Expression of aquaporin-1 is a poor prognostic factor for stage II and III colon cancer

Colorectal cancer is a major cause of cancer-related mortality worldwide, with a high incidence of recurrence following curative resection, particularly among patients with stage II and III disease. There is therefore a need for novel prognostic biomarkers for advanced colon cancer and it was recently reported that aquaporin-1 (AQP1) may be associated with aggressive characteristics of colon cancer cells in experimental data. The association of clinicopathological findings with AQP1 expression was evaluated by tissue microarray (TMA) analysis, to determine whether AQP1 is a prognostic biomarker for colon cancer. A total of 120 consecutive stage II and III colon cancer patients (51 with stage II and 69 with stage III) who underwent curative resection between 1997 and 2008 were analyzed. The TMA was prepared from archival formalin-fixed, paraffin-embedded tissue blocks. Immunostaining was graded semi-quantitatively by considering the staining intensity and the percentage of positive tumor cells. Results showed the AQP1-positive rate to be 35.8%. The expression of AQP1 was associated with lymph node metastasis, lymphovascular and vascular invasion. The 5-year survival rate of the AQP1-positive and -negative groups was 73.7 and 87.9%, respectively. The survival rate of the positive group was significantly lower compared to that of the negative group (P=0.030). Furthermore, the expression of AQP1 was an independent poor prognostic factor according to the multivariate analysis. Therefore, AQP1 may be a promising candidate as a prognostic biomarker for colon cancer.