CD44 and oral cavity squamous cell carcinoma: To investigate whether the transcriptional expression of CSC surface markers (CD24, CD44, CD133, and CD147) is regulated by epigenetic mechanisms in oral squamous cell carcinoma cells, we first treated ten OSCC cell lines (Ca9-22, HN22, HSC3, HSC4, OSC20, SAS, SCC25, YD10B, YD38, and YD9) with 5-aza-2′-deoxycytidine (5-aza-dC, DAC) and determined whether these genes were reactivated after 5-aza-dC treatment by real-time RT-PCR.