HPV 16 increased CAL27 proliferation in vitro. CAL27 cells were plated at low density (104 cells per well) and allowed to proliferate with 10% fetal bovine serum (FBS) or no serum (NS). Proliferation of CAL27 HPV16-transfected cells increased significantly from day 1 to day 3 under FBS or NS treatment (A) (n = 96, p < .01). Direct comparison of NS with FBS treatment, day 1 – day 3, demonstrated effect of HPV16 on CAL27 proliferation (B) (n = 96, p < .01). Direct comparison of day 1, day 2 and day 3 results under NS and FBS revealed HPV16 increased CAL27 proliferation 3.2-fold under NS treatment and 5.0-fold under FBS (C). Three separate, independent replications of this experiment were performed (n = 24 wells per trial).