TCF21 and head and neck squamous cell carcinoma: TCF21 antisense RNA inducing demethylation (TARID), an antisense RNA of TCF21 that is a tumor suppressor, binds and recruits GADD45a to the TCF21 promoter to facilitate demethylation in several cancers, including non-small cell lung cancer, head and neck squamous cell carcinomas and ovarian cancers [134].