Upstream open reading frames regulate proto-oncogene translation and encode HLA-presented immunogenic tumor antigens

Upstream open reading frames (uORFs) represent translational control elements within eukaryotic transcript leader sequences. Recent data showed that uORFs can encode for biologically active proteins and human leucocyte antigen (HLA)-presented peptides and suggest their potential role in cancer cell development and survival. However, it is so far unclear if uORF-encoded peptides could serve as tumor-associated antigen targets and thus also play a role in cancer immune surveillance. Combining mass spectrometry-based immunopeptidome analysis in primary tumor and healthy tissues and evaluation of proto-oncogene-associated uORF-mediated translational control we here identified a panel of HLA-presented tumor-associated uORF-derived antigens. These uORF-derived tumor antigens were further shown to induce multifunctional antigen-specific T cells, validating their suitability as antigen targets for T cell-based cancer immunotherapy. Our data further unravel the role of uORF-encoded peptides in malignant disease, suggesting uORF-derived tumor-associated antigens as targets for anti-cancer immune surveillance and immunotherapy development.