AC133 expression associated with poor prognosis in stage II colorectal cancer

Identification of high-risk prognostic markers for stage II colorectal cancer (CRC) is currently a big challenge. CD133 is one of the most commonly used CRC stem cell markers. However, its specificity is controversial. Recent studies have demonstrated that the AC133 epitope of CD133, not the CD133 protein, is responsible for cancer stem cell identification. The aim of this study was to investigate the clinical significance of AC133 expression in stage II CRC. Two antibodies against CD133, including AC133 and Ab19898, were compared for their expression characteristics. AC133 was chosen for further immunohistochemical assessment on 176 stage II CRC primary tumors with at least 12 examined lymph nodes. The cutoff value for positive rate of AC133 expression was determined by ROC curve analysis. AC133 was analyzed for correlations with clinicopathological and prognostic parameters. The results indicated that AC133 was negative in adjacent noncancerous colorectal mucosa while positive in 116 cases (65.9 %) of primary tumors. AC133 expression was significantly correlated with preoperative serum carcinoembryonic antigen level (p = 0.006) and tumor differentiation grade (p = 0.019). Furthermore, high AC133 expression was identified as a significant predictor for poor disease-free survival and overall survival at both univariate (p = 0.009, 0.013, respectively) and multivariate levels (p = 0.022, 0.026, respectively). Our data suggest that AC133 is an independent adverse prognostic factor and a potential marker for survival classification in stage II CRC patients.