For XDH, a better correlation was found between XDH mRNA levels and site-specific DNA methylation levels (Table 1): Spearman R = −0.62 for PAAD (P<1 × 10−22), R = −0.47 for HNSCC (P<1 × 10−22) and R = −0.36 for HCC (P=9.21 × 10−13). The gene discussed is XDH; the disease is head and neck squamous cell carcinoma.