Tumor-associated autoantibodies are useful biomarkers in immunodiagnosis of α-fetoprotein-negative hepatocellular carcinoma

Abstract

Aim: To determine the prevalence and diagnostic value of autoantibodies in α-fetoprotein (AFP)-negative hepatocellular carcinoma (HCC).

Methods: Fifty-six serum samples from AFP-negative HCC cases, 86 from AFP-positive HCC cases, 168 from chronic liver disease cases, and 59 from normal human controls were included in this study. Autoantibodies to nucleophosmin (NPM)1, 14-3-3zeta and mouse double minute 2 homolog (MDM2) proteins in AFP-negative HCC serum were evaluated by enzyme-linked immunosorbent assay. Partially positive sera were further evaluated by western blotting. Immunohistochemistry was used to detect the expression of three tumor-associated antigens (TAAs) in AFP-negative HCC and normal control tissues.

Results: The frequency of autoantibodies to the three TAAs in AFP-negative HCC sera was 21.4%, 19.6% and 19.6%, which was significantly higher than in the chronic liver disease cases and normal human controls (P < 0.01) as well as AFP-positive HCC cases. The sensitivity of the three autoantibodies for diagnosis of AFP-negative HCC ranged from 19.6% to 21.4%, and the specificity was approximately 95%. When the three autoantibodies were combined, the sensitivity reached 30.4% and the specificity reached 91.6%.

Conclusion: Autoantibodies to NPM1, 14-3-3zeta and MDM2 may be useful biomarkers for immunodiagnosis of AFP-negative HCC.

Keywords: 14-3-3zeta; Autoantibody; Hepatocellular carcinoma; Immunodiagnosis; Mouse double minute 2 homolog; Nucleophosmin 1; α-fetoprotein.

Figure 1

Western blot analysis of representative sera of three anti-tumor-associated antigens autoantibodies assessed by enzyme-linked immunosorbent assay. Lane 1: The polyclonal anti-NPM1 autoantibody and anti-14-3-3zeta autoantibody were used as positive control; Lanes 2 and 3: Two representative AFP-negative HCC serum samples which were positive in ELISA also had strong reactivity to 14-3-3zeta recombinant protein in western blot analysis; Lanes 4 and 5: Randomly selected chronic liver disease sera and normal human control, respectively, with negative reactivity to 14-3-3zeta recombinant protein. AFP: Alpha fetoprotein; ELISA: Enzyme-linked immunosorbent assay; HCC: Hepatocellular carcinoma.

Figure 2

Analysis to determine the presence or absence of co-expression of antibodies to any combination of two of the three tumor-associated antigens in α fetoprotein-negative hepatocellular carcinoma, α fetoprotein-positive hepatocellular carcinoma, chronic liver disease and normal human control. The height of the bar represents the percentage of sera with co-expression of two antibodies, e.g., NPM1 antibody with 14-3-3zeta antibody, and NPM1 antibody with MDM2 antibody. AFP: Alpha fetoprotein; CLD: Chronic liver disease; HCC: Hepatocellular carcinoma; NHC: Normal human control; TAAs: Tumor-associated antigens.

Figure 3

Expression of NPM1, 14-3-3zeta and MDM2 in α-fetoprotein-negative hepatocellular carcinoma tissues and normal hepatic tissues by immunohistochemistry. The three polyclonal anti-TAAs antibodies were used as a primary antibody to detect their expression in liver cancer and normal hepatic tissues. A and B: HCC tissue with positive staining and normal hepatic tissue with negative staining in anti-NPM1 antibody; C and D: HCC tissue with strong positive staining and normal hepatic tissue with negative staining in anti-14-3-3zeta antibody; E and F: HCC tissue with strong positive staining and normal hepatic tissue with negative staining in anti-MDM2 antibody. AFP: Alpha fetoprotein; HCC: Hepatocellular carcinoma; TAAs: Tumor-associated antigens.