title: Inhibition of serine-peptidase activity enhances the generation of a survivin-derived HLA-A2-presented CTL epitope in colon-carcinoma cells.
abstract: Cytotoxic T lymphocytes eliminate tumor cells expressing antigenic peptides in the context of MHC-I molecules. Peptides are generated during protein degradation by the proteasome and resulting products, surviving cytosolic amino-peptidases activity, may be presented by MHC-I molecules. The MHC-I processing pathway is altered in a large number of malignancies and modulation of antigen generation is one strategy employed by cells to evade immune control. In this study we analyzed the generation and presentation of a survivin-derived CTL epitope in HLA-A2-positive colon-carcinoma cells. Although all cell lines expressed the anti-apoptotic protein survivin, some tumors were poorly recognized by ELTLGEFLKL (ELT)-specific CTL cultures. The expression of MHC-I or TAP molecules was similar in all cell lines suggesting that tumors not recognized by CTLs may present defects in the generation of the ELT-epitope which could be due either to lack of generation or to subsequent degradation of the epitope. The cells were analyzed for the expression and the activity of extra-proteasomal peptidases. A significant overexpression and higher activity of TPPII was observed in colon-carcinoma cells which are not killed by ELT-specific CTLs, suggesting a possible role of TPPII in the degradation of the ELT-epitope. To confirm the role of TPPII in the degradation of the ELT-peptide, we showed that treatment of colon-carcinoma cells with a TPPII inhibitor resulted in a dose-dependent increased sensitivity to ELT-specific CTLs. These results suggest that TPPII is involved in degradation of the ELT-peptide, and its overexpression may contribute to the immune escape of colon-carcinoma cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Ferrara, Ferrara, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Preta
authors.forename: D
authors.initials: D
authors.lastname: Marescotti
authors.forename: C
authors.initials: C
authors.lastname: Fortini
authors.forename: P
authors.initials: P
authors.lastname: Carcoforo
authors.forename: C
authors.initials: C
authors.lastname: Castelli
authors.forename: M
authors.initials: M
authors.lastname: Masucci
authors.forename: R
authors.initials: R
authors.lastname: Gavioli
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000626:Aminopeptidases; D017951:Antigen Presentation; D000951:Antigens, Neoplasm / Q000276:immunology / Q000378:metabolism*; D002277:Carcinoma / Q000276:immunology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000276:immunology* / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018984:Epitopes, T-Lymphocyte / Q000276:immunology / Q000378:metabolism*; D015789:HLA-A2 Antigen / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008213:Lymphocyte Activation; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012697:Serine Endopeptidases / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D000077022:Survivin; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000951:Antigens, Neoplasm; C107489:BIRC5 protein, human; D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D015842:Serine Proteinase Inhibitors; D000077022:Survivin; C055604:alanyl-alanyl-phenylalanine chloromethyl ketone; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D046988:Proteasome Endopeptidase Complex