Identification of novel immunohistochemical tumor markers for primary hepatocellular carcinoma; clathrin heavy chain and formiminotransferase cyclodeaminase.

UNLABELLED: Early diagnosis of hepatocellular carcinoma (HCC) greatly improves its prognosis. However, the distinction between benign and malignant tumors is often difficult, and novel immunohistochemical markers are necessary. Using agarose two-dimensional fluorescence difference gel electrophoresis, we analyzed HCC tissues from 10 patients. The fluorescence volumes of 48 spots increased and 79 spots decreased in tumor tissues compared with adjacent nontumor tissue, and 83 proteins were identified by mass spectrometry. Immunoblot confirmed that the expression of clathrin heavy chain (CHC) and Ku86 significantly increased, whereas formiminotransferase cyclodeaminase (FTCD), rhodanese, and vinculin decreased in tumor. The protein expression in tumor and nontumor tissues was further evaluated by immunostaining. Interestingly, CHC and FTCD expression was strikingly different between tumor and nontumor tissues. The sensitivity and specificity of individual markers or a combination for the detection of HCC were 51.8% and 95.6% for CHC, 61.4% and 98.5% for FTCD, and 80.7% and 94.1% for CHC+FTCD, respectively. Strikingly, the sensitivity and specificity increased to 86.7% and 95.6% when glypican-3, another potential biomarker for HCC, was used with FTCD. Moreover, CHC and FTCD were useful to distinguish early HCC from benign tumors such as regenerative nodule or focal nodular hyperplasia, because the sensitivity and specificity of the markers are 41.2% and 77.8% for CHC, 44.4% and 80.0% for FTCD, which is comparable with those of glypican-3 (33.3% and 100%). The sensitivity significantly increased by combination of these markers, 72.2% for CHC+FTCD, and 61.1% for CHC+glypican-3 and FTCD+glypican-3, as 44.4% of glypican-3 negative early HCC were able to be detected by either CHC or FTCD staining.
CONCLUSION: Immunostaining of CHC and FTCD could make substantial contributions to the early diagnosis of HCC.