Specific combinations of the chromatin-modifying enzyme modulators significantly attenuate glioblastoma cell proliferation and viability while exerting minimal effect on normal adult stem cells growth

Abstract

The discoveries of recent decade showed that all critical changes in cancer cells, such as silencing of tumor-suppressor genes and activation of oncogenes, are caused not only by genetic but also by epigenetic mechanisms. Although epigenetic changes are somatically heritable, in contrast to genetic changes, they are potentially reversible, making them good targets for therapeutic intervention. Covalent modifications of chromatin such as methylation and acetylation of histones and methylation of DNA are the important components of epigenetic machinery. In this study, we investigated the effect of different modulators of DNA and histone covalent-modifying enzymes on the proliferation and viability of normal adult stem cells, such as human bone marrow mesenchymal stem cells (hMSCs), and on malignant tumor cells, such as glioblastoma (GB) D54 cells. Results demonstrated that specific combinations of histone methyltransferases and deacetylases inhibitors significantly attenuated D54 cells viability but having only a small effect on hMSCs growth. Taken together, these studies suggest that specific combinations of histone covalent modifiers could be an effective treatment option for the most aggressive type of primary brain tumors such as glioblastoma multiforme.

Unique combinations of epigenetic modifiers synergistically impair the viability of the U87 glioblastoma cell line while exhibiting minor or moderate effects on normal stem cell growth

“…1.a), in combinations they exhibited a synergistic effect (Fig. 1.b), as demonstrated for D54 cells [19]. However, these combinations exhibited minimal or moderate effect on AD-MSCs growth as previously demonstrated for BM-MSCs [19].…”

“…Based on these discoveries we decided to test whether the same combination of epigenetic modi ers can exhibit similar effect on another well-known glioma cell line such as U87. Results showed that while individually the DZNep, TSA and BIX01294 at their low concentrations showed a moderate effect on the viability of U87 cells, in combinations they exhibited a synergistic effect, as demonstrated for D54 cells [19]. Importantly, these combinations exhibited minimal or moderate effect on AD-MSCs growth, as demonstrated previously for BM-MSCs [19].…”

“…Results showed that while individually the DZNep, TSA and BIX01294 at their low concentrations showed a moderate effect on the viability of U87 cells, in combinations they exhibited a synergistic effect, as demonstrated for D54 cells [19]. Importantly, these combinations exhibited minimal or moderate effect on AD-MSCs growth, as demonstrated previously for BM-MSCs [19]. These results also showed that the most effective combination was the medium concentrations of TSA + BIX01295 that almost completely killed U87 cells that demonstrated with MTT test and cell count by trypan blue.…”

“…In our previous studies, we investigated the effect of different epigenetic modi ers and their combinations on the proliferation and viability of normal adult stem cells, such as human mesenchymal stem cells (hMSCs), and malignant glioma cells, such as D54 cells [19]. In these studies, hMSCs or D54 cells were exposed to either different concentrations of speci c modulators of chromatin modifying enzymes, such as inhibitors of HMTs, DNMTs, HDACs, or to combinations of these inhibitors.…”

Emerging targets for glioblastoma stem cell therapy

“…Another class of epigenetic inhibitors is HDAC inhibitors. HDACs are a family of proteins that remove acetyl groups from lysine residues of histone proteins and other proteins including TFs [ 87 ] . These enzymes regulate the conformation and activity of chromatin and mostly function as transcriptional co-repressors as part of large multi-protein complexes [ 88 ] .…”