1411 Breast cancer immunopeptidomes contain numerous shared tumor antigens

• Published in: Journal for immunotherapy of cancer 2022-11, Vol.10 (Suppl 2), p.A1467-A1467
• Main Authors: Eralda Kina, Laverdure, Jean-Philippe, Durette, Chantal, Lanoix, Joël, Courcelles, Mathieu, Zhao, Qingchuan, Apavaloaei, Anca, Jean-David Larouche, Hardy, Marie-Pierre, Krystel Vincent, Gendron, Patrick, Hesnard, Leslie, Ruiz Cuevas, Maria Virginia, Ehx, Gregory, Thibault, Pierre, Perreault, Claude
• Format: Article
• Language: English
• Subjects: Antigens; Breast cancer; Immunotherapy; Tumors
• ISSN: 2051-1426
• DOI: 10.1136/jitc-2022-SITC2022.1411

BackgroundHormone-receptor-positive breast cancer (HR+) is an immunologically cold cancer that has not benefited from advances in immunotherapy. In contrast, triple-negative breast cancer (TNBC) displays high levels of leukocytic infiltration and responds to immune checkpoint inhibitors. CD8 T cells, the main effectors of anti-cancer responses, recognize MHC I-associated peptides (MAPs). Our work aimed to characterize the repertoire of MAPs presented by HR+ and TNBC tumors.MethodsUsing a proteogenomic approach relying on mass spectrometry, we identified 57 094 unique MAPs in 26 primary breast cancer samples (14 HR+, 12 TNBC).ResultsMAP source genes showed a high overlap between both subtypes (>70%). We identified 25 tumor-specific antigens (TSAs) derived from various genomic regions, of which 24 were unmutated. TSAs were mainly identified in TNBC samples (70%) and were more highly shared among TCGA TNBC than HR+ samples. In the TNBC TCGA cohort, the predicted number of TSAs positively correlated with leukocytic infiltration (p