Fig. 3. Sublethal UV irradiation induces squamous differentiation in keratinocytes of head and neck.

Primary cells from human oral mucosa or larynx after sublethal UV irradiation (sbUV; 25 mJ/cm²) were analysed 5 h (a) or 48 h (b–d) after irradiation. a Percent of γH2AX (early DNA damage marker) positive cells according to 2 levels of intensity (1–2). b Percent of G2/M, polyploid, S or sub-G1 fractions of the cell cycle, measured as in Fig. 1. c Representative flow cytometry analyses of the differentiation marker keratin K13. Bar histogram shows the percent of K13 positive cells (K13+) as determined by a negative control antibody (see Materials and methods) d Clonogenic capacity of cells plated 48 h after irradiation (2500 cells per well in triplicates). NI: non-irradiated. *p < 0.05, **p < 0.01. Data are representative or mean ± s.e.m. of duplicate samples and two independent experiments. See also Supplementary Figure 5