Correlation between tumor regression and T cell responses in melanoma patients vaccinated with a MAGE antigen

Autophagy in cancer immunotherapy: Perspective on immune evasion and cell death interactions

Both the innate and adaptive immune systems work together to produce immunity. Cancer immunotherapy is a novel approach to tumor suppression that has arisen in response to the ineffectiveness of traditional treatments like radiation and chemotherapy. On the other hand, immune evasion can diminish immunotherapy's efficacy. There has been a lot of focus in recent years on autophagy and other underlying mechanisms that impact the possibility of cancer immunotherapy. The primary feature of autophagy is the synthesis of autophagosomes, which engulf cytoplasmic components and destroy them by lysosomal degradation. The planned cell death mechanism known as autophagy can have opposite effects on carcinogenesis, either increasing or decreasing it. It is autophagy's job to maintain the balance and proper functioning of immune cells like B cells, T cells, and others. In addition, autophagy controls whether macrophages adopt the immunomodulatory M1 or M2 phenotype. The ability of autophagy to control the innate and adaptive immune systems is noteworthy. Interleukins and chemokines are immunological checkpoint chemicals that autophagy regulates. Reducing antigen presentation to induce immunological tolerance is another mechanism by which autophagy promotes cancer survival. Therefore, targeting autophagy is of importance for enhancing potential of cancer immunotherapy.

A Genetic Vaccine Encoding Shared Cancer Neoantigens to Treat Tumors with Microsatellite Instability

Tumors with microsatellite instability (MSI) are caused by a defective DNA mismatch repair system that leads to the accumulation of mutations within microsatellite regions. Indels in microsatellites of coding genes can result in the synthesis of frameshift peptides (FSP). FSPs are tumor-specific neoantigens shared across patients with MSI. In this study, we developed a neoantigen-based vaccine for the treatment of MSI tumors. Genetic sequences from 320 MSI tumor biopsies and matched healthy tissues in The Cancer Genome Atlas database were analyzed to select shared FSPs. Two hundred nine FSPs were selected and cloned into nonhuman Great Ape Adenoviral and Modified Vaccinia Ankara vectors to generate a viral-vectored vaccine, referred to as Nous-209. Sequencing tumor biopsies of 20 independent patients with MSI colorectal cancer revealed that a median number of 31 FSPs out of the 209 encoded by the vaccine was detected both in DNA and mRNA extracted from each tumor biopsy. A relevant number of peptides encoded by the vaccine were predicted to bind patient HLA haplotypes. Vaccine immunogenicity was demonstrated in mice with potent and broad induction of FSP-specific CD8 and CD4 T-cell responses. Moreover, a vaccine-encoded FSP was processed in vitro by human antigen-presenting cells and was subsequently able to activate human CD8 T cells. Nous-209 is an "off-the-shelf" cancer vaccine encoding many neoantigens shared across sporadic and hereditary MSI tumors. These results indicate that Nous-209 can induce the optimal breadth of immune responses that might achieve clinical benefit to treat and prevent MSI tumors. SIGNIFICANCE: These findings demonstrate the feasibility of an "off-the-shelf" vaccine for treatment and prevention of tumors harboring frameshift mutations and neoantigenic peptides as a result of microsatellite instability.

Ectopic PD-L1 expression in JAK2 (V617F) myeloproliferative neoplasm patients is mediated via increased activation of STAT3 and STAT5

Escalated PD-L1 expression has been identified during malignant transformation in a number of cancer types and helps cancer cells escape an effective anti-tumor immune response. The mechanisms underlying escalated production of PD-L1 in many cancers, however, are still far from clear. We studied PD-L1, STAT3 and STAT5 mRNA expression using qRT-PCR in 72 BCR/ABL1 negative myeloproliferative neoplasm (MPN) patients (39 polycythemia vera and 33 essential thrombocythemia). Furthermore, phosphorylation status of STAT3 and STAT5 was studied using immunoblotting in the same patients. All MPN patients were first screened for JAK2 (V617F) mutation by tetra-primer ARMS-PCR, followed by quantification of JAK2 (V617F) mutation burden in all V617F positive MPN patients by ASO-PCR. Patients were screened for BCR/ABL1 fusion gene transcripts to rule out Ph positive status. Our findings showed that mRNA levels of PD-L1 and STAT3 were significantly higher in JAK2 (V617F) MPN patients, while as STAT5 was insignificantly upregulated. STAT3 and STAT5 phosphorylation was seen to be higher in JAK2 (V617F) MPN patients compared to the JAK2 (WT) patients. Upregulation of PD-L1, STAT3 and STAT5 was significantly associated with JAK2 (V617F) percentage in MPN patients. PD-L1, STAT3 and STAT5 expression significantly and positively correlated with JAK2 (V617F) allele burden. In addition, significant coexpression of PD-L1 with STAT3 and STAT5 was observed in MPN patients. In summary, JAK2 (V617F) mutation is accompanied by increased PD-L1 expression and this PD-L1 over expression is mediated by JAK2 (V617F) mainly through STAT3, while as STAT5 may play a minor role.

Dual TGF-β and PD-1 blockade synergistically enhances MAGE-A3-specific CD8+ T cell response in esophageal squamous cell carcinoma

PD-1 is highly expressed on tumor-infiltrated antigen-specific T cells and limit the antitumor function. Blocking of PD-1/PD-L1 signaling has shown unprecedented curative efficacies in patients with advanced cancer. However, only a limited population of patients benefited from such therapies. Our study aimed to explore biological properties, functional regulation and reversal of MAGE-A3-specific CD8⁺ T cells in patients with esophageal squamous cell carcinoma (ESCC). The underlying principle of deficiency and restoring MAGE-A3-specific CD8⁺ T cells function in tumor microenvironment (TME) was evaluated. MAGE-A3-specific CD8⁺ T cells could lyse HLA-A2⁺ /MAGE-A3⁺ tumor cells. Tetramer⁺ T cell frequency was higher in elder patients, but lower in patients with lymph node metastasis and late tumor stage (p < 0.05). CD107a^high expression on functional T cells was an independent prognostic factor in Cox regression analysis. PD-1 was highly expressed on dysfunctional antigen-specific CD8⁺ T cells and tumor infiltrating T lymphocytes (p < 0.05). Myeloid-derived suppressor cells (MDSCs) derived-TGF-β mediated PD-1^high expression on CD8⁺ T cells, which led to be resistance to PD-1/PD-L1 blockade in TME. Dual PD-1/PD-L1 and TGF-β signaling pathway blockades synergistically restored the function and antitumor ability of antigen-specific CD8⁺ T cells in vitro/vivo assay. The presence of functional MAGE-A3-specific CD8⁺ T cells had an independent prognostic impact on survival of patients with ESCC. Furthermore, MDSCs-derived TGF-β increased PD-1 expression on T cells and decreased the sensitivity to PD-1/PD-L1 blockade. Combining T cell-based therapy with dual PD-1/PD-L1 and TGF-β signaling pathway blockade could be considered a promising strategy for cancer treatment.

