Chemotherapeutic drugs may be used to enhance the killing efficacy of human tumor antigen peptide-specific CTLs.

The effects of anticancer chemotherapy on antigen-specific cytotoxic T lymphocytes (CTLs) are mostly unknown. We tested the effects of cytotoxic drugs such as 5-fluorouracil, gemcitabine, and oxaliplatin on the functional activity of antigen-specific CTL cultures derived from the peripheral blood mononuclear cells of human donors. We found that a biweekly drug-exposure of human HLA-A(*)02.01+ CTLs derived from bulk cultures led to completely different effects if occurring early (day second) or late (day thirteenth) after the in vitro stimulations with the cognate peptides. In the first case, there was a significant CTL inhibition, whereas in the second, there was a marked enhancement of the antigen-specific cytolytic activity. Results of immunocytofluorimetric studies and CTL/natural killer inhibition assays suggested that the latter effect could be related to a more selective drug-mediated inhibition of cohabitant T regulatory (reg) cells. These results were translated in an in vivo therapeutic mouse model where humanized HLA-A(*)02.01 transgenic mice inoculated with EL-4/humanized HLA-A(*)02.01 transgenic mice showed a prolonged survival and the greatest rate of cure when receiving a combined treatment with a thymidylate synthase-specific peptide vaccine and a multidrug chemotherapy regimen administered late after immunization. Tumor samples derived from this group of mice showed a reduced expression of the target thymidylate synthase antigen, a marked reduction of T(reg)s, and a noteworthy infiltration of C8+ T cells. These results may have clinical implications for the design of new translational anticancer regimens aimed at combining chemotherapy and immunotherapy.

Anti-angiogenetic effects of immune-reconstituted influenza virosomes assembled with parathyroid hormone-related protein derived peptide vaccine.

BACKGROUND: C-IRIV/PTR-4 is a novel anticancer vaccine construct composed of immune-reconstituted influenza virosomes (IRIV) assembled with the PTH-rP derived peptide (PTR)-4, a synthetic CTL epitope with HLA-A(*)02.01 amino acid binding motifs. This peptide is able to generate a human PTH-rP specific CTL response with anti-tumor activity in vitro and in mice. MATERIALS AND METHODS: We have investigated the immunological and preventive anti-tumor activity of C-IRIV/PTR-4 compared with the soluble PTR-4 peptide, in HHD mice inoculated with autologous PTH-rP+ tumor cells. RESULTS: Peptide vaccination with either a soluble and an IRIV formulation showed similar immunological activity and the ability to purge the tumor tissue of tumor cell clones able to produce the target antigen (PTR-rP). The most efficient protection from tumor growth was however observed in animals vaccinated with C-IRIV/PTR-4 in which an additional IRIV related anti-angiogenetic effect was detected in the tumor tissue. CONCLUSIONS: These results confirm the immunological activity of PTR-4 vaccination and suggest a more efficacious therapeutic potential of C-IRIV/PTR-4 against bone metastases and malignancies like breast, prostate and lung which very often over-express PTH-rP.

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.

Dendritic cell-mediated cross-presentation of antigens derived from colon carcinoma cells exposed to a highly cytotoxic multidrug regimen with gemcitabine, oxaliplatin, 5-fluorouracil, and leucovorin, elicits a powerful human antigen-specific CTL response with antitumor activity in vitro.

Gemcitabine, oxaliplatin, leucovorin, and 5-fluorouracil (GOLF) is a novel multidrug regimen inducing high levels of necrosis and apoptosis in colon carcinoma cells. This regimen is also able to promote a process of Ag remodeling including up-regulation of immunotherapy targets like carcinoembryonic Ag (CEA), thymidylate synthase (TS). We have conducted a preclinical study aimed to investigate whether these drug-induced modifications would also enhance colon cancer cell immunogenicity. Several CTL lines were thus generated by in vitro stimulating human HLA-A(*)02.01(+) PBMCs, from normal donors and colon cancer patients, with autologous dendritic cells cross-primed with cell lysates of colon cancer cells untreated, irradiated, or previously exposed to different drug treatments including the GOLF regimen. Class I HLA-restricted cytolytic activity of these CTL lines was tested against colon cancer cells and CEA and TS gene transfected target cells. These experiments revealed that CTLs sensitized with GOLF-treated cancer cells were much more effective than those sensitized with the untreated colon carcinoma cells or those exposed to the other treatments. CTL lines sensitized against the GOLF-treated colon cancer cells, also expressed a greater percentage of T-lymphocyte precursors able to recognize TS- and CEA-derived peptides. These results suggest that GOLF regimen is a powerful antitumor and immunomodulating regimen that can make the tumor cells a suitable means to induce an Ag-specific CTL response. These results suggest that a rationale combination of GOLF chemotherapy with cytokine-based immunotherapy could generate a chemotherapy-modulated Ag-specific T-lymphocyte response in cancer patients able to destroy the residual disease survived to the cytotoxic drugs.

Immune-reconstituted influenza virosome containing CD40L gene enhances the immunological and protective activity of a carcinoembryonic antigen anticancer vaccine.

The correct interaction of a costimulatory molecule such as CD40L with its contrareceptor CD40 expressed on the membrane of professional APCs, provides transmembrane signaling that leads to APC activation. This process can be exploited to significantly improve the efficacy of cancer vaccines and the outcome of a possible cancer vaccine-induced, Ag-specific CTL response. Therefore, we investigated whether a novel intranasal delivery of immune-reconstituted influenza virosomes (IRIV), assembled with the CD40L gene (CD40L/IRIV), could be used to improve protective immunity and the Ag-specific CTL response against carcinoembryonic Ag (CEA) generated with a novel vaccine constituted of IRIV assembled with the CEA gene (CEA/IRIV). Our results suggest that CD40L/IRIV was able to augment CEA-specific CTL activity and CEA-specific protective immunity induced by CEA/IRIV most likely through the induction of a CTL response associated with a Th1 phenotype. In conclusion, we provide evidence that CD40L/IRIV, by acting through the CD40L/CD40 signaling pathway, acts as an immune-adjuvant that could increase the efficacy of a CEA-specific cancer vaccine, which could provide an efficacious new strategy for cancer therapy.