Immunogenicity of Ra1A and its tissue-specific expression in hepatocellular carcinoma

In order to understand the immunogenicity of a tumor-associated antigen (TAA), Ras family small GTP binding protein (Ra1A) in hepatocellular carcinoma (HCC), autoantibody responses to RalA were evaluated by enzyme-linked immunosorbent assay (ELISA), Western blotting and indirect immunofluorescence assay in sera from patients with HCC and sera from normal individuals. Immunohistochemistry (IHC) study with tissue array slides was also performed to analyze protein expression profiles of RalA in HCC and control tissues. This study demonstrated that RalA had a relative higher frequency of autoantibody response in HCC (20.1%) compared to liver cirrhosis (3.3%), chronic hepatitis (0%), and normal individuals sera (0%). RalA also showed a stepwise increased expression from normal liver tissues (26.7%), liver cirrhosis tissues (45.0%) to HCC tissues (63.3%). Sensitivity and specificity of anti-RalA antibody in detection of HCC was 20.1% and 99.3%, respectively. The data suggested that RalA might contribute to liver malignant transformation, and could be used as a potential tumor marker in HCC detection.