Therapeutic cancer vaccine: building the future from lessons of the past

Anti-cancer vaccines have raised many hopes from the start of immunotherapy but have not yet been clinically successful. The few positive results of anti-cancer vaccines have been observed in clinical situations of low tumor burden or preneoplastic lesions. Several new concepts and new results reposition this therapeutic approach in the field of immunotherapy. Indeed, cancers that respond to anti-PD-1/PD-L1 (20-30%) are those that are infiltrated by anti-tumor T cells with an inflammatory infiltrate. However, 70% of cancers do not appear to have an anti-tumor immune reaction in the tumor microenvironment. To induce this anti-tumor immunity, therapeutic combinations between vaccines and anti-PD-1/PD-L1 are being evaluated. In addition, the identification of neoepitopes against which the immune system is less tolerated is giving rise to a new enthusiasm by the first clinical results of the vaccine including these neoepitopes in humans. The ability of anti-cancer vaccines to induce a population of anti-tumor T cells called memory resident T cells that play an important role in immunosurveillance is also a new criterion to consider in the design of therapeutic vaccines.

Expression of CD14, IL10, and Tolerogenic Signature in Dendritic Cells Inversely Correlate with Clinical and Immunologic Response to TARP Vaccination in Prostate Cancer Patients

Purpose: Despite the vast number of clinical trials conducted so far, dendritic cell (DC)-based cancer vaccines have mostly shown unsatisfactory results. Factors and manufacturing procedures essential for these therapeutics to induce effective antitumor immune responses have yet to be fully characterized. We here aimed to identify DC markers correlating with clinical and immunologic response in a prostate carcinoma vaccination regimen.Experimental Design: We performed an extensive characterization of DCs used to vaccinate 18 patients with prostate carcinoma enrolled in a pilot trial of T-cell receptor gamma alternate reading frame protein (TARP) peptide vaccination (NCT00908258). Peptide-pulsed DC preparations (114) manufactured were analyzed by gene expression profiling, cell surface marker expression and cytokine release secretion, and correlated with clinical and immunologic responses.Results: DCs showing lower expression of tolerogenic gene signature induced strong antigen-specific immune response and slowing in PSA velocity, a surrogate for clinical response. These DCs were also characterized by lower surface expression of CD14, secretion of IL10 and MCP-1, and greater secretion of MDC. When combined, these four factors were able to remarkably discriminate DCs that were sufficiently potent to induce strong immunologic response.Conclusions: DC factors essential for the activation of immune responses associated with TARP vaccination in prostate cancer patients were identified. This study highlights the importance of in-depth characterization of DC vaccines and other cellular therapies, to understand the critical factors that hinder potency and potential efficacy in patients. Clin Cancer Res; 23(13); 3352-64. ©2017 AACR.

AIRE polymorphism, melanoma antigen-specific T cell immunity, and susceptibility to melanoma

AIRE is involved in susceptibility to melanoma perhaps regulating T cell immunity against melanoma antigens (MA). To address this issue, AIRE and MAGEB2 expressions were measured by real time PCR in medullary thymic epithelial cells (mTECs) from two strains of C57BL/6 mice bearing either T or C allelic variant of the rs1800522 AIRE SNP. Moreover, the extent of apoptosis induced by mTECs in MAGEB2-specific T cells and the susceptibility to in vivo melanoma B16F10 cell challenge were compared in the two mouse strains.The C allelic variant, protective in humans against melanoma, induced lower AIRE and MAGEB2 expression in C57BL/6 mouse mTECs than the T allele. Moreover, mTECs expressing the C allelic variant induced lower extent of apoptosis in MAGEB2-specific syngeneic T cells than mTECs bearing the T allelic variant (p < 0.05). Vaccination against MAGEB2 induced higher frequency of MAGEB2-specific CTL and exerted higher protective effect against melanoma development in mice bearing the CC AIRE genotype than in those bearing the TT one (p < 0.05). These findings show that allelic variants of one AIRE SNP may differentially shape the MA-specific T cell repertoire potentially influencing susceptibility to melanoma.

TARP vaccination is associated with slowing in PSA velocity and decreasing tumor growth rates in patients with Stage D0 prostate cancer

T-cell receptor alternate reading frame protein (TARP) is a 58-residue protein over-expressed in prostate and breast cancer. We investigated TARP peptide vaccination's impact on the rise in PSA (expressed as Slope Log(PSA) or PSA Doubling Time (PSADT)), validated tumor growth measures, and tumor growth rate in men with Stage D0 prostate cancer. HLA-A*0201 positive men were randomized to receive epitope-enhanced (29-37-9V) and wild-type (27-35) TARP peptides administered as a Montanide/GM-CSF peptide emulsion or as an autologous peptide-pulsed dendritic cell vaccine every 3 weeks for a total of five vaccinations with an optional 6th dose of vaccine at 36 weeks based on immune response or PSADT criteria with a booster dose of vaccine for all patients at 48 and 96 weeks. 41 patients enrolled with median on-study duration of 75 weeks at the time of this analysis. Seventy-two percent of patients reaching 24 weeks and 74% reaching 48 weeks had a decreased Slope Log(PSA) compared to their pre-vaccination baseline (p = 0.0012 and p = 0.0004 for comparison of overall changes in Slope Log(PSA), respectively). TARP vaccination also resulted in a 50% decrease in median tumor growth rate (g): pre-vaccine g = 0.0042/day, post-vaccine g = 0.0021/day (p = 0.003). 80% of subjects exhibited new vaccine-induced TARP-specific IFNγ ELISPOT responses but they did not correlate with decreases in Slope Log(PSA). Thus, vaccination with TARP peptides resulted in significant slowing in PSA velocity and reduction in tumor growth rate in a majority of patients with PSA biochemical recurrence.

