Unknown,Transcriptomics,Genomics,Proteomics

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Inhibition of PARP14 restores response to α-PD1 immune checkpoint inhibition in tumours with resistance driven by IFNγ. IFNG Study.

ABSTRACT: While immune checkpoint blockade therapy (ICBT) benefits cancer patients, many fail to maintain their response due to adaptive resistance mechanisms. IFNγ is critical for cellular immunity, but also promotes adaptive resistance to ICBT. We have established a role for PARP14 in mediating IFNγ-induced adaptive resistance. We confirm that chronic pre-treatment of tumour cells with IFNγ confers resistance to α-PD-1 antibodies in syngeneic mouse tumour models. We identified that PARP14 was consistently upregulated in cancer cells treated chronically with IFNγ as well as in IFNγ-high melanoma samples. Further, we showed that PARP14 knockdown or pharmacological inhibition restores sensitivity to α-PD-1 antibodies accompanied by increased immune cell infiltration into tumours but the decreased presence of regulatory T cells. RNA sequencing analysis of tumours and cultured cells treated with PARP14 inhibitor showed an upregulation of inflammatory-related pathways. In conclusion, PARP14 is an actionable target for reversing IFNγ-driven adaptive resistance to ICBT.

INSTRUMENT(S): Illumina HiSeq 4000

ORGANISM(S): Homo sapiens

SUBMITTER: Leo Zeef

PROVIDER: E-MTAB-12196 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

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Inhibition of PARP14 restores response to α-PD1 immune checkpoint inhibition in tumours with resistance driven by IFNγ. IFNG Study.

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