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Purpose: Objective responses are reported in 34% to 37% of patients with programmed death-1 (PD-1)-naïve advanced melanoma treated with PD-1 inhibitors. Pre-existing CD8+ T-cell infiltrate and interferon (IFN) gene signature correlate with response to PD-1 blockade. Here, we report a phase Ib/II study of pembrolizumab/pegylated (PEG)-IFN combination in PD-1-naïve advanced melanoma., Patients and Methods: PEG-IFN (1, 2, and 3 μg/kg per week) was dose escalated using a modified toxicity probability interval design in three cohorts of four patients each, whereas pembrolizumab was dosed at 2 mg/kg every 3 weeks in the phase Ib portion. Thirty-one patients were enrolled in the phase II portion. Primary objectives were safety and incidence of dose-limiting toxicities. Secondary objectives included objective response rate, progression-free survival (PFS), and overall survival., Results: Forty-three patients with stage IV melanoma were enrolled in the phase Ib and II portions of the study and included in the analysis. At the data cutoff date (December 31, 2017), median follow-up duration was 25 months (range, 1 to 38 months). All 43 patients experienced at least one adverse event; grade 3/4 treatment-related adverse events occurred in 21 of 43 patients (48.8%). Objective responses were seen at all three dose levels among 43 evaluable patients. The objective response rate was 60.5%, with 46.5% of patients exhibiting ongoing response. Median PFS was 11.0 months in all patients and unreached in responders, whereas median overall survival remained unreached in all patients. The 2-year PFS rate was 46%., Conclusion: Pembrolizumab/PEG-IFN demonstrated an acceptable toxicity profile with promising evidence of clinical efficacy in PD-1-naïve metastatic melanoma. These results support the rationale to further investigate this pembrolizumab/PEG-IFN combination in this disease.

CD4+ Tregs impede T cell responses to tumors. They express multiple inhibitory receptors that support their suppressive functions, including T cell Ig and ITIM domain (TIGIT). In melanoma patients, we show that Tregs exhibit increased TIGIT expression and decreased expression of its competing costimulatory receptor CD226 as compared with CD4+ effector T cells, resulting in an increased TIGIT/CD226 ratio. Tregs failed to upregulate CD226 upon T cell activation. TIGIT+ Tregs are highly suppressive, stable, and enriched in tumors. TIGIT and CD226 oppose each other to augment or disrupt, respectively, Treg suppression and stability. A high TIGIT/CD226 ratio in Tregs correlates with increased Treg frequencies in tumors and poor clinical outcome upon immune checkpoint blockade. Altogether, our findings show that a high TIGIT/CD226 ratio in Tregs regulates their suppressive function and stability in melanoma. They provide the rationale for novel immunotherapies to activate CD226 in Tregs together with TIGIT blockade to counteract Treg suppression in cancer patients.

T cell Ig and ITIM domain (TIGIT) is an inhibitory receptor expressed by activated T cells, Tregs, and NK cells. Here, we determined that TIGIT is upregulated on tumor antigen-specific (TA-specific) CD8⁺ T cells and CD8⁺ tumor-infiltrating lymphocytes (TILs) from patients with melanoma, and these TIGIT-expressing CD8⁺ T cells often coexpress the inhibitory receptor PD-1. Moreover, CD8⁺ TILs from patients exhibited downregulation of the costimulatory molecule CD226, which competes with TIGIT for the same ligand, supporting a TIGIT/CD226 imbalance in metastatic melanoma. TIGIT marked early T cell activation and was further upregulated by T cells upon PD-1 blockade and in dysfunctional PD-1⁺TIM-3⁺ TA-specific CD8⁺ T cells. PD-1⁺TIGIT⁺, PD-1⁻TIGIT⁺, and PD-1⁺TIGIT⁻ CD8⁺ TILs had similar functional capacities ex vivo, suggesting that TIGIT alone, or together with PD-1, is not indicative of T cell dysfunction. However, in the presence of TIGIT ligand-expressing cells, TIGIT and PD-1 blockade additively increased proliferation, cytokine production, and degranulation of both TA-specific CD8⁺ T cells and CD8⁺ TILs. Collectively, our results show that TIGIT and PD-1 regulate the expansion and function of TA-specific CD8⁺ T cells and CD8⁺ TILs in melanoma patients and suggest that dual TIGIT and PD-1 blockade should be further explored to elicit potent antitumor CD8⁺ T cell responses in patients with advanced melanoma.

