Fatty acid-binding protein 5 promotes cell proliferation and invasion in human intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is a rare primary malignant liver tumor with an extremely poor prognosis. Recently its incidence has increased, however, little attention has been directed to factors related to its molecular carcinogenesis, including oncogenes, tumor suppressor genes and cell cycle-related proteins. ICC is generally characterized by strong proliferation, invasion and early metastasis. These biological behaviors of ICC, with respect to the genetic and molecular aspects, remain to be clarified. In this study, we performed a proteomic analysis to identify the proteomic alterations associated with carcinogenesis of ICC. Protein expression profiles of sixteen cases of ICC were compared with those of adjacent non-involved bile duct tissue. Among the 151 protein spots that showed a statistically significant expression difference (P<0.05), there were 50 spots with significantly increased intensity (3-fold increase) and 17 spots with decreased intensity (3-fold decrease) in cancerous tissues. Of these, increased expression of fatty acid-binding protein 5 (FABP5) was further confirmed by western blot analysis and immunohistochemical analysis. Immunohistochemical analysis of FABP5 expression in tumor specimens obtained from 43 patients with mass-forming (MF) type ICC showed a positive correlation of FABP5 immunoreactivity with tumor size (P=0.047), lymph node metastasis (P=0.013), angioinvasion (P=0.032) and staging (P=0.007). In addition, silencing FABP5 with short hairpin RNA (shRNA) suppressed cell proliferation and invasiveness in HuCCT1 cells, and conversely, overexpression of FABP5 in FABP5-negative Hep3B cells increased cell proliferation and invasiveness. Our study shows that FABP5 is significantly overexpressed in ICC combined lymph node metastasis and is involved in cell proliferation and invasion in vitro. Our data suggest that FABP5 may be associated with tumor progression in ICC.