HDAC1 and glioblastoma: Gene set enrichment analysis (GSEA) using the 26 upregulated genes identified their correlation with “HDAC1 targets” and “UV response DNA damage,” both of which our recent studies have identified as pathways downstream of the CD109-driven signals in glioblastoma tumors and their TIC models (Figure 4N).16,19 Finally, we explored the expression of PLAGL1 in primary glioblastoma edge, core lesions as well as their subsequent recurrent core tissues, which showed PLAGL1 higher in the core lesions in both primary and recurrent tumors (Figure 4O).