Figure 5. Intracellular localization and release of E2F-1 penetratin-peptide delivered with liposomes. (A) Representative images of Du-145 human prostate cancer cells incubated within 5 min with PEGylated liposomes containing E2F-1 peptide. Cell nuclei were stained with nuclear-specific dye DAPI (blue fluorescence), peptide was labeled with FITC (green fluorescence). Superimposition of images allows for detecting of cytoplasmic (green) and nuclear (cyan) localization of peptide. (B) Kinetics of the intracellular release of FITC-labeled E2F-1 peptide from PEGylated liposomes. H-69 human small cell lung cancer (peptide most sensitive) and DU145 human prostate (peptide less sensitive) cancer cells were incubated for different periods of time with PEGylated liposomes containing E2F-1 peptide. Upper panel: representative fluorescence images of cells. Bottom panel: Time course of the fluorescence intensity of FITC-labeled E2F-1 pentratin-peptide released from liposomes. Means ± SD from 6 independent measurements are shown.