Exhaustion of tumor-specific CD8⁺ T cells in metastases from melanoma patients

Reinvigorating Exhausted T Cells by Blockade of the PD-1 Pathway

T-cell exhaustion due to persistent antigen stimulation is a key feature of chronic viral infections and cancer. Programmed cell death-1 (PD-1) is a major regulator of T-cell exhaustion, and blocking the PD-1 pathway restores T-cell function and improves pathogen control and tumor eradication. Immunotherapy targeting the PD-1 inhibitory receptor pathway has demonstrated significant antitumor activity. Recently, antibodies blocking PD-1 have been approved for use in cancer patients. In this review, we summarize the role of the PD-1 pathway in chronic infection and cancer and the therapeutic potential of PD-1-directed immunotherapy in patients with chronic infection or cancer.

OX40- and CD27-mediated costimulation synergizes with anti-PD-L1 blockade by forcing exhausted CD8+ T cells to exit quiescence

Exhaustion of chronically stimulated CD8(+) T cells is a significant obstacle to immune control of chronic infections or tumors. Although coinhibitory checkpoint blockade with anti-programmed death ligand 1 (PD-L1) Ab can restore functions to exhausted T cell populations, recovery is often incomplete and dependent upon the pool size of a quiescent T-bet(high) subset that expresses lower levels of PD-1. In a model in which unhelped, HY-specific CD8(+) T cells gradually lose function following transfer to male bone marrow transplantation recipients, we have explored the effect of shifting the balance away from coinhibition and toward costimulation by combining anti-PD-L1 with agonistic Abs to the TNFR superfamily members, OX40 and CD27. Several weeks following T cell transfer, both agonistic Abs, but especially anti-CD27, demonstrated synergy with anti-PD-L1 by enhancing CD8(+) T cell proliferation and effector cytokine generation. Anti-CD27 and anti-PD-L1 synergized by downregulating the expression of multiple quiescence-related genes concomitant with a reduced frequency of T-bet(high) cells within the exhausted population. However, in the presence of persistent Ag, the CD8(+) T cell response was not sustained and the overall size of the effector cytokine-producing pool eventually contracted to levels below that of controls. Thus, CD27-mediated costimulation can synergize with coinhibitory checkpoint blockade to switch off molecular programs for quiescence in exhausted T cell populations, but at the expense of losing precursor cells required to maintain a response.

Pathogen-driven cancers and emerging immune therapeutic strategies

Infectious agents play an etiologic role in approximately 20% of cancer cases worldwide. Eleven pathogens (seven viruses, three parasites, and one bacterium) are known to contribute to oncogenesis either directly via the expression of their protein products or indirectly via chronic inflammation. Although prevention of infection and antimicrobial treatments have helped in reducing infection rates and the incidence of associated malignancies, therapies for these cancers remain limited. The importance of immune control over malignant progression is highlighted by the fact that many cancers, particularly those induced by pathogens, occur more frequently among immunosuppressed patients as compared with healthy individuals. Therefore, therapeutic strategies that can elicit a robust immune response and restore tumor detection may be a beneficial approach for treating these cancers. In addition, the study of immune escape mechanisms used by pathogens and their associated cancers may provide insight into the mechanisms of malignant transformation and improved therapies for cancer more generally.

Prevalence of tumor-infiltrating lymphocytes and PD-L1 expression in the soft tissue sarcoma microenvironment

The prognostic and predictive implications of programmed death-ligand 1 (PD-L1) is unknown in sarcoma. We sought to examine the immune milieu in sarcoma specimens. We evaluated PD-L1 expression by immunohistochemistry in sarcoma specimens and quantified tumor-infiltrating lymphocytes (TIL). We correlated expression with clinical parameters and outcomes. Fifty sarcoma patients treated at Memorial Sloan Kettering Cancer Center were selected. Using the DAKO PD-L1 immunohistochemistry assay and archival formalin-fixed paraffin-embedded tissue specimens; PD-L1 expression was examined. Macrophage and lymphocyte PD-L1 status was determined qualitatively. TIL was quantified. Associations between PD-L1 expression in tumor, macrophages and lymphocytes, TIL and clinical-pathological characteristics were performed. The median age was 46 years (range, 22-76), and 66% of patients were men. Tumor, lymphocyte and macrophage PD-L1 expression was noted in 12%, 30% and 58%, respectively, with the highest prevalence in gastrointestinal stromal tumors (29%). Lymphocyte and macrophage infiltration was present in 98% and 90%, respectively. There was no association between clinical features, overall survival and PD-L1 expression in tumor or immune infiltrates. Lymphocyte and macrophage infiltration is common in sarcoma, but PD-L1 tumor expression is uncommon in sarcoma with the highest frequency observed in gastrointestinal stromal tumors. There was no association between PD-L1 expression, TIL and clinicopathological features and overall survival; however, this is limited by the heterogenous patient sample and minimal death events in the studied cohort.

