Upregulated FFAR4 correlates with the epithelial-mesenchymal transition and an unfavorable prognosis in human cholangiocarcinoma

BACKGROUND: Free fatty acid receptor 4 (FFAR4) is associated with the epithelial mesenchymal transition (EMT) and is involved in the progression of several types of cancer. However, the role of FFAR4 in cholangiocarcinoma (CCA) remains unclear. OBJECTIVE: The present study evaluated the diagnosis and prognosis of CCA using FFAR4 as a biomarker. METHODS: Immunohistochemistry was employed to detect expression of FFAR4 in 98 samples of CCA tissues and adjacent tissues. In addition, expression of E-cadherin, vimentin, Snail-1, CK7 and CK19 in the 98 samples of CCA tissues was detected, and relationships with FFAR4 were analyzed. Correlation between FFAR4 and clinical pathological factors and prognosis was also analyzed. RESULTS: FFAR4 was highly expressed in 72.4% (71/98) of CCA tissues and 29.6% (29/98) of adjacent tissues, with a statistically significant difference between the two tissue types (P < 0.05). A negative correlation between high expression FFAR4 and E-cadherin expression in CCA tissues was also observed (r = -0.445, P < 0.001), and high expression of FFAR4 was positively correlated with vimentin (r = 0.354, P < 0.001), Snail-1(r = 0.496, P < 0.001), CK7(r = 0.494, P < 0.001) and CK19 (r = 0.532, P < 0.001). Moreover, the degree of FFAR4 expression was associated with aggressive clinicopathological characteristics, such as histological grade, perineural invasion (PNI), lymph node metastasis (LNM), advanced TNM stage and preoperative serum CA19-9 level (P < 0.05). In terms of prognosis, CCA patients with high FFAR4 expression showed shorter disease-free survival (DRS) (P < 0.05) and overall survival (OS) (P < 0.05) than did patients with low FFAR4 expression. CONCLUSIONS: FFAR4 overexpression may mediate the process of CCA EMT. In addition, FFAR4 is promising as a new diagnostic molecule and therapeutic target for CCA.