Negative costimulation on T cells is exploited by both prostate cancer and melanoma to evade antitumor immunity. Blocking such mechanisms restores antitumor immunity as was demonstrated by the improved survival of patients with metastatic melanoma after treatment with an antibody blocking the CTLA-4 inhibitory receptor (ipilimumab). Enhanced expression of another inhibitory immunoreceptor, programmed death-1 (PD-1), and its ligand, PD-L1, was found to correlate with a poor prognosis in prostate cancer and melanoma. PD-1-blocking antibodies are being developed to modulate antitumor immune responses. To support preclinical and clinical development of anti-PD-1 therapy, we sought to develop biomarker assays that can detect the effect of PD-1-blocking agents in whole blood and peripheral blood mononuclear cells. In this study, we assessed the effect of PD-1 blockade in modulating super antigen (staphylococcus enterotoxin B)-induced and recall antigen (tetanus toxoid)-induced T-cell reactivity in vitro using whole blood and peripheral blood mononuclear cells from patients with advanced melanoma, prostate cancer, and healthy controls. PD-1 blockade was found to shift antigen-induced cellular reactivity toward a proinflammatory Th1/Th17 response, as evidenced by enhanced production of interferon γ, interleukin (IL)-2, tumor necrosis factor α, IL-6, and IL-17 and reduced production of the Th2 cytokines IL-5 and IL-13. It is interesting to note that suppression of Th2 responsivity was seen with whole blood cells only from patients with cancer. Taken together, we identified novel biomarker assays that might be used to determine the functional consequences of PD-1 blockade in peripheral blood cells from patients with cancer. How these assays translate to the local antitumor response remains to be established in a clinical setting.

Purpose: The success of immunotherapy with dendritic cells (DC) to treat cancer is dependent on effective migration to the lymph nodes and subsequent activation of antigen-specificTcells. In this study, we investigated the fate of DC after intradermal (i.d.) or intranodal (i.n.) administration and the consequences for the immune activating potential of DC vaccines in melanoma patients. Experimental Design: DC were i.d. or i.n. administered to 25 patients with metastatic melanoma scheduled for regional lymph node resection. To track DC in vivo with scintigraphic imaging and in lymph nodes by immunohistochemistry, cells were labeled with both [ 111 In]-indium and superparamagnetic iron oxide. Results: After i.d. injection, maximally 4% of the DC reached the draining lymph nodes. When correctly delivered, all DC were delivered to one or more lymph nodes after i.n. injection. Independent of the route of administration, large numbers of DC remained at the injection site, lost viability, and were cleared by infiltrating CD163+ macrophages within 48 hours. Interestingly, 87 F 10% of the surviving DC preferentially migrated into the T-cell areas, where they induced antigen-specificT-cell responses. Even though more DC reached theT-cell areas, i.n. injection of DC induced similar antigen-specific immune responses as i.d. injection. Immune responses were already induced with <5 Â 10 5 DC migrating into theT-cell areas. Conclusions: Monocyte-derived DC have high immune activating potential irrespective of the route of vaccination. Limited numbers of DC in the draining lymph nodes are sufficient to induce antigen-specific immunologic responses.

Purpose: Thus far, dendritic cell (DC)-based immunotherapy of cancer was primarily based on in vitro-generated monocytederived DCs, which require extensive in vitro manipulation. Here, we report on a clinical study exploiting primary CD1c þ myeloid DCs, naturally circulating in the blood. Experimental Design: Fourteen stage IV melanoma patients, without previous systemic treatment for metastatic disease, received autologous CD1c þ myeloid DCs, activated by only brief (16 hours) ex vivo culture and loaded with tumor-associated antigens of tyrosinase and gp100. Results: Our results show that therapeutic vaccination against melanoma with small amounts (3-10 Â 10 6 ) of myeloid DCs is feasible and without substantial toxicity. Four of 14 patients showed long-term progression-free survival (12-35 months), which directly correlated with the development of multifunctional CD8þ T-cell responses in three of these patients. In particular, high CD107a expression, indicative for cytolytic activity, and IFNg as well as TNFa and CCL4 production was observed. Apparently, these T-cell responses are essential to induce tumor regression and promote long-term survival by stalling tumor growth. Conclusions:We show that vaccination of metastatic melanoma patients with primary myeloid DCs is feasible and safe and results in induction of effective antitumor immune responses that coincide with improved progression-free survival. Clin Cancer Res; 22(9); 2155-66. Ó2015 AACR.

