Prognostic significance of the combined expression of neutral endopeptidase and dipeptidyl peptidase IV in intrahepatic cholangiocarcinoma patients after surgery resection

AIM The aim of this study was to investigate the relationship between the expression of neutral endopeptidase (NEP) and dipeptidyl peptidase IV (DPP IV) proteins, and the clinical significance of the two proteins in patients with intrahepatic cholangiocarcinomas (IHCC). METHODS Expression patterns and subcellular localizations of NEP and DPP IV proteins in 186 primary IHCC and 60 noncancerous liver tissue specimens were detected by immunohistochemistry. RESULTS Both the expression of NEP and DPP IV proteins in IHCC tissues were significantly higher than those in noncancerous liver tissues (both P<0.001). Of 186 patients with IHCC, 128 (68.82%) highly expressed both NEP and DPP IV proteins. In addition, the coexpression of NEP and DPP IV proteins was significantly associated with advanced tumor stage (P=0.009), positive lymph node metastasis (P=0.016) and distant metastasis (P=0.013), and the presence of recurrence (P=0.027). Moreover, Kaplan-Meier analysis showed that IHCC patients with high NEP expression, high DPP IV expression, and combined overexpression of NEP and DPP IV proteins all had poorer overall survival and early recurrence after surgery. Furthermore, Cox analysis suggested that NEP expression, DPP IV expression, and combined expression of NEP and DPP IV proteins were all independent prognostic markers for overall survival and recurrence-free survival in patients with IHCC. CONCLUSION Our data suggest, for the first time, that both the expression of NEP and DPP IV proteins may be upregulated in human IHCC tissues and the combined expression of NEP and DPP IV proteins may play important roles in progression and prognosis of patients with IHCC.