The histone deacetylase inhibitor PCI-24781 as a putative radiosensitizer in pediatric glioblastoma cell lines.
BACKGROUND
Glioblastoma (GBM) is considered to be one of the most aggressive tumors of the central nervous system (CNS). Even with the use of modern treatment protocols, the prognosis remains reserved, with children with GBM having a mean survival of 12-15 months.


METHODS
In the present study we investigated the potential radiosensitizing effect of PCI-24781, a potent pan-histone deacetylase inhibitor (HDACi), on the SF188 and KNS42 cell lines of pediatric GBM. Cell proliferation rates, clonogenicity and apoptosis were compared in the presence and absence of treatment with PCI-24781. We also compared the clonogenicity rates of the irradiated SF188 and KNS42 cell lines with or without previous treatment with PCI-24781 at the doses of 0.25-16 μM. In addition, we investigated the effects of PCI-24781 on the expression of some of the main proteins responsible for the repair of double-strand DNA breaks caused by irradiation.


RESULTS
The inhibitor blocked cell proliferation, induced death by apoptosis and reduced the colony forming capacity of the cell lines, both of them showing a significant decrease of colony formation at all irradiation doses. The expression of the Rad51 protein, important for the homologous recombination (HR) repair pathway, and of the DNA-PKcs, Ku70 and Ku86 proteins, important for the non-homologous end joining (NHEJ) repair pathway, was more reduced when the irradiated cell line was previously treated with PCI-24781 than when it was treated exclusively with radiotherapy.


CONCLUSIONS
These findings demonstrate that HDACi PCI-24781 has a radiosensitizing profile that compromises the repair of double-strand DNA breaks in cells of pediatric GBM treated with radiotherapy.
Department of Pediatrics, Ribeirão Preto Medical School, Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto-USP, University of São Paulo, 7º andar. Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil.
Pamela Viani
PV
de Andrade
Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil.
Augusto Faria
AF
Andrade
Department of Pediatrics, Ribeirão Preto Medical School, Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto-USP, University of São Paulo, 7º andar. Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil.
Rosane Gomes
RG
de Paula Queiroz
Department of Pediatrics, Ribeirão Preto Medical School, Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto-USP, University of São Paulo, 7º andar. Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil.
Carlos Alberto
CA
Scrideli
Department of Pediatrics, Ribeirão Preto Medical School, Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto-USP, University of São Paulo, 7º andar. Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil ; Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil.
Luiz Gonzaga
LG
Tone
Department of Pediatrics, Ribeirão Preto Medical School, Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto-USP, University of São Paulo, 7º andar. Av. Bandeirantes, 3900, Bairro Monte Alegre, Ribeirão Preto, SP CEP 14048-900 Brazil.
Elvis Terci
ET
Valera
Double-strand DNA breaks; Epigenetics; Glioblastoma; HDAC inhibitors; Radiation