[Methylation status of RARbeta gene promoter in low and high grade cerebral glioma. Comparison with normal tissue. Immuno-histochemical study of nuclear RARbeta expression in low and high grade cerebral glioma cells. Comparison with normal cells. 48 tumors]. / Statut de méthylation du promoteur du gène RARB dans les tumeurs cérébrales gliales de bas et de haut grade. Comparaison avec le tissu sain. Etude immuno-histochimique du marquage au RARbeta des noyaux des cellules tumorales dans les gliomes de bas et de haut grade. Comparaison avec les cellules saines, à propos de 48 tumeurs.

ABSTRACT

Retinoic acid receptor beta (RARbeta) is a nuclear receptor often deregulated in tumors. An immunohistochemical study was conducted to examine the level of expression of this receptor in the nucleus of glial cell tumors (low and high grade glioma) as well as a study of the methylation status of the gene promoter coding this receptor on the same tumor samples. A comparison with normal tissue was done each time. 48 tumors were eligible for the study (15 glioblastomas, 20 grade III oligodendrogliomas and 13 grade II oligodendrogliomas). A constant decrease of RARbeta expression was found by comparison with normal tissue whatever the histological grade of the tumor, suggesting a deregulation of RARbeta gene expression. Methylation of RARbeta promoter gene was a rare event (12.5% of all cases), except for grade III oligodendrogliomas (20%), and is thus not a major event of this gene deregulation. Other reasons of this deregulation of RARbeta should be studied, such as loss of 3p24 heterozygoty, mRNA studies and RARbeta interactions with other retinoid receptors.