The transcription factor FoxO1 sustains expression of the inhibitory receptor PD-1 and survival of antiviral CD8(+) T cells during chronic infection

Protein kinase B (also known as AKT) and the mechanistic target of rapamycin (mTOR) are central regulators of T cell differentiation, proliferation, metabolism, and survival. Here, we show that during chronic murine lymphocytic choriomeningitis virus infection, activation of AKT and mTOR are impaired in antiviral cytotoxic T lymphocytes (CTLs), resulting in enhanced activity of the transcription factor FoxO1. Blockade of inhibitory receptor programmed cell death protein 1 (PD-1) in vivo increased mTOR activity in virus-specific CTLs, and its therapeutic effects were abrogated by the mTOR inhibitor rapamycin. FoxO1 functioned as a transcriptional activator of PD-1 that promoted the differentiation of terminally exhausted CTLs. Importantly, FoxO1-null CTLs failed to persist and control chronic viral infection. Collectively, this study shows that CTLs adapt to persistent infection through a positive feedback pathway (PD-1?FoxO1?PD-1) that functions to both desensitize virus-specific CTLs to antigen and support their survival during chronic viral infection.

Phenotypic characterization and anti-tumor effects of cytokine-induced killer cells derived from cord blood

BACKGROUND AIMS

Cytokine-induced killer (CIK) cell therapy represents a feasible immunotherapeutic option for treating malignancies. However, the number of anti-tumor lymphocytes cannot be easily obtained from the cancer patients with poor immunity status, and older patients cannot tolerate repeated collection of blood. Cord blood-derived CIK (CB-CIK) cells have shown efficacy in treating the patients with cancer in several clinical trials. This study was conducted to evaluate the biological characteristics and anti-tumor function of CB-CIK cells.

METHODS

The immunogenicity, chemokine receptors and proliferation of CB-CIK cells were analyzed by flow cytometry. The CIK cells on day 13 were treated with cisplatin and the anti-apoptosis capacity was analyzed. The function of CB-CIK cells against the human cancer was evaluated both in vitro and in vivo.

RESULTS

Compared with peripheral blood-derived CIK (PB-CIK) cells, CB-CIK cells demonstrated lower immunogenicity and increased proliferation rates. CB-CIK cells also had a higher percentage of main functional fraction CD3(+)CD56(+). The anti-apoptosis ability of CB-CIK cells after treatment with cisplatin was higher than that of PB-CIK cells. Furthermore, CB-CIK cells were effective for secreting interleukin-2 and interferon-γ and a higher percentage of chemokine receptors CCR6 and CCR7. In addition, tumor growth was greatly inhibited by CB-CIK treatment in a nude mouse xenograft model.

CONCLUSIONS

CB-CIK cells exhibit more efficient anti-tumor activity in in vitro analysis and in the preclinical model and may serve as a potential therapeutic approach for the treatment of cancer.

T cell differentiation in chronic infection and cancer: functional adaptation or exhaustion?

Chronic viral infections and malignant tumours induce T cells that have a reduced ability to secrete effector cytokines and have upregulated expression of the inhibitory receptor PD1 (programmed cell death protein 1). These features have so far been considered to mark terminally differentiated 'exhausted' T cells. However, several recent clinical and experimental observations indicate that phenotypically exhausted T cells can still mediate a crucial level of pathogen or tumour control. In this Opinion article, we propose that the exhausted phenotype results from a differentiation process in which T cells stably adjust their effector capacity to the needs of chronic infection. We argue that this phenotype is optimized to cause minimal tissue damage while still mediating a critical level of pathogen control. In contrast to the presently held view of functional exhaustion, this new concept better reflects the pathophysiology and clinical manifestations of persisting infections, and it provides a rationale for emerging therapies that enhance T cell activity in chronic infection and cancer by blocking inhibitory receptors.

Tim-3 is highly expressed in T cells in acute myeloid leukemia and associated with clinicopathological prognostic stratification

T cells immunoglobulin mucin 3 (Tim-3) is an important inhibitory stimulatory molecule, which has been reported to play a vital role in the tumor immune escape and be correlated with clinicopathological prognostic stratification in solid tumor. However, the related research is rare of Tim-3 in non-solid tumor, such as acute myeloid leukemia (AML). In this study, we investigated the expression characteristics of Tim-3 on the peripheral blood T cells of newly diagnosed AML patients and its clinical significance. Peripheral blood was obtained from 36 patients with newly diagnosed AML before intervention, with peripheral blood from 20 cases of healthy volunteers collected as normal control. Expression levels of Tim-3 on the peripheral blood T cells were assayed with flow cytometry. We found that Tim-3 expression on the peripheral blood CD4+ T cells and CD8+ T cells in newly diagnosed AML patients were significantly increased compared with that of normal control. CD4+ T cells/CD8+ T cell ratio (CD4/CD8) of peripheral blood in AML patients was significantly correlated with NCCN high risk group. The higher expression level of Tim-3 on CD4+ T cells in the peripheral blood of AML patients had significant correlation with FLT3-ITD mutation, the higher expression level of Tim-3 on CD8+ T cells in AML patients was significantly correlated with NCCN high risk group. To conclude, our results support the concept that Tim-3 is highly expressed on the peripheral blood T cells of AML patients, and Tim-3 expression significantly correlates with clinicopathological prognostic stratification in AMLTim-3, T cell, acute myeloid leukemia, tumor immune escape, clinicopathological prognostic stratification.