The melanoma-associated antigen 1 (MAGEA1) protein stimulates the E3 ubiquitin-ligase activity of TRIM31 within a TRIM31-MAGEA1-NSE4 complex

The MAGE (Melanoma-associated antigen) protein family members are structurally related to each other by a MAGE-homology domain comprised of 2 winged helix motifs WH/A and WH/B. This family specifically evolved in placental mammals although single homologs designated NSE3 (non-SMC element) exist in most eukaryotes. NSE3, together with its partner proteins NSE1 and NSE4 form a tight subcomplex of the structural maintenance of chromosomes SMC5–6 complex. Previously, we showed that interactions of the WH/B motif of the MAGE proteins with their NSE4/EID partners are evolutionarily conserved (including the MAGEA1-NSE4 interaction). In contrast, the interaction of the WH/A motif of NSE3 with NSE1 diverged in the MAGE paralogs. We hypothesized that the MAGE paralogs acquired new RING-finger-containing partners through their evolution and form MAGE complexes reminiscent of NSE1-NSE3-NSE4 trimers. In this work, we employed the yeast 2-hybrid system to screen a human RING-finger protein library against several MAGE baits. We identified a number of potential MAGE-RING interactions and confirmed several of them (MDM4, PCGF6, RNF166, TRAF6, TRIM8, TRIM31, TRIM41) in co-immunoprecipitation experiments. Among these MAGE-RING pairs, we chose to examine MAGEA1-TRIM31 in detail and showed that both WH/A and WH/B motifs of MAGEA1 bind to the coiled-coil domain of TRIM31 and that MAGEA1 interaction stimulates TRIM31 ubiquitin-ligase activity. In addition, TRIM31 directly binds to NSE4, suggesting the existence of a TRIM31-MAGEA1-NSE4 complex reminiscent of the NSE1-NSE3-NSE4 trimer. These results suggest that MAGEA1 functions as a co-factor of TRIM31 ubiquitin-ligase and that the TRIM31-MAGEA1-NSE4 complex may have evolved from an ancestral NSE1-NSE3-NSE4 complex.

MAGE-A3: an immunogenic target used in clinical practice

Melanoma antigen family A, 3 (MAGE-A3) is a cancer-testis antigen whose expression has been demonstrated in a wide array of malignancies including melanoma, brain, breast, lung and ovarian cancer. In addition, its ability to elicit spontaneous humoral and cellular immune responses has been shown in cancer patients. As antigen-specific immune responses can be stimulated by immunization with MAGE-A3, several clinical trials have used MAGE-A3 vaccines to observe clinical responses. The frequent expressions of this antigen in various tumors and its immunogenicity in cancer patients have led to application of this antigen in cancer immunotherapy. However, the results of recent clinical trials indicate that there is a need for research in the vaccine design, adjuvant selection as well as patient selection criteria.

Cancer vaccines: Looking to the future

These are exciting times for the field of cancer immunotherapy. Although the clinical efficacy of monoclonal antibodies has been demonstrated since the early 1990s, the therapeutic profile of other immunotherapeutic approaches-especially vaccines-has not yet been formally clarified. However, the recent success of several immunotherapeutic regimens in cancer patients has boosted the development of this treatment modality. These achievements stemmed from recent scientific advances demonstrating the tolerogenic nature of cancer and the fundamental role of the tumor immune microenvironment in the suppression of antitumor immunity. New immunotherapeutic strategies against cancer attempt to promote protective antitumor immunity while disrupting the immunoregulatory circuits that contribute to tumor tolerance. Cancer vaccines differ from other anticancer immunotherapeutics in that they initiate the dynamic process of activating the immune system so as to successfully re-establish a state of equilibrium between tumor cells and the host. This article reviews recent clinical trials involving several different cancer vaccines and describes some of the most promising immunotherapeutic approaches that harness antitumor T-cell responses. In addition, we describe strategies whereby cancer vaccines can be exploited in combination with other therapeutic approach to overcome-in a synergistic fashion-tumor immunoevasion. Finally, we discuss prospects for the future development of broad spectrum prophylactic anticancer vaccines.

Circulating Type-1 Anti-Tumor CD4(+) T Cells are Preferentially Pro-Apoptotic in Cancer Patients

Cancer patients frequently exhibit a deficiency in Type-1 (but not Type-2 or regulatory) CD4⁺ T cell responses against tumor-associated antigens (TAA), which may limit protection against disease progression or responsiveness to immunotherapy in these individuals. Since such deficiency was acutely evident in patients with active disease (AD), where chronic stimulation of anti-tumor CD4⁺ T cells would be expected and activation-induced cell death may be prevalent, we employed MHC Class II-peptide tetramers to characterize the frequency and apoptotic status of TAA- vs. influenza (FluM1) virus-specific CD4⁺ T cells in the peripheral blood of HLA-DR*0401⁺ patients with melanoma or renal cell carcinoma. We observed that Flu-specific CD4⁺ T cells ranged from 0.17 to 3.89%, while up to approximately 1% of CD4⁺ T cells reacted against individual TAA epitopes derived from the EphA2 or MAGE-6 proteins. The frequencies of EphA2 and MAGE-6-specific CD4⁺ T cells in patients were significantly correlated with AD and gender of the patient (i.e., females > males), while frequencies of Flu-specific CD4⁺ T cells were distributed within a normal range in all patients. Notably, patient CD4⁺ T cells reactive with MHC class II-TAA (but not MHC class II-Flu) tetramers were significantly enriched for a pro-apoptotic (Annexin-V⁺) phenotype, particularly amongst the Th1 (T-bet⁺) subset. These results suggest that the preferential sensitivity of TAA (but not viral)-specific CD4⁺ Th1 cells to apoptosis in melanoma patients with AD will need to be overcome for optimal clinical benefit of immunotherapeutic approaches to be realized.

MAGE proteins regulate KRAB zinc finger transcription factors and KAP1 E3 ligase activity

Expression of Melanoma AntiGen Encoding (MAGE) genes, particularly MAGE-A3, has been correlated with aggressive clinical course, the acquisition of resistance to chemotherapy and poor clinical outcomes of melanoma and other malignancies. MAGE proteins bind to KAP1, a gene repressor and ubiquitin E3 ligase which also binds KRAB domain containing zinc finger transcription factors (KZNFs), and MAGE expression may affect KZNF mediated gene regulation. To investigate mechanisms for these effects, we tested the hypothesis that differences in KRAB domain composition affect KZNF poly-ubiquitination and determine whether MAGE expression increases, decreases, or has no effect on KZNFs mediated gene repression. Using an integrated reporter gene responsive to repression by KRAB domain fusion proteins, we found that MAGE-A3 relieved KZNF mediated repression and induced KZNF poly-ubiquitination and degradation in association with expression of the A+B box KRAB domain. In contrast, MAGE-A3 enhanced KAP1 mediated repression of KZNFs expressing A or A+b box KRAB domains but caused no increase in poly-ubiquitination or degradation. MAGE-A3 has no significant impact on KZNFs with KRAB domains containing the Scan box motif. These data support our hypothesis by showing that the effects of MAGE-A3 on gene repression depend on the type of KZNF KRAB domain involved.

A phase II trial evaluating the clinical and immunologic response of HLA-A2(+) non-small cell lung cancer patients vaccinated with an hTERT cryptic peptide

OBJECTIVES

The immunological and clinical responses of patients with NSCLC treated, in the context of an expanded action program, with the cryptic hTERT-targeting Vx-001 vaccine are presented.

MATERIALS AND METHODS

Forty-six HLA-A*0201-positive patients with advanced NSCLC and residual (n=27) or progressive (n=19) disease following front-line treatment received two subcutaneous injections of the optimized TERT572Y peptide followed by four injections of the native TERT572 peptide, every 3 weeks. Peptide-specific immune responses were monitored by enzyme-linked immunosorbent spot assay at baseline, and after the 2nd and the 6th vaccinations. Thirty-eight HLA-A*0201-positive matched patients were used as historical controls.

