Differential Over Expression Of ERK Regulated By HER2 And RKIP In Adenocarcinoma Of The Esophagogastric Junction And Distal Stomach

Objective: Gastric cancer is one of the most common malignant tumors in our country,the morbidity of gastric cancer accounted for the third place in malignant tumors,and the first place in malignant tumors of digestive tract all over the world.AEJ(Adenocarcinoma of the esophagogastric junction)is a special type of gastric cancer,with 10% ~ 15% incidence of the overall incidence of gastric cancer.Compared to distal gastric adenocarcinoma(DGA),in recent decades,epidemiological studies have shown that the incidence of AEJ appears rising trend gradually in some developed countries like Europe and the United States.Similar changes in high-risk areas of China were also found,but the reasons were still unclear.Tumorigenesis and progression of gastric carcinoma are multistage processes accompanied with changes in gene expression.HER2 is a proto-oncogene,which encodes a molecular weight of 185 across a membrane protein tyrosine kinase receptor and has tyrosine kinase activity.HER2 can form its homologous dimers or heterodimers with other HER family members,leading to downstream PI3K/Akt(phosphatidyl inositol-3 / protein kinase B)and Ras/MAPK(mitogen activated protein kinase)signal transduction pathways activated,thus regulate the process of tumor cell proliferation,differentiation,survival and apoptosis.Many studies have shown that HER2 gene amplification and/or protein overexpression in lots of malignant tumors including breast cancer,gastric cancer,ovarian cancer and adenocarcinoma of lung.At present,there is still a dispute that the relationship of HER2 gene amplification and/or protein overexpression with site,differentiation and lymph node metastasis of gastric cancer.Raf kinase inhibiting Protein(Raf kinase inhibitor Protein)belongs to thePhosphatidyl ethanolamine binding Protein(PEBPs)family.It is a tumor suppressor.RKIP mainly through combined with Raf-1 and restrain the activation,thus affects the dowm stream MEK and ERK activation,then the Raf-1/ MEK/ERK signaling pathway way blocked,Interfering with the process of tumor cell growth,proliferation,differentiation and apoptosis.Recent studies have suggested AEJ tends to have a greater tendency towards deeper wall penetration,more lymph node metastasis,and poorer prognosis than gastric cancer at other sites.It is reported that AEJ might be a special subtype or an independent entity of gastric carcinoma.Therefore,it is important to evaluate the differences between AEJ and DGA of abnormal signal transduction pathway activation caused by gene expression and may reveal unique pathogenesis and pathological characteristics to guide clinical diagnosis and treatment.In this study,we examined the expression of HER2,RKIP,and ERK proteins in AEJ and DGA by immunohistochemistry(IHC).Special attention was given to the differences between AEJ and DGA.Additionally,the potential associations between the expression patterns of the three markers and their associations with the clinico-patholigical features of gastric cancers patients were evaluated.Methods:The expression of HRR2,RKIP and ERK was studied in 30 cases of normal gastric mucosa(NGM),59 cases of adenocarcinoma of the esophagogastric junction(AEJ)and 65 cases of distal gastric adenocarcinoma(DGA)with ElivisionTM plus two-step.The correlation between their expression and the clinical pathological features were analyzed.The experimental data were analyzed with Chi-square test,Fisher's exact test and correlation with statistics software of SPSS16.0 edition.Results: 1 Immunohistochemical staining results of HER2 1.1 Expressions of HER2 in AEJ and DGAThe strong expression rate of HER2 in AEJ and DGA is 23.7% and 7.7% respectively.While the expression of HER2 in all 30 cases of normal gastric mucosa tissues were negative.The strong expression rate of HER2 in AEJ was significantly higher than that in DGA and normal gastric mucosa(P<0.05).1.2 The relationship of HER2 overexpression with the clinical characteristic factorsNo statistically significant relationship was found between HER2 overexpression and the age and gender of the patients,differatiation,size,depth of tumor invasion and lymph node metastasis in both AEJ and DGA(P>0.05).2 Immunohistochemical staining results of RKIP 2.1 Expressions of RKIP in AEJ and DGAThe positive expression rate was 86.7% in normal gastric mucosa tissues,while the positive expression rate were 39.0% and 46.2% in AEJ and DGA respectively,which were all significantly higher than that in normal gastric mucosa(P<0.05).2.2 The relationship of RKIP protein expression with the clinical characteristic factorsAmong the AEJ cases,compared to the well/moderate-differentiated group,the RKIP positive expression rate in poor-differentiated group is lower(57.1% vs 12.5%).Moreover,the positive expression rate was also higher in cases without lymph node metastasis than that in lymph node metastasis group(60.9% vs 25.0%).The differences was statistically significant(P<0.05).There is no correlation between RKIP protein expression and the patient's gender,age,tumor size and depth of tumor invasion.While in DGA,the positive expression of RKIP in well/ moderatedifferentiated group(90.0%)is higher than that in poor-differentiated group(26.7%).It was also higher in cases without lymph node metastasis than that with lymph node metastasis group(71.4% vs 27.0%).The differences were statistically significant(P<0.05).There is no correlation between RKIP protein expression and the patient's gender,age,tumor size and depth of tumor invasion.3 Immunohistochemical staining results of ERK 3.1 Expressions of ERK in AEJ and DGAThe positive expression rate of ERK protein in the normal gastric mucosa is 20%,while the positive expression rate were 54.2% and 55.4% in AEJ and DGA respectively,which were all significantly higher than that in normal gastric mucosa(P<0.05).3.2 The relationship of ERK protein expression with the clinical characteristic factorsAmong the AEJ cases,the positive expression rate of ERK protein in poor-differentiated group was 83.3%,significantly higher than 34.3% in the well/moderate-differentiated group(P<0.05).Infiltrating serous layer set positive expression rate is 63.8%,significantly higher than not infiltrate serous layer group,which positive expression rate is 16.7%(P < 0.05).In lymph node metastasis group,the positive expression rate is 66.7%,obviously higher than that without lymph node metastasis group 34.8%(P < 0.05).ERK protein expression has nothing to do with the patients' gender,age and tumor size(P > 0.05).In DGA,the positive expression rate of ERK protein with lymph node metastasis group was 75.7%,significantly higher than without lymph node metastasis group 28.6%(P<0.05).There is no correlation between ERK protein expression and gender,age,tumor size,differentiation and the depth of tumor invasion(P>0.05).4 The relationship among HER2,RKIP and ERK in AEJ and DGAThere was positive correlation between expression of HER2 and ERK in AEJ(r=0.352,P=0.007).Negative correlation between expression of RKIP and ERK were found in AEJ and DGA(r=-0.521,P=0.000;r=-0.287,P=0.021).There was no correlation could be found between HER2 and ERK in DGA(P>0.05).Conclusions:1 Overexpression of HER2 in AEJ is more common than that in DGA.It is demonstrated that HER2 overexpression may be one of the important factors causing biology characteristic differences in different sites of gastric cancer.2 The significant decrease of RKIP expression were found in AEJ and DGA,however,there was no difference between AEJ and DGA.Moreover,the expression of RKIP was respectively related with differatiation and lymph node metastasis in AEJ and DGA.3 The significant increased of ERK expression was found in AEJ and DGA,but no significant difference was seen between AEJ and DGA.It is suggested that there was a more close correlation between ERK expression and clinico-patholigical features in AEJ than in DGA.4 The over-expression of HER2 and low-expression of RKIP may all regulate MAPK signal pathways in AEJ,however,the low-expression of RKIP was seen mainly in DGA.It is suggested that the regulation of MAPK signaling pathway may be different between AEJ and DGA.