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Amplification and overexpression of E2F3 in human bladder cancer.

ABSTRACT: We demonstrate that, in human bladder cancer, amplification of the E2F3 gene, located at 6p22, is associated with overexpression of its encoded mRNA transcripts and high levels of expression of E2F3 protein. Immunohistochemical analyses of E2F3 protein levels have established that around one-third (33/101) of primary transitional cell carcinomas of the bladder overexpress nuclear E2F3 protein, with the proportion of tumours containing overexpressed nuclear E2F3 increasing with tumour stage and grade. When considered together with the established role of E2F3 in cell cycle progression, these results suggest that the E2F3 gene represents a candidate bladder cancer oncogene that is activated by DNA amplification and overexpression. Keywords: Tumour vs normal comparison, array CGH

ORGANISM(S): Homo sapiens

PROVIDER: GSE6123 | GEO | 2006/10/27

SECONDARY ACCESSION(S): PRJNA97619

REPOSITORIES: GEO

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Project description:Background: Previous array CGH analyses have revealed several recurring genomic alterations in urothelial carcinoma. The most common genomic amplifications occur at 6p22 and 1q21-24. The main target gene at 6p22 is believed to be E2F3. This gene is frequently co-amplified with CDKAL1 and SOX4 and there are reports on 6p22 amplifications that do not include the E2F3 locus. Previous array CGH analyses have indicated multiple possible target regions at 1q21-24. However, due to complex rearrangements it has been difficult to identify specific 1q21-24 target regions and target genes. Results: We show that the most commonly amplified gene at 6p22 is SOX4 and that SOX4 can be amplified and over expressed without E2F3 or CDKAL1 being included in the amplicon. Hence, our data point to SOX4 as an auxiliary amplification target at 6p22. We further show that at least three amplified regions are observed at 1q21-24. Copy number data, combined with gene expression data, highlighted BCL9 and CHD1L as possible targets in the most proximal region and MCL1, SETDB1, and HIF1B as targets in the middle region, whereas no obvious gene targets could be determined in the most distal amplicon. We also highlight the enrichment of G4 quadruplex sequence motifs and the high number of intraregional sequence duplications, both known to contribute to genomic instability, as prominent features of the 1q21-24 region. Conclusions: Our detailed analyses of the 6p22 amplicon in urothelial carcinomas suggest SOX4 as an auxiliary target gene for amplification. We further demonstrate three separate target regions for amplification at 1q21-24 and identified BCL9, CHD1L, MCL1, SETDB1, and HIF1B as likely target genes within these regions. The study was conducted on genomic DNA from 68 primary fresh-frozen urothelial carcinoma tumors analysed using a Agilent SurePrint G3 4x180k Custom CGH Microarray Platform (028432). Samples were selected based on the presence of copy number alterations observed on lower resolution genomic data (32K BAC array). The majority of the BAC data is publicly available in GEO submissions GSE32535 and GSE19915. CN profiles for a minority of samples were derived from Illumina Methylation27k arrays according to Lauss et al 2012 [PMID: 22705924] and can be recreated from the data deposited in GSE33510 (derived CN data). Sample names are the same between all studies. This dataset also partly overlaps with Series GSE32894 (gene expression data). Names of the overlapping sample names are the same and indicated in the description field. Data from GSE32894 was used to calculate correlations between CN and gene expression.

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Amplification and overexpression of E2F3 in human bladder cancer.

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