Immune checkpoint inhibitors show great promise as therapy for advanced melanoma, heightening the need to determine the most effective use of these agents. Here, we report that programmed death-1(high) (PD-1(high)) tumor antigen (TA)-specific CD8(+) T cells present at periphery and at tumor sites in patients with advanced melanoma upregulate IL10 receptor (IL10R) expression. Multiple subsets of peripheral blood mononucleocytes from melanoma patients produce IL10, which acts directly on IL10R(+) TA-specific CD8(+) T cells to limit their proliferation and survival. PD-1 blockade augments expression of IL10R by TA-specific CD8(+) T cells, thereby increasing their sensitivity to the immunosuppressive effects of endogenous IL10. Conversely, IL10 blockade strengthened the effects of PD-1 blockade in expanding TA-specific CD8(+) T cells and reinforcing their function. Collectively, our findings offer a rationale to block both IL10 and PD-1 to strengthen the counteraction of T-cell immunosuppression and to enhance the activity of TA-specific CD8(+) T cell in advanced melanoma patients., (©2015 American Association for Cancer Research.)

Although melanoma vaccines stimulate tumor antigen-specific CD8(+) T cells, objective clinical responses are rarely observed. To investigate this discrepancy, we evaluated the character of vaccine-induced CD8(+) T cells with regard to the inhibitory T-cell coreceptors PD-1 and Tim-3 in patients with metastatic melanoma who were administered tumor vaccines. The vaccines included incomplete Freund's adjuvant, CpG oligodeoxynucleotide (CpG), and the HLA-A2-restricted analog peptide NY-ESO-1 157-165V, either by itself or in combination with the pan-DR epitope NY-ESO-1 119-143. Both vaccines stimulated rapid tumor antigen-specific CD8(+) T-cell responses detected ex vivo, however, tumor antigen-specific CD8(+) T cells produced more IFN-γ and exhibited higher lytic function upon immunization with MHC class I and class II epitopes. Notably, the vast majority of vaccine-induced CD8(+) T cells upregulated PD-1 and a minority also upregulated Tim-3. Levels of PD-1 and Tim-3 expression by vaccine-induced CD8(+) T cells at the time of vaccine administration correlated inversely with their expansion in vivo. Dual blockade of PD-1 and Tim-3 enhanced the expansion and cytokine production of vaccine-induced CD8(+) T cells in vitro. Collectively, our findings support the use of PD-1 and Tim-3 blockades with cancer vaccines to stimulate potent antitumor T-cell responses and increase the likelihood of clinical responses in patients with advanced melanoma., (©2013 AACR.)

Patients with advanced melanoma can develop spontaneous cellular and humoral responses to tumor antigens. Understanding the failure of spontaneous or vaccine-induced tumor antigen-specific T-cell responses to promote the immunologic clearance of melanomas is critical. Multiple mechanisms of melanoma-induced immune escape, which are likely to cause the failure of the spontaneous or vaccine-induced immune responses to promote tumor regression in humans, have been elucidated. In addition, a number of negative factors in the tumor microenvironment dampen antitumor immune responses, including cytokines (like transforming growth factor-β or interleukin-10), suppressive cells (regulatory T cells and myelosuppressive dendritic cells), defective antigen presentation by tumor cells (human leukocyte antigen or T antigen expression loss, antigen processing machinery defects), amino acid catabolizing enzymes (indoleamine-2-3 dioxygenase, arginase), and immune inhibitory pathways (like cytotoxic T-lymphocyte antigen 4/cluster of differentiation 28, programmed death 1/programmed death 1 ligand 1). This information has been used to develop a number of therapies to specifically target these negative regulators of antimelanoma immune responses to enhance tumor antigen-specific immune responses and to increase the likelihood of clinical benefits in patients with advanced melanoma., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Cytotoxic T cells that are present in tumors and capable of recognizing tumor epitopes are nevertheless generally impotent in eliciting tumor rejection. Thus, identifying the immune escape mechanisms responsible for inducing tumor-specific CD8(+) T-cell dysfunction may reveal effective strategies for immune therapy. The inhibitory receptors PD-1 and Tim-3 are known to negatively regulate CD8(+) T-cell responses directed against the well-characterized tumor antigen NY-ESO-1. Here, we report that the upregulation of the inhibitory molecule BTLA also plays a critical role in restricting NY-ESO-1-specific CD8(+) T-cell expansion and function in melanoma. BTLA-expressing PD-1(+)Tim-3(-) CD8(+) T cells represented the largest subset of NY-ESO-1-specific CD8(+) T cells in patients with melanoma. These cells were partially dysfunctional, producing less IFN-γ than BTLA(-) T cells but more IFN-γ, TNF, and interleukin-2 than the highly dysfunctional subset expressing all three receptors. Expression of BTLA did not increase with higher T-cell dysfunction or upon cognate antigen stimulation, as it does with PD-1, suggesting that BTLA upregulation occurs independently of functional exhaustion driven by high antigen load. Added with PD-1 and Tim-3 blockades, BTLA blockade enhanced the expansion, proliferation, and cytokine production of NY-ESO-1-specific CD8(+) T cells. Collectively, our findings indicate that targeting BTLA along with the PD-1 and Tim-3 pathways is critical to reverse an important mechanism of immune escape in patients with advanced melanoma.

