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IDO1 inhibition and subsequent metabolic adaptations constrains anti-tumor immune responses in the tumor microenvironment of patients with ovarian cancer

ABSTRACT: To uncover underlying mechanisms associated with failure of indoleamine 2, 3-dioxygenase 1 (IDO1) blockade in clinical trials, we conducted a pilot, window-of-opportunity clinical study testing the immunological and metabolic effects of the IDO1 inhibitor, epacadostat, in seventeen patients with newly diagnosed advanced high grade serous ovarian cancer prior to their standard tumor debulking surgery. Comprehensive immunologic, transcriptomic, and metabolomic characterization of the tumor microenvironment using baseline and post-treatment tissue biopsies revealed efficient blockade of the kynurenine pathway of tryptophan degradation. This blockade was accompanied by a metabolic adaptation that shunted tryptophan catabolism towards the serotonin pathway and elevated nicotinamide adenine dinucleotide (NAD)+ biosynthetic pathways, which was detrimental for T cell proliferation and function. Treatment of mice bearing IDO1 over-expressing ovarian tumors with the NAMPT inhibitor, FK866, did not improve tumor control by epacadostat. Because NAD+ metabolites could be ligands for purinergic receptors, we investigated the impact of blocking purinergic receptors in the presence of NAD+. We demonstrated that A2a and A2b, or the combination of A2a and A2b purinergic receptor antagonists rescued NAD+-mediated suppression of T cell proliferation, and the combination of IDO inhibition and A2a/A2b receptor blockade improved survival in the IDO1 over-expressing ovarian tumor bearing hosts. These findings unravel previously unrecognized downstream adaptive metabolic consequences of IDO1 blockade that may undermine efforts to induce tumor-specific T cell responses.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE155164 | GEO | 2020/12/28

REPOSITORIES: GEO

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Project description:Many tumors escape by activating multiple cellular pathways that induce immunosuppression. One pivotal immune-suppressive mechanism is the production of tryptophan metabolites along the kynurenine pathway by IFNγ-induced IDO1 enzyme production 4-8. Phase III clinical trials using chemical inhibition of IDO1 in combination with PD1 pathway blockade, however, failed to improve melanoma treatment 9-12. This points at an incomplete understanding of the role of IDO1 and the consequent tryptophan degradation on mRNA translation and cancer progression. Here, we investigated the effects of prolonged IFNγ treatment on mRNA translation in melanoma cells by ribosome profiling. Surprisingly, we observed a massive accumulation of ribosomes ~20 amino acids downstream of tryptophan codons (termed here as W-Bumps) along with their expected stalling at the tryptophan codon itself. This indicated ribosomal bypass of the tryptophan codons in the absence of tryptophan. Detailed examination of W-Bumps position and its corresponding peptide sequences pinpointed towards ribosomal frameshifting events and their effects in the ribosome exit tunnel. In particular, W-Bumps strength was associated with the disorderedness level of potential out-of-frame peptides predicted downstream of tryptophan codons. Indeed, reporter assays demonstrated the induction of ribosomal frameshifting, and the generation of trans-frame proteins and their presentation at the cell surface after IFNγ treatment. Proteomics and immunopeptidomics analyses verified the production of IFNγ-induced trans-frame and out-of-frame aberrant peptides and their presentation on HLA class I molecules. Priming of naïve T cells from healthy donors with aberrant peptides resulted in identification of reactive, peptide-specific T cells. Altogether, our results suggest that IFNγ-induced IDO1-mediated tryptophan depletion plays a role in the immune recognition of melanoma cells by contributing to the diversity of the peptidome landscape, and by inducing the presentation of aberrant peptides.