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Glioblastoma is the most common and most malignant primary brain tumor with a median survival of 15 months. N-(p-coumaroyl) serotonin (CS) is an indole alkaloid with antioxidant, cardioprotective effects after ischemia and antitumor activity. In the present study we sought to determine whether could exert cytotoxic and cytostatic effects in glioma cells in vitro. CS was tested for toxicity in zebrafish. We investigated the effect of CS in U251MG and T98G glioblastoma cell lines. Viability and proliferation of the cells were examined with trypan blue exclusion assay and the xCELLigence system. Cell cycle, activation of caspase-8, mitochondrial membrane potential and CD24/CD44/CD56/CD15/CD71 expression were tested with flow cytometry. Treatment with CS significantly reduced cell viability in both cell lines tested. Induction of cell death and cell cycle arrest at G2/M and S-phase was confirmed with flow cytometry in both cell lines. CS produced significant higher activity of caspase-8 compared to control. After treatment with CS there was a dose-dependent increase in CD15 and CD71 expression, whereas there was no change in CD24/CD44/CD56 expression in both cell lines. The zebrafish mortality on the fifth post fertilization day was zero for even 1 mM of CS concentration. The treatment of glioblastoma cell lines with CS may represent a novel strategy for targeting glioblastoma. Further studies are obviously needed to elucidate the complete mechanism of its antitumor activity.

Background: Glioblastoma is the most common primary brain tumor in adults with a dismal prognosis. To date, several anticancer agents have been isolated from plants. Helleborus odorus subsp. Cyclophyllus is an endemic plant of the Balcan flora. Herewith, we investigated for the first time, the anti-glioma effect of deglucohellebrin (DGH) extracted from the roots of Helleborus. Methods: We investigated the effect of DGH in U251MG, T98G and U87G glioblastoma cell lines. We selected the T98G cells because of their inherent temozolomide resistance. Results: The IC50 value of reduced viability for DGH was 7x10-5M in U251MG cells, 5x10-5M for the T98G cells and 4x10-5M in U87G cells during 72h treatment. DGH induced G2/M cell cycle arrest, caspace-8 activation and significant mitochondrial membrane depolarization, suggesting the activation of the intrinsic, mitochondrial- dependent apoptotic pathway. DGH and temozolomide induced changes in CDs’ expression in U251MG and T98G cells. In zebrafish, DGH did not induce toxicity or behavioral alterations. Conclusion: The present study is the first to determine the anti-glioma activity of DGH. DGH may be a potent agent for glioblastoma treatment and further studies are needed.

Curcumin, a bioactive polyphenol, is known to have anticancer properties. In this study, the effectiveness of curcumin pretreatment as a strategy for radio-sensitizing glioblastoma cell lines was explored. For this, U87 and T98 cells were treated with curcumin, exposed to 2 Gy or 4 Gy of irradiation, and the combined effect was compared to the antiproliferative effect of each agent when given individually. Cell viability and proliferation were evaluated with the trypan blue exclusion assay and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The synergistic effects of the combination treatment were analyzed with CompuSyn software. To examine how the co-treatment affected different phases of cell-cycle progression, a cell-cycle analysis via flow cytometry was performed. Treatment with curcumin and radiation significantly reduced cell viability in both U87 and T98 cell lines. The combination treatment arrested both cell lines at the G2/M phase to a higher extent than radiation or curcumin treatment alone. The synergistic effect of curcumin when combined with temozolomide resulted in increased tumor cell death. Our results demonstrate for the first time that low doses of curcumin and irradiation exhibit a strong synergistic anti-proliferative effect on glioblastoma cells in vitro. Therefore, this combination may represent an innovative and promising strategy for the treatment of glioblastoma, and further studies are needed to fully understand the molecular mechanism underlying this effect.