Myeloid-derived suppressor cells and their role in CTLA-4 blockade therapy

Immune checkpoints are a series of inhibitory pathways that are crucial for modulating the intensity and duration of immune response. Among these checkpoints, cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) has been shown to be a key regulator of the early activation of naïve and memory T cells. Immune checkpoint blockade is emerging as one of the most promising therapeutic approaches directed toward the activation of the immune response against tumors. The first of these therapies that has been FDA approved is ipilimumab, a fully human monoclonal antibody that blocks CTLA-4. The in cis effects that CTLA-4 blockade has on T cells have been properly described, but there are still questions to be answered regarding the indirect or in trans effects. One of the alternative cellular populations that may play a role in the outcome of CTLA-4 blockade therapy is myeloid-derived suppressor cells (MDSCs), which have recently been associated with clinical outcome in advanced melanoma. In addition to this, MDSCs have been shown to be decreased in number and functional potential after treatment with ipilimumab. A better clarification of what effects CTLA-4 blockade may have on these cellular populations is likely to provide insights on possible predictive biomarkers for CTLA-4 blockade therapy.

Triggering through Toll-like receptor 2 limits chronically stimulated T-helper type 1 cells from undergoing exhaustion

Chronic infections result in T-cell exhaustion, a state of functional unresponsiveness. To control the infection, it is important to salvage the exhausted T cells. In this study, we delivered signals through Toll-like receptor 2 (TLR-2) to reinvigorate functionality in chronically activated T-helper type 1 (Th1) cells. This process significantly augmented the expression of T-bet, interferon γ, interleukin 2, and the antiapoptotic molecule Bcl-2, whereas it dampened the display of the exhaustion markers programmed death receptor 1 (PD-1) and lymphocyte activation gene 3 (Lag-3). Additionally, TLR-2 signaling bolstered the ability of chronically stimulated Th1 cells to activate B cells. Finally, the results were substantiated by observing reduced lung pathology upon administration of TLR-2 agonist in the chronic infection model of tuberculosis. These data demonstrated the importance of TLR-2 in rescuing chronically activated Th1 cells from undergoing exhaustion. This study will pave a way for targeting TLR-2 in developing therapeutic strategies to treat chronic diseases involving loss of Th1 cell function.

The effect of adjuvanting cancer vaccines with herpes simplex virus glycoprotein D on melanoma-driven CD8+ T cell exhaustion

Two vaccines expressing CD4(+) and CD8(+) T cell epitopes of melanoma-associated Ags (MAAs) by a chimpanzee-derived replication-defective AdC68 vector were compared in a mouse model of melanoma. In one vaccine, termed AdC68-gDMelapoly, the epitopes were expressed as a fusion protein within HSV-1 glycoprotein D (gD), which blocks immunoinhibitory signaling through the herpes virus entry mediator pathway. The other vaccine, termed AdC68-Melapoly, expressed only the MAA epitopes. AdC68-gDMelapoly induced more potent MAA-specific CD8(+) T cell responses especially to the subdominant MAA epitopes. Upon prophylactic vaccination, mice that developed CD8(+) T cell responses to the two vaccines that were comparable in magnitude showed equal protection against tumor challenge. When mice were first challenged with tumor cells and then vaccinated results differed. In animals with comparable CD8(+) T cell responses, the AdC68-gDMelapoly vaccine was more efficacious compared with the AdC68-Melapoly vaccine in delaying tumor growth. This effect was linked to reduced expression of 2B4, LAG-3, and programmed death-1 on tumor-infiltrating MAA-specific CD8(+) T cells elicited by the gD-adjuvanted vaccine, suggesting that CD8(+) T cells induced in presence of gD are less susceptible to tumor-driven exhaustion.