RESULTS

Twenty-three patients (50%) completed the vaccination protocol and 87% received at least two administrations. Twelve patients (26%) without disease progression after the 6th vaccination received boost vaccinations. Three (7%) patients achieved a partial response and 13 (28%) disease stabilization. The disease control rate was significantly higher in patients with non-squamous histology compared to those with squamous-cell histology [n=14 (45%) versus n=2 (13%); p=0.03]. The median progression-free survival (PFS) and overall survival (OS) was 3.8 (range, 0.7-99.4) and 19.8 months (range, 0.7-99.4), respectively. Patients who developed immune response had a numerically higher PFS compared to those who failed to mount any (6.7 versus 2.7 months; p=0.090). However, the median OS for the immune-responders was significantly prolonged compared to non-responders (40.0 versus 9.2 months, respectively; p=0.02). Toxicity was <grade 2.

CONCLUSION

Vx-001 vaccine is well tolerated and induced a TERT-specific immunological response, which was significantly correlated with improved clinical outcome.

Expression and clinical significance of cancer-testis genes in clear cell renal cell carcinoma

Cancer-testis (CT) antigens, which are encoded by CT genes, have been recognized as a group of highly attractive targets for cancer immunotherapy. However, the expression and clinical relevance of CT genes in clear cell renal cell carcinoma (ccRCC) remains largely unknown. The present study aims to analyze the expression profile of 6 individual CT genes including MAGE-A1, MAGE-A3, MAGE-A12, cTAGE-1, cTAGE-2, and NY-ESO-1 in ccRCC and further investigate their possible correlations with clinicopathologic characteristics. The mRNA expressions of these CT genes were detected using reverse transcriptase-polymerase chain reaction (RT-PCR) in 105 ccRCC tissue samples (T1-2 in 70 samples, T3-4 in 35 samples; G1-2 in 65 samples, G3-4 in 40 samples) as well as the paired adjacent normal tissues. The most frequently expressed CT gene was MAGE-A3 (27.6%), followed by MAGE-A12 (23.8%), NY-ESO-1 (21%), MAGE-A1 (20%), cTAGE-1 (17.1%), and cTAGE-2 (14.3%). In contrast, no expression of CT genes was detected in the paired adjacent normal tissues. Furthermore, the MAGE-A3 protein expression was determined by Western blot and immunohistochemistry. MAGE-A3 protein was expressed in 21.9% ccRCC samples with a cytoplasmic staining pattern. No MAGE-A3 protein expression was found in the paired adjacent normal tissues. There was a significant correlation between MAGE-A3 expression at both mRNA (P =0.045) and protein (P = 0.03) levels with advanced stages of the disease. Taken together, CT genes may serve as promising targets of specific immunotherapy for ccRCC and particularly, MAGE-A3 may serve as a potential prognostic marker for ccRCC patients.

MAGE-A3 is highly expressed in a cancer stem cell-like side population of bladder cancer cells

Cancer stem cells (CSCs), which have the abilities of tumor-initiating, self-renewal and differentiation, are thought to cause post-therapeutic recurrence and the progression of cancer. However, CSCs are commonly resistant to current cancer therapies including chemotherapy and radiotherapy. In this study, we isolated cancer stem celllike side population (SP) cells from human bladder cancer cell line SW780 by a flow cytometry-based SP technique. SP cells were only about 3.6% of SW780 cells and showed higher expression of ATP-binding cassette sub-family G member 2 (ABCG2) and CD133. In vitro assay of tumor sphere growth as well as in vivo assay of xenograft transplantation confirmed the higher tumorigenicity of isolated SP cells. These data indicated that SP cells were enriched with CSCs of bladder cancer. Furthermore, we determined the expression of melanoma antigen family A, 3 (MAGEA3), one of the most studied cancer testis (CT) antigens, in these SP and main population (MP) cells derived from SW780 cells. SW780 SP cells representing CSCs of bladder cancer showed an up-regulated expression of MAGE-A3 and a positive coexpression of MAGE-A3 and CD133, indicating that MAGE-A3 was a novel CT antigen preferentially expressed in the CSCs of bladder cancer. In summary, our findings confirmed the existence of cancer stem cell-like SP cells in bladder cancer cells, and further indicated that MAGE-A3 is a novel CSC antigen and therefore may serve as an immunotherapeutic target for CSCs of bladder cancer.

Tumour antigens recognized by T lymphocytes: at the core of cancer immunotherapy

In this Timeline, we describe the characteristics of tumour antigens that are recognized by spontaneous T cell responses in cancer patients and the paths that led to their identification. We explain on what genetic basis most, but not all, of these antigens are tumour specific: that is, present on tumour cells but not on normal cells. We also discuss how strategies that target these tumour-specific antigens can lead either to tumour-specific or to crossreactive T cell responses, which is an issue that has important safety implications in immunotherapy. These safety issues are even more of a concern for strategies targeting antigens that are not known to induce spontaneous T cell responses in patients.

Identification of an HLA-A24-Restricted OY-TES-1 Epitope Recognized by Cytotoxic T-Cells

OY-TES-1 was identified as a human homologue of the mouse, guinea pig, and pig proacrosin binding protein sp32 precursor. Differential expression levels of OY-TES-1 mRNA between testis and other normal tissues, and its expression in cancers indicated that OY-TES-1 would be classified as a cancer/testis antigen and considered to be a candidate of target antigen for cancer immunotherapy. In this study, we showed identification of HLA-A24-binding OY-TES-1 peptide, TES(401-409) (KTPFVSPLL) recognized by CD8 T-cells. Purified CD8 T-cells from healthy donors stimulated in vitro with the peptide-pulsed autologous DC and PBMC produced IFNgamma in response to the peptide-pulsed PBMC and showed cytotoxicity against the peptide-pulsed autologous EBV-B specifically. Furthermore, cytotoxicity was also observed against an OY-TES-1 mRNA-expressing tumor line, LK79. The retention time of the fraction in HPLC of the acid eluate from LK79 cells that showed positive sensitization against autologous EBV-B cells in recognition by CD8 CTL was the same as that of the fraction of the TES(401-409) peptide itself, suggesting that the TES(401-409) was a naturally processed peptide on LK79.

Mobilizing and evaluating anticancer T cells: pitfalls and solutions

Immunotherapy is a promising means to fight cancer, prompting a steady increase in clinical trials and correlative laboratory studies in this field. As antitumor T cells play central roles in immunity against malignant diseases, most immunotherapeutic protocols aim to induce and/or strengthen their function. Various treatment strategies have elicited encouraging clinical responses; however, major challenges have been uncovered that should be addressed in order to fully exploit the potential of immunotherapy. Here, we outline pitfalls for the mobilization of antitumor T cells and offer solutions to improve their therapeutic efficacy. We provide a critical perspective on the main methodologies used to characterize T-cell responses to cancer therapies, with a focus on discrepancies between T-cell attributes measured in vitro and protective responses in vivo. This review altogether provides recommendations to optimize the design of future clinical trials and highlights important considerations for the proficient analysis of clinical specimens available for research.

