[show abstract][hide abstract] ABSTRACT: CTL-associated antigen 4 (CTLA4) is a costimulatory molecule expressed on activated T cells that delivers an inhibitory signal to these T cells. CTLA4 blockade with antibody treatment has been shown to augment antitumor immunity in animal models and is being developed as a treatment for cancer patients. As has been seen in preclinical models, combining CTLA4 blockade and granulocyte macrophage colony-stimulating factor (GM-CSF)-based immunotherapies can enhance the antitumor efficacy of this approach. We therefore examined whether CTLA4 blockade could be combined with GM-CSF administration. We treated 24 patients with metastatic, castration-resistant prostate cancer in a phase I trial where sequential cohorts were treated with increasing doses of ipilimumab, a fully human anti-CTLA4 antibody. Study subjects also received s.c. injections of GM-CSF at a fixed dose. Of the six patients treated at the highest dose level, three had confirmed PSA declines of >50%, including one patient that had a partial response in visceral metastases. Expansion of activated, circulating CD25(+) CD69(+) CD8(+) T cells occurred more frequently at higher doses of treatment and was greater in magnitude than was seen in patients who received the same doses of either ipilimumab or GM-CSF alone. By screening sera with protein arrays, we showed that our treatment can induce antibody responses to NY-ESO-1. These results show that this combination immunotherapy can induce the expansion not only of activated effector CD8 T cells in vivo but also of T cells that are specific for known tumor-associated antigens from the endogenous immune repertoire.
Cancer Research 01/2009; 69(2):609-15. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cytotoxic T lymphocyte-associated antigen 4 (CTLA4) delivers inhibitory signals to activated T cells. CTLA4 is constitutively expressed on regulatory CD4(+) T cells (Tregs), but its role in these cells remains unclear. CTLA4 blockade has been shown to induce antitumor immunity. In this study, we examined the effects of anti-CTLA4 antibody on the endogenous CD4(+) T cells in cancer patients. We show that CTLA4 blockade induces an increase not only in the number of activated effector CD4(+) T cells, but also in the number of CD4(+) FoxP3(+) Tregs. Although the effects were dose-dependent, CD4(+) FoxP3(+) regulatory T cells could be expanded at lower antibody doses. In contrast, expansion of effector T cells was seen only at the highest dose level studied. Moreover, these expanded CD4(+) FoxP3(+) regulatory T cells are induced to proliferate with treatment and possess suppressor function. Our results demonstrate that treatment with anti-CTLA4 antibody does not deplete human CD4(+) FoxP3(+) Tregs in vivo, but rather may mediate its effects through the activation of effector T cells. Our results also suggest that CTLA4 may inhibit Treg proliferation similar to its role on effector T cells. This study is registered at http://www.clinicaltrials.gov/ct2/show/NCT00064129, registry number NCT00064129.
[show abstract][hide abstract] ABSTRACT: Heteroclitic peptides are used to enhance the immunogenicity of tumor-associated Ags to break T cell tolerance to these self-proteins. One such altered peptide ligand (Cap1-6D) has been derived from an epitope in human carcinoembryonic Ag, CEA(605-613) (Cap1). Clinical responses have been seen in colon cancer patients receiving a tumor vaccine comprised of this altered peptide. Whether Cap1-6D serves as a T cell agonist for Cap1-specific T cells or induces different T cells is unknown. We, therefore, examined the T cell repertoires elicited by Cap1-6D and Cap1. Human CTL lines and clones were generated with either Cap1-6D peptide (6D-CTLs) or Cap1 peptide (Cap1-CTLs). The TCR Vbeta usage and functional avidity of the T cells induced in parallel against these target peptides were assessed. The predominant CTL repertoire induced by agonist Cap1-6D is limited to TCR Vbeta1-J2 with homogenous CDR3 lengths. In contrast, the majority of Cap1-CTLs use different Vbeta1 genes and also had diverse CDR3 lengths. 6D-CTLs produce IFN-gamma in response to Cap1-6D peptide with high avidity, but respond with lower avidity to the native Cap1 peptide when compared with the Cap1-CTLs. Nevertheless, 6D-CTLs could still lyse targets bearing the native epitope. Consistent with these functional results, 6D-CTLs possess TCRs that bind Cap-1 peptide/MHC tetramer with higher intensity than Cap1-CTLs but form less stable interactions with peptide/MHC as measured by tetramer decay. These results demonstrate that priming with this CEA-derived altered peptide ligand can induce distinct carcinoembryonic Ag-reactive T cells with different functional capacities.
The Journal of Immunology 03/2008; 180(3):1526-34. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Developing a process to generate dendritic cells (DCs) applicable for multicenter trials would facilitate cancer vaccine development. Moreover, targeting multiple antigens with such a vaccine strategy could enhance the efficacy of such a treatment approach. We performed a phase 1/2 clinical trial administering a DC-based vaccine targeting multiple tumor-associated antigens to patients with advanced colorectal cancer (CRC). A qualified manufacturing process was used to generate DC from blood monocytes using granulocyte macrophage colony-stimulating factor and IL-13, and matured for 6 hours with Klebsiella-derived cell wall fraction and interferon-gamma (IFN-gamma). DCs were also loaded with 6 HLA-A*0201 binding peptides derived from carcinoembryonic antigen (CEA), MAGE, and HER2/neu, as well as keyhole limpet hemocyanin protein and pan-DR epitope peptide. Four planned doses of 35x10(6) cells were administered intradermally every 3 weeks. Immune response was assessed by IFN-gamma enzyme-linked immunosorbent spot (ELISPOT). Matured DC possessed an activated phenotype and could prime T cells in vitro. In the trial, 21 HLA-A2+ patients were apheresed, 13 were treated with the vaccine, and 11 patients were evaluable. No significant treatment-related toxicity was reported. T-cell responses to a CEA-derived peptide were detected by ELISPOT in 3 patients. T cells induced to CEA possessed high avidity T-cell receptors. ELISPOT after in vitro restimulation detected responses to multiple peptides in 2 patients. All patients showed progressive disease. This pilot study in advanced CRC patients demonstrates DC-generated granulocyte macrophage colony-stimulating factor and IL-13 matured with Klebsiella-derived cell wall fraction and IFN-gamma can induce immune responses to multiple tumor-associated antigens in patients with advanced CRC.
Journla of Immunotherapy 11/2007; 30(7):762-72. · 3.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: an increase not only in the number of activated effector CD4 T cells, but also in the number of CD4 FoxP3 Tregs. Although the effects were dose-depen- dent, CD4 FoxP3 regulatory T cells could be expanded at lower antibody doses. In contrast, expansion of effector T cells was seen only at the highest dose level studied. Moreover, these expanded CD4 FoxP3 regulatory T cells are in- duced to proliferate with treatment and possess suppressor function. Our results demonstrate that treatment with anti-CTLA4 antibody does not deplete human CD4 FoxP3 Tregs in vivo, but rather may medi- ateitseffectsthroughtheactivationofeffec- tor T cells. Our results also suggest that CTLA4 may inhibit Treg proliferation similar to its role on effector T cells. This study is registered at http://www.clinicaltrials.gov/ ct2/show/NCT00064129, registry number NCT00064129. (Blood. 2008;112:1175-1183)