[Expression and significance of APC, beta-catenin, C-myc, and Cyclin D1 proteins in colorectal carcinoma]

Abstract

Background & objective: The abnormal oncogenes and antioncogenes in Wnt signaling transduction pathway activate downstream specific target genes, and may play important roles in tumorigenesis and tumor progression. This study was to examine the expression of adenomatous polyposis coli (APC), beta-catenin, C-myc, and Cyclin D1 in different colorectal tissues, and investigate their possible roles in the carcinogenesis of colorectal carcinoma.

Methods: The expression of APC, beta-catenin, C-myc, and Cyclin D1 in 30 specimens of normal colorectal mucosa, 30 specimens of colorectal adenoma, 10 specimens of colorectal adenoma with malignancy, and 50 specimens of colorectal carcinoma was examined by immunohistochemistry. The expression of beta-catenin on cell membrane was regarded as normal, and its expression in cytoplasm and nuclei was defined as ectopic expression.

Results: The positive rate of APC was significantly lower in colorectal carcinoma and colorectal adenoma with malignancy than in colorectal adenoma and normal colorectal mucosa (44.0% and 40.0% vs. 86.7% and 100.0%, P<0.01). The ectopic expression rate of beta-catenin was significantly higher in colorectal carcinoma, colorectal adenoma with malignancy, and colorectal adenoma than in normal colorectal mucosa (62.0%, 50.0%, and 30.0% vs. 0%, P<0.01), and significantly higher in colorectal carcinoma than in colorectal adenoma (P<0.01). The positive rate of C-myc was significantly higher in colorectal carcinoma, colorectal adenoma with malignancy, and colorectal adenoma than in normal colorectal mucosa (56.0%, 60.0%, and 46.7% vs. 0%, P<0.01). The positive rate of Cyclin D1 was significantly higher in colorectal carcinoma, colorectal adenoma with malignancy, and colorectal adenoma than in normal colorectal mucosa (66.0%, 60.0%, and 30.0% vs. 0%,P<0.01), and significantly higher in colorectal carcinoma than in colorectal adenoma (P<0.01). The ectopic expression of beta-catenin was positively correlated to the expression of C-myc and Cyclin D1 (r=0.63,P<0.01; r=0.57, P<0.01), and negatively correlated to the expression of APC (r=-0.39, P<0.05).

Conclusion: The reduced expression of APC, ectopic expression of beta-catenin, overexpression of C-myc and Cyclin D1 exist in colorectal carcinoma, which may play important roles in the carcinogenesis of colorectal carcinoma.