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

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.

Circulating oncometabolite 2-hydroxyglutarate (2HG) as a potential surrogate biomarker in patients with isocitrate dehydrogenase mutant (IDHm) intrahepatic cholangiocarcinoma (ICC)

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Background: Mutations in the genes encoding for IDH1 and IDH2 occur in ~20% of ICC patients (pts), and they lead to the production of the oncometabolite 2HG. We examined whether serum 2HG levels in IDHm ICC pts may 1) serve as a surrogate biomarker for IDH status, 2) correlate with tumor burden, and 3) correlate with circulating proangiogenic biomarkers. Methods: Blood samples from 33 ICC pts [11 IDHm, 22 IDH wild-type (IDHwt)] of different AJCC stages from MGH and 39 surgically resected ICC patients (7 IDHm, 32 IDHwt) from HKU were analyzed for serum 2HG concentration by reverse-phase liquid chromatography coupled to mass spectrometry. Eight circulating proangiogenic biomarkers were measured in plasma using multiplex ELISA. Results: In the MGH cohort, median serum 2HG levels were significantly elevated in IDHm (478 ng/ml [interquartile range 174–643]) versus IDHwt ICC pts (118ng/ml [68–160])(p<0.001). Similarly, in the HKU cohort, the pre-resection median serum 2HG levels were significantly elevated in IDHm (343ng/ml [192–596]) versus IDHwt ICC pts (56ng/ml [42–81]) (p<0.0001). The area under ROC curve for prediction of an IDH mutation using 2HG was 93%; with a threshold of 2HG≥170ng/ml, the sensitivity was 83% and specificity was 90%. IDH2 mutations were more frequent in the HKU cohort (3/7, 43%) compared with the MGH cohort (0/11, 0%) (p<0.05), but 2HG levels did not differ among the specific IDH1 or IDH2 allelic variants. 2HG levels correlated directly with tumor burden (Spearman’s rho=0.89; p<0.05) in the HKU cohort. Median plasma levels of PlGF—a growth factor from the VEGF-family—were higher in IDHm (35pg/ml [33–40]) versus IDHwt ICC pts (median 26pg/ml [24–34]) from the HKU cohort (p<0.05). No other associations were seen between proangiogenic biomarkers and IDH status. Conclusions: IDHm ICC pts had significantly higher serum 2HG levels compared to IDHwt ICC pts. High serum 2HG correlated with increased tumor burden. Pre-resection circulating PlGF levels were higher in IDHm ICC versus IDHwt pts. These data support further exploration of circulating 2HG as potential surrogate and response biomarker in IDHm ICC.

Functional SNPs in vascular endothelial growth factor (VEGF-A) and overall survival (OS) in bevacizumab-treated patients with metastatic colorectal cancer (mCRC)

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Background: Functional SNPs in VEGF-A are prognostic for OS in several malignancies, but not described definitively in mCRC. In bevacizumab-treated patients with advanced breast cancer, VEGF -2578AA and -1154A were predictive of OS—the latter SNP reported in a recent mCRC series as well. We examined the association between five functional VEGF-A SNPs and OS in a large cohort of bevacizumab-treated patients with mCRC. Methods: 403 patients with mCRC treated from 2004-2010 were included in a retrospective analysis. DNA extraction, genotyping, and SNP evaluation were performed according to standard protocols. Survival was calculated from the time of Stage IV diagnosis until death. Data were censored as of 12/31/2010. Results: There were 279 deaths in this group of 403 patients (69%). Median age was 55.7 (24-86 y), and 54% of patients were male. Age, sex, race, tumor grade, chemotherapies, and curative surgery (metastatectomy to negative margins) were considered. Significant clinical predictors of OS in univariate Cox modeling were cetuximab treatment [HR=1.46; 95% CI 1.13-1.88; p=0.0014], irinotecan treatment [HR=2.10; 1.32-3.35; p<0.001], and curative surgery [HR=0.36; 0.25-0.75; p<0.001]. Significant negative interaction was found between both cetuximab and irinotecan and curative surgery, and in modeling that included this interaction, only surgery remained predictive. In multivariate analysis, no association was found between VEGF-A and OS (Table). Conclusions: There was no association between five functional VEGF-A SNPs and OS in this large bevacizumab-treated mCRC cohort. [Table: see text]

Frequent mutation of isocitrate dehydrogenase (IDH)1 and IDH2 in cholangiocarcinoma identified through broad-based tumor genotyping

Cancers of origin in the gallbladder and bile ducts are rarely curable with current modalities of cancer treatment. Our clinical application of broad-based mutational profiling for patients diagnosed with a gastrointestinal malignancy has led to the novel discovery of mutations in the gene encoding isocitrate dehydrogenase 1 (IDH1) in tumors from a subset of patients with cholangiocarcinoma. A total of 287 tumors from gastrointestinal cancer patients (biliary tract, colorectal, gastroesophageal, liver, pancreatic, and small intestine carcinoma) were tested during routine clinical evaluation for 130 site-specific mutations within 15 cancer genes. Mutations were identified within a number of genes, including KRAS (35%), TP53 (22%), PIK3CA (10%), BRAF (7%), APC (6%), NRAS (3%), AKT1 (1%), CTNNB1 (1%), and PTEN (1%). Although mutations in the metabolic enzyme IDH1 were rare in the other common gastrointestinal malignancies in this series (2%), they were found in three tumors (25%) of an initial series of 12 biliary tract carcinomas. To better define IDH1 and IDH2 mutational status, an additional 75 gallbladder and bile duct cancers were examined. Combining these cohorts of biliary cancers, mutations in IDH1 and IDH2 were found only in cholangiocarcinomas of intrahepatic origin (nine of 40, 23%) and in none of the 22 extrahepatic cholangiocarcinomas and none of the 25 gallbladder carcinomas. In an analysis of frozen tissue specimens, IDH1 mutation was associated with highly elevated tissue levels of the enzymatic product 2-hydroxyglutarate. Thus, IDH1 mutation is a molecular feature of cholangiocarcinomas of intrahepatic origin. These findings define a specific metabolic abnormality in this largely incurable type of gastrointestinal cancer and present a potentially new target for therapy.