Hypermethylation Status And Protein Expression Of E-cadherin, P16 In GISTs

Background and Objective:Gastrointestinal stromal tumors(GISTs)are the most common mesenchymal tumors of the gastrointestinal tract,have possibility of recurrence or metastasis.Recent investigations have demonstrated that hypermethylation is a frequent mechanism for silencing tumor suppressor genes and may serve as the epigenetic biomarker for both diagnosis and prognosis of human tumors.E-cadherin,p16 are all acts as suppressor of tumour.The aim of study was to investigate the hypermethylation status of CpG-island in E-cadherin(CDH1),p16 promoter region,protein expression and to analyze their role in GISTs.Methods:56 cases of surgically resected GISTs,among them 20 cases with fresh tissue, were collected from 2003 to 2006.The routine H&E-stained sections and CD117,CD34,SMA, S-100-immunoreactive were reviewed to verify the morphologic diagnosis.Hypermethylation status of the E-cadherin,p16 promoter region was analyzed by methylation specific polymerase chain reaction(MSP).Study for the expression of p16,E-cadherin by immunohistochemistry. Western-blot analysis was used to detect the expression of E-cadherin and Dysadherin.Statistical analysis was performed using the SPSS 11.5 software.Results:1.The frequency of E-cadherin(CDH1)gene hypermethylation was 32%(18 of 56 cases) in GISTs.The rate was 9%(1 of 11 cases),21%(4 of 19 cases),41.6%(5 of 12),and 57%(8 of 14)for very low risk,low risk,intermediate risk,and high risk GISTs;p16 hypermethylation was found in 19 of 56(34%)cases.The rate was 0%(0 of 11 cases),16%(3 of 19 cases),50%(6 of 12),and 71%(10 of 14)for very low risk,low risk,intermediate risk,and high risk GISTs. Statistical analysis indicated that there was significant association of E-cadherin and/or p16 hypermethylation with tumor risk of malignant behavior and site(P＜0.05),the rate of hypermethylation(E-cadherin and/or p16)achieved(23/56,41%).2.There was no association of E-cadherin and/or p16 hypermethylation with age and sex, histologic subtype(P＞0.05).3.p16 hypermethylation was found in 19 of 56(34%)cases,p16 protein underexpression rates was 44.6%(25/56).There was significance difference between the expression of p16 and grade(P＜0.05).p16 gene 5'CpG island hypermethylation maybe induce p16 protein inactivation. p16 gene hypermethylation was one of the important event in the development of GISTs.4.There did not exist any relationship between expression of p16 protein and sex,age, histologic subtype as well as location of tumor(P＞0.05). 5.There was higher Dysadherin expression in different GISTs risk of malignant behavior. Expression was significantly correlated with GISTs grade(P＜0.05).There was only weak E-cadherin expression in GISTs.Conclusion:1.Combined detection of E-cadherin and p16 promoter hypermethylation maybe a helpful method for GISTs risk assessment,and may shed light on new therapeutic option to treat GISTs.2.p16 down-regulation is implied in GISTs progression.A cutoff at 50%positivity was used for prognostic analysis,and p16 promoter methylation is one of its causes.Furthermore,our results indicate the immunohistochemical assessment of p16 status as a possible method of GISTs prognostication in the immediate future.3.The weak E-cadherin expression in GISTs maybe an important reason for recurrence and metastatic in GISTs.Dysadherin expression associated with GISTs risk grade,which was a possible mechanism of E-cd decreased expression,and may be become a desired tumor marker of prognostic in GISTs.