Siderol Inhibits Proliferation of Glioblastoma Cells and Acts Synergistically with Temozolomide

Maria Giannakopoulou; Kiriakos Dimitriadis; Maria Koromili; Vasiliki Zoi; Evrysthenis Vartholomatos; Vasiliki Galani; Athanassios P Kyritsis; George A Alexiou; Diamanto Lazari

doi:10.3390/biomedicines10123216

Siderol Inhibits Proliferation of Glioblastoma Cells and Acts Synergistically with Temozolomide

Biomedicines. 2022 Dec 12;10(12):3216. doi: 10.3390/biomedicines10123216.

Authors

Maria Giannakopoulou¹, Kiriakos Dimitriadis², Maria Koromili², Vasiliki Zoi¹, Evrysthenis Vartholomatos¹, Vasiliki Galani³, Athanassios P Kyritsis¹, George A Alexiou^{1

4}, Diamanto Lazari²

Affiliations

¹ Neurosurgical Institute, University of Ioannina, 45500 Ioannina, Greece.
² Laboratory of Pharmacognosy, Division of Pharmacognosy-Pharmacology, School of Pharmacy, Faculty of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
³ Department of Anatomy Histology-Embryology, School of Medicine, University of Ioannina, 45110 Ioannina, Greece.
⁴ Department of Neurosurgery, University of Ioannina, 45500 Ioannina, Greece.

Abstract

Glioblastoma (GBM) is the most aggressive primary central nervous system (CNS) tumor in adults with dismal prognosis. Currently, the therapeutic interventions include gross total resection, when possible, followed by radiotherapy and chemotherapy. However, despite treatment, tumor usually recurs within 7-9 months. The presence of glioma cells with stem-like properties and tumor's heterogeneity have been identified as the most important factors driving recurrence. Recently, research efforts have been focused on the use of natural substances as treatment for GBM. Siderol is an ent-kaurane diterpenoid, isolated from the genus Sideritis. Sideritis extracts have already been investigated for their anti-inflammatory, antioxidant, and anticancer effects. In this study, we investigated the antitumoral effects of siderol in GBM T98 and U87 cell lines, as well as the effects of combined treatment with temozolomide (TMZ). Cell viability was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and trypan blue exclusion assay. Different concentrations of siderol were used in order to calculate the IC50 values at 72 h after treatment. Flow cytometry used for the DNA cell cycle analysis after treatment with siderol in concentrations of IC50 and twice the IC50 values for 72 h. Furthermore, the effect of siderol in cell's migratory ability was tested using wound healing assay. Cell viability and proliferation, after combined treatment with siderol and TMZ, also were evaluated with the trypan blue exclusion assay and the effects of the combination treatment were analyzed with CompuSyn software. Treatment with siderol significantly reduced cell viability in T98 and U87 cell lines in a dose-dependent manner and IC50 values were calculated, 18 μM and 13 μM, respectively. Moreover, siderol induced G₀/G₁ cell cycle arrest in a dose-dependent manner and inhibited the migration in both cell lines. In addition, siderol and TMZ seem to have synergistic action in the majority of tested concentrations in both T98 and U87 cells. In conclusion, siderol may represent an innovative strategy for the treatment of GBM, and further studies are needed on siderol's efficacy and mode of action.

Keywords: cell cycle arrest; cell viability; glioblastoma; siderol; temozolomide.

Grants and funding

This research received no external funding.