Apoptosis and cell cycle parameters for sub-populations of NOK. Apoptotic rates and cell cycle parameters for CD44high and CD44low cell fractions of early passage normal oral keratinocytes. CD44high cells (right panel of each pair) show lower rates of apoptosis and a higher proportion of cells in G2 (both p < 0.05) than the CD44low sub-population (left panel of each pair) (A, B). Treatment with UVB and Cisplatin increases apoptosis (C, E), but the proportion of CD44high cells in apoptosis remains markedly lower (p < 0.01). UVB and NCZ treatment is also associated with increases in the proportion of CD44high cells in G2 and decrease in G1 phase of the cell cycle (D, F).