PCNA and glioblastoma: When analyzing the expression level of PCNA in total cells extracts from nine GBM and three GIC cell lines, two of the GICs had higher PCNA levels than the GBM cell lines (GICs marked in Figure 1C); however, linear regression of PCNA levels plotted against IC50s did not suggest a correlation between PCNA levels and ATX-101 sensitivity (Figure 1C, r = −0.51)).