Serum levels of anti-sperm-associated antigen 9 antibody are elevated in patients with hepatocellular carcinoma.

At present, there is a high incidence of viral hepatitis and high mortality rates due to hepatocellular carcinoma (HCC) in China. In the current study, the quantification of antibodies against the cancer-testis antigen sperm-associated antigen 9 (SPAG9), alone and combined with α-fetoprotein (AFP), were evaluated as biomarkers for the diagnosis of HCC. The levels of anti-SPAG9 antibody and AFP were quantified in serum samples from patients with HCC and hepatitis or cirrhosis, as well as healthy volunteers. The results revealed that the serum levels of anti-SPAG9 immunoglobulin G antibody in patients with HCC were significantly higher compared with those in patients with hepatitis/cirrhosis and healthy controls. Using receiver operator characteristic curves, the area under the curve (AUC, 0.870) of SPAG9 as a diagnostic marker of HCC was significant [P<0.001; 95% confidence interval (CI), 0.793-0.947], whereas the AUC of AFP was 0.832 (P<0.001; 95% CI, 0.736-0.928). Serum anti-SPAG9 antibody levels exhibited significant potential for the differential diagnosis of HCC, with an AUC value of 0.729, (P=0.008; 95% CI, 0.559-0.899). Similarly, serum AFP levels exhibited significant value for the differential diagnosis of HCC, with an AUC value of 0.842 (P<0.001; 95% CI, 0.732-0.953). When combined with quantification of AFP, the diagnostic sensitivity and specificity of anti-SPAG9 levels were increased. In summary, the results suggested that anti-SPAG9 antibody is a potential early diagnostic marker of HCC.