We investigated expression profiles of microRNA (miRNA) in gastric carcinomas by use of a miRNA microarray platform covering a total of 470 human miRNAs. We identified 39 differentially expressed miRNAs in gastric carcinoma, of which six were significantly downregulated and the other 33 were upregulated. We found that miRNA-375 (miR-375) was the most downregulated and that its ectopic expression in gastric carcinoma cells markedly reduced cell viability via the caspase-mediated apoptosis pathway. Interestingly, we found that expression of miR-375 inhibited expression of PDK1, which is a direct target of miR-375, followed by suppression of Akt phosphorylation. Further analysis by gene expression microarray revealed that 14-3-3zeta, a potent antiapoptotic gene, was significantly downregulated at both the mRNA and protein levels in cells transfected with miR-375. The activity of a luciferase reporter containing the miR-375 binding sequence at the 3' untranslated region (UTR) of 14-3-3zeta mRNA was repressed by the ectopic expression of miR-375, suggesting that miR-375 targets the 3' UTR of 14-3-3zeta. In addition, knockdown of either PDK1 or 14-3-3zeta in gastric carcinoma cells induced caspase activation, which was also observed in miR-375-transfected cells, suggesting that miR-375 may exert its proapoptotic function, at least in part, through the downregulation of PDK1 and 14-3-3zeta. Taken together, we propose that miR-375 is a candidate tumor suppressor miRNA in gastric carcinoma.

We investigated expression profiles of microRNA (miRNA) in renal cell carcinoma [clear cell carcinomas (CCC) and chromophobe renal cell carcinomas (ChCC)] and in normal kidneys by using a miRNA microarray platform which covers a total of 470 human miRNAs (Sanger miRBase release 9.1). Unsupervised hierarchical cluster analysis revealed that CCC and ChCC were separable and that no subgroups were identified in CCCs. We found that 43 miRNAs were differentially expressed between CCC and normal kidney, of which 37 were significantly down-regulated in CCC and the other 6 were up-regulated. We also found that 57 miRNAs were differentially expressed between ChCC and normal kidney, of which 51 were significantly down-regulated in ChCC and the other 6 were up-regulated. Together, these observations indicate that expression of miRNAs tends to be down-regulated in both CCC and ChCC compared with normal kidney. We observed that miR-141 and miR-200c were the most significantly down-regulated miRNAs in CCCs. Indeed, in all cases of CCC analysed, both miR-141 and miR-200c were down-regulated in comparison with normal kidney. Microarray data and quantitative RT-PCR showed that these two miRNAs were expressed concordantly. TargetScan algorithm revealed that ZFHX1B mRNA is a hypothetical target of both miR-141 and -200c. We established by quantitative RT-PCR that, in CCCs in which miR-141 and miR-200c were down-regulated, ZFHX1B, a transcriptional repressor for CDH1/E-cadherin, tended to be up-regulated. Furthermore, we found that overexpression of miR-141 and miR-200c caused down-regulation of ZFHX1B and up-regulation of E-cadherin in two renal carcinoma cell lines, ACHN and 786-O. On the basis of these findings, we suggest that down-regulation of miR-141 and miR-200c in CCCs might be involved in suppression of CDH1/E-cadherin transcription via up-regulation of ZFHX1B.

Genomic copy number aberrations (CNAs) are believed to play a major role in the development and progression of human cancers. Although many CNAs have been reported in gastric cancer, their genome-wide transcriptional consequences are poorly understood. In this study, to reveal the impact of CNAs on genome-wide expression in gastric cancer, we analysed 30 cases of gastric cancers for their CNAs by array comparative genomic hybridization (array CGH) and 24 of these 30 cases for their expression profiles by oligonucleotide-expression microarray. We found that with the application of laser microdissection, most CNAs were detected at higher frequency than in previous studies. Notably, gain at 20q13 was detected in almost all cases (97%), suggesting that this may play an important role in the pathogenesis of gastric cancer. By comparing the array CGH data with expression profiles of the same samples, we showed that both genomic amplification and deletion strongly influence the expression of genes in altered genomic regions. Furthermore, we identified 125 candidate genes, consisting of 114 up-regulated genes located in recurrent regions (>10%) of amplification and 11 down-regulated genes located in recurrent regions of deletion. Up-regulation of several candidate genes, such as CDC6, SEC61G, ANP32E, BYSL and FDFT1, was confirmed by immunohistochemistry. Interestingly, some candidate genes were localized at genomic loci adjacent to well-known genes such as EGFR, ERBB2 and SMAD4, and concordantly deregulated by genomic alterations. Based on these results, we propose that our list of candidate genes may contain novel genes involved in the pathogenesis of advanced gastric cancer.

Arpp, a protein containing an ankyrin repeat domain, PEST sequence, and proline-rich region, is a novel ankyrin-repeated protein highly homologous to Carp, which is proposed to be the putative genetic marker for cardiac hypertrophy. In this study, we comparatively analyzed expression of Arpp and Carp protein in skeletal and cardiac muscles and rhabdomyosarcomas (RMSs). In adult skeletal muscle, Arpp was preferentially expressed in the nucleus and cytoplasm of type I fibers, whereas Carp was barely detectable in skeletal muscle. On the other hand, in adult cardiac muscle, interestingly, Arpp was expressed in ventricles mostly, whereas Carp was expressed throughout the atrium and ventricle. Furthermore, although Carp was identified in fetal heart at 11 developmental weeks, Arpp was very low or undetectable in these fetal hearts. These results suggest that Arpp and Carp are differentially expressed and function in both skeletal and cardiac muscle of fetus and adult. We found that Arpp expression was induced during the differentiation of C2C12 cells in vitro, suggesting that Arpp-expression may be associated with the differentiation stage during myogenesis. Both Arpp and Carp were found to be expressed in all of the RMS cases studied. Because the expression patterns of Arpp in RMS were different from those of muscle actin or desmin, Arpp may be detectable in RMS cases that do not express other existing RMS markers.