P06.05 The natural HLA ligandome of glioblastoma stem-like cells: Antigen discovery for T-cell based immunotherapy

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2017-05, Vol.19 (suppl_3), p.iii50-iii50
• Main Authors: Neidert, M. C., Kowalewski, D. J., Wolpert, F., Stevanovic, S., Rammensee, H., Lamszus, K., Westphal, M., Regli, L., Weller, M., Eisele, G.
• Format: Article
• Language: English
• Subjects: POSTER PRESENTATIONS
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/nox036.179

Introduction: Glioblastoma stem-like cells (GSC) play a major role in tumor initiation and maintenance as well as in therapy resistance and recurrence. Thus, targeting this cellular subset may be key to effective immunotherapy. Here, we present a mass spectrometry-based analysis of HLA-presented peptidomes of GSC and glioblastoma patient specimens. Materials and Methods: HLA class I and class II ligands of culture-expanded GSC lines (GS-2, GS-5, GS-9) and snap frozen freshly resected glioblastoma samples (n=9) were isolated by immunoprecipitation and characterized using liquid chromatography and tandem mass spectrometry (LC-MS/MS). HLA ligandomes of GSC and freshly resected patient samples were compared to a comprehensive HLA ligandome database of human normal tissues including human brain. Immunogenicity of top-ranking candidates was shown by T-cell priming followed by intracellular cytokine staining and HLA multimer staining. Results: We identified 15 antigens represented by 38 different HLA ligands showing natural presentation both on GSC and patient samples. Importantly, in vitro immunogenicity assays clearly suggest these peptides to be epitopes of functional CD8 T-cell responses thus rendering them prime candidates for immunotherapy. Conclusions: We present an antigen discovery approach based on the comparative analysis of the HLA class I and HLA class II peptidomes of GSC and patient samples. The characterization of the natural GSC-immunopeptidome is an important step towards the informed design of highly specific T-cell immunotherapy targeting the glioblastoma stem cell niche.