In positive ion model, R2Y-value was 0.894, Q2-value was 0.648 (Figure 7B); in negative ion model, R2Y-value was 0.910, Q2-value was 0.603 in MDM2 methylated group and MDM2 unmethylated group of HBV-related HCC (Figure 7D). The gene discussed is MDM2; the disease is hepatocellular carcinoma.