The Expression and Role of NADPH Oxidase 2 in Colon Cancer

Background/Aim: Recent studies have reported that nicotinamide adenine dinucleotide phosphate oxidases (NOXs) are expressed in various cancers and play important roles in tumor progression. However, no studies have examined the expression and role of NOX2 in colon cancer. The aim of this study is to investigate the pathophysiological roles of NOX2 in colon cancer patients and cell lines. Patients and Methods: One-hundred and sixteen primary colon cancer samples of patients who underwent radical resection for locally advanced colon cancer were used for immunohistochemistry of NOX2 protein. The relationship between NOX2 expression and clinicopathological factors was assessed and the prognostic significance of NOX2 expression was evaluated in colon cancer patients. NOX2 siRNA transfection experiments were performed using two colon cancer cell lines (HCT116 and RKO) to analyze impact of NOX2 expression on cellular physiological functions. Results: The expression of NOX2 protein noncancerous tissue was scarcely observed, and 45 samples (38.8%) showed positively stained NOX2 expression cancer tissue. There were no clinicopathological factors significantly associated with NOX2 expression. The 5-year recurrence-free survival rate of the NOX2 positive group was significantly lower than that of the NOX2 negative group (61.1% vs. 79.3%, p=0.029). NOX2 depletion significantly inhibited cell proliferation with G1 arrest, and motility in two cell lines. Conclusion: NOX2 expression level has close association with the prognosis of colon cancer patients and physiological functions of colon cancer cells. NOX2 may be a useful prognostic biomarker for colon cancer patients.