DNA methylation status of the KRT13 promoter in OSCC cells. (A) Schematic of the KRT13 gene promoter region. The tick represents individual CpG sites and the arrow represents the transcription start site. The bar indicates the region (-470 to -190) subjected to DNA methylation analysis. (B) CpG methylation status of the KRT13 promoter in the three OSCC cell lines and HaCaT cells. Open and closed circles represent methylated and unmethylated CpG sites, respectively. The absence of circles indicates missing data.