Identification of novel candidate tumour marker genes for intrahepatic cholangiocarcinoma☆

Background/Aims

Specific markers are required for early detection and diagnosis of intrahepatic cholangiocarcinoma (ICC); however, the tumour markers currently in use are not specific for ICC.

Methods

We compared an ICC cDNA library with that of hepatocellular carcinoma (HCC) by serial analysis of gene expression (SAGE). The expression patterns in each were confirmed by quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR), immunoblotting and immunohistochemical analysis of 74 samples including 16 ICC samples.

Results

A comparison of the two libraries revealed distinct gene expression patterns for each type of liver cancer. In addition to the known tumour markers, we detected nine novel genes associated with ICC. By comparing the mean transcript abundance in the ICC library with those in other libraries, including gastric, colon, prostate and breast cancer, together with our RT-PCR results, we identified three genes as specific markers of ICC: biglycan, insulin-like growth factor-binding protein 5 and claudin-4. Immunoblotting and immunohistochemical analyses showed that claudin-4 was highly expressed in ICC. Moreover, discrimination analysis revealed that a combination of these genes could be used to distinguish ICC from HCC or metastatic adenocarcinoma.

Conclusions

We identified novel marker genes of ICC that are potentially useful for the diagnosis of liver cancer.

Abbreviations: ICC, intrahepatic cholangiocarcinoma, HCC, hepatocellular carcinoma, AFP, alpha-foetoprotein, KRT, keratin, CEA, carcinoembryonic antigen, CA19-9, carbohydrate antigen 19-9, SAGE, serial analysis of gene expression, HBV, hepatitis B virus, HCV, hepatitis C virus, NL, normal liver, CLD, chronic liver disease, RT-PCR, reverse transcriptase-polymerase chain reaction, polyA-RNA, polyadenylated RNA, mRNA, messenger RNA, GAPDH, glyceraldehyde-3-phosphate dehydrogenase, CITED4, Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 4, GSTP1, glutathione-S-transferase pi, BGN, biglycan, IGFBP5, insulin-like growth factor-binding protein 5, CLDN4, claudin-4, PFKP, platelet type phosphofructokinase, TM4SF1, transmembrane 4 L six family member 1, CAPN1, calpain 1 (μ/l) large subunit, CLDN10, claudin-10, S100A6, S100 calcium-binding protein A6, Wnt, wingless-type MMTV integration site, TGF-beta, transforming growth factor-beta

Keywords: Differential diagnosis, Hepatocellular carcinoma, Intrahepatic cholangiocarcinoma, SAGE