NY-ESO-1 and LAGE-1 represent highly homologous cancer-germline Ags frequently coexpressed by many human cancers, but not by normal tissues, except testis. In contrast to NY-ESO-1, little is known about spontaneous immune responses to LAGE-1. In the current study, we report on spontaneous LAGE-1-specific CD4(+) T cells isolated from PBLs of patients with advanced LAGE-1(+)/NY-ESO-1(+) melanoma and directed against three promiscuous and immunodominant epitopes. Strikingly, although the three LAGE-1-derived epitopes are highly homologous to NY-ESO-1-derived epitopes, LAGE-1-specific CD4(+) T cells did not cross-react with NY-ESO-1. LAGE-1-specific CD4(+) T cells produced Th1-type and/or Th2-type cytokines and did not exert inhibitory effects on allogenic T cells. We observed that most patients with spontaneous NY-ESO-1-specific responses exhibited spontaneous CD4(+) T cell responses to at least one of the three immunodominant LAGE-1 epitopes. Additionally, nearly half of the patients with spontaneous LAGE-1-specific CD4(+) T cell responses had circulating LAGE-1-specific Abs that recognized epitopes located in the C-terminal portion of LAGE-1, which is distinct from NY-ESO-1. Collectively, our findings define the hierarchy of immunodominance of spontaneous LAGE-1-specific CD4(+) T cell responses in patients with advanced melanoma. These findings demonstrate the capability of LAGE-1 to stimulate integrated cellular and humoral immune responses that do not cross-react with NY-ESO-1. Therefore, they provide a strong rationale for the inclusion of LAGE-1 peptides or protein in vaccine trials for patients with NY-ESO-1(+)/LAGE-1(+) tumors.

The paradoxical coexistence of spontaneous tumor antigen-specific immune responses with progressive disease in cancer patients furthers the need to dissect the molecular pathways involved in tumor-induced T cell dysfunction. In patients with advanced melanoma, we have previously shown that the cancer-germline antigen NY-ESO-1 stimulates spontaneous NY-ESO-1-specific CD8(+) T cells that up-regulate PD-1 expression. We also observed that PD-1 regulates NY-ESO-1-specific CD8(+) T cell expansion upon chronic antigen stimulation. In the present study, we show that a fraction of PD-1(+) NY-ESO-1-specific CD8(+) T cells in patients with advanced melanoma up-regulates Tim-3 expression and that Tim-3(+)PD-1(+) NY-ESO-1-specific CD8(+) T cells are more dysfunctional than Tim-3(-)PD-1(+) and Tim-3(-)PD-1(-) NY-ESO-1-specific CD8(+) T cells, producing less IFN-γ, TNF, and IL-2. Tim-3-Tim-3L blockade enhanced cytokine production by NY-ESO-1-specific CD8(+) T cells upon short ex vivo stimulation with cognate peptide, thus enhancing their functional capacity. In addition, Tim-3-Tim-3L blockade enhanced cytokine production and proliferation of NY-ESO-1-specific CD8(+) T cells upon prolonged antigen stimulation and acted in synergy with PD-1-PD-L1 blockade. Collectively, our findings support the use of Tim-3-Tim-3L blockade together with PD-1-PD-L1 blockade to reverse tumor-induced T cell exhaustion/dysfunction in patients with advanced melanoma.

