Up-regulation and subcellular localization of hnRNP A2/B1 in the development of hepatocellular carcinoma

• Published in: BMC cancer Vol. 10; no. 1; p. 356
• Main Authors: Cui, Huaqing, Wu, Feng, Sun, Yanling, Fan, Guocai, Wang, Qingming
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 06.07.2010; BioMed Central; BMC
• Subjects: Amino Acid Sequence; Animals; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Blotting, Western; Carcinoma, Hepatocellular - genetics; Carcinoma, Hepatocellular - metabolism; Care and treatment; Cell Nucleus - metabolism; Cells, Cultured; Cytoplasm - metabolism; Cytoplasm - pathology; Diagnosis; Female; Fluorescent Antibody Technique; Genetic aspects; Health aspects; Hepatocytes - immunology; Hepatocytes - metabolism; Hepatocytes - pathology; Hepatoma; Heterogeneous-Nuclear Ribonucleoprotein Group A-B - genetics; Heterogeneous-Nuclear Ribonucleoprotein Group A-B - immunology; Heterogeneous-Nuclear Ribonucleoprotein Group A-B - metabolism; Humans; Immunoenzyme Techniques; Immunohistochemistry; Liver - metabolism; Liver - pathology; Liver Neoplasms - genetics; Liver Neoplasms - metabolism; Molecular Sequence Data; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Ribonucleoproteins; Risk factors; RNA, Messenger - genetics; Single-Chain Antibodies - genetics; Single-Chain Antibodies - immunology; Single-Chain Antibodies - isolation & purification; Up-Regulation; China
• ISSN: 1471-2407; 1471-2407
• DOI: 10.1186/1471-2407-10-356

Hepatocellular carcinoma (HCC) is one of the world's leading causes of death among cancer patients. It is important to find a new biomarker that diagnoses HCC and monitors its treatment. In our previous work, we screened a single-chain antibody (scFv) N14, which could specifically recognize human HepG2 HCC cells but not human non-cancerous liver LO2 cells. However, the antigen it recognized in the cells remained unknown. Recombinant scFv N14 antibody was expressed as an active antibody. Using this antibody with a combination of immunological and proteomic approaches, we identified the antigen of scFv N14 antibody as the heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1). The expression of hnRNP A2/B1 in HCC cells was then investigated by semi-quantitative RT-PCR and immunohistochemistry. We found that the up-regulation of hnRNP A2/B1 was measured at both transcriptional and translational levels in rat HCC cells but not in rat hepatic cells. We also found that in various human hepatic tissues, hnRNP A2/B1 was highly expressed in both human hepatitis virus positive liver tissues and human HCC tissues but not in normal liver tissues. Interestingly, we observed that the localization of hnRNP A2/B1 in HCC cells was altered during the development of HCC. In human hepatitis virus infected tissues hnRNP A2/B1 resides exclusively in the nuclei of hepatocytes. However, when the HCC progressed from a well differentiated to a poorly differentiated stage, hnRNP A2/B1 was increasingly localized in the cytoplasm. In contrast, the HCC tissues with hnRNP A2/B1 highly expressed in the nucleus decreased. This work is the first to show that hnRNP A2/B1 is the antigen specifically recognized by the scFv N14 antibody in HCC cells. The over-expression of hnRNP A2/B1 was confirmed in cultured human and rat HCC cell lines, human virus related hepatitis liver tissues and human HCC tissues. The increased localization of hnRNP A2/B1 in the cytoplasm of HCC cells was revealed during the dedifferentiation of hepatocellular carcinoma. Therefore, we suggest that the increased expression and cytoplasmic localization of hnRNP A2/B1 can be used as a diagnostic biomarker to assess the risk of human liver cancer.