[Tissue array technology for translational research. From gene discovery to application].

Large scale scanning of the human genome has become possible with the introduction of DNA microarray. The ability to survey the expression of up to 5000 to 50,000 genes in a single experiment provides significant new opportunities, as well as new challenge. It will be important to translate genomic scale information on cancer biology to functional or clinical application. This requires prioritization of hundreds of targets discovered, functional validation of these targets, as well as a thorough knowledge of the involvement of the candidate target genes in vivo in human tissue. We have developed a tissue array technology for genome scale expressional and clinical cancer research. This technology enables high-throughput molecular analysis of large number of specimens. Our tissue arrays are constructed by arranging the cylindrical biopsies of 2.0 mm diameter from 60 individual tumor tissues into a tissue array block, which is then sliced into 200 or more identical slides for probing RNA or protein targets. A single immunohistochemistry or in situ hybridization experiment provides information on all 60 specimens on the slides, while subsequent sections can be analyzed with other probes or antibodies. We produced gastric cancer tissue array slides with various kinds of subsets, including 600 subsequent cancer cases, 100 preneoplastic lesions, 60 metastatic lesions, 60 synchronous cancers, 60 metachronous cancers, 60 young age patients, and 120 familial cases. We searched the presence of Epstein-Barr virus in those cancer specimens. We also applied 10 antibodies in those samples and stratify the prognostic significance of these antibodies. Tissue array technology expand the scope of high-throughput molecular analysis of archival tissue specimens with multiple probes for specific genes or proteins for functional or clinical application.

Assessment of markers for the identification of microsatellite instability phenotype in gastric neoplasms.

We tested three mononucleotide, 45 dinucleotide, and five tetranucleotide repeats in 30 gastric adenomas and 30 gastric carcinomas for microsatellite instability (MSI) in order to evaluate which microsatellites might indicate the MSI status in gastric neoplasms. Along with the increase in tested markers, the proportion of low-frequency MSI (MSI-L) tumors increased. On immunohistochemistry, MSI-L gastric neoplasms did not show any alteration in hMLH1 or hMSH2 protein expression, while most of the high-frequency MSI (MSI-H) tumors did show alterations in the above mismatch repair proteins. The above findings suggested that MSI-L tumors cannot be distinguished from microsatellite stable tumors. Two mononucleotides, BAT25 and BAT26, were sufficient for the screening of MSI. An additional three dinucleotides, D17S786, D6S105 and D19S188, were also highly sensitive and specific in identifying MSI phenotype tumors.