Upon analysis of LDOC1 protein expression in an immortalized normal oral keratinocyte cell line CGHNK2 [27], a dysplasia oral keratinocyte (DOK) cell line derived from a heavy smoker [28], and four OSCC cell lines established from patients who were smokers [29], we observed high expression of LDOC1 in CGHNK2 cells, whereas it was downregulated in the DOK cell line and nearly undetectable in all OSCC cell lines tested (Figure S1). The gene discussed is LDOC1; the disease is dysplasia.