Fig. 6. A–F, BrdUrd incorporation (24 h) in HaCaT cells grown at different densities. Double immunofluorescence with antiBrdUrd (green) antibodies and anti-K1 (A–C, red) or anti-Bek (D–F, red) antibodies of cells cultured for 3 days (A, D), 6 days (B, E) and 11 days (C, F). Codistribution of the nuclear BrdUrd and the cytosolic K1 signals, as well as of BrdUrd and KGFR signals, visible by overlapping the single images, is evident in a significant portion of suprabasal cells expressing K1 and KGFR after either 6 days or 11 days of culture (B, C, E, F). Arrows (A), basal cells expressing K1. Arrowheads (D and E), cells in mitosis. G and H, BrdUrd incorporation (12 h) and K1 expression in HaCaT cells cultured for 9 days and treated with KGF (G) for an additional 2 days or kept untreated (H). The number of cells double-positive for the BrdUrd nuclear staining (green) and for the cytosolic K1 signal (red) is increased in KGF-treated cultures (G, arrows) compared with the untreated cultures (H). The number of K1-expressing cells appears unmodified by the KGF treatment. Bar, 40 µm.