The differential expression of cytosolic carbonic anhydrase in human hepatocellular carcinoma.

Cytosolic carbonic anhydrases (CAs), including CAI, CAII and CAIII are present in normal hepatocytes. This study was aimed to investigate the expression status of CAs in hepatocellular carcinomas (HCC) and cholangiocellular carcinoma (CCC) and the role of tumor progression. The activity, protein expression pattern and messenger RNA of cytosolic CA were analyzed by CA activity analysis, immunoblot and RT-PCR in 60 human hepatocellular carcinomas and 10 human cholangiocellular carcinoma surgical specimens. The in situ distribution of CAI, CAII and CAIII in hepatocellular carcinomas tissues were analyzed by immunohistochemistry. The result showed that in each of 60 human hepatocellular carcinomas and 10 cholangiocellular carcinoma, CA activity and protein expression in tumor area was significantly lower than that of paired adjacent normal tissues (P < 0.01), and mRNA expressions in tumor areas were also reduced (P < 0.001). Furthermore, the immunohistochemical studies have further confirmed this reduction of CAI, CAII and CAIII protein expression in tumor areas. There was a statistically significant reduction in the expression of cytosolic CAII in poorly differentiated cancer (P < 0.001). Furthermore, the reduction of CAI, CAII and CAIII in HCC tumor areas was also revealed in this study and this reduction might promote tumor cell motility and contribute to tumor growth and metastasis.