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Background and Aim: Glioblastoma is the most lethal brain tumor. No effective curative treatment is available yet, and it is treated by surgery, temozolomide (TMZ), and radiotherapy, with an average overall survival of around 15 months. Inhibitors of histone deacetylases (HDACs) are being explored against a variety of tumors, including glioblastoma. Specific inhibitors of HDAC6, such as tubastatin A (Tub A), may potentially be beneficial as HDAC6 has been demonstrated to be the most expressed HDACs in glioblastoma. Our aim was to test whether Tub A could reverse the malignant phenotype of U87MG cells via the inhibition of HDAC6. Materials and Methods: U87MG cells were treated with cyclopamine (Cyp), TMZ, and Tub A. Two double treatments were performed as well (Cyp + Tub A and TMZ + Tub A). Colony formation, wound healing, Caspase‑Glo 3/7, quantitative reverse transcription–polymerase chain reaction, luciferase assay, and Western blot assays were conducted to determine clonogenic and migration capacity, apoptosis, activation of the Sonic Hedgehog pathway, acetylation of α‑tubulin and epithelial‑to‑mesenchymal transition, and autophagic flux of U87MG glioblastoma cells, respectively. Results: Tub A treatment caused a reversal of the U87MG malignant phenotype by reducing its clonogenic and migratory cellular potential, and inducing apoptosis. Sonic Hedgehog pathway inhibition, together with reversal of epithelial‑to‑mesenchymal transition and reduced autophagic flux, was also induced by the effect of Tub A. Conclusions: HDAC6 might be a good target for glioblastoma treatment.

Background: Glioblastoma multiforme (GBM) is the most malignant primary brain tumor. Current treatment against this tumor consists of maximal surgical resection without threatening the patient's life, followed by a treatment with temozolomide, with or without combined radiotherapy. GBM is resistant to the conventional antitumor therapies, so in this research, we tried to inhibit tumor growth with the combination of three drugs: (1) panobinostat, an inhibitor of histone deacetylases, (2) 3-Dezaneplanocin-A (DZNep), an inhibitor of EZH2, a protein which belongs to the polycomb repressor complex 2, acting as a histone methylase, and (3) temozolomide, an alkylating agent. Methods: The T98G GBM commercial cell line was used. Cells were exposed to single treatments of the drugs and to the three possible combinations among them. Soon after, two-dimensional (2D) and 3D clonogenic assays were assessed for in vitro tumorigenicity testing. Real-time quantitative polymerase chain reaction of 2 proapoptotic genes (BAX and NOXA) and 2 antiapoptotic genes (BCL2 and BCL-XL) was also assessed. Results: The panobinostat and temozolomide combination produced a positive effect against T98G glioblastoma cells by reducing soft agar colony formation, by inducing high expression levels of NOXA, and by reducing BCL-XL expression. Equally, the panobinostat and DZNep combination produced a positive effect against T98G glioblastoma cells by reducing colony formation in adherent conditions and by inducing high expression levels of BAX. Finally, temozolomide alone was the most efficient drug for decreasing BCL2 expression. Conclusion: Panobinostat and temozolomide combination or panobinostat and DZNep combination might be more efficient against glioblastoma cells than just temozolomide.

Aim: Glioblastoma is the most malignant primary brain tumor. The treatment consists of surgery, with or without radiotherapy, and temozolomide, with a life expectancy of 12–15 months after diagnosis. Glioblastoma is resistant to conventional antitumor therapies. In this work, we present a preliminary in vitro study of two epigenetic drugs against GOS-3 glioblastoma cells. Methods: We used (1) panobinostat, a histone deacetylase inhibitor, and (2) 3-deazaneplanocin-A (DZ-Nep), an inhibitor of enhancer of zeste homolog 2 (EZH2) (enzyme of the polycomb repressor complex 2, polycomb group of proteins that trimethylate lysine 27 of histone 3-H3K27 me3-), as treatments that might modulate the PI3K pathway, affected in GOS-3 cells due to PTEN haploinsufficiency. The glioblastoma cell line GOS-3 was exposed to DZ-Nep and panobinostat treatments, separately and in combination, over a period of 2 days, after which cell migration, clonogenicity, and molecular expression characterization assays were performed. Results: Panobinostat alone or the combination of panobinostat plus DZ-Nep inhibited clonogenicity, metastasis, angiogenesis, epithelial–mesenchymal transition, and entry in the S phase of the cell cycle and induced apoptosis in GOS-3 glioblastoma cells. On the contrary, DZ-Nep inhibited cell migration (single treatment) and O(6)-methylguanine-DNA methyltransferase expression (DZ-Nep or double treatment). Conclusion: Panobinostat alone or the combination of panobinostat and DZ-Nep induce apoptosis and inhibit in vitro tumorigenesis and metastasis in GOS-3 glioblastoma cell lines.