Demethylation and epigenetic modification with 5-Azacytidine reduces IDH1 mutant glioma growth in combination with Temozolomide

Abstract

Background

Isocitrate Deyhydrogenase (IDH) mutant gliomas are comprised of the majority of grade II-III gliomas and nearly all secondary glioblastomas. These progressive gliomas arise from mutations in IDH1 or IDH2 that pathologically produces D-2-hydroxyglutarate (2HG). 2-HG interferes with cell reactions using alpha ketoglutarate leading to a hypermethylated genome and epigenetic dysregulation of gene expression initiating tumorigenesis.

Methods

Human IDH1 WT and IDH1R132H cell lines and patient derived xenografts (PDX) were used to evaluate the FDA-approved DNA demethylating agent 5-Azacytidine (5-Aza). Cell growth, protein and gene expression, chromatin immunoprecipitation, and nucleosome position assays were performed in 5-Aza treated cells. To evaluate antitumor activity in vivo, 5-Aza was administered alone and in combination with Temozolomide (TMZ) in a patient-derived xenograft (PDX) glioma models harboring IDH1R132H mutation.

Results

5-Aza treatment has been found to reduce cell growth and increase Glial Fibrillary Acid Protein expression. Chromatin immunoprecipitation and nucleosome position assay showed that the mechanism of increased GFAP expression induction is associated with histone modification and nucleosome repositioning of the GFAP promoter, respectively. In vivo, 5-Aza treatment extended survival in IDH1R132H mutant, but not in an IDH1 WT glioma model. Additionally, 5-Aza enhances the therapeutic effect of DNA damaging agent TMZ in both subcutaneous and orthotopic PDX models of IDH1R132H mutant glioma.

Conclusion

5-Aza provides a survival benefit as a single agent but worked best in combination with TMZ in two different IDH1R132H mutant glioma models.