Cancer immunotherapy: a paradigm shift for prostate cancer treatment

Prostate cancer remains a significant health problem for men in the Western world. Although treatment modalities are available, these do not confer long-term benefit and are accompanied by deleterious side effects. Immunotherapy represents a valuable alternative to conventional treatments by inducing tumour-specific immune responses that control the growth of cancer cells. Sipuleucel-T is approved by the FDA as an immunotherapeutic agent for the treatment of patients with asymptomatic or minimally symptomatic castration-resistant prostate cancer (CRPC). Although this approval has raised cost-versus-benefit issues, it has provided proof of concept for the therapeutic potential of active immunotherapy approaches for metastatic CRPC. Numerous clinical studies have demonstrated clinical benefit using immunotherapy compared to traditional chemotherapy and several active immunotherapy approaches (at various developmental stages)have demonstrated the potential to change the face of prostate cancer treatment.

Modulation of microenvironment acidity reverses anergy in human and murine tumor-infiltrating T lymphocytes

Stimulating the effector functions of tumor-infiltrating T lymphocytes (TIL) in primary and metastatic tumors could improve active and adoptive T-cell therapies for cancer. Abnormal glycolysis, high lactic acid production, proton accumulation, and a reversed intra-extracellular pH gradient are thought to help render tumor microenvironments hostile to roving immune cells. However, there is little knowledge about how acidic microenvironments affect T-cell immunity. Here, we report that lowering the environmental pH to values that characterize tumor masses (pH 6-6.5) was sufficient to establish an anergic state in human and mouse tumor-specific CD8(+) T lymphocytes. This state was characterized by impairment of cytolytic activity and cytokine secretion, reduced expression of IL-2Rα (CD25) and T-cell receptors (TCR), and diminished activation of STAT5 and extracellular signal-regulated kinase (ERK) after TCR activation. In contrast, buffering pH at physiologic values completely restored all these metrics of T-cell function. Systemic treatment of B16-OVA-bearing mice with proton pump inhibitors (PPI) significantly increased the therapeutic efficacy of both active and adoptive immunotherapy. Our findings show that acidification of the tumor microenvironment acts as mechanism of immune escape. Furthermore, they illustrate the potential of PPIs to safely correct T-cell dysfunction and improve the efficacy of T-cell-based cancer treatments.

Polymeric multilayer capsule-mediated vaccination induces protective immunity against cancer and viral infection

Recombinant antigens hold high potential to develop vaccines against lethal intracellular pathogens and cancer. However, they are poorly immunogenic and fail to induce potent cellular immunity. In this paper, we demonstrate that polymeric multilayer capsules (PMLC) strongly increase antigen delivery toward professional antigen-presenting cells in vivo, including dendritic cells (DCs), macrophages, and B cells, thereby enforcing antigen presentation and stimulating T cell proliferation. A thorough analysis of the T cell response demonstrated their capacity to induce IFN-γ secreting CD4 and CD8 T cells, in addition to follicular T-helper cells, a recently identified CD4 T cell subset supporting antibody responses. On the B cell level, PMLC-mediated antigen delivery promoted the formation of germinal centers, resulting in increased numbers of antibody-secreting plasma cells and elevated antibody titers. The functional relevance of the induced immune responses was validated in murine models of influenza and melanoma. On a mechanistic level, we have demonstrated the capacity of PMLC to activate the NALP3 inflammasome and trigger the release of the potent pro-inflammatory cytokine IL-1β. Finally, using DC-depleted mice, we have identified DCs as the key mediators of the immunogenic properties of PMLC.

Defining the critical hurdles in cancer immunotherapy

Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators; others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet if overcome, have the potential to improve outcomes of patients with cancer.

A CCR4 antagonist combined with vaccines induces antigen-specific CD8+ T cells and tumor immunity against self antigens

Regulatory T cells (Tregs) may impede cancer vaccine efficacy in hematologic malignancies and cancer. CCR4 antagonists, an emergent class of Treg inhibitor, have been shown to block recruitment of Tregs mediated by CCL22 and CCL17. Our aim was to demonstrate the ability of a CCR4 antagonist (a small chemical molecule identified in silico) when combined with vaccines to break peripheral tolerance controlled by Tregs, a prerequisite for the induction of CD8(+) T cells against self Ags. Immunization of transgenic or normal mice expressing tumor-associated self Ags (Her2/neu, OVA, gp100) with a CCR4 antagonist combined with various vaccines led to the induction of effector CD8(+) T cells and partial inhibition of tumor growth expressing self Ags in both prophylactic and therapeutic settings. The CCR4 antagonist was more efficient than cyclophosphamide to elicit anti-self CD8(+) T cells. We also showed that the population of Tregs expressing CCR4 corresponded to memory (CD44(high)) and activated (ICOS(+)) Tregs, an important population to be targeted to modulate Treg activity. CCR4 antagonist represents a competitive class of Treg inhibitor able to induce functional anti-self CD8(+) T cells and tumor growth inhibition when combined with vaccines. High expression of CCR4 on human Tregs also supports the clinical development of this strategy.

Clinical outcome of patients with various advanced cancer types vaccinated with an optimized cryptic human telomerase reverse transcriptase (TERT) peptide: results of an expanded phase II study

BACKGROUND

TERT (telomerase reverse transcriptase) plays a critical role in tumor cell growth and survival. In an expanded phase II study, we evaluated the immunological and clinical responses to the TERT-targeting Vx-001 vaccine in patients with advanced solid tumors.

METHODS

HLA-A*0201-positive patients received two subcutaneous injections of the optimized TERT(572Y) peptide followed by four injections of the native TERT(572) peptide, every 3 weeks. Peptide-specific immune responses were evaluated by enzyme-linked immunosorbent spot at baseline, and after the second and the sixth vaccinations.

RESULTS

Fifty-five patients were enrolled and 34 (62%) completed the six vaccinations. A TERT-specific T-cell immune response was observed in 55% and 70% of patients after the second and the sixth vaccinations, respectively. The disease control rate (DCR) was 36% [95% confidence interval (CI) 24% to 49%], including one complete and one partial response. Immunologically responding patients had a better clinical outcome than nonresponders [DCR: 44% versus 14% (P = 0.047); progression-free survival (PFS): 5.2 versus 2.2 months (P = 0.0001) and overall survival: 20 versus 10 months (P = 0.041)]. Multivariate analysis revealed that the immunological response was an independent variable associated with increased PFS (hazard ratio = 3.35; 95% CI 1.7-6.7).

