Characterization of genes with increased expression in human glioblastomas

In the present study, we have used the gene expression data available in the SAGE database in an attempt to identify glioblastoma molecular markers. Of 129 genes with more than 5-fold difference found by comparison of nine glioblastoma with five normal brain SAGE libraries, 44 increased their expression in glioblastomas. Most corresponding proteins were involved in angiogenesis, host-tumor immune interplay, multidrug resistance, extracellular matrix (ECM) formation, IGF-signalling, or MAP-kinase pathway. Among them, 16 genes had a high expression both in glioblastomas and in glioblastoma cell lines suggesting their expression in transformed cells. Other 28 genes had an increased expression only in glioblastomas, not in glioblastoma cell lines suggesting an expression possibly originated from host cells. Many of these genes are among the top transcripts in activated macrophages, and involved in immune response and angiogenesis. This altered pattern of gene expression in both host and tumor cells, can be viewed as a molecular marker in the analysis of malignant progression of astrocytic tumors, and as possible clues for the mechanism of disease. Moreover, several genes overexpressed in glioblastomas produce extracellular proteins, thereby providing possible therapeutic targets. Further characterization of these genes will thus allow them to be exploited in molecular classification of glial tumors, diagnosis, prognosis, and anticancer therapy.