Fig. 5

Female GBM astrocytes exhibit greater capacity for p21 induction and growth inhibition in response to etoposide. a The effect of etoposide treatment (10 μg/ml for 24 h) on p16, p21 and p27 RNA expression was measured by quantitative PCR. Etoposide induced p21 mRNA expression in both male and female GBM astrocytes but the level of increase was greater in females compared to male GBM astrocytes. b Expression of p16, p21 and p27 protein was measured by Western blot analysis. Means and SEM of protein expression was calculated from three independent experiments. Values were normalized within each experiment to male control. ** = p < 0.005 and *** = p < 0.0005 as determined by one-way ANOVA with Sidaks’ multiple comparisons test. c Etoposide treatment resulted in equivalent induction of histone H2AX phosphorylation (γH2AX) in male and female GBM astrocytes. Shown is a representative Western blot and accompanying quantification of three independent experiments. d Etoposide had greater clastogenic effects in male compared to female GBM astrocytes. Shown are representative metaphase spreads of etoposide-treated male and female GBM astrocytes. Male and female GBM astrocytes contained 2 N and 4 N subpopulations. Etoposide induced chromosomal fragmentation in both sexes but there was a substantially greater clastogenic effect in male compared to female GBM astrocytes