In summary, the expression of mutant IDH1 in glioma cells increases their sensitivity to treatment with an HDACi such as belinostat; this is further supported by the finding that a patient with a GBM harboring an IDH1 mutation also showed a much greater response to a belinostat-containing treatment regimen than other wild-type IDH GBMs in our clinical trial. This evidence concerns the gene IDH1 and glioblastoma.