Deciphering the immunopeptidome in vivo reveals novel tumor antigens

ABSTRACT: Effective immunosurveillance of cancer requires the presentation of peptide antigens on major histocompatibility complex Class I (MHC-I). Recent developments in proteomics have improved the identification of peptides that are naturally presented by MHC-I, collectively known as the “immunopeptidome”. Current approaches to profile tumor immunopeptidomes have been limited to in vitro investigation, which fails to capture the in vivo repertoire of MHC-I peptides, or bulk tumor lysates, which are obscured by the lack of cancer cell-specific MHC-I isolation. To overcome these limitations, we report here the engineering of a Cre recombinase-inducible affinity tag into the endogenous mouse MHC-I gene and targeting of this allele to the KrasLSL-G12D/+; p53fl/fl (KP) mouse model (KP/KbStrep). This novel approach has allowed us to precisely isolate MHC-I peptides from autochthonous pancreatic ductal adenocarcinoma (PDAC) and lung adenocarcinoma (LUAD) in vivo. With this powerful analytical tool, we were able to profile the evolution of the LUAD immunopeptidome from the alveolar type 2 cell-of-origin through late-stage disease. Differential peptide presentation in LUAD is not driven by increased mRNA expression or translation rate and is likely driven by post-translational mechanisms. Vaccination of mice with peptides presented by LUAD in vivo provoked CD8 T-cell responses in naïve and tumor bearing mice. Many peptides unique to LUAD, including immunogenic peptides, exhibited very low expression of the cognate mRNA provoking reconsideration of antigen prediction pipelines that triage peptides according to transcript abundance. Beyond cancer, the KbStrep allele is compatible with a broad range of Cre-driver lines to explore antigen presentation in vivo in the pursuit of understanding basic immunology, infectious disease, and autoimmunity.

INSTRUMENT(S): Q Exactive Plus, Orbitrap Exploris 480

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Spleen, Heart, Liver, Lung, Lung Adenocarcinoma Cell, Pancreatic Ductal Carcinoma Cell

SUBMITTER: Ryuhjin Ahn  

LAB HEAD: Forest White

PROVIDER: PXD033232 | Pride | 2022-06-20

REPOSITORIES: Pride