The metabolomic landscape plays a critical role in glioma oncogenesis

Cancer cells depend on metabolic reprogramming for survival, undergoing profound shifts in nutrient sensing, nutrient uptake and flux through anabolic pathways, in order to drive nucleotide, lipid, and protein synthesis and provide key intermediates needed for those pathways. Although metabolic enzymes themselves can be mutated, including to generate oncometabolites, this is a relatively rare event in cancer. Usually, gene amplification, overexpression, and/or downstream signal transduction upregulate rate‐limiting metabolic enzymes and limit feedback loops, to drive persistent tumor growth. Recent molecular‐genetic advances have revealed discrete links between oncogenotypes and the resultant metabolic phenotypes. However, more comprehensive approaches are needed to unravel the dynamic spatio‐temporal regulatory map of enzymes and metabolites that enable cancer cells to adapt to their microenvironment to maximize tumor growth. Proteomic and metabolomic analyses are powerful tools for analyzing a repertoire of metabolic enzymes as well as intermediary metabolites, and in conjunction with other omics approaches could provide critical information in this regard. Here, we provide an overview of cancer metabolism, especially from an omics perspective and with a particular focus on the genomically well characterized malignant brain tumor, glioblastoma. We further discuss how metabolomics could be leveraged to improve the management of patients, by linking cancer cell genotype, epigenotype, and phenotype through metabolic reprogramming.

Quantitation of 2-hydroxyglutarate in human plasma via LC–MS/MS using a surrogate analyte approach

Aim: 2-Hydroxyglutarate (2-HG) is a target engagement biomarker in patients after treatment with inhibitors of mutated isocitrate dehydrogenase (mIDH). Accurate measurement of 2-HG is critical for monitoring the inhibition effectiveness of the inhibitors. Materials & methods: Human plasma samples were spiked with stable isotope labelled internal standard, processed by protein precipitation, and analyzed using LC–MS/MS. This method was validated following regulatory guidance and has been successfully applied in a clinical study for mIDH inhibition. Results: An LC–MS/MS method with a surrogate analyte approach was developed and validated to measure 2-HG in human plasma with acceptable intra- and inter-assay accuracy and precision. Conclusion: A sensitive and robust LC–MS/MS method was developed and validated for measuring 2-HG in human plasma.

Emerging pharmacotherapies for elderly acute myeloid leukemia patients

INTRODUCTION

Acute myeloid leukemia (AML) is a disease mainly seen in the elderly, for which treatment is undergoing rapid changes. Although recent studies have supported the survival benefit of induction chemotherapy in fit patients and that of hypomethylating agents (HMAs) in non-induction candidates, treatment of this patient age population remains a significant challenge for the treating oncologist.

AREAS COVERED

In this review, we will examine effectiveness and safety outcomes of upcoming novel treatment strategies in elderly (≥60 years old) patients with AML, highlight the current literature and ongoing trials able to maximize therapeutic options in this heterogeneous patient population.

EXPERT OPINION

Current developments including new chemotherapeutic strategies and combinations of HMAs with novel drugs targeting epigenetic or immunomodulatory pathways are underway to improve patient survival and quality of life.

Isocitrate dehydrogenase 1 and 2 mutations, 2-hydroxyglutarate levels, and response to standard chemotherapy for patients with newly diagnosed acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) cells harboring mutations in isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) produce the oncometabolite 2-hydroxyglutarate (2HG). This study prospectively evaluated the 2HG levels, IDH1/2 mutational status, and outcomes of patients receiving standard chemotherapy for newly diagnosed AML.

METHODS

Serial samples of serum, urine, and bone marrow aspirates were collected from patients newly diagnosed with AML, and 2HG levels were measured with mass spectrometry. Patients with baseline serum 2HG levels greater than 1000 ng/mL or marrow pellet 2HG levels greater than 1000 ng/2 × 10⁶ cells, which suggested the presence of an IDH1/2 mutation, underwent serial testing. IDH1/2 mutations and estimated variant allele frequencies were identified. AML characteristics were compared with the Wilcoxon test and Fisher's exact test. Disease-free survival and overall survival (OS) were evaluated with log-rank tests and Cox regression.

RESULTS

Two hundred and two patients were treated for AML; 51 harbored IDH1/2 mutations. IDH1/2-mutated patients had significantly higher 2HG levels in serum, urine, bone marrow aspirates, and aspirate cell pellets than wild-type patients. A serum 2HG level greater than 534.5 ng/mL was 98.8% specific for the presence of an IDH1/2 mutation. Patients with IDH1/2-mutated AML treated with 7+3-based induction had a 2-year event-free survival (EFS) rate of 44% and a 2-year OS rate of 57%. There was no difference in complete remission rates, EFS, or OS between IDH1/2-mutated and wild-type patients. Decreased serum 2HG levels on day 14 as a proportion of the baseline were significantly associated with improvements in EFS (P = .047) and OS (P = .019) in a multivariate analysis.

