Three human TSCC cell lines, SCC-9, CAL-27 and SCC-15, as well as normal gingival epithelial cells (ATCC® PCS-200-014™) were purchased from the American Type Culture Collection (ATCC). Previous studies (26 (link),27 (link)) have used the normal gingival epithelial cells as a control for TSCC cell lines. Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin solution (all Invitrogen; Thermo Fisher Scientific, Inc.) was utilized for cell culture. All cells were maintained in a humidified incubator at 5% CO2 and 37°C.