Article
Valproic acid modifies total DNA methylation level and attenuates temozolomide effect in glioblastoma cell lines
Valproinsäure verändert den gesamten DNA-Methylierungsgrad und schwächt den Temozolomid-Effekt ab in Glioblastomzelllinien
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Authors
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Anna-Maria Barciszewska
- Heliodor Swiecicki Clinical Hospital in Poznan, Department of Neurosurgery and Neurotraumatology, Posen, Polen
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Agnieszka Belter
- Polish Academy of Sciences, Institute of Bioorganic Chemistry, Posen, Polen
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Paweł Głodowicz
- Polish Academy of Sciences, Institute of Bioorganic Chemistry, Posen, Polen
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Mirosława Naskręt-Barciszewska
- Polish Academy of Sciences, Institute of Bioorganic Chemistry, Posen, Polen
| Published: | June 4, 2021 |
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Outline
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Objective: Valproic acid (VPA) is a first-line antiepileptic drug for glioblastoma patients. There is also some evidence that it improves the clinical outcome in those patients. However, the exact mechanism of VPA action is vague. Therefore, we decided to look more precisely at a mode of VPA action. Epigenetics provides a new explanatory area for many pathological processes. It offers a connection between genetic and environmental factors that influence the development of the disease. Epigenetic regulation of gene expression is a dynamic, responsive, and reversible process. The best-characterized epigenetic mark is 5-methylcytosine (m5C) in DNA. Temozolomide (TMZ) is a gold standard chemotherapeutic in glioblastoma. The aim of that project is to show the effects of VPA administration, alone and in combination with TMZ, on the total DNA methylation level.
Methods: Using the nucleotide post-labeling method, we analyzed the total amount of 5-methylcytosine, the main DNA epigenetic mark, in DNA of glioblastoma (T98G, U118, U138), cancer (HeLa) and normal (HaCaT) cell lines treated with VPA, and a combination of VPA and with TMZ.
Results: We adjusted the VPA doses used in the study to the ones virtually achieved in the central nervous system during treatment. We observed dose-dependent changes in the total DNA methylation in neoplastic cell lines and the lack of such effect in a normal cell line. VPA alone produced a clear dose-dependent increase in total DNA methylation in glioblastoma cell lines and scarce in the non-neoplastic cell line. In GBM cell lines, TMZ decreased the level of m5C. However, the exposition of glioblastoma cells to the combination of VPA and TMZ caused an adverse synergistic effect resulting in DNA demethylation. The highest loss of m5C was observed at the highest concentration of TMZ (100 μM) and VPA (350 μM), after 3 h of incubation in the T98G cell line.
Conclusion: Total DNA methylation changes in glioma cell lines under VPA treatment suggest the new mechanism of that drug action and promote clinical implications for adjusting VPA and TMZ therapy in glioblastoma patients. The results of our study show the potential and possible obstacles of the combined therapy of temozolomide with valproic acid. Our experiments show that combined therapy with both drugs leads to total DNA hypomethylation. Therefore the conclusion would be to stop VPA administration during TMZ chemotherapy temporarily.
