Circulating oncometabolite 2-hydroxyglutarate is a potential surrogate biomarker in patients with isocitrate dehydrogenase-mutant intrahepatic cholangiocarcinoma

Abstract

Purpose: Mutations in the IDH1 and IDH2 (IDH1/2) genes occur in approximately 20% of intrahepatic cholangiocarcinoma and lead to accumulation of 2-hydroxyglutarate (2HG) in the tumor tissue. However, it remains unknown whether IDH1/2 mutations can lead to high levels of 2HG circulating in the blood and whether serum 2HG can be used as a biomarker for IDH1/2 mutational status and tumor burden in intrahepatic cholangiocarcinoma.

Experimental design: We initially measured serum 2HG concentration in blood samples collected from 31 patients with intrahepatic cholangiocarcinoma in a screening cohort. Findings were validated across 38 resected patients with intrahepatic cholangiocarcinoma from a second cohort with tumor volume measures. Circulating levels of 2HG were evaluated relative to IDH1/2 mutational status, tumor burden, and a number of clinical variables.

Results: Circulating levels of 2HG in the screening cohort were significantly elevated in patients with IDH1/2-mutant (median, 478 ng/mL) versus IDH1/2-wild-type (median, 118 ng/mL) tumors (P < 0.001). This significance was maintained in the validation cohort (343 ng/mL vs. 55 ng/mL, P < 0.0001) and levels of 2HG directly correlated with tumor burden in IDH1/2-mutant cases (P < 0.05). Serum 2HG levels ≥170 ng/mL could predict the presence of an IDH1/2 mutation with a sensitivity of 83% and a specificity of 90%. No differences were noted between the allelic variants IDH1 or IDH2 in regard to the levels of circulating 2HG.

Conclusions: This study indicates that circulating 2HG may be a surrogate biomarker of IDH1 or IDH2 mutation status in intrahepatic cholangiocarcinoma and that circulating 2HG levels may correlate directly with tumor burden. Clin Cancer Res; 20(7); 1884-90. ©2014 AACR.

Figure 1

The distribution of circulating 2HG levels in blood samples collected across the two cohorts. Serum 2HG levels were measured and compared between patients with IDH1-mutant or IDH2-mutant (IDH-Mut) versus IDH-wild-type (IDH-WT) ICCs in the A) Screening cohort (n=31) and B) in the Validation cohort (n=38). For each column, the dark grey box represents the 2HG values in the 75^th quartile and the light grey box represents values in the 50^th quartile. The lines extending vertically from the boxes indicate the variability outside the upper and lower quartiles. A significant elevation of circulating 2HG levels was seen in IDH-Mut ICC patients compared to IDH-WT ICC patients (p<0.001).

Figure 2

Correlation between serum 2HG level and tumor volume measured at surgery in IDH1-mutant and IDH2-mutant ICC patients from the Validation cohort.