ICOS-based chimeric antigen receptors program bipolar TH17/TH1 cells

With the notable exception of B-cell malignancies, the efficacy of chimeric antigen receptor (CAR) T cells has been limited, and CAR T cells have not been shown to expand and persist in patients with nonlymphoid tumors. Here we demonstrate that redirection of primary human T cells with a CAR containing the inducible costimulator (ICOS) intracellular domain generates tumor-specific IL-17-producing effector cells that show enhanced persistence. Compared with CARs containing the CD3ζ chain alone, or in tandem with the CD28 or the 4-1BB intracellular domains, ICOS signaling increased IL-17A, IL-17F, and IL-22 following antigen recognition. In addition, T cells redirected with an ICOS-based CAR maintained a core molecular signature characteristic of TH17 cells and expressed higher levels of RORC, CD161, IL1R-1, and NCS1. Of note, ICOS signaling also induced the expression of IFN-γ and T-bet, consistent with a TH17/TH1 bipolarization. When transferred into mice with established tumors, TH17 cells that were redirected with ICOS-based CARs mediated efficient antitumor responses and showed enhanced persistence compared with CD28- or 4-1BB-based CAR T cells. Thus, redirection of TH17 cells with a CAR encoding the ICOS intracellular domain is a promising approach to augment the function and persistence of CAR T cells in hematologic malignancies.

Pilot study of intratumoral injection of recombinant heat shock protein 70 in the treatment of malignant brain tumors in children

Intratumoral injections of recombinant heat shock protein (Hsp)70 were explored for feasibility in patients with brain tumors. Patients aged 4.5–14 years with untreated newly diagnosed tumors (n=12) were enrolled. After tumor resection, five injections of recombinant Hsp70 (total 2.5 mg) were administered into the resection cavity through a catheter. Before administration of Hsp70 and after the last injection, specific immune responses to the autologous tumor lysate were evaluated using the delayed-type hypersensitivity test. Further, peripheral blood was monitored to identify possible changes in lymphocyte subpopulations, cytokine levels, and the cytolytic activity of natural killer cells. The follow-up period in this trial was 12 months. Intratumoral injections of Hsp70 were well tolerated by patients. One patient had a complete clinical response documented by radiologic findings and one patient had a partial response. A positive delayed-type hypersensitivity test was observed in three patients. In peripheral blood, there was a shift from cytokines provided by Th₂ cells toward cytokines of a Th₁-cell-mediated response. These data corresponded to changes in lymphocyte subpopulations. Immunosuppressive T-regulatory cell levels were also reduced after injection of Hsp70, as well as production of interleukin-10. The cytolytic activity of natural killer cells was unchanged. The present study demonstrates the feasibility of intratumoral delivery of recombinant Hsp70 in patients with cancer. Further randomized clinical trials are recommended to assess the optimum dose of the chaperone, the treatment schedule, and clinical efficacy.

Transplanted terminally differentiated induced pluripotent stem cells are accepted by immune mechanisms similar to self-tolerance

The exact nature of the immune response elicited by autologous induced pluripotent stem cell (iPSC) progeny is still not well understood. Here we show in murine models that autologous iPSC-derived endothelial cells (iECs) elicit an immune response that resembles the one against a comparable somatic cell, the aortic endothelial cell (AEC). These cells exhibit long-term survival in vivo and prompt a tolerogenic contexture of intra-graft characterized by elevated IL-10 expression. In contrast, undifferentiated iPSCs elicit a very different immune response with high lymphocytic infiltration and elevated IFN-γ, granzyme-B, and perforin intra-graft. Furthermore, the clonal structure of infiltrating T cells from iEC grafts is statistically indistinguishable from that of AECs, but is different from that of undifferentiated iPSC grafts. Taken together, our results indicate that the differentiation of iPSCs results in a loss of immunogenicity and leads to the induction of tolerance, despite expected antigen expression differences between iPSC-derived versus original somatic cells.

Transcriptional profiling of melanoma sentinel nodes identify patients with poor outcome and reveal an association of CD30(+) T lymphocytes with progression

Sentinel lymph nodes set the stance of the immune system to a localized tumor and are often the first site to be colonized by neoplastic cells that metastasize. To investigate how the presence of neoplastic cells in sentinel lymph nodes may trigger pathways associated with metastatic progression, we analyzed the transcriptional profiles of archival sentinel node biopsy specimens obtained from melanoma patients. Biopsies from positive nodes were selected for comparable tumor infiltration, presence or absence of further regional node metastases, and relapse at 5-year follow-up. Unsupervised analysis of gene expression profiles revealed immune response to be a major gene ontogeny represented. Among genes upregulated in patients with progressing disease, the TNF receptor family member CD30/TNFRSF8 was confirmed in biopsy specimens from an independent group of patients. Immunohistochemical analysis revealed higher numbers of CD30(+) lymphocytes in nodes from progressing patients compared with nonprogressing patients. Phenotypic profiling demonstrated that CD30(+) lymphocytes comprised a broad population of suppressive or exhausted immune cells, such as CD4(+)Foxp3(+) or PD1(+) subpopulations and CD4(-)CD8(-) T cells. CD30(+) T lymphocytes were increased in peripheral blood lymphocytes of melanoma patients at advanced disease stages. Our findings reinforce the concept that sentinel nodes act as pivotal sites for determining progression patterns, revealing that the presence of CD30(+) lymphocytes at those sites associate positively with melanoma progression.

