gms | German Medical Science

128. Kongress der Deutschen Gesellschaft für Chirurgie

Deutsche Gesellschaft für Chirurgie

03.05. - 06.05.2011, München

MSI-induced frameshift mutations are ideal tumor-associated antigenes

Meeting Abstract

  • Michael Linnebacher - Chirurgische Universitätsklinik Rostock, Abteilung für Allgemeine Chirurgie, Rostock
  • Claudia Maletzki - Chirurgische Universitätsklinik Rostock, Abteilung für Allgemeine Chirurgie, Rostock
  • Ernst Klar - Chirurgische Universitätsklinik Rostock, Abteilung für Allgemeine Chirurgie, Rostock
  • Michael Schmitt - Klinik für Innere Medizin, Abteilung für Hämatologie und Onkologie, Rostock

Deutsche Gesellschaft für Chirurgie. 128. Kongress der Deutschen Gesellschaft für Chirurgie. München, 03.-06.05.2011. Düsseldorf: German Medical Science GMS Publishing House; 2011. Doc11dgch550

DOI: 10.3205/11dgch550, URN: urn:nbn:de:0183-11dgch5509

Published: May 20, 2011

© 2011 Linnebacher et al.
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Outline

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Introduction: Microsatellite instability (MSI), resulting from functional inactivation of the cellular DNA mismatch repair system, is a form of genetic instability found in colorectal, gastric, endometrial cancers and has recently been described in subtypes of haematological disorders linked to immunosuppression. MSI affecting coding regions of genes can lead to frameshift (FS) mutations and the production of modified proteins, which may represent potential targets for T cells. The aim of the present study was to analyze, whether MSI-induced FS-peptides (FSP) function as general antigens for MSI-positive tumors.

Materials and methods: Autologous B cells were loaded with FSPs (FSP26 derived from the (−1)-mutated Caspase-5, FSP31 derived from the (−1)-mutated form of MSH-3) and irradiated (30 Gy). They were added to purified CD3 autologous T cells at a ratio of 4:1 (T:CD40 Bs). Reactivity of T cells stimulated with the cognate FSP was quantified in IFN-γ ELISpot assays. In each experiment, MSI cell lines and T2 targets exogenously loaded with the cognate peptide were employed. Supplementary, lytic activity towards tumor cells was analyzed by chromium release assay.

Results: Peptide-stimulated T cells were mostly CD8+ and activated. T cells specific for FSP26 were sensitized for release of IFN-γ in the presence of HLA-A2 tumor cell lines HCT116, HSB-2 and Nalm6. Similarly, CTV-1, Nalm6 and HCT116 cells harbouring the mutated form of MSH-3 (FSP31) were recognized by FSP31-stimulated T cells. As detected by 51Cr release, T cells were also able to efficiently kill tumor targets expressing the underlying mutation. Peptide-specificity was formally confirmed by efficient recognition and killing of peptide-loaded T2 cells. Target cells loaded with irrelevant peptide were not recognized.

Conclusion: The present study is the first report on MSI-induced FSPs as tumor-specific antigens shared between colorectal cancer and leukemia. We could show that FSPs are presented in the context of HLA-molecules and thus allow for functional tumor cell recognition by FSP-specific T-cells. This has important implicatiopns for the development of general immunotherapeutic approaches.