Mutations in isocitrate dehydrogenase 1 and 2 (IDH1, 2) have been demonstrated in the majority of World Health Organization grade 2 and grade 3 gliomas in adults. These mutations are associated with the accumulation of 2-hydroxyglutarate (2HG) within the tumor. Here we report the noninvasive detection of 2HG by proton magnetic resonance spectroscopy (MRS). The pulse sequence was developed and optimized with numerical and phantom analyses for 2HG detection. The concentrations of 2HG were estimated using spectral fitting in the tumors of 30 patients. Detection of 2HG correlated with mutations in IDH1 or IDH2 and with increased levels of D-2HG by mass spectrometry of resected tumor. Noninvasive detection of 2HG may prove to be a valuable diagnostic and prognostic biomarker.

Approximately 10% to 15% of human cancers lack detectable telomerase activity, and a subset of these maintain telomere lengths by the telomerase-independent telomere maintenance mechanism termed alternative lengthening of telomeres (ALT). The ALT phenotype, relatively common in subtypes of sarcomas and astrocytomas, has rarely been reported in epithelial malignancies. However, the prevalence of ALT has not been thoroughly assessed across all cancer types. We therefore comprehensively surveyed the ALT phenotype in a broad range of human cancers. In total, two independent sets comprising 6110 primary tumors from 94 different cancer subtypes, 541 benign neoplasms, and 264 normal tissue samples were assessed by combined telomere-specific fluorescence in situ hybridization and immunofluorescence labeling for PML protein. Overall, ALT was observed in 3.73% (228/6110) of all tumor specimens, but was not observed in benign neoplasms or normal tissues. This is the first report of ALT in carcinomas arising from the bladder, cervix, endometrium, esophagus, gallbladder, kidney, liver, and lung. Additionally, this is the first report of ALT in medulloblastomas, oligodendrogliomas, meningiomas, schwannomas, and pediatric glioblastoma multiformes. Previous studies have shown associations between ALT status and prognosis in some tumor types; thus, further studies are warranted to assess the potential prognostic significance and unique biology of ALT-positive tumors. These findings may have therapeutic consequences, because ALT-positive cancers are predicted to be resistant to anti-telomerase therapies.

Despite being the most common liver cancer in children, hepatoblastoma (HB) is a rare neoplasm. Consequently, few pretreatment tumors have been molecularly profiled, and there are no validated prognostic or therapeutic biomarkers for HB patients. We report on the first large-scale effort to profile pretreatment HBs at diagnosis. Our analysis of 88 clinically annotated HBs revealed three risk-stratifying molecular subtypes that are characterized by differential activation of hepatic progenitor cell markers and metabolic pathways: high-risk tumors were characterized by up-regulated nuclear factor, erythroid 2-like 2 activity; high lin-28 homolog B, high mobility group AT-hook 2, spalt-like transcription factor 4, and alpha-fetoprotein expression; and high coordinated expression of oncofetal proteins and stem-cell markers, while low-risk tumors had low lin-28 homolog B and lethal-7 expression and high hepatic nuclear factor 1 alpha activity. Conclusion: Analysis of immunohistochemical assays using antibodies targeting these genes in a prospective study of 35 HBs suggested that these candidate biomarkers have the potential to improve risk stratification and guide treatment decisions for HB patients at diagnosis; our results pave the way for clinical collaborative studies to validate candidate biomarkers and test their potential to improve outcome for HB patients. (HEPATOLOGY 2017;65:104-121).H epatoblastoma (HB) is the most common pediatric liver tumor. It has an annual incidence rate of approximately 1.8 diagnosed cases per million in the United States, and this rate is increasing at more than 4.3% annually.(1) HBs are embryonal neoplasms that are most commonly diagnosed during the first 3 years of life. They are believed to arise from hepatic cell precursors and are characterized by heterogeneous histological patterns reminiscent of liver developmental stages.(2) Therapeutic strategies combining surgical resection and chemotherapy have improved outcomes for children with HB, but the prognosis for patients with advanced or chemotherapy-refractory disease remains poor.(1) In addition, the most effective platinum-based agents for treatment of HB often lead to serious long-term adverse effects, including ototoxicity and nephrotoxicity.(1)We describe the results of a comprehensive genomic analysis of the largest set of clinically annotated HBs reported to date. Such efforts have previously identified

