Comprehensive genomic characterization defines human glioblastoma genes and core pathways

Abstract

Human cancer cells typically harbour multiple chromosomal aberrations, nucleotide substitutions and epigenetic modifications that drive malignant transformation. The Cancer Genome Atlas (TCGA) pilot project aims to assess the value of large-scale multi-dimensional analysis of these molecular characteristics in human cancer and to provide the data rapidly to the research community. Here we report the interim integrative analysis of DNA copy number, gene expression and DNA methylation aberrations in 206 glioblastomas—the most common type of adult brain cancer—and nucleotide sequence aberrations in 91 of the 206 glioblastomas. This analysis provides new insights into the roles of ERBB2, NF1 and TP53, uncovers frequent mutations of the phosphatidylinositol-3-OH kinase regulatory subunit gene PIK3R1, and provides a network view of the pathways altered in the development of glioblastoma. Furthermore, integration of mutation, DNA methylation and clinical treatment data reveals a link between MGMT promoter methylation and a hypermutator phenotype consequent to mismatch repair deficiency in treated glioblastomas, an observation with potential clinical implications. Together, these findings establish the feasibility and power of TCGA, demonstrating that it can rapidly expand knowledge of the molecular basis of cancer. The Cancer Genome Atlas, a large-scale genomics project to catalogue cancer-linked mutations, is starting to produce results. Glioblastoma, the most common brain cancer, was the first target for the project and the initial results, published AOP on 4 September, are now in print. Genes newly implicated in glioblastoma include tumour suppressors (NF1, RB1, ATM and APC) and several tyrosine kinase genes. Glioblastoma is extremely resistant to therapy, hence the potential importance of the development of a possible model system. Zheng et al. report that mice lacking the tumour suppressors p53 and Pten develop tumours resembling human glioblastomas, associated with increased Myc protein levels. As well as offering a potential system for testing therapeutics, this points to c-Myc as a possible drug target. With a comprehensive analysis of sequencing data, DNA copy number, gene expression and DNA methylation in a large number of human glioblastomas, The Cancer Genome Atlas project initiative provides a broad overview of the genes and pathways that are altered in this cancer type.