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

Huaqing Cui,Qingming Wang,Feng Wu,Guocai Fan,Yanling Sun

doi:10.1186/1471-2407-10-356

Abstract

BackgroundHepatocellular 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.MethodsRecombinant 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.ResultsWe 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.ConclusionsThis 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.

Highlights

Hepatocellular carcinoma (HCC) is one of the world’s leading causes of death among cancer patients
This result was further confirmed by immunofluorescent staining the cells that Heterogeneous nuclear ribonucleoprotein (hnRNP) hepatocellular carcinoma (A2/B1) was mainly localized in the nuclei of HepG2 cells (Figure 1E)
We found that hnRNP A2/B1 expression at transcriptional and translational level was up-regulated in the proliferative HCC cells rather than in the quiescent hepatocytes, and this agrees with the fact that the overexpression of hnRNP A2/B1 is required for cell proliferation

Summary

Introduction

Hepatocellular carcinoma (HCC) is one of the world’s leading causes of death among cancer patients. We screened a single-chain antibody (scFv) N14, which could recognize human HepG2 HCC cells but not human non-cancerous liver LO2 cells. The antigen it recognized in the cells remained unknown. Hepatocellular carcinoma (HCC) is one of the world’s most common types of cancer, and an estimated 500,000 to 1,000,000 patients die of HCC each year [1]. We have been working with screening human HCC cell specific antibodies in order to deliver some efficient biomarkers for the prevention, diagnosis and treatment of HCC.

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Results

Conclusion