Gene Expression Profile of Glioblastoma Multiforme Invasive Phenotype Points to New Therapeutic Targets

The invasive phenotype of glioblastoma multiforme (GBM) is a hallmark of malignant process, yet molecular mechanisms that dictate this locally invasive behavior remain poorly understood. Gene expression profiles of human glioma cells were assessed from laser capture-microdissected GBM cells collected from paired patient tumor cores and white matter-invading cell populations. Changes in gene expression in invading GBM cells were validated by quantitative reverse transcription polymerase chain reaction (QRT-PCR) and immunohistochemistry in an independent sample set. QRT-PCR confirmed the differential expression in 19 of 21 genes tested. Immunohistochemical analyses of autotaxin (ATX), ephrin B3, B-cell lymphoma-w (BCLW), and protein tyrosine kinase 2 beta showed them to be expressed in invasive glioma cells. The known GBM markers, insulin-like growth factor binding protein 2 and vimentin, were robustly expressed in the tumor core. A glioma invasion tissue microarray confirmed the expression of ATX and BCLW in invasive cells of tumors of various grades. GBM phenotypic and genotypic heterogeneity is well documented. In this study, we show an additional layer of complexity: transcriptional differences between cells of tumor core and invasive cells located in the brain parenchyma. Gene products supporting invasion may be novel targets for manipulation of brain tumor behavior with consequences on treatment outcome.