ERβ in humans is expressed as 5 different isoforms ERβ1, ERβ2, ERβ3, ERβ4, and ERβ5, resulting from alternative splicing of exon 8, which is the last coding exon, and these 5 isoforms add another layer of complexity in ERβ functions.51 Structural analysis revealed that ERβ1 is the only full-length functional isoform with the native ligand-binding domain.51,52 Off note, GBM cells express isoforms ERβ1 and ERβ5. Here, ESR2 is linked to glioblastoma.