NOL4 and head and neck cancer: Nucleolar protein 4 (Nol4) gene might be involved in a process of determining cell specificity.37 As a tumor suppressor gene showed tissue-specific distribution,37 it was considered as a potential biomarker of head and neck cancer, as it was highly hypermethylated in the patients suffering from these malignancies,38,39 Its role in the OIR would need to be elucidated.