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. This evidence concerns the gene NOL4 and neoplasm.