Aberrant methylation and reduced expression of LHX9 in malignant gliomas of childhood.
High-grade gliomas (HGGs) of childhood represent approximately 7% of pediatric brain tumors. They are highly invasive tumors and respond poorly to conventional treatments in contrast to pilocytic astrocytomas, which usually are well demarcated and frequently can be cured by surgery. The molecular events for this clinical relevant finding are only partially understood. In the current study, to identify aberrantly methylated genes that may be involved in the tumorigenesis of pediatric HGGs, we performed a microarray-based differential methylation hybridization approach and found frequent hypermethylation of the LHX9 (human Lim-homebox 9) gene encoding a transcription factor involved in brain development. Bisulfite genomic sequencing and combined bisulfite restriction analysis showed that HGGs were frequently methylated at two CpG-rich LHX9 regions in comparison to benign, nondiffuse pilocytic astrocytomas and normal brain tissues. The LHX9 hypermethylation was associated with reduced messenger RNA expression in pediatric HGG samples and corresponding cell lines. This epigenetic modification was reversible by pharmacological inhibition (5-aza-2'-deoxycytidine), and reexpression of LHX9 transcript was induced in pediatric glioma cell lines. Exogenous expression of LHX9 in glioma cell lines did not directly affect cell proliferation and apoptosis but specifically inhibited glioma cell migration and invasion in vitro, suggesting a possible implication of LHX9 in the migratory phenotype of HGGs. Our results demonstrate that the LHX9 gene is frequently silenced in pediatric malignant astrocytomas by hypermethylation and that this epigenetic alteration is involved in glioma cell migration and invasiveness.
Vladimirova
Valentina
V
Department of Neuropathology, University of Bonn Medical Center, Bonn, Germany. valentina.vladimirova@ukb.uni-bonn.de
Mikeska
Thomas
T
Waha
Andreas
A
Soerensen
Niels
N
Xu
Jingying
J
Reynolds
Patrick C
PC
Pietsch
Torsten
T
D000293:Adolescent; D017209:Apoptosis / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000235:genetics*; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D002648:Child; D002675:Child, Preschool; D019175:DNA Methylation / Q000235:genetics*; D005910:Glioma / Q000235:genetics*; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D060850:LIM-Homeodomain Proteins; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D009361:Neoplasm Invasiveness / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors
D018398:Homeodomain Proteins; C492149:LHX9 protein, human; D060850:LIM-Homeodomain Proteins; D012333:RNA, Messenger; D014157:Transcription Factors