Abstract: Objective:To determine whether CD 46, CD 55, and CD 59are differentially expressed in neoplastic and adjacent nor -mal colon tissues and to investigate their influence on clinicopathologic variables. Methods:Immunohistochemistry (a modified two-step method) was used to detect the expression of CD 46, CD 55, and CD 59in a tissue microarray of 121 cases of colon cancer and corre -sponding adjacent non- tumor tissues with detailed clinical information, including gender, age, differentiation, TNM classification, tu -mor location, and tumor histotype. The colon carcinoma microarray was constructed from patients' samples obtained from the Depart-ment of Gastrointestinal Surgery of Xijing Hospital of the Fourth Military Medical University between October 2004and June 2006. The correlation between expression and clinicopathologic features was analyzed.Results: The expression levels of CD 46, CD 55, and CD59were significantly higher in colon cancer tissues compared with those in normal adjacent colon tissues (P<0.001). CD46expres -sion was not related to any specific patient characteristics, such as age, gender, grade of tumor differentiation, or TNM classification ( P>0.05). The expression levels of CD55and CD59were correlated with the grade of colon cancer differentiation. Low levels of CD55and CD59were detected in cancer cells of highly differentiated cancer, whereas stronger staining for CD 55and CD59was mainly observed in cancer cells of moderately and poorly differentiated colon cancer ( P<0.05). In addition, the expression levels of CD 55and CD59 were higher in stages III and IV colon cancer than those in stages I and II according to TNM classification ( P<0.05). Conclusion: CD46, CD 55, and CD 59are up-regulated in colon cancer. Specifically, CD55and CD59are of clinical relevance to differentiation and TNM staging of colon cancer, and their expression might be closely related to clinical biological behaviors.