Silencing of Histone Deacetylase 6 Decreases Cellular Malignancy and Contributes to Primary Cilium Restoration, Epithelial-to-Mesenchymal Transition Reversion, and Autophagy Inhibition in Glioblastoma Cell Lines

Glioblastoma multiforme, the most common type of malignant brain tumor as well as the most aggressive one, lacks an effective therapy. Glioblastoma presents overexpression of mesenchymal markers Snail, Slug, and N-Cadherin and of the autophagic marker p62. Glioblastoma cell lines also present increased autophagy, overexpression of mesenchymal markers, Shh pathway activation, and lack of primary cilia. In this study, we aimed to evaluate the role of HDAC6 in the pathogenesis of glioblastoma, as HDAC6 is the most overexpressed of all HDACs isoforms in this tumor. We treated glioblastoma cell lines with siHDAC6. HDAC6 silencing inhibited proliferation, migration, and clonogenicity of glioblastoma cell lines. They also reversed the mesenchymal phenotype, decreased autophagy, inhibited Shh pathway, and recovered the expression of primary cilia in glioblastoma cell lines. These results demonstrate that HDAC6 might be a good target for glioblastoma treatment

Fluorescence-guided surgical sampling of glioblastoma identifies phenotypically distinct tumour-initiating cell populations in the tumour mass and margin.

BACKGROUND: Acquiring clinically annotated, spatially stratified tissue samples from human glioblastoma (GBM) is compromised by haemorrhage, brain shift and subjective identification of 'normal' brain. We tested the use of 5-aminolevulinic acid (5-ALA) fluorescence to objective tissue sampling and to derive tumour-initiating cells (TICs) from mass and margin. METHODS: The 5-ALA was administered to 30 GBM patients. Samples were taken from the non-fluorescent necrotic core, fluorescent tumour mass and non-fluorescent margin. We compared the efficiency of isolating TICs from these areas in 5-ALA versus control patients. HRMAS (1)H NMR was used to reveal metabolic alterations due to 5-ALA. We then characterised TICs for self-renewal in vitro and tumorigenicity in vivo. RESULTS: The derivation of TICs was not compromised by 5-ALA and the metabolic profile was similar between tumours from 5-ALA patients and controls. The TICs from the fluorescent mass were self-renewing in vitro and tumour-forming in vivo, whereas TICs from non-fluorescent margin did not self-renew in vitro but did form tumours in vivo. CONCLUSION: Our data show that 5-ALA does not compromise the derivation of TICs. It also reveals that the margin contains TICs, which are phenotypically different from those isolated from the corresponding mass

Inhibition of histone deacetylase 6 by tubastatin A as an experimental therapeutic strategy against glioblastoma

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