Induction of CD4(+) and CD8(+) T-cell responses to the human stromal antigen, fibroblast activation protein: implication for cancer immunotherapy.
OBJECTIVE
The propensity of tumor cells to escape immune elimination could limit, if not defeat, the long-term benefits of effective immunotherapeutic protocols. Immunologic targeting of tumor stroma could significantly reduce the ability of tumors to evade immune elimination. Murine studies have shown that inducing immunity against angiogenesis-associated products engenders potent antitumor immunity without significant pathology. It is, however, not known whether T cells corresponding to stromal products are present in humans. In this study, we describe a method to screen for human stromal products that have not triggered significant tolerance and could therefore serve as candidate antigens for cancer immunotherapy.


METHODS
To identify candidates for human stromal antigens, we used an in vitro-screening method to determine whether dendritic cells transfected with mRNA encoding products, which are overexpressed in the tumor stroma, are capable of stimulating cytotoxic CD8(+) (CTL) responses from human peripheral blood mononuclear cells.


RESULTS
CTL responses could be consistently generated against fibroblast activation protein (FAP) but not against matrix metalloproteinase-9 (MMP-9) or MMP-14. To enhance the immunogenicity of the mRNA-translated FAP product, a lysosomal targeting signal derived from lysosome-associated membrane protein-1 (LAMP-1) was fused to the COOH terminus of FAP to redirect the translated product into the class II presentation pathway. Dendritic cells transfected with mRNA encoding the FAP-LAMP fusion product stimulated enhanced CD4(+) and CD8(+) T-cell responses.


CONCLUSIONS
This study identifies FAP, a protease preferentially expressed in tumor-associated fibroblasts, as a candidate human stromal antigen to target in the setting of cancer immunotherapy, and shows that differential expression of stromal products is not a sufficient criteria to indicate its immunogenicity in a vaccination setting.
Fassnacht
Martin
M
Center for Translational Research, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.
Lee
Jaewoo
J
Milazzo
Caterina
C
Boczkowski
David
D
Su
Zhen
Z
Nair
Smita
S
Gilboa
Eli
E
D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D019496:Cancer Vaccines; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D003713:Dendritic Cells / Q000166:cytology; D010450:Endopeptidases; D005347:Fibroblasts / Q000378:metabolism; D018093:Gelatinases; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated; D008565:Membrane Proteins; D008666:Metalloendopeptidases / Q000378:metabolism; D051379:Mice; D009369:Neoplasms / Q000276:immunology* / Q000628:therapy*; D009389:Neovascularization, Pathologic; D010957:Plasmids / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D000099167:Fibroblast Activation Protein Alpha
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D019496:Cancer Vaccines; D017931:DNA Primers; D010450:Endopeptidases; D018093:Gelatinases; D020780:Matrix Metalloproteinase 9; D053504:Matrix Metalloproteinases, Membrane-Associated; D008565:Membrane Proteins; D008666:Metalloendopeptidases; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D000099167:Fibroblast Activation Protein Alpha