Tiling resolution array CGH and high density expression profiling of urothelial carcinomas delineate genomic amplicons and candidate target genes specific for advanced tumors.

ABSTRACT: BACKGROUND: Urothelial carcinoma (UC) is characterized by nonrandom chromosomal aberrations, varying from one or a few changes in early-stage and low-grade tumors, to highly rearranged karyotypes in muscle-invasive lesions. Recent array-CGH analyses have shed further light on the genomic changes underlying the neoplastic development of UC, and have facilitated the molecular delineation amplified and deleted regions to the level of specific candidate genes. In the present investigation we combine detailed genomic information with expression information to identify putative target genes for genomic amplifications. METHODS: We analyzed 38 urothelial carcinomas by whole-genome tiling resolution array-CGH and high density expression profiling to identify putative target genes in common genomic amplifications. When necessary expression profiling was complemented with Q-PCR of individual genes. RESULTS: Three genomic segments were frequently and exclusively amplified in high grade tumors; 1q23, 6p22 and 8q22, respectively. Detailed mapping of the 1q23 segment showed a heterogeneous amplification pattern and no obvious commonly amplified region. The 6p22 amplicon was defined by a 1.8 Mb core region present in all amplifications, flanked both distally and proximally by segments amplified to a lesser extent. By combining genomic profiles with expression profiles we could show that amplification of E2F3, CDKAL1, SOX4, and MBOAT1 as well as NUP153, AOF1, FAM8A1 and DEK in 6p22 was associated with increased gene expression. Amplification of the 8q22 segment was primarily associated with YWHAZ (14-3-3-zeta) and POLR2K over expression. The possible importance of the YWHA genes in the development of urothelial carcinomas was supported by another recurrent amplicon paralogous to 8q22, in 2p25, where increased copy numbers lead to enhanced expression of YWHAQ (14-3-3-theta). Homozygous deletions were identified at 10 different genomic locations, most frequently affecting CDKN2A/CDKN2B in 9p21 (32%). Notably, the latter occurred mutually exclusive with 6p22 amplifications. CONCLUSION: The presented data indicates 6p22 as a composite amplicon with more than one possible target gene. The data also suggests that amplification of 6p22 and homozygous deletions of 9p21 may have complementary roles. Furthermore, the analysis of paralogous regions that showed genomic amplification indicated altered expression of YWHA (14-3-3) genes as important events in the development of UC

Molecular Characterization of Genomic Amplifications in Pancreatic Cancer

Pancreatic cancer includes multiple histologic subtypes that show large differences in their clinical and biological characteristics. Despite this diversity, more than 85% of the neoplasms in the organ are malignant ductal adenocarcinomas, which are the focus of the present thesis. At the genetic level this tumor type is characterized by highly rearranged karyotypes, resulting in a large number of DNA copy number alterations. As these are believed to play a major role in pancreatic tumorigenesis, the aim of the present thesis was to molecularly characterize such imbalances, particularly genomic amplifications, in a panel of 32 pancreatic carcinoma cell lines. The first study was based on previously generated CGH data, which indicated frequent local amplifications of 12p11-12. For precise characterization of this region, we used single-copy FISH analysis and PCR-based STS mapping. This delineated a commonly amplified segment of 3.5 Mb in six cases. To identify potential target genes in this region, a chromosome segment-specific cDNA array containing 29 genes/ESTs, were used to search for consistently overexpressed genes. This analysis identified four genes/ESTs, including PPFIBP1 and DEC2. In the second study we performed array-based CGH for high-resolution mapping of genome-wide DNA copy number alterations. For this purpose, two separate microarray platforms were used, the first containing >3,500 BAC clones and the second encompassing >25,000 cDNA clones. In total, 60 amplifications at 32 different genomic loci were characterized in detail. The most frequently amplified regions were located in 8q23-24 and 12p11-12. Apart from the large number of genomic amplifications, the array-based CGH analyses identified several homozygously deleted segments, including sequences within 9p24, 9p21, 9q32, 10p12, 10q22, 12q24, and 18q23. In the third study we performed expression profiling to investigate the transcriptional consequences of the genomic alterations identified by the array-based CGH analyses. This investigation showed a strong correlation between DNA copy numbers and gene expression levels in pancreatic cancer. Moreover, the expression analysis revealed that the most commonly amplified regions do not appear to have a single target gene. Instead, the results suggested that several target genes may be of importance in each amplified segment, and that these may show varying degrees of overexpression in individual amplifications. Nevertheless, the expression profiling study identified new genes in both the 8q23-24, and the 12p11-12, amplicons of potential importance for the development of pancreatic cancer

Tiling resolution array comparative genomic hybridization analysis of a fibrosarcoma of bone.

