XDH and hepatocellular carcinoma: In HCC, patients with a high XDH mRNA expression level had significantly prolonged OS (hazard ratio (HR) 0.55, 95% confidence interval (CI) 0.38 to 0.78, P = 0.00072) and slower disease progression (recurrence-free survival (RFS) HR 0.68, 95% CI 0.49 to 0.95, P = 0.024; progression-free survival (PFS) HR 0.69, 95% CI 0.5 to 0.0.94, P = 0.017; disease-specific survival (DSS) HR 0.53, 95% CI 0.33 to 0.83, P = 0.0045) than patients with a low XDH mRNA expression level (Fig. 2A–D).