IRX1 and head and neck squamous cell carcinoma: In two other studies, Bennett et al also showed the association between IRX1 methylation and recurrence and between four other genes and clinicopathological parameters such as HPV status, alcohol and tobacco usage (8) and they investigated the interactions with some molecules of the TGF-β pathway, and their transcriptional inactivation by methylation in HNSCC caused the decrease in apoptosis and differentiation, and increased proliferation (34).