Epigenetic modifications in cell lines of human astrocytoma differentially regulate expression of apoptotic genes.
OBJECTIVE
Epigenetic alterations, known as epimutations, act by deregulating gene expression. These epimutations are reversible through the action of chromatin modifiers such as DNA methylation (DNA-met) and histone deacetylases (HDAC) inhibitors. The present study evaluated the effect of 5-azacitidine (5-aza) and sodium butyrate (NaBu) as inhibitors of DNA-met and HDAC, respectively, in the expression of genes involved in apoptosis.


METHODS
D54-MG, U373-MG, and T98G cell lines were exposed to 8 mM of NaBu and 12 μM of 5-aza, as well as a combination of both, for 24 h. The expression of the Bcl-2, Bak-1, Bax, Caspase-3, and Caspase-9 genes was assessed by RT-PCR.


RESULTS
They show that the Bcl-2, Caspase-3, and Caspase-9 genes were not expressed by the U373-MG and T98G lines, and that the D54-MG line did not express Bak-1. After treatment, however, these cell lines expressed all of the genes due to the effect of 5-aza on Bak-1 in D54-MG and Caspase-9 in T98G, which suggests repression by DNA-met. Meanwhile, Bcl-2, Caspase-3, and Caspase-9 were in the U373-MG and T98G lines expressed after NaBu treatment. The effect of 5-aza induced an increase in the expression of Bax and Bcl-2, while NaBu produced a similar effect on the Bak-1 and Bax genes.


CONCLUSIONS
Results reveal that histone deacetylation is the principle mechanism for repressing these genes and that their basal expression is regulated primarily by this form of histone modification.
Departamento de Patología, Hospital Infantil de México Federico Gómez, Mexico City, Mexico.
Mario
M
Solís-Paredes
Pilar
P
Eguía-Aguilar
Fernando
F
Chico-Ponce de León
Stanislaw
S
Sadowinski-Pine
Mario
M
Pérezpeña-Diazconti
Francisco
F
Arenas-Huertero
D017209:Apoptosis / Q000502:physiology*; D001254:Astrocytoma / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D044127:Epigenesis, Genetic / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans