Expression of OV‐6 in primary colorectal cancer and rectal cancer with preoperative chemoradiotherapy: a clinicopathological study

Abstract

OV-6 is among the best available markers of liver stem cells. The aim of this study was to investigate OV-6 expression and its clinical implications in colorectal cancer. Expression of OV-6 and its clinical implications were investigated in 94 patients with American Joint Committee on Cancer (AJCC) stage I-III primary colorectal cancer and in 37 rectal cancer patients who had received preoperative chemoradiotherapy. The two main expression patterns of OV-6 were cytoplasmic and membranous. Overexpression of OV-6, which was identified on the basis of overall staining intensity, was associated with perineural invasion, lymphovascular invasion, and early relapses. Membranous OV-6 overexpression was also significantly associated with depth of tumour invasion, AJCC stage, lymphovascular and perineural invasion, and postoperative early relapse. Disease-free survival and overall survival were significantly poorer in patients with high overall OV-6 expression than in those with low overall OV-6 expression (P=0.015 and P=0.029, respectively), and significantly poorer in patients with high membranous OV-6 expression than in those with low membranous OV-6 expression (P<0.001 and P<0.001, respectively). Membranous OV-6 expression was a more reliable prognostic marker than overall expression. OV-6 is not unique to the hepatobiliary system, and may be a novel prognostic marker in colorectal cancer.