Targeting T cell immunometabolism for cancer immunotherapy; understanding the impact of the tumor microenvironment

The immune system has a key role to play in controlling cancer initiation and progression. T cell activation, which is central to anti-tumor immune responses, coincides with changes in cellular metabolism. Naïve T cells predominantly require an ATP generating metabolic profile, whereas proliferating effector T cells require anabolic metabolic profiles that promote rapid growth and proliferation. Furthermore, specific T cell subsets require distinct energetic and biosynthetic pathways to match their functional requirements. The often hostile tumor microenvironment can affect T cell immune responses by altering the resulting cellular metabolism. Tailoring immune responses by manipulating cellular metabolic pathways may provide an exciting new option for cancer immunotherapy. T cell responses might also be skewed via metabolic manipulation to treat the complications of obesity-associated inflammation, which is a rapidly growing global health problem and a major risk factor for many malignancies. In this review, the diverse metabolic requirements of T cells in anti-tumor immunity are discussed, as well as the profound influence of the tumor microenvironment and the possible avenues for manipulation to enhance anti-tumor immunity.

Hapten-induced contact hypersensitivity, autoimmune reactions, and tumor regression: plausibility of mediating antitumor immunity

Haptens are small molecule irritants that bind to proteins and elicit an immune response. Haptens have been commonly used to study allergic contact dermatitis (ACD) using animal contact hypersensitivity (CHS) models. However, extensive research into contact hypersensitivity has offered a confusing and intriguing mechanism of allergic reactions occurring in the skin. The abilities of haptens to induce such reactions have been frequently utilized to study the mechanisms of inflammatory bowel disease (IBD) to induce autoimmune-like responses such as autoimmune hemolytic anemia and to elicit viral wart and tumor regression. Hapten-induced tumor regression has been studied since the mid-1900s and relies on four major concepts: (1) ex vivo haptenation, (2) in situ haptenation, (3) epifocal hapten application, and (4) antigen-hapten conjugate injection. Each of these approaches elicits unique responses in mice and humans. The present review attempts to provide a critical appraisal of the hapten-mediated tumor treatments and offers insights for future development of the field.

Dynamic Treg interactions with intratumoral APCs promote local CTL dysfunction

Tregs control various functions of effector T cells; however, where and how Tregs exert their immunomodulatory effects remain poorly understood. Here we developed a murine model of adoptive T cell therapy and found that Tregs induce a dysfunctional state in tumor-infiltrating CTLs that resembles T cell exhaustion and is characterized by low expression of effector cytokines, inefficient cytotoxic granule release, and coexpression of coinhibitory receptors PD-1 and TIM-3. Induction of CTL dysfunction was an active process, requiring local TCR signals in tumor tissue. Tregs infiltrated tumors only subsequent to Ag-dependent activation and expansion in tumor-draining LNs; however, Tregs also required local Ag reencounter within tumor tissue to induce CTL dysfunction and prevent tumor rejection. Multiphoton intravital microscopy revealed that in contrast to CTLs, Tregs only rarely and briefly interrupted their migration in tumor tissue in an Ag-dependent manner and formed unstable tethering-interactions with CD11c+ APCs, coinciding with a marked reduction of CD80 and CD86 on APCs. Activation of CTLs by Treg-conditioned CD80/86lo DCs promoted enhanced expression of both TIM-3 and PD-1. Based on these data, we propose that Tregs locally change the costimulatory landscape in tumor tissue through transient, Ag-dependent interactions with APCs, thus inducing CTL dysfunction by altering the balance of costimulatory and coinhibitory signals these cells receive.

Immune-based antitumor effects of BRAF inhibitors rely on signaling by CD40L and IFNγ

B-Raf(V600E) inhibitors have been suggested to promote tumor regression with the help of host immunity, but this hypothesis has not been examined directly in detail. In this study, we profiled immunologic changes in the tumor microenvironment and tumor-infiltrating lymphocytes (TIL) in a B-RafV600E/Pten-driven murine model of melanoma after administration of the B-Raf(V600E) small molecule inhibitor PLX4720. In this model, we found that as tumors developed, they gradually acquired immunosuppressive features, including accumulation of regulatory T cells (Treg) and CD11b(+)/Gr-1(+) myeloid cells and loss of Th1 effector functions on CD4(+) TILs, such as CD40L and IFNγ expression. PLX4720 administration promoted development of a more immune stimulatory microenvironment associated with a relative increase in CD40L and IFNγ expression on intratumoral CD4(+) TILs and a reduced accumulation of Tregs and CD11b(+)/Gr-1(+) myeloid cells. Strikingly, CD40L or IFNγ blockade compromised the ability of PLX4720 to inhibit melanoma growth. Supporting this result, agonistic CD40 antibody was sufficient to evoke antitumor immunity and suppress tumor growth in tumor-bearing mice. Taken together, our results establish the critical role of immune-related changes, with key contributions for CD40L and IFNγ signaling in the antitumor responses triggered in vivo by B-Raf(V600E) inhibitors.

