BACKGROUND A recent genomewide mutational analysis of glioblastomas (World Health Organization [WHO] grade IV glioma) revealed somatic mutations of the isocitrate dehydrogenase 1 gene (IDH1) in a fraction of such tumors, most frequently in tumors that were known to have evolved from lower-grade gliomas (secondary glioblastomas). METHODS We determined the sequence of the IDH1 gene and the related IDH2 gene in 445 central nervous system (CNS) tumors and 494 non-CNS tumors. The enzymatic activity of the proteins that were produced from normal and mutant IDH1 and IDH2 genes was determined in cultured glioma cells that were transfected with these genes. RESULTS We identified mutations that affected amino acid 132 of IDH1 in more than 70% of WHO grade II and III astrocytomas and oligodendrogliomas and in glioblastomas that developed from these lower-grade lesions. Tumors without mutations in IDH1 often had mutations affecting the analogous amino acid (R172) of the IDH2 gene. Tumors with IDH1 or IDH2 mutations had distinctive genetic and clinical characteristics, and patients with such tumors had a better outcome than those with wild-type IDH genes. Each of four tested IDH1 and IDH2 mutations reduced the enzymatic activity of the encoded protein. CONCLUSIONS Mutations of NADP+-dependent isocitrate dehydrogenases encoded by IDH1 and IDH2 occur in a majority of several types of malignant gliomas.

Centrosome- and cilia-associated proteins play crucial roles in establishing polarity and regulating intracellular transport in post-mitotic cells. Using genetic mapping and positional candidate strategy, we have identified an in-frame deletion in a novel centrosomal protein CEP290 (also called NPHP6), leading to early-onset retinal degeneration in a newly identified mouse mutant, rd16. We demonstrate that CEP290 localizes primarily to centrosomes of dividing cells and to the connecting cilium of retinal photoreceptors. We show that, in the retina, CEP290 associates with several microtubule-based transport proteins including RPGR, which is mutated in approximately 15% of patients with retinitis pigmentosa. A truncated CEP290 protein (DeltaCEP290) is detected in the rd16 retina, but in considerably reduced amounts; however, the mutant protein exhibits stronger association with specific RPGR isoform(s). Immunogold labeling studies demonstrate the redistribution of RPGR and of phototransduction proteins in the photoreceptors of rd16 retina. Our findings suggest a critical function for CEP290 in ciliary transport and provide insights into the mechanism of early-onset photoreceptor degeneration.

Point mutations of the NADP + -dependent isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) occur early in the pathogenesis of gliomas. When mutated, IDH1 and IDH2 gain the ability to produce the metabolite (R)-2-hydroxyglutarate (2HG), but the downstream effects of mutant IDH1 and IDH2 proteins or of 2HG on cellular metabolism are unknown. We profiled >200 metabolites in human oligodendroglioma (HOG) cells to determine the effects of expression of IDH1 and IDH2 mutants. Levels of amino acids, glutathione metabolites, choline derivatives, and tricarboxylic acid (TCA) cycle intermediates were altered in mutant IDH1-and IDH2-expressing cells. These changes were similar to those identified after treatment of the cells with 2HG. Remarkably, N-acetyl-aspartyl-glutamate (NAAG), a common dipeptide in brain, was 50-fold reduced in cells expressing IDH1 mutants and 8.3-fold reduced in cells expressing IDH2 mutants. NAAG also was significantly lower in human glioma tissues containing IDH mutations than in gliomas without such mutations. These metabolic changes provide clues to the pathogenesis of tumors associated with IDH gene mutations.ifferences in cellular metabolism between cancer and normal cells have long been noted by cancer researchers (1). Genetic alterations that occur in cancer, such as mutations and copy number changes that alter K-Ras and c-Myc, are thought to be responsible for at least some of these metabolic differences (2, 3). The genetic alterations that drive cancer pathogenesis may do so in part by deregulating cellular metabolism. Such deregulation could aberrantly signal cells to proliferate and provide molecular building blocks for cellular replication (4). This possibility has generated enthusiasm for the idea that that drug targets for the specific killing of cancer cells can be identified by studying the metabolic differences between normal and cancer cells.Gliomas are tumors of the central nervous system that respond poorly to therapy and are associated with a heterogeneous collection of genetic alterations (5, 6), including mutations in IDH1 and IDH2 (7,8). IDH1 and IDH2 are the cytoplasmic and mitochondrial NADP + -dependent isocitrate dehydrogenases, respectively, and are homologs. Isocitrate dehydrogenase 3 (IDH3), which is unrelated to IDH1 and IDH2, is a NAD + -dependent isocitrate dehydrogenase and has not been found to be mutated in cancer (Fig. S1A). These enzymes convert isocitrate to α-ketoglutarate (Fig. S1B). IDH1 catalyzes this reaction in the cytosol and peroxisome to mediate a variety of cellular housekeeping functions, whereas IDH2 and IDH3 catalyze a step in the tricarboxylic acid (TCA) cycle (reviewed in ref. 9). IDH1-R132 mutations occur frequently (50-93%) in astrocytomas and oligodendrogliomas, as well as in secondary glioblastomas, and may be the initiating lesion in these glioma subtypes (7,8). Mutations in the analogous IDH2-R172 codon also occur at a lower rate (3-5%) in these cancers (8). Interestingly, mutations in IDH1 and IDH2 were observed subsequently in 22% of ac...

