Novel Strategy Proposed To Enhanced Treatment of Cholangiocarcinoma With IDH1 Mutations
Key findings
- In this study, a genetically engineered mouse model was used to investigate the function of mutant isocitrate dehydrogenase 1 (mIDH1) in the maintenance of intrahepatic cholangiocarcinoma
- Mutant IDH1 drove cholangiocarcinoma growth through two mechanisms mediated by the oncogenic metabolite (R)-2-hydroxyglutarate: suppression of CD8+ T cells and inhibition of interferon-gamma/TET2 signaling
- Immune checkpoint activation limited mIDH1 inhibitor efficacy, leading to eventual tumor progression, but CTLA4 blockade resulted in complete and durable responses
- It can be concluded restoration of anti-tumor immunity is a central mechanism of therapeutic response to inhibition of the mIDH1 oncogene
Mutations in the isocitrate dehydrogenase 1 gene (mIDH1) are common in intrahepatic cholangiocarcinoma (ICC). Like most genetic subsets of the disease, they're associated with poor outcomes, even after immune checkpoint therapy. mIDH1 inhibition can be beneficial, but that strategy typically delays progression rather than significantly shrinking tumors, and resistance eventually develops.
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Altered activity of the IDH1 enzyme results in the production of an oncometabolite called (R)-2-hydroxyglutarate [(R)-2HG], which impairs the function of diverse proteins involved in epigenetics, DNA, repairs, and cell metabolism. Massachusetts General Hospital researchers, Meng-Ju Wu, PhD, Nabeel Bardeesy, PhD, and Robert Manguso, PhD, of the Massachusetts General Hospital Cancer Center, and colleagues recently discovered how mIDH1 supports sustained growth of ICC via (R)-2HG. In Cancer Discovery, the team also report findings that suggest a novel strategy for improving the effectiveness of mIDH1 inhibiting drugs.
A Central (R)-2HG–controlled Pathway
The researchers created a genetically engineered mouse model that recapitulates aggressive human ICC's genetics and histopathologic features. They determined that mutant IDH1 drives cholangiocarcinoma through two mechanisms mediated by (R)-2HG:
- Suppression of CD8+ T-cell recruitment
- De-repression of the DNA demethylating enzyme TET2, which is required for tumor cells to respond to interferon-gamma
mIDH1 inhibition reversed the immune evasion phenotype, as it:
- Prompted rapid CD8+ T-cell recruitment and effector function
- Resulted in TET2-dependent response to interferon-gamma in tumor cells
- Decreased tumor growth
Immune checkpoint activation limited mIDH1 inhibitor efficacy, leading to eventual tumor progression. Blockade of cytotoxic T lymphocyte antigen-4, a key negative regulator of T-cell activation, overcame immunosuppression and provided therapeutic synergy, resulting in complete and durable responses.
Improving Immunotherapy
These findings show that immune function and the interferon-gamma/TET2 axis are essential for response to mIDH1 inhibition. Immune checkpoint therapy may synergize with mIDH1 inhibition in the treatment of ICC.
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