MART-1 peptide vaccination plus IMP321 (LAG-3Ig fusion protein) in patients receiving autologous PBMCs after lymphodepletion: results of a Phase I trial

Background

Immunotherapy offers a promising novel approach for the treatment of cancer and both adoptive T-cell transfer and immune modulation lead to regression of advanced melanoma. However, the potential synergy between these two strategies remains unclear.

Methods

We investigated in 12 patients with advanced stage IV melanoma the effect of multiple MART-1 analog peptide vaccinations with (n = 6) or without (n = 6) IMP321 (LAG-3Ig fusion protein) as an adjuvant in combination with lymphodepleting chemotherapy and adoptive transfer of autologous PBMCs at day (D) 0 (Trial registration No: NCT00324623). All patients were selected on the basis of ex vivo detectable MART-1-specific CD8 T-cell responses and immunized at D0, 8, 15, 22, 28, 52, and 74 post-reinfusion.

Results

After immunization, a significant expansion of MART-1-specific CD8 T cells was measured in 83% (n = 5/6) and 17% (n = 1/6) of patients from the IMP321 and control groups, respectively (P < 0.02). Compared to the control group, the mean fold increase of MART-1-specific CD8 T cells in the IMP321 group was respectively >2-, >4- and >6-fold higher at D15, D30 and D60 (P < 0.02). Long-lasting MART-1-specific CD8 T-cell responses were significantly associated with IMP321 (P < 0.02). At the peak of the response, MART-1-specific CD8 T cells contained higher proportions of effector (CCR7⁻ CD45RA^+/−) cells in the IMP321 group (P < 0.02) and showed no sign of exhaustion (i.e. were mostly PD1⁻CD160⁻TIM3⁻LAG3⁻2B4^+/−). Moreover, IMP321 was associated with a significantly reduced expansion of regulatory T cells (P < 0.04); consistently, we observed a negative correlation between the relative expansion of MART-1-specific CD8 T cells and of regulatory T cells_. Finally, although there were no confirmed responses as per RECIST criteria, a transient, 30-day partial response was observed in a patient from the IMP321 group.

Conclusions

Vaccination with IMP321 as an adjuvant in combination with lymphodepleting chemotherapy and adoptive transfer of autologous PBMCs induced more robust and durable cellular antitumor immune responses, supporting further development of IMP321 as an adjuvant for future immunotherapeutic strategies.

Reprogramming antitumor immunity

Regenerative medicine holds great promise in replacing tissues and organs lost to degenerative disease and injury. Application of the principles of cellular reprogramming for the treatment of cancer, however, is not well established. Here, we present an overview of cellular reprogramming techniques used in regenerative medicine, and within this context, envision how the scope of regenerative medicine may be expanded to treat metastatic cancer by revitalizing an exhausted and senescent immune system.

PD-1 identifies the patient-specific CD8⁺ tumor-reactive repertoire infiltrating human tumors

Adoptive transfer of tumor-infiltrating lymphocytes (TILs) can mediate regression of metastatic melanoma; however, TILs are a heterogeneous population, and there are no effective markers to specifically identify and select the repertoire of tumor-reactive and mutation-specific CD8⁺ lymphocytes. The lack of biomarkers limits the ability to study these cells and develop strategies to enhance clinical efficacy and extend this therapy to other malignancies. Here, we evaluated unique phenotypic traits of CD8⁺ TILs and TCR β chain (TCRβ) clonotypic frequency in melanoma tumors to identify patient-specific repertoires of tumor-reactive CD8⁺ lymphocytes. In all 6 tumors studied, expression of the inhibitory receptors programmed cell death 1 (PD-1; also known as CD279), lymphocyte-activation gene 3 (LAG-3; also known as CD223), and T cell immunoglobulin and mucin domain 3 (TIM-3) on CD8⁺ TILs identified the autologous tumor-reactive repertoire, including mutated neoantigen-specific CD8⁺ lymphocytes, whereas only a fraction of the tumor-reactive population expressed the costimulatory receptor 4-1BB (also known as CD137). TCRβ deep sequencing revealed oligoclonal expansion of specific TCRβ clonotypes in CD8⁺PD-1⁺ compared with CD8⁺PD-1- TIL populations. Furthermore, the most highly expanded TCRβ clonotypes in the CD8⁺ and the CD8⁺PD-1⁺ populations recognized the autologous tumor and included clonotypes targeting mutated antigens. Thus, in addition to the well-documented negative regulatory role of PD-1 in T cells, our findings demonstrate that PD-1 expression on CD8⁺ TILs also accurately identifies the repertoire of clonally expanded tumor-reactive cells and reveal a dual importance of PD-1 expression in the tumor microenvironment.