CD4(+) regulatory T cells (Tregs) accumulate at tumor sites and play a critical role in the suppression of immune responses against tumor cells. In this study, we show that two immunodominant epitopes derived from the tumor Ags (TAs) NY-ESO-1 and TRAG-3 stimulate both CD4+ Th cells and Tregs. TA-specific Tregs inhibit the proliferation of allogenic T cells, act in a cell-to-cell contact dependent fashion and require activation to suppress IL-2 secretion by T cells. TRAG-3 and NY-ESO-1-specific Tregs exhibit either a Th1-, a Th2-, or a Th0-type cytokine profile and dot not produce IL-10 or TGF-beta. The Foxp3 levels vary from one Treg clone to another and are significantly lower than those of CD4+CD25high Tregs. In contrast to NY-ESO-1-specific Th cells, the NY-ESO-1-specific and TRAG-3-specific Treg clonotypes share a common TCR CDR3 Vbeta usage with Foxp3+CD4+CD25high and CD4+CD25- T cells and were not detectable in PBLs of other melanoma patients and of healthy donors, suggesting that their recruitment occurs through the peripheral conversion of CD4+CD25- T cells upon chronic Ag exposure. Collectively, our findings demonstrate that the same epitopes spontaneously stimulate both Th cells and Tregs in patients with advanced melanoma. They also suggest that TA-specific Treg expansion may be better impaired by therapies aimed at depleting CD4+CD25high Tregs and preventing the peripheral conversion of CD4+CD25- T cells.

The programmed death 1 (PD-1) receptor is a negative regulator of activated T cells and is up-regulated on exhausted virus-specific CD8(+) T cells in chronically infected mice and humans. Programmed death ligand 1 (PD-L1) is expressed by multiple tumors, and its interaction with PD-1 resulted in tumor escape in experimental models. To investigate the role of PD-1 in impairing spontaneous tumor Ag-specific CD8(+) T cells in melanoma patients, we have examined the effect of PD-1 expression on ex vivo detectable CD8(+) T cells specific to the tumor Ag NY-ESO-1. In contrast to EBV, influenza, or Melan-A/MART-1-specific CD8(+) T cells, NY-ESO-1-specific CD8(+) T cells up-regulated PD-1 expression. PD-1 up-regulation on spontaneous NY-ESO-1-specific CD8(+) T cells occurs along with T cell activation and is not directly associated with an inability to produce cytokines. Importantly, blockade of the PD-1/PD-L1 pathway in combination with prolonged Ag stimulation with PD-L1(+) APCs or melanoma cells augmented the number of cytokine-producing, proliferating, and total NY-ESO-1-specific CD8(+) T cells. Collectively, our findings support the role of PD-1 as a regulator of NY-ESO-1-specific CD8(+) T cell expansion in the context of chronic Ag stimulation. They further support the use of PD-1/PD-L1 pathway blockade in cancer patients to partially restore NY-ESO-1-specific CD8(+) T cell numbers and functions, increasing the likelihood of tumor regression.

Analog peptides represent a promising tool to further optimize peptide-based vaccines in promoting the expansion of tumor antigen-specific cytotoxic T lymphocytes. Here, we report the results of a pilot trial designed to study the immunogenicity of the analog peptide NY-ESO-1 157-165V in combination with CpG 7909/PF3512676 and Montanide ISA 720 in patients with stage III/IV NY-ESO-1-expressing melanoma. Eight patients were immunized either with Montanide and CpG (arm 1, 3 patients); Montanide and peptide NY-ESO-1 157-165V (arm 2, 2 patients); or with Montanide, CpG, and peptide NY-ESO-1 157-165V (arm 3, 3 patients). Only the 3 patients immunized with Montanide, CpG, and peptide NY-ESO-1 157-165V in arm 3 developed a rapid increase of effector-memory NY-ESO-1-specific CD8+ T cells, detectable ex vivo. The majority of these cells exhibited an intermediate/late-stage differentiated phenotype (CD28-). Our study further demonstrated that our vaccine approach stimulated spontaneous tumor-reactive NY-ESO-1-specific CD8+ T cells in 2 patients with advanced disease, but failed to prime tumor-reactive NY-ESO-1-specific T cells in 1 patient with no spontaneously tumor-induced CD8+ T-cell responses to NY-ESO-1. Collectively, our data support the capability of the analog peptide NY-ESO-1 157-165V in combination with CpG and Montanide to promote the expansion of NY-ESO-1-specific CD8+ T cells in patients with advanced cancer. They also suggest that the presence of tumor-induced NY-ESO-1-specific T cells of well-defined clonotypes is critical for the expansion of tumor-reactive NY-ESO-1-specific CD8+ T cells after peptide-based vaccine strategies.