CONCLUSION

Vx-001 vaccine was well tolerated and induced a TERT-specific immunological response, which was significantly correlated with improved clinical outcome.

Methylation status of CpG sites in the promoter region of the OY-TES-1 gene in hepatoma cell lines

AIM: To detect the methylation status of CpG sites in the promoter region of the OY-TES-1 gene in six hepatoma cell lines and to investigate the influence of DNA methyltransferase inhibitor 5-Aza-CdR on methylation status of OY-TES-1 promoter in hepatoma cell line BEL-7404.

METHODS: Online bioinformatic tools were used to predict the promoter region of the OY-TES-1 gene and putative transcription factor binding sites. Bisulfite sequencing PCR (BSP) was applied to detect the methylation status of CpG sites in the promoter region of the OY-TES-1 gene. After treatment of BEL-7404 cells with 5-Aza-CdR, the methylation status of CpG sites in the promoter region of OY-TES-1 gene was detected again.

RESULTS: The promoter region of the OY-TES-1 gene was predicted to be located between -184 bp and +67 bp, which contains several potential transcription factor binding sites. The frequency of promoter methylation of the OY-TES-1 gene ranged between 51.25% and 87.92% in six hepatoma cell lines. 5-Aza-CdR treatment decreased the frequency of promoter methylation of the OY-TES-1 gene from 87.08% to 21.25% in BEL-7404 cells.

CONCLUSION: The OY-TES-1 gene shows relatively high frequency of promoter methylation in six hepatoma cell lines. DNA methyltransferase inhibitor could significantly decrease the frequency of promoter methylation of the OY-TES-1 gene in hepatoma cell line BEL-7404.

Immune suppression in tumors as a surmountable obstacle to clinical efficacy of cancer vaccines

Human tumors are usually not spontaneously eliminated by the immune system and therapeutic vaccination of cancer patients with defined antigens is followed by tumor regressions only in a small minority of the patients. The poor vaccination effectiveness could be explained by an immunosuppressive tumor microenvironment. Because T cells that infiltrate tumor metastases have an impaired ability to lyse target cells or to secrete cytokine, many researchers are trying to decipher the underlying immunosuppressive mechanisms. We will review these here, in particular those considered as potential therapeutic targets. A special attention will be given to galectins, a family of carbohydrate binding proteins. These lectins have often been implicated in inflammation and cancer and may be useful targets for the development of new anti-cancer therapies.

Bacillus Calmette-Guerin immunotherapy of bladder cancer induces selection of human leukocyte antigen class I-deficient tumor cells

Bacillus Calmette-Guerin (BCG) immunotherapy is a standard treatment for high-risk non-muscle-infiltrating bladder cancer patients. Although the outcomes are good, cancer relapse is observed in around 40% of patients. We present the comparative analysis of human leukocyte antigen (HLA) class I expression in recurrent bladder tumors in patients treated with mitomycin or BCG. HLA class I expression was analyzed by RT-Q-PCR and immunohistochemical techniques. Loss of heterozygosity (LOH) was determined by microsatellite amplification of markers in chromosome 6 and 15. More profound alterations in HLA class I expression were found in post-BCG recurrent tumors than in pre-BCG lesions, whereas mitomycin treatment did not change the HLA class I expression pattern. Post-BCG recurrent tumors also showed a higher incidence of structural defects underlying altered HLA class I expression. We hypothesize that the immunotherapy-activated immune system recognizes and eliminates tumor cells with reversible ("soft") HLA class I changes but not transformed cells with additional, irreversible ("hard") alterations. To our knowledge, this is the first clinical evidence of immunotherapy-induced immunoselection of HLA class I loss tumor variants in bladder cancer, although the study involved a small number of patients.

Insights into the processing of MHC class I ligands gained from the study of human tumor epitopes

The molecular definition of tumor antigens recognized by cytolytic T lymphocytes (CTL) started in the late 1980s, at a time when the MHC class I antigen processing field was in its infancy. Born together, these two fields of science evolved together and provided each other with critical insights. Over the years, stimulated by the potential interest of tumor antigens for cancer immunotherapy, scientists have identified and characterized numerous antigens recognized by CTL on human tumors. These studies have provided a wealth of information relevant to the mode of production of antigenic peptides presented by MHC class I molecules. A number of tumor antigenic peptides were found to result from unusual mechanisms occurring at the level of transcription, translation or processing. Although many of these mechanisms occur in the cell at very low level, they are relevant to the immune system as they determine the killing of tumor cells by CTL, which are sensitive to low levels of peptide/MHC complexes. Moreover, these unusual mechanisms were found to occur not only in tumor cells but also in normal cells. Thereby, the study of tumor antigens has illuminated many aspects of MHC class I processing. We review here those insights into the MHC I antigen processing pathway that result from the characterization of human tumor antigens recognized by CTL.

A MAGE-C2 antigenic peptide processed by the immunoproteasome is recognized by cytolytic T cells isolated from a melanoma patient after successful immunotherapy

We have pursued our analysis of a melanoma patient who showed almost complete tumor regression following vaccination with MAGE-A1 and MAGE-A3 antigens. We previously described high frequencies of tumor-specific CTL precursors in blood samples collected after but also before vaccination. A set of CTL clones were derived that recognized antigens different from those of the vaccine. Two of these antigens were peptides encoded by another MAGE gene, MAGE-C2. Here we describe the antigen recognized by another tumor-specific CTL clone. It proved to be a third antigenic peptide encoded by gene MAGE-C2, ASSTLYLVF. It is presented by HLA-B57 molecules and proteasome-dependent. Tumor cells exposed to interferon-gamma (IFN-γ) were better recognized by the anti-MAGE-C2(42-50) CTL clone. This mainly resulted from a better processing of the peptide by the immunoproteasome as compared to the standard proteasome. Mass spectrometric analyses showed that the latter destroyed the antigenic peptide by cleaving between two internal hydrophobic residues. Despite its higher "chymotryptic-like" (posthydrophobic) activity, the immunoproteasome did not cleave at this position, in line with the suggestion that hydrophobic residues immediately downstream from a cleavage site impair cleavage by the immunoproteasome. We previously reported that one of the other MAGE-C2 peptides recognized by CTL from this patient was also better processed by the immunoproteasome. Together, these results support the notion that the tumor regression of this patient was mediated by an antitumor response shaped by IFN-γ and dominated by CTL directed against peptides that are better produced by the immunoproteasome, such as the MAGE-C2 peptides.

Is antigen specificity the key to efficient adoptive T-cell therapy?

