Effects of HPV 16 on cell spreading in vitro. CAL27 cells from adhesion and proliferation assays (A-E) and CAL27-HPV16-transfected cells (F-J) were cultured in media containing NS-no serum (B,D,G,I) or FBS-fetal bovine serum (C,E, H, J). Cells were fixed with formalin and stained with crystal violet. Analysis revealed that HPV16+ cells increased in number and ratio of spreading under FBS treatment (H, J) and under NS treatment (G, I) to a greater extent than non-transfected cells under FBS (C, E) or NS treatments (B, D). No measurable differences in cell number or morphology were apparent in the 30-minute adhesion assays (A, F).