Comparative Studies On The Expression Of P15^INK4b, Cyclind1 And CDK4 Between Cardiac And Distal Gastric Adenocarcinoma

Objective: Over the past several decades, the incidence of gastric cancer has been decreased all over the world with the improvement of living standards and the medical advances, however, the location and histology types of gastric carcinoma have underwent a dramatic shift. The incidence of adenocarcinoma at distal stomach and antrum was decreased, while adenocarcinoma at esophagogastric junction (EGJ, the proximal stomach and distal esophagus) was increased significantly. At the same time, the incidence of esophageal squamous cell carcinoma decreased while that of adenocarcinoma increased. This change has caused widespread concern of scientists home and abroad. Comparative studies on the possible differences in the carcinogenesis and biological behavior between the gastric adenocarcinomas in different subsites were carried out.Adenocarcinoma of esophagogastric junction(AEG) is the adenocarcinoma located around esophagogastric junction(EGJ), including distal esophageal adenocarcinoma and gastric cardia adenocarcinoma. As the specificity of anatomical position and the complexity of histology, there are different classifications on esophagogastric junction adenocarcinoma. Nowadays, Siewert classification is generally accepted and applied. The AEG was classified into three types based on the distance between tumor center and Z line. AEG I is distal esophageal adenocarcinoma, mostly originating in Barrett esophagus; AEG II is the real cardiac adenocarcinoma, the tumor center locates within 1 cm above and 2 cm below the EGJ. AEG III is subcardiac adenocarcinoma. In our country, gastric candiac adenocarcinoma (GCA) has been generally used for Siewert type II and III AEG. Recent years in our country, the incidence of GCA was also found to be increased, which was more obvious in the high incidence area of esophageal and gastric cancer, but it is still not unclear about the causes. Previous study in our lab showed the immunohistochemical pattern of GCA was different from that of distal gastric adenocarcinoma.The abnormality of cell cycle is an important mechanism in carcinogenesis. Cyclin, cyclin-dependent protein kinase (CDK) and CDK inhibitory proteins (CDKI) play important roles in controlling cell cycle transition. p15^INK4b is a member of CDKIs, and the p15 protein encoded by it could compete with Cyclin D1 to combined with CDK4/6, which in turn causes the inhibition of Rb protein phosphorylation as well as the G1 phase arrest of cell cycle. Meanwhile, a variety of evidences showed that the changes of p15^INK4b molecular such as mutation, loss or methylation existed in many human tumors. Statistical study further showed that p15^INK4b gene was inactivated among over 80% of tumor cell strains. As for the gastric carcinoma, it also showed that p15^INK4b gene was related with the tumor growth and lymph node metastasis.In this study, the expressions of p15^INK4b, CyclinD1 and CDK4 in gastric cardia adenocarcinoma and distal gastric carcinoma were comparatively studied using immunohistochemical methods in order to explore the biological specificity of GCA and to evaluate the possible differences of GCA and distal gastric carcinoma in the development and progression,Method: The cases used in this study were the archive tissue blocks in Department of Pathology, the Fourth Hospital, Hebei Medical University in the year 2010. All the specimens were from radical gastroctomy operation for GCA or DCA. Among the cases studied 54 cases were normal gastric mucosa, 54 cases were gastric cardia adenocarcinoma(the tumor center within 1 cm above and 2 cm below the anatomic esophagogastric junction) and the other 26 cases were distal gastric carcinoma. The expressions of p15^INK4b,CyclinD1 and CDK4 were comparatively studied by SP immunohistochemical staining method. The experimental data were statically analyzed with Chi-square test, Fisher's exact test and correlation with SPSS16.0.Results:1 Immunohistochemical staining results of p15^INK4b1.1 Expressions of p15^INK4b in GCA and GDAPositive immunoreaction was located in nucleus and/or cytoplasm. The positive expression rate of p15^INK4b in normal gastric mucosa was 64.8%. The positive expression rate of p15^INK4b in GCA and GDA was 31.5% and 7.7% respectively, which were all significantly lower than that in normal gastric mucosa(P<0.05). Statistical significance was found in the difference of p15^INK4b expression between GCA and GDA(P<0.05).1.2 The clinical pathological significance of p15^INK4b expression in GCA and GDAIn GCA, the positive expression rate of p15^INK4b in well-differentiated group(52.2%) was significantly lower than that in low- differentiated group(16.1%,P<0.05). The positive expression rate of p15^INK4b in no lymph node metastasis group was 75%, which was