ABSTRACT
Gene expression levels are regulated at many levels. Integration of genome-wide analyses for the study of DNA and RNA provides a unique tool to detect genetic alterations in the cancer genome. In this study, we generated and integrated DNA amplification data from comparative genomic hybridization (CGH) and serial analyses of gene expression (SAGE) in order to obtain a molecular profile of gastroesophageal junction (GEJ) carcinomas. DNA amplifications mapped to specific chromosomal regions and were frequently seen at 1q, 4q, 5q, 6p, 7p, 8q, 17q, and 20q. Using SAGE, we obtained over 156,432 tags from GEJ adenocarcinomas and normal gastric mucosa. These tags were assigned to UniGene clusters. Chromosomal positions for overexpressed genes were obtained to produce a GEJ carcinoma transcriptome map. A total of 123 genes was significantly overexpressed (more than fivefold; P <.01) in one or more SAGE libraries. This gene overexpression map was integrated and compared to the chromosomal CGH ideogram. Several chromosomal arms that had frequent DNA amplifications showed frequent gene expression alterations such as chromosomes 1 (15 genes), 2 (9 genes), 6 (6 genes), 11 (6 genes), 12 (8 genes), and 17 (13 genes). Despite the relatively large DNA amplification regions, overexpressed genes frequently mapped and clustered to small chromosomal regions at early-replicating (Giemsa light) bands such as 1q21.3 (nine genes), 6p21.3 (five genes), and 17q21 (eight genes). These results provide a comprehensive tool to search for DNA amplifications and overexpressed genes in GEJ carcinoma. The observed phenomenon of the presence of large amplification areas, yet clustering of overexpressed genes to relatively small loci, may suggest a high organization of chromatin and cancer-related genes in the nucleus.
Subject(s)
Adenocarcinoma/genetics , Chromosomes, Human/genetics , Esophageal Neoplasms/genetics , Gene Expression , Genome, Human , Stomach Neoplasms/genetics , Adenocarcinoma/pathology , Esophageal Neoplasms/pathology , Gastric Mucosa/metabolism , Gastric Mucosa/pathology , Gene Amplification , Gene Expression Profiling , Gene Silencing , Humans , Multigene Family , Nucleic Acid Hybridization , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction , Stomach Neoplasms/pathologyABSTRACT
Urothelial carcinomas (TCC) constitute the vast majority of bladder cancers in most of the world. On the other hand, squamous cell bladder carcinoma, a rare subtype in the Western world, is a common subtype in areas with endemic Schistosoma infection. Although schistosomal infection has been reported to influence DNA methylation, the pattern and extent of CpG island hypermethylation in squamous cell carcinomas remain unknown. In this study, we used methylation-specific PCR to characterize 12 cancer-related genes in 41 bladder cancer samples from Egypt (31 squamous cell carcinomas (SCC), 21 of them associated with Schistosoma and 10 TCC, five of which were Schistosoma-associated). The genes analyzed included E-cadherin, DAP-Kinase, O6MGMT, p14, p15, p16, FHIT, APC, RASSF1A, GSTP1, RARbeta and p73. Methylation of at least one gene was detected in all squamous cell tumors except two, and 45% of samples had at least three methylated genes. The average methylation index was 0.24, corresponding to three of the 12 analyzed genes. Schistosoma-associated tumors had more genes methylated than non-Schistosoma tumors (average MI: 0.29 vs 0.14) (P = 0.027). Although the extent of methylation in TCC (average MI: 0.16) was lower than in squamous cell carcinomas (SCC), the overall profile of methylation was similar, with Schistosoma-associated cases having a higher methylation index. Our results suggest that schistosomal involvement associates with a greater degree of epigenetic changes in the bladder epithelium.
