5-fluorouracil-based chemotherapy enhances the antitumor activity of a thymidylate synthase-directed polyepitopic peptide vaccine.
BACKGROUND
Thymidylate synthase (TS), a key enzyme in DNA synthesis, is often overexpressed in cancer cells. Some chemotherapeutic agents, such as 5-fluorouracil (5-FU), act by inhibiting TS expression. We evaluated whether a novel 28-amino acid multiepitope peptide, TS/PP, that contains the sequences of three TS-derived epitopes with binding motifs for HLA-A(*)02.01 could induce a TS-directed cytotoxic T-lymphocyte (CTL) response with antitumor activity.


METHODS
TS/PP peptide immunologic activity in CTL lines derived from human leukocyte antigen (HLA)-A(*)02.01+ peripheral blood mononuclear cells (PBMCs) was tested in the presence of interleukin-2 and autologous TS/PP peptide-loaded dendritic cells. Immunologic and antitumor activities of TS/PP and its toxicity were also evaluated in vivo in HLA-A(*)02.01 transgenic (HHD) mice that were vaccinated with TS/PP, control, or TS-peptide cocktail and treated with or without 5-FU chemotherapy. The mice were also inoculated subcutaneously with TS-expressing EL-4/HHD lymphoma cells to assess immune response against these tumor cells.


RESULTS
TS/PP-specific CTL lines showed a TS-multiepitopic specificity and were able to kill TS+/HLA-A(*)02.01+ breast and colon carcinoma cells. The killing ability against target cells previously exposed to sublethal doses of 5-FU was statistically significantly greater than against untreated target cells (43.5% versus 26.5% at 25/1 effector to target ratio [Difference {diff} = 17.0]; 95% confidence interval [CI] = 12.6 to 20.4) for MDA-MB-231 breast carcinoma cells and 73.5 versus 48.5 (diff = 25.0; 95% CI = 16.2 to 33.8) for the SW-1463 colon carcinoma cells. HHD mice vaccinated with TS/PP manifested a TS-peptide-specific CTL response with no sign of autoimmunity or toxicity. Furthermore, treatment of these mice with 5-FU delayed or prevented the occurrence of tumors formed by inoculation with autologous (TS+)EL-4/HHD lymphoma cells.


CONCLUSIONS
The multiepitopic TS/PP vaccine induces a tumor-specific immune response in mice and is especially potent when used in combination with 5-FU-based chemotherapy.
Correale
Pierpaolo
P
Siena University School of Medicine, Viale Bracci 1, 53100 Siena, Italy.
Del Vecchio
Maria Teresa
MT
Di Genova
Giuseppa
G
Savellini
Gianni Gori
GG
La Placa
Marco
M
Terrosi
Chiara
C
Vestri
Marzio
M
Urso
Renato
R
Lemonnier
Francois
F
Aquino
Angelo
A
Bonmassar
Enzo
E
Giorgi
Giorgio
G
Francini
Guido
G
Cusi
Maria Grazia
MG
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy; D019496:Cancer Vaccines / Q000276:immunology / Q000494:pharmacology*; D002277:Carcinoma / Q000188:drug therapy; D018929:Cell Culture Techniques; D003110:Colonic Neoplasms / Q000188:drug therapy; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D003713:Dendritic Cells; D018984:Epitopes, T-Lymphocyte / Q000494:pharmacology*; D005260:Female; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology*; D015234:HLA-A Antigens; D006801:Humans; D007150:Immunohistochemistry; D008223:Lymphoma / Q000188:drug therapy; D051379:Mice; D008822:Mice, Transgenic; D010455:Peptides / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects* / Q000276:immunology; D013940:Thymidylate Synthase / Q000378:metabolism*; D014162:Transfection; D014185:Transplantation, Isogeneic
D000964:Antimetabolites, Antineoplastic; D019496:Cancer Vaccines; D018984:Epitopes, T-Lymphocyte; D015234:HLA-A Antigens; D010455:Peptides; D013940:Thymidylate Synthase; D005472:Fluorouracil