Adoptive transfer of T cells remains a promising approach in melanoma. Initial clinical trials performed with polyclonal tumor-infiltrating lymphocyte gave limited clinical results. Nonetheless, encouraging results have been reported in adjuvant setting (stage III melanoma), and when tumor-infiltrating lymphocytes were associated with lymphodepleting regimens. Specificity of adoptive cell therapy has been achieved with the infusion of antigen specific cytotoxic T-lymphocyte clones, associated with some clinical responses. Antigen specificity can also be obtained by the allogeneic transfer of high-avidity T-cell receptors into autologous T cells. We propose an alternative strategy based on the selection of antigen-specific T cells with magnetic beads coated with HLA–peptide multimers. Future improvements of adoptive melanoma immunotherapy may be achieved by its association with other therapeutic strategies such as targeted therapy against signaling pathways.

Requisite considerations for successful adoptive immunotherapy with engineered T-lymphocytes using tumor antigen-specific T-cell receptor gene transfer

INTRODUCTION

Although engineered T-cell-based antitumor immunotherapy using tumor-antigen-specific T-cell receptor (TCR) gene transfer is undoubtedly a promising strategy, a number of studies have revealed that it has several drawbacks.

AREAS COVERED

This review covers selected articles detailing recent progress in this field, not only for solid tumors, but also for leukemias. In terms of achieving uniform therapeutic quality of TCR gene-modified T cells as an 'off-the-shelf' product, the authors abstract and discuss the requisite conditions for successful outcome, including: i) the optimal target choice reflecting the specificity of the introduced TCR, ii) the quality and quantity of expressed TCRs in gene-modified T cells, and additional genetic modification reflecting enhanced antitumor functionality, and iii) 'on-' and 'off-target' adverse events caused by the quality of the introduced TCRs and other adverse events related to genetic modification itself. Readers will be able to readily abstract recent advances in TCR gene-transferred T-cell therapy, centering notably on efforts to obtain uniformity in the therapeutic functionality of engineered T cells.

EXPERT OPINION

Harmonizing the functionality and target specificity of TCR will allow the establishment of clinically useful adoptive immunotherapy in the near future.

Expression profile of cancer-testis genes in transitional cell carcinoma of the bladder

OBJECTIVES

To explore the expression profile of multiple cancer testis (CT) genes in transitional cell carcinoma of bladder (TCC), and investigate its possible correlation with clinicopathologic characteristics.

METHODS

The mRNA expression of 6 CT genes was detected using reverse transcription polymerase chain reaction (RT-PCR) for 102 TCC samples (59 Ta-T1, 43 T2-T4, 44 G1, 32 G2, and 26 G3 samples) as well as the matching adjacent normal bladder mucosa for each sample. The MAGE-A3 protein expression was also determined by immunoblotting. Immunohistochemistry was performed in selected samples to confirm the MAGE-A3 protein expression.

RESULTS

The mRNA expression of all 6 CT genes was detected with relatively high frequencies in TCC tissues. The percent of samples positive for each gene in the TCC samples are: MAGE-A3, 58.8%; MAGE-A1, 56.9%; cTAGE-1, 52.9%; MAGE-A12, 51%; cTAGE-2, 49%; and NY-ESO-1, 45.1%. Furthermore, MAGE-A3 protein expression was positive in 52.9% of TCC tissues by immunoblotting. Immunohistochemistry showed an exclusively cytoplasmic staining pattern of MAGE-A3 protein. Neither CT gene mRNA expression nor MAGE-A3 protein expression was found in the adjacent normal tissue. There was no significant correlation between CT gene expression and clinicopathologic characteristics (P > 0.05).

CONCLUSIONS

All six CT genes are highly expressed in TCC, and may serve as therapeutic targets of specific immunotherapy for TCC, especially in multi-antigen vaccine preparations.

Antigen spreading contributes to MAGE vaccination-induced regression of melanoma metastases

A core challenge in cancer immunotherapy is to understand the basis for efficacious vaccine responses in human patients. In previous work we identified a melanoma patient who displayed a low-level antivaccine cytolytic T-cell (CTL) response in blood with tumor regression after vaccination with melanoma antigens (MAGE). Using a genetic approach including T-cell receptor β (TCRβ) cDNA libraries, we found very few antivaccine CTLs in regressing metastases. However, a far greater number of TCRβ sequences were found with several of these corresponding to CTL clones specific for nonvaccine tumor antigens, suggesting that antigen spreading was occurring in regressing metastases. In this study, we found another TCR belonging to tumor-specific CTL enriched in regressing metastases and detectable in blood only after vaccination. We used the TCRβ sequence to detect and clone the desired T cells from tumor-infiltrating lymphocytes isolated from the patient. This CD8 clone specifically lysed autologous melanoma cells and displayed HLA-A2 restriction. Its target antigen was identified as the mitochondrial enzyme caseinolytic protease. The target antigen gene was mutated in the tumor, resulting in production of a neoantigen. Melanoma cell lysis by the CTL was increased by IFN-γ treatment due to preferential processing of the antigenic peptide by the immunoproteasome. These results argue that tumor rejection effectors in the patient were indeed CTL responding to nonvaccine tumor-specific antigens, further supporting our hypothesis. Among such antigens, the mutated antigen we found is the only antigen against which no T cells could be detected before vaccination. We propose that antigen spreading of an antitumor T-cell response to truly tumor-specific antigens contributes decisively to tumor regression.

A phase II study of the cancer vaccine TG4010 alone and in combination with cytokines in patients with metastatic renal clear-cell carcinoma: clinical and immunological findings

MUC1 over-expression in renal clear-cell carcinoma (RCC) is associated with poor prognosis. This phase II study determined the efficacy and tolerability of TG4010, a cancer vaccine based on a modified vaccinia virus expressing MUC1 and interleukin-2, in combination with cytokines, as first-line therapy in metastatic RCC. Thirty-seven patients with progressive, MUC1-positive RCC received TG4010 10(8) pfu/inj weekly for 6 weeks, then every 3 weeks until progression, when TG4010 was continued in combination with interferon-α2a and interleukin-2. Assessments included clinical response (primary endpoint), safety, time to treatment failure (TTF), overall survival (OS), and immune response. No objective clinical responses occurred. Five of the 27 evaluable patients (18%) had stable disease for >6 months with TG4010 alone and six of 20 patients (30%) had stable disease for >6 months with TG4010 plus cytokines. Median TTF was 4.1, 3.6, and 9.3 months for monotherapy, combination therapy, and overall, respectively. Median OS was 19.3 months for all patients and 22.4 months combination therapy recipients. The most frequent TG4010-related adverse events were minor-to-moderate injection-site reactions, fatigue, and flu-like symptoms. Six of 28 patients showed a MUC1 CD4+ T cell proliferative response during therapy. Anti-MUC1 CD8+ T cells were detected before and after therapy in 3 and 4 patients, respectively. MUC1-specific CD8+ T cell responses were associated with longer survival. Therapy with TG4010 plus cytokines appears to be feasible and well tolerated in patients with metastatic RCC. However, these data should be interpreted with caution, as additional prospective studies are necessary to clarify the clinical efficacy of this therapy.

