Targeting IDH2 promotes antitumor immunity through epigenetic activation of cGAS-STING pathway

Area of Science:

• Cancer Immunology
• Metabolic Reprogramming
• Tumor Microenvironment

Background:

• Reductive carboxylation is vital for cancer cell proliferation and T cell differentiation.
• The role of reductive carboxylation in cancer cell-mediated tumor immunity is not well understood.
• IDH2, a key enzyme in reductive carboxylation, has an unclear function in anti-tumor immunity.

Purpose of the Study:

• To investigate the role of isocitrate dehydrogenase 2 (IDH2) in cancer cell-mediated tumor immunity.
• To explore the potential of targeting IDH2 for cancer immunotherapy.

Main Methods:

• Analysis of TCGA database for correlations between IDH expression and immune cell infiltration.
• Gene Set Enrichment Analysis (GSEA) to identify pathways associated with IDH2.
• Experimental manipulation of IDH2 expression (shRNA, inhibitor AGI-6780) in lung cancer cells.
• Measurement of intracellular metabolites (α-ketoglutarate, ATP, SAM), STING promoter methylation, and STING expression.
• Assessment of type I interferon pathway activation and anti-tumor immune responses in mice.

Main Results:

• IDH2 expression negatively correlates with CD8+ T cell presence in lung and breast cancers.
• IDH2-associated genes are enriched in immune-related pathways, particularly the type I interferon pathway.
• Depletion of IDH2 in lung cancer cells activates the type I interferon pathway.
• IDH2 inhibition increases intracellular α-ketoglutarate, decreases ATP and SAM, reduces STING promoter methylation, and elevates STING expression.
• STING upregulation drives type I interferon pathway activation and enhances anti-tumor immune responses in vivo.

Conclusions:

• IDH2 plays a critical role in suppressing anti-tumor immunity by inhibiting the STING-mediated type I interferon pathway.
• Targeting IDH2 represents a promising strategy to enhance cancer immunotherapy by boosting immune responses within the tumor microenvironment.