Another study identified five frequently methylated tumor suppressor genes, including IRX1 (iroquois homeobox 1), EBF3 (early B cell factor 3), SLC5A8 (solute carrier family 5 member 8), SEPT9 (septin 9), and SKOR2 (SKI family transcriptional corepressor 2), in HNSCC following radiotherapy. This evidence concerns the gene SEPTIN9 and head and neck squamous cell carcinoma.