KMT2B and head and neck squamous cell carcinoma: Histone-lysine N-methyltransferase 2D (KMT2D; also known as MLL2) and histone-lysine N-methyltransferase 2 B (KMT2B; also known as MLL4), both encoding histone-lysine N-methyltransferases, were frequently mutated in HNSCC and OSCC [5,6,7,8,9].