TERT and glioblastoma: Furthermore, GABPA/B1, B1-L, B1-S proteins in the primary GBMs of our cohort exhibit a significant upregulation compared to the normal brain tissue which can confirm at some point the finding of Mancini et al. He proved, that the B1L isoform is the main regulator of TERT expression in promoter mutated glioblastomas and there is a positive association between TERT and B1L mRNA expression, unlike our correlation results [22].