DNMT1 and head and neck squamous cell carcinoma: As an example, mRNA expression of DNA methyltransferase 1 (DNMT1), 3A (DNMT3A), and 3B (DNMT3B) was increased in tumors compared to normal tissue, and aberrant expression of DNMT1 showed a significant correlation with poor clinical outcomes and relapse-free survival in HNSCC patients [16].