Elevated keratin 18 protein expression indicates a favorable prognosis in patients with breast cancer.

This study was performed to determine if keratin 18 (K18) has prognostic significance in breast cancer cell lines and patients with breast carcinoma. Paraffin sections of primary breast carcinoma tumors and human breast carcinoma cell lines were examined for K18 expression by immunohistochemical staining with the monoclonal antibody CK2. K18 protein expression was low in highly metastatic cell lines and, conversely, high in weakly metastatic cell lines, suggesting that it may function as a prognostic indicator. K18 expression was consequently examined in 134 patients with breast cancer. The staining intensity was compared with clinicopathological variables and follow-up data spanning 8 years. A definitive positive staining was observed in 22 (16.4%) women. The mortality rate was 4. 5% in the K18-positive group and 44.6% in the K18-negative group. Multivariate analysis found K18 expression to be an independent and significant predictor for overall survival.