CONCLUSIONS

Among patients with IDH1/2-mutated AML, 2HG levels are highly specific for the mutational status at diagnosis, and they have prognostic relevance in patients receiving standard chemotherapy.

The role of IDH mutations in acute myeloid leukemia

Isocitrate dehydrogenases (IDHs) are enzymes involved in multiple metabolic and epigenetic cellular processes. Mutations in IDH1 or IDH2 are detected in approximately 20% of patients with acute myeloid leukemia (AML) and induce amino acid changes in conserved residues resulting in neomorphic enzymatic function and production of an oncometabolite, 2-hydroxyglutarate (R-2-HG). This leads to DNA hypermethylation, aberrant gene expression, cell proliferation and abnormal differentiation. IDH mutations diversely affect prognosis of patients with AML based on the location of the mutation and other co-occurring genomic abnormalities. Recently, novel therapies specifically targeting mutant IDH have opened new avenues of therapy for these patients. In the present review, we will provide an overview of the biological, clinical and therapeutic implications of IDH mutations in AML.

Oncometabolites: A New Paradigm for Oncology, Metabolism, and the Clinical Laboratory

BACKGROUND

Pediatric clinical laboratories commonly measure tricarboxylic acid cycle intermediates for screening, diagnosis, and monitoring of specific inborn errors of metabolism, such as organic acidurias. In the past decade, the same tricarboxylic acid cycle metabolites have been implicated and studied in cancer. The accumulation of these metabolites in certain cancers not only serves as a biomarker but also directly contributes to cellular transformation, therefore earning them the designation of oncometabolites.

CONTENT

D-2-hydroxyglutarate, L-2-hydroxyglutarate, succinate, and fumarate are the currently recognized oncometabolites. They are structurally similar and share metabolic proximity in the tricarboxylic acid cycle. As a result, they promote tumorigenesis in cancer cells through similar mechanisms. This review summarizes the currently understood common and distinct biological features of these compounds. In addition, we will review the current laboratory methodologies that can be used to quantify these metabolites and their downstream targets.

SUMMARY

Oncometabolites play an important role in cancer biology. The metabolic pathways that lead to the production of oncometabolites and the downstream signaling pathways that are activated by oncometabolites represent potential therapeutic targets. Clinical laboratories have a critical role to play in the management of oncometabolite-associated cancers through development and validation of sensitive and specific assays that measure oncometabolites and their downstream effectors. These assays can be used as screening tools and for follow-up to measure response to treatment, as well as to detect minimal residual disease and recurrence.

Replication Study: The common feature of leukemia-associated IDH1 and IDH2 mutations is a neomorphic enzyme activity converting alpha-ketoglutarate to 2-hydroxyglutarate

In 2016, as part of the Reproducibility Project: Cancer Biology, we published a Registered Report (Fiehn et al., 2016), that described how we intended to replicate selected experiments from the paper "The common feature of leukemia-associated IDH1 and IDH2 mutations is a neomorphic enzyme activity converting alpha-ketoglutarate to 2-hydroxyglutarate" (Ward et al., 2010). Here, we report the results of those experiments. We found that cells expressing R172K mutant IDH2 did not display isocitrate-dependent NADPH production above vector control levels, in contrast to the increased production observed with wild-type IDH2. Conversely, expression of R172K mutant IDH2 resulted in increased alpha-ketoglutarate-dependent consumption of NADPH compared to wild-type IDH2 or vector control. These results are similar to those reported in the original study (Figure 2; Ward et al., 2010). Further, expression of R172K mutant IDH2 resulted in increased 2HG levels within cells compared to the background levels observed in wild-type IDH2 and vector control, similar to the original study (Figure 3D; Ward et al., 2010). In primary human AML samples, the 2HG levels observed in samples with mutant IDH1 or IDH2 status were higher than those observed in samples without an IDH mutation, similar to what was observed in the original study (Figure 5C; Ward et al., 2010). Finally, we report meta-analyses for each result.

Measurement of Oncometabolites D-2-Hydroxyglutaric Acid and L-2-Hydroxyglutaric Acid

We describe a liquid chromatography-tandem mass spectrometry assay for measurement of D-2-hydroxyglutaric acid and L-2-hydroxyglutaric acid. These metabolites are increased in specific inborn errors of metabolism and are now recognized as oncometabolites. The measurement of D-2-hydroxyglutarate in peripheral blood may be used as a biomarker for screening and follow-up of patients with IDH-mutated acute myeloid leukemia.