Stem cell genetics research may be critical to our understanding of carcinogenesis, as both stem cells and cancer cells possess the ability to self-renew. Recent discoveries have indicated that the piwi family of genes plays an essential role in stem cell selfrenewal in diverse organisms. The hiwi gene, the human homolog of the piwi family, participates in germ cell proliferation and its overexpression may cause the development of germ cell malignancy, but its expression and function in epithelial solid cancers have not been explored. In the present study, we investigated whether there was an association between hiwi expression and human gastric cancer and its potential mechanism. RT-PCR findings demonstrated that hiwi was expressed in different gastric cancer cell lines. To identify the HIWI protein in gastric cancer, we developed a specific monoclonal antibody against HIWI and immunohistochemistry was performed on various gastric tissues. We found that the expression ratio of hiwi in normal gastric tissues, atrophic gastritis, intestinal metaplasia and gastric cancers was 10% (5/50), 36% (18/50), 36% (18/50) and 76% (38/50), respectively, which was consistent with precancerous development. Notably, the expression pattern of hiwi in gastric cancer tissues was similar to that of Ki67, which was used as a marker of proliferation. Moreover, the suppression of hiwi by antisense or RNAi inhibited the growth of gastric cancer cells and induced cell cycle arrest in G 2 /M phase. These results suggest that hiwi may be involved in the development of gastric cancer and is a potential target for cancer therapy. ' 2005 Wiley-Liss, Inc.Key words: hiwi; expression; gastric cancer; proliferation Although there is a high incidence of gastric cancer in Asia and gastric cancer remains one of the leading causes of cancer-related death worldwide, 1 the molecular mechanisms underlying its development are poorly understood. Stem cell research will greatly expand our understanding of the mechanisms of carcinogenesis because the homeostatic mechanisms mediating stem cell proliferation are the same processes that become dysregulated in carcinogenesis.2,3 Therefore, the study of stem cell genes may be critical to furthering our understanding of carcinogenesis and to the development of novel strategies for preventing and managing cancer. 4 Because of this, there is a growing interest in studying the roles of genes, which were initially found to be involved in stem cell selfrenewal, in the development of cancer. 5-7The hiwi gene is a human member of the piwi family, which represents the first class of genes known to be required for stem cell self-renewal in diverse organisms.8 Recent discoveries have shown that hiwi may participate in germ cell proliferation and its overexpression may cause germ cell malignancy development. 9These findings raise the hypothesis that hiwi may be present in other types of stem cells and likewise may be involved in the development of cancers.The hiwi gene, located in 12q24.33, was originally isolated from a h...