title: An MSI tumor specific frameshift mutation in a coding microsatellite of MSH3 encodes for HLA-A0201-restricted CD8+ cytotoxic T cell epitopes.
abstract: BACKGROUND
  Microsatellite instability (MSI) resulting from inactivation of the DNA mismatch repair system (MMR) characterizes a highly immunological subtype of colorectal carcinomas. Those tumors express multiple frameshift-mutated proteins which present a unique pool of tumor-specific antigens. The DNA MMR protein MSH3 is frequently mutated in MSI(+) colorectal tumors, thus making it an attractive candidate for T cell-based immunotherapies.
  
  
  RESULTS
  FSP-specific CD8(+) T cells were generated from a healthy donor using reverse immunology. Those T cells specifically recognized T2 cells sensitized with the respective peptides. Specific recognition and killing of MSI(+) colorectal carcinoma cells harbouring the mutated reading frame was observed. The results obtained with T cell bulk cultures could be reproduced with T cell clones obtained from the same cultures. Blocking experiments (using antibodies and cold target inhibition) confirmed peptide as well as HLA-A0201-specificity.
  
  
  CONCLUSIONS
  We identified two novel HLA-A0201-restricted cytotoxic T cell epitopes derived from a (-1) frameshift mutation of a coding A(8) tract within the MSH3 gene. These were (386)-FLLALWECSL (FSP18) and (387)-LLALWECSL (FSP19) as well as (403)-IVSRTLLLV (FSP23) and (402)-LIVSRTLLLV (FSP31), respectively. These results suggest that MSH3(-1) represents another promising MSI(+)-induced target antigen. By identifying two distinct epitopes within MSH3(-1), the sustained immunogenicity of the frameshift mutated sequence was confirmed. Our data therefore encourage further exploitation of MSH3 as a piece for peptide-based vaccines either for therapeutic or--even more important--preventive purposes.
authors: National Center for Radiation Research in Oncology, Dresden, Germany.
authors: Yvette
authors: Y
authors: Garbe
authors: Claudia
authors: C
authors: Maletzki
authors: Michael
authors: M
authors: Linnebacher
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D002999:Clone Cells / Q000276:immunology; D015179:Colorectal Neoplasms / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D018450:Disease Progression; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D016368:Frameshift Mutation; D015789:HLA-A2 Antigen / Q000276:immunology*; D006801:Humans; D051379:Mice; D053842:Microsatellite Instability; D018895:Microsatellite Repeats / Q000235:genetics; D000074081:MutS Homolog 3 Protein; D041681:NIH 3T3 Cells; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology
chemical_list: D004268:DNA-Binding Proteins; D018984:Epitopes, T-Lymphocyte; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; C078444:MSH3 protein, human; D000074081:MutS Homolog 3 Protein