Fig. 1.

HPV induces caspase activation in cells induced to differentiate in organotypic raft cultures and by suspension in methylcellulose. (A) Sections of organotypic raft cultures generated from untransfected HFKs (Upper) and HFKs stably transfected with HPV-31 (HFK-31) (Lower) were stained with H&E (I and IV), an antibody specific for active caspase-3 (II and V), as well as DAPI to visualize nuclei (III and VI). Arrows indicate the basal layer of the epithelium. (B) Western blot analysis of cell lysates from untransfected HFKs (HFK) and HPV-31-positive HKFs (HFK-31) by using antibodies specific for the active and pro forms of capsase-9, -3, and -7. Lysates were harvested from undifferentiated (T0) monolayer cultures or after suspension in methylcellulose to induce differentiation for 12 and 24 h. GAPDH served as a loading control. The results shown are representative of three independent experiments by using two different HFK backgrounds. Hr, hours; MC, methylcellulose.