiment.Results:1 For the MBD4, methylation was detected in 46 of 77 (59.7%) GCA tissues and 9 of 46(19.6%) adjacent non-cancerous tissues;the methylation rate of GCA tissues was significantly higher than the adjacent non-cancerous tissues (P=0.000). There is no correlation between methylation status of MBD4 gene and clinical data(P>0.05).2 For the 36 GCA tissues that match the data of mRNA expression , we found no correlation between MBD4 mRNA expression and clinic pathology data(P>0.05).3 Compared with the adjacent non-cancerous group,expression level of MBD4 gene mRNA in GCA group was significantly lower (P=0.015). No significantly difference was found between methylated and unmethylated GCA(P=0.107).4 Compared with the rate of 84%(21/25) in adjacent non-cancerous group, positive expression rate of HMLH1 protein in GCA group was 20%(6/30), significantly lower than the former rate (P=0.000).5 The expression rate of HMLH1 in MBD4 methylated group of 28 tissues is 32%,while the rate in MBD4 unmethylated group of 26 tissues is 69%. They were significantly different (P=0.007).Also,we found negative correlation between HMLH1protain and MBD4.(Pearson R=-0.371) 6 MBD4 mRNA expression level in HMLH1 positive group was 0.533±0.475,compared with 0.627±0.484 in HMLH1 negative group .Also ,the date showed no significantly different .(P=0.676)Conclusions:1 The methylation of MBD4 promoter may be one of the reasons which cause the inactivation of GCA .The methylation of MBD4 promoter may be involved in the early process of GCA.2 The methylation of MBD4 promoter has no correlation with clinical pathology data .3 The depression of HMLH1 maybe another trigger to cause GCA .4 In GCA , promoter methylation of MBD4 gene may be a trigger to cause depression of HMLH1 .