PAX1 and head and neck squamous cell carcinoma: Indeed, in HNSCC, in addition to the tumor suppressor genes that are downregulated due to cancer-specific methylation of their promoter, such as PAX1 and PAX5, tumor suppressor genes that are inactivated by both promoter methylation and somatic mutations (GABRB3, HOXC12, PARP15, SLCO4C1, CDKN2A, PAX1, PIK3AP1, HOXC6, PLCB1, and ZIC4) have also been recognized [18].