Sprouty-2 regulates HIV-specific T cell polyfunctionality

The ability of individual T cells to perform multiple effector functions is crucial for protective immunity against viruses and cancer. This polyfunctionality is frequently lost during chronic infections; however, the molecular mechanisms driving T cell polyfunctionality are poorly understood. We found that human T cells stimulated by a high concentration of antigen lacked polyfunctionality and expressed a transcription profile similar to that of exhausted T cells. One specific pathway implicated by the transcription profile in control of T cell polyfunctionality was the MAPK/ERK pathway. This pathway was altered in response to different antigen concentrations, and polyfunctionality correlated with upregulation of phosphorylated ERK. T cells that were stimulated with a high concentration of antigen upregulated sprouty-2 (SPRY2), a negative regulator of the MAPK/ERK pathway. The clinical relevance of SPRY2 was confirmed by examining SPRY2 expression in HIV-specific T cells, where high levels of SPRY2 were seen in HIV-specific T cells and inhibition of SPRY2 expression enhanced the HIV-specific polyfunctional response independently of the PD-1 pathway. Our findings indicate that increased SPRY2 expression during chronic viral infection reduces T cell polyfunctionality and identify SPRY2 as a potential target for immunotherapy.

Frequencies of circulating MDSC correlate with clinical outcome of melanoma patients treated with ipilimumab

Metastatic melanoma has a poor prognosis with high resistance to chemotherapy and radiation. Recently, the anti-CTLA-4 antibody ipilimumab has demonstrated clinical efficacy, being the first agent to significantly prolong the overall survival of inoperable stage III/IV melanoma patients. A major aim of patient immune monitoring is the identification of biomarkers that predict clinical outcome. We studied circulating myeloid-derived suppressor cells (MDSC) in ipilimumab-treated patients to detect alterations in the myeloid cell compartment and possible correlations with clinical outcome. Lin(-) CD14(+) HLA-DR(-) monocytic MDSC were enriched in peripheral blood of melanoma patients compared to healthy donors (HD). Tumor resection did not significantly alter MDSC frequencies. During ipilimumab treatment, MDSC frequencies did not change significantly compared to baseline levels. We observed high inter-patient differences. MDSC frequencies in ipilimumab-treated patients were independent of baseline serum lactate dehydrogenase levels but tended to increase in patients with severe metastatic disease (M1c) compared to patients with metastases in skin or lymph nodes only (M1a), who had frequencies comparable to HD. Interestingly, clinical responders to ipilimumab therapy showed significantly less lin(-) CD14(+) HLA-DR(-) cells as compared to non-responders. The data suggest that the frequency of monocytic MDSC may be used as predictive marker of response, as low frequencies identify patients more likely benefitting from ipilimumab treatment. Prospective clinical trials assessing MDSC frequencies as potential biomarkers are warranted to validate these observations.

Reversal of NK-cell exhaustion in advanced melanoma by Tim-3 blockade

The immunoregulatory protein T-cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) mediates T-cell exhaustion and contributes to the suppression of immune responses in both viral infections and tumors. Tim-3 blockade reverses the exhausted phenotype of CD4+ and CD8+ T cells in several chronic diseases, including melanoma. Interestingly, natural killer (NK) cells constitutively express Tim-3; however, the role of Tim-3 in modulating the function of these innate effector cells remains unclear, particularly in human diseases. In this study, we compared the function of Tim-3 in NK cells from healthy donors and patients with metastatic melanoma. NK cells from the latter were functionally impaired/exhausted, and Tim-3 blockade reversed this exhausted phenotype. Moreover, Tim-3 expression levels were correlated with the stage of the disease and poor prognostic factors. These data indicate that Tim-3 can function as an NK-cell exhaustion marker in advanced melanoma and support the development of Tim-3-targeted therapies to restore antitumor immunity.

Tumor-specific IL-9-producing CD8+ Tc9 cells are superior effector than type-I cytotoxic Tc1 cells for adoptive immunotherapy of cancers

Because cytokine-priming signals direct CD8(+) T cells to acquire unique profiles that affect their ability to mediate specific immune responses, here we generated IL-9-skewed CD8(+) T (Tc9) cells by priming with Th9-polarized condition. Compared with type-I CD8(+) cytotoxic T (Tc1) cells, Tc9 secreted different cytokines and were less cytolytic in vitro but surprisingly elicited greater antitumor responses against advanced tumors in OT-I/B16-OVA and Pmel-1/B16 melanoma models. After adoptive transfer, Tc9 cells persisted longer and differentiated into IFN-γ- and granzyme-B (GrzB)-producing cytolytic Tc1-like effector cells. Phenotypic analysis revealed that adoptively transferred Tc9 cells secreted IL-2 and were KLRG-1(low) and IL-7Rα(high), suggesting that they acquired a signature of "younger" phenotype or became long-term lived cells with capacity of self-renewal. Our results also revealed that Tc9-mediated therapeutic effect critically depended on IL-9 production in vivo. These findings have clinical implications for the improvement of CD8(+) T-cell-based adoptive immunotherapy of cancers.

