The human oral keratinocyte cell line OKF6/TERT1 was grown in keratinocyte serum free medium (KSFM) supplemented with L-glutamine and penicillin-streptomycin-fungizone (Sigma-Aldrich) in the presence of 0.03 M calcium chloride and bovine pituitary extract as described previously11 (link). Primary cultures of normal human gingival epithelial cells were grown as previously described19 (link),20 (link).