Tumor vaccines and beyond

For the last two decades the immunotherapy of patients with solid and hematopoietic tumors has met with variable success. We have reviewed the field of tumor vaccines to examine what has worked and what has not, why this has been the case, how the anti-tumor responses were examined, and how we can make tumor immunity successful for the majority of individuals rather than for the exceptional patients who currently show successful immune responses against their tumors.

Identification of a lung cancer antigen evading CTL attack due to loss of human leukocyte antigen (HLA) class I expression

The human lung cancer cell line, C831L, lost HLA class I expression due to a mutation of the β2-microglobulin (β2m) gene, and it may have been the result of immunoediting by CTL cytotoxicity. By restoration of HLA class I expression, we could identify the antigen that may be associated with HLA downregulation. Such an antigen might be a promising target of immunotherapy because it potentially may induce a sufficient immune response to eradicate cancer cells. The CTL clone could be established from lymph node lymphocytes in patient C831 by stimulation with wild-type β2m-transduced C831L (C831L-wβ2m). The CTL clone showed reactivity against C831L-wβ2m in a HLA-B*0702-restricted manner, but not Parental-C831L or autologous normal cells. The cDNA expression cloning method was used to identify the antigen coding gene recognized by the CTL clone. The cDNA clone exhibited a homology with a part of the mRNA that codes for leucine rich repeat containing eight family member A (LRRC8A). A transfection analysis of minigenes indicated that the antigen peptide was derived from protein translated from the downstream of the registered open reading frame in LRRC8A mRNA. The antigenic 9-mer peptide (GPRESRPPA) was identified. The present methodology should be useful to find the crucial tumor antigens, which are potentially associated with loss of HLA expression. Furthermore, such an antigen may help in achieving a better understanding of the immunological escape mechanisms and it may also provide a favorable immune response in cancer immunotherapy.

Evaluation of cellular immune responses in cancer vaccine recipients: lessons from NY-ESO-1

The rigorous evaluation of cancer vaccination requires evidence of benefit to patients with cancer or those at risk of relapse from the disease. Clinical trials are expensive and require considerable human and clinical resources in order to demonstrate this benefit. In the era of defined cancer antigens, it is possible to evaluate immunogenic targets, and assess the quality and magnitude of immune responses against these antigens following vaccination. Analyzing these surrogate end points complements clinical assessment and provides a depth of understanding to better inform trial evaluation and design. We have used the immunogenic cancer testis antigen NY-ESO-1 as a model antigen. This article summarizes our experience in monitoring immunity against NY-ESO-1.

Frequent occurrence of high affinity T cells against MELOE-1 makes this antigen an attractive target for melanoma immunotherapy

We recently showed that the infusion of tumor infiltrating lymphocytes specific for the MELOE-1 antigen was associated with a prolonged relapse-free survival for HLA-A2(+) melanoma patients who received tumor infiltrating lymphocytes therapy. Here, we characterized the MELOE-1/A2-specific T-cell repertoire in healthy donors and melanoma patients to further support an immunotherapy targeting this epitope. Using tetramer enrichment followed by multicolor staining, we found that MELOE-1-specific T cells were present in the blood of healthy donors and patients at similar frequencies (around 1 in 1x10(5) CD8(+) cells). These cells mainly displayed a naïve phenotype in 4/6 healthy donors and 3/6 patients, whereas high proportions of memory cells were observed in the remaining individuals of both groups. There was a recurrent usage of the Valpha12.1 chain for 17/18 MELOE-1-specific T-cell clones derived from healthy donors or patients, associated with diverse Vbeta chains and V(D)J junctional sequences. All clones derived from melanoma patients (9/9) were reactive against the MELOE-1(36-44) peptide and against HLA-A2(+) melanoma cell lines. This study documents the existence of a large TCR repertoire specific for the MELOE-1/A2 epitope and its capacity to give rise to antitumor CTL that supports the development of immunotherapies targeting this epitope.

The CD4+ T-cell epitope-binding register is a critical parameter when generating functional HLA-DR tetramers with promiscuous peptides

Detection of CD4(+) T cells specific for tumor-associated antigens is critical to investigate the spontaneous tumor immunosurveillance and to monitor immunotherapy protocols in patients. We investigated the ability of HLA-DR 1101 multimers to detect CD4(+) T cells specific for three highly promiscuous MAGE-A3 derived peptides: MAGE-A3(191-205) (p39), MAGE-A3(281-295) (p57) and MAGE-A3(286-300) (p58). Tetramers stained specific CD4(+) T cells only when loaded with p39, although all peptides activated the specific T cells when presented by plastic-bound HLA-DR 1101 monomers. This suggested that tetramer staining ability was determined by the mode rather than the affinity of peptide binding to HLA-DR 1101. We hypothesized that peptides should bear a single P1 anchor residue to bind all arms of the multimer in a homogeneous register to generate peptide-HLA-DR conformers with maximal avidity. Bioinformatics analysis indicated that p39 contained one putative P1 anchor residue, whereas the other two peptides contained multiple ones. Designing p57 and p58 analogues containing a single anchor residue generated HLA-DR 1101 tetramers that stained specific CD4(+) T cells. Producing HLA-DR 1101 monomers linked with the optimized MAGE-A3 analogues, but not with the original epitopes, further improved tetramer efficiency. Optimization of CD4(+) T-cell epitope-binding registers is thus critical to generate functional HLA-DR tetramers.

Induction of a CD8+ T-cell response to the MAGE cancer testis antigen by combined treatment with azacitidine and sodium valproate in patients with acute myeloid leukemia and myelodysplasia

Epigenetic therapies, including DNA methyltransferase and histone deacetylase inhibitors, represent important new treatment modalities in hematologic malignancies, but their mechanism of action remains unknown. We reasoned that up-regulation of epigenetically silenced tumor antigens may induce an immunologically mediated antitumor response and contribute to their clinical activity. In this study, we demonstrate that azacitidine (AZA) and sodium valproate (VPA) up-regulate expression of melanoma-associated antigens (MAGE antigens) on acute myeloid leukemia (AML) and myeloma cell lines. In separate studies, we observed that prior exposure to AZA/VPA increased recognition of myeloma cell lines by a MAGE-specific CD8(+) cytotoxic T-lymphocyte (CTL) clone. We therefore measured CTL responses to MAGE antigens in 21 patients with AML or myelodysplasia treated with AZA/VPA. CTL responses to MAGE antigens were documented in only 1 patient before therapy; however, treatment with AZA/VPA induced a CTL response in 10 patients. Eight of the 11 patients with circulating MAGE CTLs achieved a major clinical response after AZA/VPA therapy. This is the first demonstration of a MAGE-specific CTL response in AML. Furthermore, it appears that epigenetic therapies have the capacity to induce a CTL response to MAGE antigens in vivo that may contribute to their clinical activity in AML.