Summary Mammalian cells generate citrate by decarboxylating pyruvate in the mitochondria to supply the tricarboxylic acid (TCA) cycle. In contrast, hypoxia and other impairments of mitochondrial function induce an alternative pathway that produces citrate by reductively carboxylating α-ketoglutarate (AKG) via NADPH-dependent isocitrate dehydrogenase (IDH). It is unknown how cells generate reducing equivalents necessary to supply reductive carboxylation in the setting of mitochondrial impairment. Here we identified shared metabolic features in cells using reductive carboxylation. Paradoxically, reductive carboxylation was accompanied by concomitant AKG oxidation in the TCA cycle. Inhibiting AKG oxidation decreased reducing equivalent availability and suppressed reductive carboxylation. Interrupting transfer of reducing equivalents from NADH to NADPH by nicotinamide nucleotide transhydrogenase increased NADH abundance and decreased NADPH abundance while suppressing reductive carboxylation. The data demonstrate that reductive carboxylation requires bidirectional AKG metabolism along oxidative and reductive pathways, with the oxidative pathway producing reducing equivalents used to operate IDH in reverse.

Renal aging, by itself, is associated with alterations in renal morphology and a decline in renal function, which is accelerated and/or accentuated by diseases such as diabetes mellitus and hypertension. The aging-related renal insufficiency has important implications with regards to body homeostasis, drug toxicity, and renal transplantation. An understanding of renal aging and its distinction from renal insufficiency secondary to diseases is essential for individualized care of the elderly. Toward this end, investigations are underway to elucidate the molecular mechanisms of renal aging. This review summarizes the structural and functional changes of the aging kidney and highlights the advances made in our understanding of the renal aging process.

Through unbiased metabolomics, we identified elevations of the metabolite 2-hydroxyglutarate (2HG) in renal cell carcinoma (RCC). 2HG can inhibit 2-oxoglutaratre (2-OG) dependent dioxygenases which mediate epigenetic events including DNA and histone demethylation. 2HG accumulation, specifically the D- enantiomer, can result from gain of function mutations of isocitrate dehydrogenase (IDH1, IDH2) found in several different tumors. In contrast, kidney tumors demonstrate elevations of the L enantiomer of 2HG (L-2HG). High 2HG tumors demonstrate reduced DNA levels of 5-hydroxymethylcytosine (5hmC) consistent with 2-HG mediated inhibition of TET (Ten Eleven Translocation) enzymes which convert 5-methylcystoine (5mC) to 5hmC. L-2HG elevation is mediated in part by reduced expression of L-2HG dehydrogenase (L2HGDH). L2HGDH reconstitution in RCC cells lowers L-2HG and promotes 5hmC accumulation. Additionally, L2HGDH expression in RCC cells reduces histone methylation and suppresses in vitro tumor phenotypes. Our report identifies L-2HG as an epigenetic modifier and putative oncometabolite in kidney cancer.

Wilms tumor is the most common childhood kidney cancer. Here we report the whole-exome sequencing of 44 Wilms tumors, identifying missense mutations in the microRNA (miRNA)-processing enzymes DROSHA and DICER1 and novel mutations in MYCN, SMARCA4 and ARID1A. Examination of tumor miRNA expression, in vitro processing assays, and genomic editing in human cells demonstrate that DICER1 and DROSHA mutations influence miRNA processing through distinct mechanisms. DICER1 RNase IIIB mutations preferentially impair processing of miRNAs deriving from the 5′ arm of pre-miRNA hairpins, while DROSHA RNase IIIB mutations globally inhibit miRNA biogenesis through a dominant-negative mechanism. Both DROSHA and DICER1 mutations impair expression of tumor-suppressing miRNAs including the let-7 family, important regulators of MYCN, LIN28 and other Wilms tumor oncogenes. These results provide new insights into the mechanisms through which mutations in miRNA biogenesis components reprogram miRNA expression in human cancer and suggest that these defects define a distinct subclass of Wilms tumors.

Throughout the animal kingdom, p53 genes govern stress response networks by specifying adaptive transcriptional responses. The human member of this gene family is mutated in most cancers, but precisely how p53 functions to mediate tumor suppression is not well understood. Using Drosophila and zebrafish models, we show that p53 restricts retrotransposon activity and genetically interacts with components of the piRNA (piwi-interacting RNA) pathway. Furthermore, transposon eruptions occurring in the p53 − germline were incited by meiotic recombination, and transcripts produced from these mobile elements accumulated in the germ plasm. In gene complementation studies, normal human p53 alleles suppressed transposons, but mutant p53 alleles from cancer patients could not. Consistent with these observations, we also found patterns of unrestrained retrotransposons in p53-driven mouse and human cancers. Furthermore, p53 status correlated with repressive chromatin marks in the 5 ′ sequence of a synthetic LINE-1 element. Together, these observations indicate that ancestral functions of p53 operate through conserved mechanisms to contain retrotransposons. Since human p53 mutants are disabled for this activity, our findings raise the possibility that p53 mitigates oncogenic disease in part by restricting transposon mobility.