PCNA and glioblastoma: Spearman’s rank correlation analysis of the TCGA GBM database also revealed positive correlations between E2F1 and PCNA or MMP2 mRNA transcript levels (n=669, r =0.5488, p < 0.001 in E2F1-PCNA, n = 156, r = 0.1722, p < 0.001 in E2F1-MMP2, Figure 5C).