PARP activity (Figure 4B) in GSC and GBM lines significantly correlated with the expression of PARP-1 protein (Spearman’s correlation = 0.72, P = 0.008, n = 12) that accounts for more than 90% of total cellular poly(ADP-ribosyl)ating activity [12]. The gene discussed is PARP1; the disease is glioblastoma.