Overexpression of the X-linked Ribosomal Protein S4 Predicts Poor Prognosis in Patients with Intrahepatic Cholangiocarcinoma.

X-linked ribosomal protein S4 (RPS4X) has previously been reported to be associated with cisplatin resistance and clinical outcome in bladder and ovarian cancer. However, the value of RPS4X as a diagnostic and prognostic marker in intrahepatic cholangiocarcinoma (ICC) has not yet been investigated. The present study evaluated the expression pattern, and diagnostic and prognostic value of RPS4X in patients with ICC. Retrospective analysis was performed for a total of 201 patients with intrahepatic cholangiocarcinoma, and 8 patients with inflammation of the bile duct. Immunohistochemistry was performed using tissue microarrays to characterize the expression profile of RPS4X. Receiver operating characteristic (ROC) curves, the Kaplan-Meier estimator and Cox regression analysis were applied to evaluate the potential diagnostic and prognostic value of RPS4X in ICC. RPS4X was significantly upregulated in ICC tissues compared with the inflamed bile duct tissues. When differentiating ICC from normal controls, ROC analysis of RPS4X gave an area under the curve value of 0.9030 (sensitivity, 82.59%; specificity, 100%). RPS4X expression was significantly positively correlated with serum alkaline phosphatase levels. Survival analysis demonstrated that RPS4X expression levels were an independent prognostic factor for overall survival. Therefore, RPS4X expression levels may serve as a novel diagnostic and prognostic marker in ICC.