Prognostic significance of 2-hydroxyglutarate levels in acute myeloid leukemia in China

Abstract

The 2-hydroxyglutarate (2-HG) has been reported to result from mutations of isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) genes and to function as an "oncometabolite." To evaluate the clinical significance of serum 2-HG levels in hematologic malignancies, acute myeloid leukemia (AML) in particular, we analyzed this metabolite in distinct types of human leukemia and lymphoma and established the range of serum 2-HG in appropriate normal control individuals by using gas chromatograph-time-of-flight mass spectrometry. Aberrant serum 2-HG pattern was detected in the multicenter group of AML, with 62 of 367 (17%) patients having 2-HG levels above the cutoff value (2.01, log2-transformed from 4.03 μg/mL). IDH1/2 mutations occurred in 27 of 31 (87%) AML cases with very high 2-HG, but were observed only in 9 of 31 (29%) patients with moderately high 2-HG, suggesting other genetic or biochemical events may exist in causing 2-HG elevation. Indeed, glutamine-related metabolites exhibited a pattern in favor of 2-HG synthesis in the high 2-HG group. In AML patients with cytogenetically normal AML (n = 234), high 2-HG represented a negative prognostic factor in both overall survival and event-free survival. Univariate and multivariate analyses confirmed high serum 2-HG as a strong prognostic predictor independent of other clinical and molecular features. We also demonstrated distinct gene-expression/DNA methylation profiles in AML blasts with high 2-HG compared with those with normal ones, supporting a role that 2-HG plays in leukemogenesis.

Keywords: biomarker; prognosis.

Fig. 1.

The distribution of 2-HG in different hematological malignancies and healthy controls and the correlation between a high level of 2-HG and cytogenetic abnormalities, gene mutation status, and metabolic pathway changes. Box plots show the distribution of serum 2-HG levels in healthy controls (HC) and several hematological malignancies (A), and in AML patients with normal or high 2-HG levels (B). ALL, acute lymphoblastic leukemia; CML, chronic myeloid leukemia; MDS, myelodysplastic syndrome, MM, multiple myeloma; NHL, non-Hodgkin lymphoma; PMF, primary myelofibrosis. Note that rare cases with high 2-HG were observed in ALL (5 of 150, 3.3%) and NHL (1 of 64, 1.6%), whereas no case with increased 2-HG was found in other disease types. Circos diagrams representing correlation between high levels of 2-HG and distinct cytogenetic abnormalities in AML (C) or with gene mutation events in CN-AML (D). Cytogenetic subtypes: favorable: t(15;17)/PML-RARA, t(8;21)/AML1-ETO, and inv16/CBFβ-MYH11; unfavorable: t(9;22), inv(3)/t(3;3), −5, −7, del(5q), del(7p), 11q23, and complex translocations. CN-AML indicates cases having no cytogenetically identifiable abnormalities. Note the comparison of concentrations of metabolites directly related to the 2-HG production pathway (E) between high and normal 2-HG AML groups (F).

Fig. 2.

Kaplan–Meier survival analysis of CN-AML patients. H 2-HG, high 2-HG; N 2-HG, normal 2-HG; WT IDH1/2: wild-type IDH1/2; IDH1/2 Mut: IDH1/2 mutations. (Top row) OS (A) and EFS (B) curves of the patients according to 2-HG levels. (Middle row) OS (C) and EFS (D) curves of patients with four categories of 2-HG levels [<1.85 (µg/mL, log₂); 1.85–2.01 (µg/mL, log₂); 2.01–2.69 (µg/mL, log₂); >2.69 (µg/mL, log₂), by using the median of 2-HG levels in normal and high groups in CN-AML]. Note the dose–effect tendency of the four curves depending on 2-HG levels for both OS and EFS, with the two curves of high 2-HG being statistically significantly worse compared with the curve with lowest 2-HG (P values: < 0.001, respectively). (Bottom row) Cases are stratified into four subgroups: N 2-HG with WT IDH1/2, H 2-HG with WT IDH1/2, N 2-HG with IDH1/2 Mut and H 2-HG with IDH1/2 Mut. P values of OS (E) and EFS (F) are shown in subgroup analysis with stratification on IDH1/2 mutation status. P values were calculated by the log-rank test.

Fig. 3.

Gene-expression/DNA methylation patterns in leukemia blasts of AML patients with high 2-HG compared with those with normal 2-HG. (A) Display of 1,224 genes with significant differences of expression levels between AML cases with high and normal 2-HG. (B) Quantitative RT-PCR results for eight genes showing different expression levels between AML cases with high and normal 2-HG. *P < 0.05, **P < 0.01. (C) DNA segments of 203 genes with significant differences of methylation levels between AML cases with high or normal 2-HG. (D) Display of 67 genes with correlation between modification of DNA methylation patterns and changes in expression levels in the high 2-HG group compared with the normal 2-HG group.