Fibrosarcoma of bone is a rare malignant tumor accounting for less than 5% of all primary malignant bone neoplasms. There is very limited knowledge regarding the molecular genetics of this tumor, and there are no cytogenetic data available. In the present study, a fibrosarcoma deriving from the left iliac bone of a 10-year-old girl was characterized using cytogenetics, fluorescence in situ hybridization (FISH), and whole genome tiling resolution array comparative genomic hybridization (CGH). Cytogenetic and FISH analyses revealed a ring chromosome 6 as the sole acquired aberration, a finding corroborated by array CGH. The ring formation, however, did not result in any gain of genetic material. Nor did the breakpoints in 6p25 and 6q14 seem to affect any known gene loci in such a way that the ring formation could have resulted in the creation of a fusion gene or in the exchange of regulatory sequences. Thus, a reasonable interpretation of the pathogenetic significance of the ring formation would be that it resulted in the loss of one or more putative tumor suppressor gene loci distal to the two breakpoints

Single-cell sequencing in translational cancer research and challenges to meet clinical diagnostic needs

The ability to capture alterations in the genome or transcriptome by next-generation sequencing has provided critical insight into molecular changes and programs underlying cancer biology. With the rapid technological development in single-cell sequencing, it has become possible to study individual cells at the transcriptional, genetic, epigenetic, and protein level. Using single-cell analysis, an increased resolution of fundamental processes underlying cancer development is obtained, providing comprehensive insights otherwise lost by sequencing of entire (bulk) samples, in which molecular signatures of individual cells are averaged across the entire cell population. Here, we provide a concise overview on the application of single-cell analysis of different modalities within cancer research by highlighting key articles of their respective fields. We furthermore examine the potential of existing technologies to meet clinical diagnostic needs and discuss current challenges associated with this translation

Tiling resolution array CGH of dic(7;9)(p11 approximately 13;p11 approximately 13) in B-cell precursor acute lymphoblastic leukemia reveals clustered breakpoints at 7p11.2 approximately 12.1 and 9p13.1.

The dic( 7; 9)( p11 similar to 13; p11 similar to 13) is a recurrent chromosomal abnormality in acute lymphoblastic leukemia (ALL), mainly of B-lineage. Although more than 20 dic(7; 9)-positive ALLs have been reported to date, the molecular genetic consequences of this aberration are unknown. We performed tiling resolution (32K) genome-wide array-based comparative genomic hybridization ( array CGH) analysis of three cases with dic(7; 9) in order to characterize the breakpoints on 7p and 9p. The analysis showed a clustering of breakpoints within 9p13.1 in all three cases and within 7p11.2 in two cases; the array CGH revealed two different breakpoints - 7p12.1 and 7p14.1 - in the remaining case. Based on these findings the abnormality should hence be designated dic(7; 9)(p11.2 similar to 12.1; p13.1). Locus-specific fluorescence in situ hybridization analysis of one of the cases narrowed down the 7p11.2 breakpoint to a < 500-kb segment in this sub-band, a region containing three known genes. Unfortunately, lack of material precluded further molecular genetic studies, and it thus remains unknown whether the pathogenetically important outcome of the dic(7; 9) is formation of a chimeric gene or loss of 7p and/or 9p material. Copyright (c) 2007 S. Karger AG, Basel

Altered expression of TGFB receptors and mitogenic effects of TGFB in pancreatic carcinomas

Alteration of the transforming growth factor beta (TGFB) signalling pathway is important in pancreatic carcinogenesis, as shown by the frequent inactivation of the downstream target SMAD4. We recently analysed a series of pancreatic carcinoma cell lines with respect to alterations of five SMAD genes involved in TGFB signalling, and showed that SMAD4 was structurally rearranged in 42% of these. This pathway may, however, also be affected by alterations of genes whose products regulate the activation of TGFB as well as of TGFB receptor genes. We therefore studied the expression of UPA, UPAR, IGF2R, ALK5 (TGFBR1), TGFBR2, TGFBR3, ENG, ALK1, TGFB1, TGFB2, and TGFB3 in a series of 14 pancreatic carcinoma cell lines. We also analysed ALK5 and TGFBR2 for mutations, cell surface localisation of TGFBR2 and ENG, and TGFB1 response. No mutations of ALK5 or TGFBR2 were found. However, 4 cell lines were methylated within the ALK5 promoter region. ALK5 expression was strongly reduced in 9 cases, whereas TGFBR2 expression was increased in 12 of the cell lines. The TGFB signalling associated receptors ENG and ALK1 were co-expressed in 4 of the cell lines. There was no evidence for disruption of the UPAR-IGF2R TGFB activating pathway. The response to TGFB1 was analysed in 12 cell lines, and 6 of these (50%) showed increased proliferation. The cell lines stimulated by TGFB showed frequent mutations of SMAD4, KRAS2, and TP53, as well as frequent absence of CDKN2B expression. These results suggest that the ALK5-SMAD4 part of the TGFB signalling pathway is a major target for inactivation in pancreatic carcinomas, that the expression of TGFBR2, TGFBR3, and receptors involved in TGFB activation are maintained, and that alterations of components of the TGFB signalling pathway may be accompanied by a positive effect of TGFB on cell growth