Circulating Oncometabolite 2-hydroxyglutarate as a Potential Biomarker for Isocitrate Dehydrogenase (IDH1/2) Mutant Cholangiocarcinoma

Isocitrate dehydrogenase (IDH) enzymes catalyze the decarboxylation of isocitrate to alpha-ketoglutarate (αKG). IDH1/2 mutations preferentially convert αKG to R-2-hydroxyglutarate (R2HG), resulting in R2HG accumulation in tumor tissues. We investigated circulating 2-hydroxyglutate (2HG) as potential biomarkers for patients with IDH-mutant (IDHmt) cholangiocarcinoma (CCA). R2HG and S-2-hydroxyglutarate (S2HG) levels in blood and tumor tissues were analyzed in a discovery cohort of patients with IDHmt glioma and CCA. Results were validated in cohorts of patients with CCA and clear-cell renal cell carcinoma. The R2HG/S2HG ratio (rRS) was significantly elevated in tumor tissues, but not in blood for patients with IDHmt glioma, while circulating rRS was elevated in patients with IDHmt CCA. There were overlap distributions of circulating R2HG and total 2HG in patients with both IDHmt and wild-type (IDHwt) CCA, while there was minimal overlap in rRS values between patients with IDHmt and IDHwt CCA. Using the rRS cut-off value of 1.5, the sensitivity of rRS was 90% and specificity was 96.8%. Circulating rRS is significantly increased in patients with IDHmt CCA compare with patients with IDHwt CCA. Circulating rRS is a sensitive and specific surrogate biomarker for IDH1/2 mutations in CCA. It can potentially be used as a tool for monitoring IDH-targeted therapy.

Mutant-IDH inhibits Interferon-TET2 signaling to promote immunoevasion and tumor maintenance in cholangiocarcinoma

Isocitrate dehydrogenase 1 mutations (mIDH1) are common in cholangiocarcinoma. (R)-2-hydroxyglutarate generated by the mIDH1 enzyme inhibits multiple a-ketoglutarate-dependent enzymes, altering epigenetics and metabolism. Here, by developing mIDH1-driven genetically engineered mouse models, we show that mIDH1 supports cholangiocarcinoma tumor maintenance through an immunoevasion program centered on dual (R)-2-hydroxyglutarate-mediated mechanisms - suppression of CD8+ T cell activity and tumor cell-autonomous inactivation of TET2 DNA demethylase. Pharmacological mIDH1 inhibition stimulates CD8+ T cell recruitment and IFN-y expression and promotes TET2-dependent induction of IFN-y response genes in tumor cells. CD8+ T cell depletion or tumor cell-specific ablation of TET2 or Interferon-gamma receptor 1 causes treatment resistance. Whereas immune checkpoint activation limits mIDH1 inhibitor efficacy, CTLA4 blockade overcomes immunosuppression, providing therapeutic synergy. The findings in this mouse model of cholangiocarcinoma demonstrate that immune function and the IFN-y-TET2 axis are essential for response to mIDH1 inhibition and suggest a novel strategy for harnessing these inhibitors therapeutically.

Molecular and morphological changes induced by ivosidenib correlate with efficacy in mutant-IDH1 cholangiocarcinoma

Background: IDH1 mutations occur in approximately 13% of intrahepatic cholangiocarcinomas (IHCCs). The oral, targeted, mutant IDH1 (mIDH1) inhibitor ivosidenib (AG-120) suppresses production of the oncometabolite D-2-hydroxyglutarate, promoting disease stabilization and improved progression-free survival (PFS) in mIDH1 IHCC. Materials & methods: Harnessing matched baseline and on-treatment biopsies, we investigate the potential mechanisms underlying ivosidenib's efficacy. Results: mIDH1 inhibition leads to decreased cytoplasm and expression of hepatocyte lineage markers in patients with prolonged PFS. These findings are accompanied by downregulation of biliary fate, cell cycle progression and AKT pathway activity. Conclusion: Ivosidenib stimulates a hepatocyte differentiation program in mIDH1 IHCC, a phenotype associated with clinical benefit. mIDH1 inhibition could be a paradigm for differentiation-based therapy in solid tumors. Clinical trial registration: NCT02073994 (ClinicalTrials.gov).

Precision medicine for gastrointestinal cancers: a conference report

As cancer management evolves into precision medicine national/international cancer meetings bring novel therapeutic approaches and potentially practice-changing results of clinical studies are presented. This year, the ASCO GI Symposium 2020 had also several updates from ongoing and finalized clinical trials. Although there were no groundbreaking results that impact the daily practice directly, several highly important data from ongoing studies were shared with the audience. In this report, the highlights of the ASCO GI Symposium 2020 are presented with a future perspective.