5-fluorouracil-based chemotherapy enhances the antitumor activity of a thymidylate synthase-directed polyepitopic peptide vaccine

J Natl Cancer Inst. 2005 Oct 5;97(19):1437-45. doi: 10.1093/jnci/dji188.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology*
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology
  • Breast Neoplasms / drug therapy
  • Cancer Vaccines / immunology
  • Cancer Vaccines / pharmacology*
  • Carcinoma / drug therapy
  • Cell Culture Techniques
  • Colonic Neoplasms / drug therapy
  • Cytotoxicity, Immunologic / drug effects*
  • Dendritic Cells
  • Epitopes, T-Lymphocyte / pharmacology*
  • Female
  • Flow Cytometry
  • Fluorouracil / pharmacology*
  • HLA-A Antigens
  • Humans
  • Immunohistochemistry
  • Lymphoma / drug therapy
  • Mice
  • Mice, Transgenic
  • Peptides / pharmacology
  • T-Lymphocytes, Cytotoxic / drug effects*
  • T-Lymphocytes, Cytotoxic / immunology
  • Thymidylate Synthase / metabolism*
  • Transfection
  • Transplantation, Isogeneic


  • Antimetabolites, Antineoplastic
  • Cancer Vaccines
  • Epitopes, T-Lymphocyte
  • HLA-A Antigens
  • Peptides
  • Thymidylate Synthase
  • Fluorouracil