Immunohistochemical analysis of the mTOR pathway in intrahepatic cholangiocarcinoma

Abstract

The aim of the study was to evaluate the expression of activated mammalian rapamycin (mTOR) and its downstream effectors, phosphorylated p70 ribosomal protein S6 kinase (p70S6K) and eukaryotic initiation factor 4E-binding protein 1 (4EBP1), in intrahepatic cholangiocarcinomas (ICC), in order to strengthen the rationale for targeted therapy using mTOR inhibitors in patients with ICC. p-mTOR (Ser 2448), p-4EBP1 (Thr 70) and p-p70S6K (Thr 389) were detected in 77 primary ICC tumors by immunohistochemistry. High levels of p-mTOR, p-4EBP1 and p-p70S6K expression were defined in 48.1% (37/77), 50.6% (39/77) and 51.9% (40/77) of all tumors, respectively. No significant correlation was observed between mTOR pathway proteins overexpression with clinicopathological characteristics and patient's prognosis, except that high p-p70S6K expression correlated with the poorly differentiated subtype, and high expression of p-4EBP1 predicted poor prognosis in ICC patients and retained an independent prognostic factor in multivariate analysis. In conclusion, our results showed high prevalence of activation of mTOR pathway in ICC tumors, suggesting that a high proportion of ICC patients might benefit from mTOR pathway targeted therapies. In addition, p-4EBP1 phosphorylation at Thr 70 could be a useful prognostic biomarker for ICC patients.