Imaging of gene expression in glioblastoma

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DESCRIPTION (provided by applicant): Differences in the pattern of gene expression between normal brain and its tumors of glial origin can provide information useful for malignant glioma diagnosis and therapy. These tumors cannot be diagnosed until they become visible on MRI scans and cannot be currently treated (mean survival of patients = 6-12 months). Markers for glioma tumor formation and malignant progression are becoming available through gene profiling methods, such as serial analysis of gene expression (SAGE). Recently, SAGE data for malignant glioma (GBM) has become available through efforts of the Cancer Genome Anatomy Project (CGAP) and several genes have been identified that are over-expressed in GBM and not in normal brain. This information can be exploited to design selective markers for imaging and treatment of these tumors. Specifically, this project proposes to: 1- Verify that candidate SAGE-identified GBM genes are truly overexpressed in GBMs, 2- Isolate the relevant promoter fragments from transcriptionally overactive genes, and 3-Test the ability of cloned transcriptionally over-active promoters to provide GBM-specific cDNA expression for imaging and therapy in both.in vitro and in vivo models. SAGE data on GBM-specific genes will be verified in GBM tumor cells and compared to normal cells using laser-capture microdissection and quantitative RT-PCR analyses. Truly overexpressed genes will be investigated and events other than transcription that may be causing overexpression will be ruled out. Promoter sequences of candidate genes will be isolated through the appropriate bacterial artificial chromosome (BAG) containing the genomic sequence of the candidate genes. A novel method of converting these BACs into infectious vectors will be used to study and confirm promoter functionality and selectivity in GBM cells. GBM overactive and selective promoters will then used to direct transcription of an imaging cDNA and/or of a "suicide" gene in glioma cells, first in tissue culture and then in in vivo models of cancer. These studies will provide an avenue for translating CGAP data into useful diagnostic and therapeutic modalities not only for malignant tumors in the brain, but also for other tumors. The conceptual scheme presented herein is also potentially applicable to a variety of diseases for which gene profiling analyses is available.