Expression of Ang-2/Tie-2 and PI3K/AKT in Colorectal Cancer

Abstract

Purpose: To study the expression of angiogenin-2 (Ang-2) and its receptor Tie-2 in colorectal cancer anddiscuss the possible mechanisms behind this process. Materials and <br/><b>Methods</b>: Using the streptavidin-peroxidase(SP) immunohistochemical method, paraffin sections from 100 colorectal cancer samples and 10 samples fromtumor-adjacent normal tissue (> 2 cm from the edge of the gross tumor) were tested for protein expression ofAng-2, Tie-2, PI3K, and AKT. Reverse transcription-polymerase chain reaction and Western blots were furtherused to measure expression of the 4 genes and proteins in 20 freshly-resected colorectal cancer samples andtumor-adjacent normal tissues. <br/><b>Results</b>: In colorectal cancer tissues, the expression of the Ang-2, Tie-2, PI3K,and AKT genes and their proteins was significantly higher than in tumor-adjacent normal tissues. Proteinexpression in poorly-differentiated adenocarcinoma was higher than that in well and moderately differentiatedadenocarcinoma. According to Duke’s classification, the protein expression in Stages C and D was significantlyhigher than that in Stages A and B. In the group with lymphatic metastasis, the protein expression was higherthan that without lymphatic metastasis. <br/><b>Conclusions</b>: In colorectal cancer, the expression of the Ang-2, Tie-2,PI3K, and AKT genes and their proteins is markedly higher than those in tumor-adjacent normal tissues. Nocorrelation was observed between protein expression and gender, location, or histologic type. Correlations didexist between protein expression and differentiation level, stage of Duke’s classification, and lymphatic metastasis;in colorectal cancer tissues with lower differentiation levels, higher stages of Duke’s classification, and lymphaticmetastasis, the expression of all 4 proteins was higher. The study of their expression patterns and relationshipswith aggression and metastasis will provide a valuable experimental foundation for assessing prognosis andtargeted therapy of colorectal cancer.