significantly higher than that in lymph node metastasis group(13.2%, P<0.05). No relationship between positive expression of p15^INK4b in GCA and the age and sex of the patients, size and infiltrating depth of tumor was found(P>0.05).In GDA, the positive expression rate of p15^INK4b in no lymph node metastasis group was 33.3%, which was significantly higher than that in lymph node metastasis group(0, P<0.05). But, there was no relationship between the expression of of p15^INK4b in GDA and the age and sex of the patients, differentiation and infiltrating depth of tumor(P>0.05).Thus, the clinical pathological significance of p15^INK4b expression in GCA and GDA was difference. The positive expression of in GCA was significantly related with differentiation, lymph node metastasis, but only lymph node metastasis was related in GDA.2 Immunohistochemical staining results of CyclinD1 2.1 Expressions of CyclinD1 in GCA and GDAPositive immunohistochemical staining products were located in nuclei. The positive expression was found in 18.5% cases of normal gastric mucosa, which was significantly lower than that in gastric adenocarcinoma(42.5%, P<0.05).There is no significant difference in the expression of CyclinD1 among gastric adenocarcinoma of different subsite (GCA: 40.1% vs GDA: 46.2%, P>0.05).2.2 The clinical pathological significance of CyclinD1 expression in GCA and GDAAmong the GCA cases, the immunohistochemical staining results showed that significantly higher CyclinD1 positive expression rate was found in well-differentiated cases (74.0% vs 16.1% in low-differentiated cases,P<0.05). The positive expression of CyclinD1 in GCA was not related with age and sex of the patients, infiltrating depth of tumor(P>0.05).In the GCA cases, the positive Cyclin D1 expression rate in cases with lymph node metastasis was significantly higher than that without(60% vs 0%, respectively, P<0.05). No statistically significant differences were found in CyclinD1 expression among cases with different age, sex, differentiation, infiltrating depth in GDA(P>0.05).The results showed that the positive expression of CyclinD1 in GCA was significantly related with differentiation and lymph node metastasis. While there was no such correlation in GDA.3 Immunohistochemical staining results of CDK43.1 Expressions of CDK4 in GCA and GDAPositive immunohistochemical staining products were located in nucleus and/or cytoplasm. Among the 54 cases of GCA, 32 cases showed positive CDK4 expression (59.3%), which was slightly lower than that in GDA(P>0.05). The positive expression rate of CDK4 in normal gastric mucosa was 31.5% and 7.7% respectively, which were all significantly lower than that in GCA and GDA (P<0.05).3.2 The clinical pathological significance of CDK4 expression in GCA and GDAIn the GCA cases, the immunohistochemical staining results showed that the positive expression of CDK4 was significantly lower in well-differentiated group(69.6%) than that in low-differentiated group(93.5%,P<0.05). It was lower in cases without lymph node metastasis than that in cases with lymph node metastasis(94.7%,P<0.05). The positive expression of CDK4 in GCA was not related with age and sex the patients, size and infiltrating depth of tumor(P>0.05).In GDA, there was no relationship between the expression of CDK4 and the age and sex of the patients, differentiation, size and infiltrating depth of tumor and lymph node metastasis(P>0.05).The results shows that the positive expression of CDK4 in GCA was significantly related with differentiation and lymph node metastasis. While there was no such relation in GDA. 4 Correlation among p15^INK4b,CyclinD1 and CDK4 expression in GCA and GDANegative correlation could be found between p15^INK4b and CyclinD1 in GCA and GDA(P<0.05). There was negative correlation between expression of p15^INK4b and CDK4 in GCA and GDA(P<0.05), but positive correlation could be found between CyclinD1 and CDK4 in GCA and GDA(P>0.05).Conclusions:1. The significantly lower expression of p15^INK4b was observed both in GCA and GDA as compared with that in normal gastric mucosa. But the expression of CyclinD1 and CDK4 in GCA and DGA was significantly higher that in normal gastric mucosa.2. The expression of p15^INK4b in GCA was higher than that in GDA, but no significant differences could be found in the expression of CyclinD1 and CDK4 between the two tumors.3.In GCA cases, the expression of p15^INK4b and CDK4 was respectively related with differentiation and lymph node metastasis, but CyclinD1 was related with lymph node metastasis. While in GDA, the expression of p15^INK4b and CyclinD1 were related with lymph node metastasis. The results suggested that the expression and clinical pathological significance of p15^INK4b, CyclinD1 and CDK4 in GCA and GDA were different, the p15^INK4b-CyclinD1-CDK4 pathway may play more important role in the carcinogenesis of GCA.