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

Aims 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. Methods and results 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. Conclusions OV-6 is not unique to the hepatobiliary system, and may be a novel prognostic marker in colorectal cancer.