1. ¹Department of Surgery, Graduate School of Medicine and Health Science, Osaka University, Osaka, Japan
2. ²Department of Health Science, Graduate School of Medicine and Health Science, Osaka University, Osaka, Japan
3. ³Department of Molecular Pathology, Graduate School of Medicine and Health Science, Osaka University, Osaka, Japan
4. ⁴DNA Chip Research Inc., Kanagawa, Japan

Correspondence: Dr H Nagano, Department of Surgery, Graduate School of Medicine, Osaka University, 2-2, Yamadaoka E-2, Suita, Osaka 565-0871 Japan. E-mail: hnagano@gesurg.med.osaka-u.ac.jp

Received 5 January 2009; Revised 9 March 2009; Accepted 30 March 2009; Published online 28 April 2009.

Abstract

Type I IFN receptor type 2 (IFNAR2) expression correlates significantly with clinical response to interferon (IFN)-/5-fluorouracil (5-FU) combination therapy for hepatocellular carcinoma (HCC). However, some IFNAR2-positive patients show no response to the therapy. This result suggests the possibility of other factors, which would be responsible for resistance to IFN-/5-FU therapy. The aim of this study was to examine the mechanism of anti-proliferative effects of IFN-/5-FU therapy and search for a biological marker of chemoresistance to such therapy. Gene expression profiling and molecular network analysis were used in the analysis of non-responders and responders with IFNAR2-positive HCC. The Wnt/-catenin signalling pathway contributed to resistance to IFN-/5-FU therapy. Immunohistochemical analysis showed positive epithelial cell adhesion molecule (Ep-CAM) expression, the target molecule of Wnt/-catenin signalling, only in non-responders. In vitro studies showed that activation of Wnt/-catenin signalling by glycogen synthesis kinase-3 inhibitor (6-bromoindirubin-3'-oxime (BIO)) induced chemoresistance to IFN-/5-FU. BrdU-based cell proliferation ELISA and cell cycle analysis showed that concurrent addition of BIO and IFN-/5-FU significantly to hepatoma cell cultures reduced the inhibitory effects of the latter two on DNA synthesis and accumulation of cells in the S-phase. The results indicate that activation of Wnt/-catenin signalling pathway induces chemoresistance to IFN-/5-FU therapy and suggest that Ep-CAM is a potentially useful marker for resistance to such therapy, especially in IFNAR2-positive cases.