Monoamine Oxidase B Expression is a Prognostic Factor in Patients With Colorectal Cancer

Monoamine oxidases (MAOs) produce hydrogen peroxide through an oxidative reaction and mediate the production of reactive oxygen species. MAO expression has been correlated with the prognosis in several tumor types. Accordingly, we aimed to evaluate MAOA and MAOB expression in patients with colorectal cancer (CRC) using immunohistochemistry as well as to assess their clinicopathologic behavior and prognostic significance. High MAOB expression (169 patients, 51.7%) was significantly associated with poor tumor differentiation, high pT classification, presence of lymphovascular invasion, lymph node metastasis, distant metastasis, and high MAOA expression. MAOA expression (245 patients, 74.9%) was not significantly correlated with any other clinicopathologic factors. Patients with high MAOB expression had significantly worse overall survival than those with low MAOB expression [hazard ratio (HR)=2.974; 95% CI: 1.855-4.767; P<0.001]. MAOA expression was not significantly correlated with overall survival in patients with CRC. Further, high MAOB expression (HR=1.680; 95% CI: 1.014-2.784; P=0.044) was an independent poor prognostic factor in patients with CRC. In conclusion, high MAOB expression is correlated with aggressive clinicopathologic behavior and may be a poor prognostic marker in patients with CRC.