Genetic and epigenetic
characterization of stem cell-like subpopulations from primary
high-grade malignant gliomas.
High-grade malignant gliomas are
difficult to treat because of their resistance to surgical resection,
radiation and chemotherapy,with nearly 100% recurrence following
treatment. There is increasing evidence that this clinical
phenotype is associated with subpopulations of tumor stem cells (TSCs)
that have stem cell-like
properties and the potential for self-renewal and multi-linage
differentiation that recapitulates the phenotype of the original
tumors. In an effort to better understand TSCs, we compared
thegenome-wide gene expression and DNA methylation profiles of TSCs
with normal neural stem/progenitor cells (NSPCs) using microarray
technologies. Normal brain and resected high-grade malignant
tumors were enzyme dissociated and placed in a serum-free defined
medium supplemented with growth factors to facilitate the growth of
spheres. All dissociated TSC tumor spheres and NSPC neurospheres
exhibited the capacity of self-renewal by forming secondary spheres and
upon the withdrawal of mitogens, differentiated to form neuronal and
glial cell types. To
further characterize and understand the tumorigenic
phenotype associated with high-grade malignant gliomas, we
performed whole–genome gene expression analyses on TSC and NSPC samples
with Illumina Bead Arrays. We also conducted genome-wide DNA
methylation analyses using Methylated CpG Island Amplification coupled
with a 105K custom-designed Agilent CpG island oligonucleotide array
(MCAM) on the same samples. The integrated gene expression and DNA
methylation analyses were performed using Partek Genomics Suite
software. We are currently investigating the differential gene
expression and methylation status
of candidate genes in the matched primary tumor tissues as wellas the
expression profile during the differentiation process.