TCRs exhibit a high degree of specificity but may also recognize multiple and distinct peptide-MHC complexes, illustrating the so-called cross-reactivity of TCR-peptide-MHC recognition. In this study, we report the first evidence of CD4(+) T cells recognizing the same tumor peptide-epitope from NY-ESO-1, in the context of multiple HLA-DR and HLA-DP molecules. These cross-reactive CD4(+) T cells recognized not only autologous but also allogenic dendritic cells previously loaded with the relevant protein (i.e., the normally processed and presented epitope). Using clonotypic real-time RT-PCR, we have detected low frequencies of CD4(+) T cells expressing one cross-reactive TCR from circulating CD4(+) T cells of patients with stage IV melanoma either spontaneously or after immunization but not in normal donors. The maintenance of cross-reactive tumor Ag-specific CD4(+) T cells in PBLs of cancer patients required the presence of tumor Ag/epitope in the context of the MHC molecule used to prime the Ag-specific CD4(+) T cells. Our findings have significant implications for the optimization of TCR gene transfer immunotherapies widely applicable to cancer patients.

The taxol resistance gene TRAG-3 was initially isolated from cancer cell lines that became resistant to taxol in vitro. TRAG-3 is a cancer germline Ag expressed by tumors of different histological types including the majority of melanoma, breast, and lung cancers. In the present study, we report that patients with stage IV melanoma and breast cancers developed spontaneous IFN-gamma-producing CD4+ T cell responses against a single immunodominant and promiscuous peptide epitope from TRAG-3 presented in the context of multiple HLA-DR molecules. The TRAG-3-specific CD4+ T cells and clones were expanded in vitro and recognized not only peptide pulsed APCs but also autologous dendritic cells (DCs) loaded with the TRAG-3 protein. All stage IV melanoma patients with TRAG-3-expressing tumors developed spontaneous CD4+ T cell responses against TRAG-3, demonstrating its strong immunogenicity. None of these patients had detectable IgG Ab responses against TRAG-3. TCRbeta gene usage studies of TRAG-3-specific CD4+ T cell clones from a melanoma patient and a normal donor suggested a restricted TCR repertoire in patients with TRAG-3-expressing tumors. Altogether, our data define a novel profile of spontaneous immune responses to cancer germline Ag-expressing tumors, showing that spontaneous TRAG-3-specific CD4+ T cells are directed against a single immunodominant epitope and exist independently of Ab responses. Because of its immunodominance, peptide TRAG-3(34-48) is of particular interest for the monitoring of spontaneous immune responses in patients with TRAG-3-expressing tumors and for the development of cancer vaccines.

The phosphatidylinositol 3-kinase inhibitor, wortmannin, is extensively used in molecular signaling studies and has been proposed as a potential antineoplastic agent. The failure to detect wortmannin in mouse plasma after i.v. administration prompted in vitro studies of wortmannin metabolism. Wortmannin was incubated with mouse tissue homogenates, homogenate fractions, or purified, recombinant human carbonyl reductase in the presence of specified cofactors and inhibitors. Reaction products were characterized and quantified with liquid chromatography (LC)/mass spectrometry. Reaction rates were characterized using Michaelis-Menten kinetics. Wortmannin was metabolized to a material 2 atomic mass units greater than wortmannin. Liver homogenate had the highest metabolic activity. Some metabolism occurred in kidney and lung homogenates. Very little metabolism occurred in brain or red blood cell homogenates. Liver S9 fraction and cytosol metabolized wortmannin in the presence of NADPH and, to a much lesser extent, in the presence of NADH. Microsomal metabolism of wortmannin was minimal. Purified, recombinant human carbonyl reductase metabolized wortmannin. Quercetin, a carbonyl reductase inhibitor, greatly decreased wortmannin metabolism by S9, cytosol, and carbonyl reductase. The K(M) for wortmannin metabolism by purified, recombinant human carbonyl reductase was 119 +/- 9 microM, and the V(max) was 58 +/- 9 nmol/min/mg of protein. LC-tandem mass spectrometry spectra indicated that carbonyl reductase metabolized wortmannin to 17-OH-wortmannin. Wortmannin reduction by carbonyl reductase may partly explain why wortmannin is not detected in plasma after being administered to mice. Metabolism of wortmannin to 17-OH-wortmannin has mechanistic, and possibly toxicologic, implications because 17-OH-wortmannin is 10-fold more potent an inhibitor of phosphatidylinositol 3-kinase than is wortmannin.