Comparative Study on Expression of β-catenin in Hunman Advanced Colorectal Carcinoma and Metastatic Lymph Nodes

Objective To investigate the expression of β-catenin mRNA and protein in hunman advanced colorectal cancer and their metastatic lymph nodes,discuss the correlation between the expression of β-catenin and the biological behaviour of colorectal cancer,and explore a new possible target on molecular level to diagnose and treat colorectal cancer.Methods The methods of immunohistochemical staining,semiquantitative RT-PCR and western blot were used to detect and compare the expressions of β-cat mRNA and protein in 45 cases of human advanced colorectal cancer and their metastatic lymph nodes.And the mechanism by wich β-cat reexpress in metastatic lymph nodes of colorectal cancer was explored.Results The re-expression level of β-cat in metastatic lymph nodes was closely related to the differentiating degree and histological type of tumor.(1) Immunohistochemical results:the abnormal expression rate of β-cat was 80%(36/45) in 45 primary tumors of human advanced colorectal cancers,and the re-expression rate of β-cat in metastatic lymph nodes was 40%(18/45) .The re-expression rate ofβ-cat in well-differentiated colorectal cancer was significantly higher than that in poorly differentiated,54.2%(13/24) versus 23.8%(5/21) .The re-expression rate of β-cat in metastatic lymph nodes of tubular or papillary adenocarcinoma and mucinous adenocarcinoma was 35.7%(10/28) and 47.1%(8/17) ,respectively.The re-expression rate of β-cat in metastatic lymph nodes was independent with the tumor location,invasion depth,and the gender and age of patients.(2) RT-PCR results:There were different expression levels ofβ-cat mRNA in 45 cases of hunman advanced colorectal cancers and their metastatic lymph nodes.The relative expression value of β-cat mRNA in colorectal cancers was(0.724±0.006) ,which was significantly lower than that in the normal colorectal mucosa(0.785±0.017,t=21.066,P0.01) .The relative expression value of β-cat mRNA in metastatic lymph nodes was significantly higher than that in primarily focus,and significantly lower than that in normal colorectal mucosa.At the same time,the expressions ofβ-cat mRNA in metastatic lymph nodes were significantly correlated with the differentiating degree and histological type of tumor.(3) Western-blot results:There wereβ-cat protein expression in all the 25 cases of normal colorectal mucosa,while the different levels of β-cat protein expression were detected in 41 cases of primary tumors and the corresponding metastatic lymph nodes of total 45 cases.The β-cat protein expression was not detected in the primary tumors of 4 cases of colorectal cancer,but was detected in the metastatic lymph nodes of one of the four cases of colorectal cancer.The relative strength of β-cat protein in primary tumors was 6～108(54.3±38.1) in 41 cases of colorectal cancer,which was significantly lower than that in normal colorectal mucous membrane 15～172(95.4±49.8) .The β-cat protein expression in metastatic lymph nodes was significantly higher than that in primary focus,but was lower than in the normal colorectal mucosa.In metastatic lymph nodes from well-differentiated and moderately differentiated primary cancers,the relative intensity of β-cat protein expression were significantly higher than that from poorly differentiated cancers.Theβ-cat protein expression in tubular or papillary adenocarcinoma was significantly higher than that in mucinous adenocarcinoma.Conclusions In the development and progression of colorectal cancer,there is a certain changing characteristics of β-cat expression in the gene and protein levels.The characteristics make β-cat possible to become a new target for the diagnosis and treatment of colorectal cancer.