Efficacy of azacitidine in meningiomas and explorative analyses of underlying molecular mechanisms.

Treatment of meningiomas refractory to resection and/or radiotherapy represents a therapeutic challenge. Azacitidine (AZA), a DNA methyltransferase inhibitor, is successfully used in the treatment of leukemia and sarcomas. Efficacy of Decitabine (DCT) - a chemical analogue of AZA - was demonstrated in a subset of primary meningioma cells. We aimed to investigate the efficacy of AZA and underlying molecular alterations in primary meningioma cells. Effects of AZA on cell viability and proliferation in primary meningioma cells were analyzed using a CellTiter-Glo Cell Viability Assay and immunofluorescence staining of Ki-67-expression. Immunofluorescence for DNA methyltransferases (DNMT1,3a,3b) was used to investigate the molecular preconditions for efficacy. Genome-wide DNA methylation analyses were performed prior and after drug exposition. 72 h after drug application (10 µM AZA), cell viability significantly decreased in 13 of 19 (68%) primary cells. In 9 of 16 cases (56%) we found a decrease in Ki67-expression after application of AZA. Furthermore, AZA significantly reduced DNMT1, DNMT3a and 3b expression in 44%, 27% and 18% of primary cells 72 h after drug exposition. DNMT expression was independent of cell viability and proliferation. Methylation profiles of cells sensitive or resistant to AZA as well as before or after treatment did not significantly differ. Compared to DCT, AZA more effectively reduced viability and proliferation in primary meningioma cells. Molecular impact was largely independent of DNMT expression and methylation profile. Next to inducing DNA demethylation and epigenetic reprogramming, efficacy of AZA may be due to other molecular mechanisms of action.