Purpose: The success of cancer immunotherapy depends on the balance between effector T cells and suppressive immune regulatory mechanisms within the tumor microenvironment. In this study we investigated whether transient monoclonal antibody-mediated depletion of CD25 high regulatory T cells (Treg) is capable of enhancing the immunostimulatory efficacy of dendritic cell vaccines.Experimental Design: Thirty HLA-A2.1 + metastatic melanoma patients were vaccinated with mature dendritic cells pulsed with tumor peptide and keyhole limpet hemocyanin (KLH). Half of the patients were pretreated with daclizumab, a humanized antibody against the interleukin-2 (IL-2) receptor α-chain (CD25), either four or eight days before dendritic cell vaccinations. Clinical and immunologic parameters were determined.Results: Daclizumab efficiently depleted all CD25 high immune cells, including CD4 + FoxP3 + CD25 high cells, from the peripheral blood within four days of administration. Thirty days after administration, daclizumab was cleared from the circulation and all CD25 + cells reappeared. The presence of daclizumab during dendritic cell vaccinations prevented the induction of specific antibodies in vivo but not the presence of antigen-specific T cells. Daclizumab, however, did prevent these CD25 + T cells from acquiring effector functions. Consequently, significantly less patients pretreated with daclizumab developed functional, vaccine-specific effector T cells and antibodies compared with controls. Daclizumab pretreatment had no significant effect on progression-free survival compared with the control group.Conclusions: Although daclizumab depleted the CD4 + FoxP3 + CD25 high Tregs from the peripheral circulation, it did not enhance the efficacy of the dendritic cell vaccine. Residual daclizumab functionally suppressed de novo induced CD25 + effector cells during dendritic cell vaccinations. Our results indicate that for immunotherapeutic benefit of transient Treg depletion, timing and dosing as well as Treg specificity are extremely important. Clin Cancer Res; 16(20); 5067-78. ©2010 AACR.Melanoma is considered one of the most immunogenic types of cancers. This is based on the following arguments: (a) several melanoma-specific antigens have been identified (1, 2); (b) functional lymphocytes specific for melanoma antigens are increased in melanoma patients (3); (c) immune-stimulating agents can have a positive effect on disease outcome (4, 5); and (d) spontaneous melanoma regressions with simultaneous onset of vitiligo have been reported (6).Immunotherapeutic clinical trials have succeeded in expanding melanoma-specific effector T cells in vivo, but favorable outcomes are still limited because tumor-induced mechanisms of immune evasion may render the host tolerant for melanoma antigens (7,8). Immunosuppression at the tumor microenvironment mediated by regulatory T cells (Treg) is one of the most critical mechanisms of tumor-immune escape and a major hurdle for successful immunotherapy (9-11).In melanoma patients, selective...

The brain is a specialized immune site representing a unique tumor microenvironment. The availability of fresh brain tumor material for ex vivo analysis is often limited because large parts of many brain tumors are resected using ultrasonic aspiration. We analyzed ultrasonic tumor aspirates as a biosource to study immune suppressive mechanisms in 83 human brain tumors. Lymphocyte infiltrates in brain tumor tissues and ultrasonic aspirates were comparable with respect to lymphocyte content and viability. Applying ultrasonic aspirates, we detected massive infiltration of CD4+FoxP3+CD25(high) CD127(low) regulatory T cells (Tregs) in glioblastomas (n = 29) and metastatic brain tumors (n = 20). No Treg accumulation was observed in benign tumors such as meningiomas (n = 10) and pituitary adenomas (n = 5). A significant Treg increase in blood was seen only in patients with metastatic brain tumors. Tregs in high-grade tumors exhibited an activated phenotype as indicated by decreased proliferation and elevated CTLA-4 and FoxP3 expression relative to blood Tregs. Functional analysis showed that the tumor-derived Tregs efficiently suppressed cytokine secretion and proliferation of autologous intratumoral lymphocytes. Most tumor-infiltrating Tregs were localized in close proximity to effector T cells, as visualized by immunohistochemistry. Furthermore, 61% of the malignant brain tumors expressed programmed death ligand-1 (PD-L1), while the inhibitory PD-1 receptor was expressed on CD4+ effector cells present in 26% of tumors. In conclusion, using ultrasonic tumor aspirates as a biosource we identified Tregs and the PD-L1/PD-1 pathway as immune suppressive mechanisms in malignant but not benign human brain tumors.