Fig. 4

Female GBM astrocytes exhibit greater capacity for p16 induction and growth inhibition in response to serum starvation. a p16, p21 and p27 expression was measured by quantitative PCR in male and female GBM astrocytes grown in the presence or absence of 10% serum. Female GBM astrocytes express higher levels of p16 in response to serum withdrawal (n = 3 independent litters, p < 0.05 as determined by one-way ANOVA and post-hoc Dunnett’s test). b Expression of p16, p21 and p27 protein was measured by Western blot analysis in the presence or absence of 10% serum (+). Means and SEM of protein expression was calculated from three independent experiments. Values were normalized within each experiment to male control. ** = p < 0.005 as determined by one-way ANOVA with Sidaks’ multiple comparisons test. c Flow cytometric analysis of cell cycle distribution of EDU-labelled male and female GBM astrocytes indicated that male and female cells contain 2 N and 4 N sub-populations and that under 10% serum containing conditions both are synthesizing DNA. Upon serum deprivation (0.1%), male, but not female, GBM astrocytes continue to incorporate EDU into both the 2 N and 4 N populations albeit at substantially lower levels than control. d Under basal serum containing conditions, male GBM astrocytes incorporate significantly greater levels of EDU than their female counterparts (n = 3,* = p = 0.01 as determined by paired t-test). Upon serum deprivation, male cells incorporate significantly more EDU than female cells (* = p = 0.03 as determined by paired t-test)