343 Defining and therapeutically targeting a fusion-derived public neoantigen in desmoplastic small round cell tumor using T-cell receptor gene therapy
Journal for ImmunoTherapy of Cancer(2023)
摘要
Background
Sarcomas are a heterogenous group of malignancies of mesenchymal cell origin that are difficult to treat with often poor prognoses. Approximately 30% of sarcomas are characterized by expression of fusion proteins that function as oncogenic drivers. Desmoplastic small round cell tumor (DSRCT) is a prototypical fusion-driven sarcoma defined by a pathognomonic EWSR1-WT1 fusion event. The resultant EWSR1-WT1 oncogenic fusion protein contains a shared junctional amino acid sequence divergent from normal self-proteins. We hypothesized that clonally conserved fusion proteins might yield an immunogenic subset of shared, or public, neoantigens (NeoAgs) potentially serving as targets for novel immunotherapeutic approaches.Methods and Results
Using an HLA-immunoprecipitation/mass spectrometry (HLA-IP/MS) screen, we identified a 9-amino acid peptide sequence (SSYGQQSEK) derived from the junction of the EWSR1-WT1 fusion protein and presented in the context of HLA-A*03 and -A*11, two prevalent HLA alleles that frequently bind homologous peptides. We confirmed that the same peptide sequence is physiologically presented by HLA-A*03+ DSRCT cells. Using fluorophore-conjugated HLA-multimers (dextramers) loaded with the MS-identified NeoAg, we detected circulating T cells that bind the fusion NeoAg in a subset of HLA+ DSRCT patients, confirming immunogenicity. We subsequently used in vitro antigen-directed clonal expansion of fusion NeoAg-specific T cells to isolate n=3 HLA-A*03-restricted and n=1 HLA-A*11-restricted fusion NeoAg-reactive clones. Using single-cell sequencing, we retrieved the TCRab gene sequences of the T cell receptors (TCRs) expressed by these T cells and cloned them into retroviral expression vectors. Polyclonal CD8+ T cells transduced with the retrieved TCR genes bound fusion NeoAg-loaded dextramers but not viral peptide-loaded control dextramers. Additionally, CD8+ T cells expressing candidate TCRs robustly upregulated TNFα after coculture with cells expressing the requisite HLA allele and EWSR1-WT1 fusion and specifically lysed HLA+ DSRCT cells. Interestingly, we identified one unique TCR which binds the fusion NeoAg in a peptide-centric manner that can specifically lyse both HLA-A*03+ and -A*11+ DSRCT cells, but did not engage fusion NeoAg presented in the context of HLA-A*02. This implies that a single TCR therapeutic could cover >36% of all North American DSRCT patients.Conclusions
Our data establishes that the junction of the recurrent EWSR1-WT1 fusion is naturally processed and presented in the context of prevalent HLA alleles by DSRCT cells. These findings establish proof-of-principle that fusion-derived public NeoAgs are an actionable source of therapeutic targets for fusion-driven malignancies. This work establishes a foundation for the clinical translation of a new class of T cell-based therapies targeting EWSR1-WT1 and other recurrent oncogenic fusions.查看译文
关键词
tumor,fusion-derived,t-cell
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