TNF-α-dependent hematopoiesis following Bcl11b deletion in T cells restricts metastatic melanoma

Using several tumor models, we demonstrate that mice deficient in Bcl11b in T cells, although having reduced numbers of T cells in the peripheral lymphoid organs, developed significantly less tumors compared with wild-type mice. Bcl11b(-/-) CD4(+) T cells, with elevated TNF-α levels, but not the Bcl11b(-/-) CD8(+) T cells, were required for the reduced tumor burden, as were NK1.1(+) cells, found in increased numbers in Bcl11b(F/F)/CD4-Cre mice. Among NK1.1(+) cells, the NK cell population was predominant in number and was the only population displaying elevated granzyme B levels and increased degranulation, although not increased proliferation. Although the number of myeloid-derived suppressor cells was increased in the lungs with metastatic tumors of Bcl11b(F/F)/CD4-Cre mice, their arginase-1 levels were severely reduced. The increase in NK cell and myeloid-derived suppressor cell numbers was associated with increased bone marrow and splenic hematopoiesis. Finally, the reduced tumor burden, increased numbers of NK cells in the lung, and increased hematopoiesis in Bcl11b(F/F)/CD4-Cre mice were all dependent on TNF-α. Moreover, TNF-α treatment of wild-type mice also reduced the tumor burden and increased hematopoiesis and the numbers and activity of NK cells in the lung. In vitro treatment with TNF-α of lineage-negative hematopoietic progenitors increased NK and myeloid differentiation, further supporting a role of TNF-α in promoting hematopoiesis. These studies reveal a novel role for TNF-α in the antitumor immune response, specifically in stimulating hematopoiesis and increasing the numbers and activity of NK cells.

Tumor-infiltrating lymphocytes and their significance in melanoma prognosis

The role of the tumor-infiltrating lymphocyte (TIL) and its relationship to prognosis has been most extensively studied in malignant melanoma. The purpose of this chapter is to discuss in depth the immunobiology and molecular aspects of lymphocyte function in general and particularly TIL function in the context of antimelanoma immunity. Emphasis is placed upon the role of these inflammatory mediators in the enhancement and impairment of progression of this often fatal human cancer. In addition, the analysis of TILs in melanoma and their direct relationship to prognosis as well as their effect on the positivity of the sentinel lymph node will be discussed. Furthermore, details of lymph node responses to metastatic melanomas and their prognostic significance will be clarified. Finally, the importance of TILs for the evaluation of therapeutic response and how TIL immunobiology could critically inform the design of novel melanoma immunotherapeutic protocols will be elucidated.

Virus infection, inflammation and prevention of cancer

Our molecular understanding of cancer biology has made substantial progress during the last two decades. During recent years it became evident that inflammation is a major driving force in tumor development since chronic virus infection and carcinogenesis are closely correlated. These insights refined our view on the decisive role of persistent virus infection and chronic inflammation in tumor onset, growth, and metastatic progression. Explanations have been delivered how tumor cells interact and correspond with neighbouring epithelia and infiltrating immune cells for shaping the so-called 'tumor-microenvironment' and establishing tumor-specific tolerance. This extended view on malignant diseases should now allow for rational design of interventions targeting inflammation and underlying pathways for prevention and therapy of inflammation-associated cancer. This chapter outlines the role of virus-mediated inflammations in tumorigenesis thereby shedding light on the mechanisms of cancer-related inflammation and on characteristic features of the tumor-microenvironment, which has been recently identified to play a key role in maintenance and progression of tumors. Finally, the chapter discusses latest aspects in prevention of inflammation-related cancer and provides a short outlook on the future prospects of cancer immunotherapy.

A patient-specific therapeutic approach for tumour cell population extinction and drug toxicity reduction using control systems-based dose-profile design

BACKGROUND

When anti-tumour therapy is administered to a tumour-host environment, an asymptotic tapering extremity of the tumour cell distribution is noticed. This extremity harbors a small number of residual tumour cells that later lead to secondary malignances. Thus, a method is needed that would enable the malignant population to be completely eliminated within a desired time-frame, negating the possibility of recurrence and drug-induced toxicity.

METHODS

In this study, we delineate a computational procedure using the inverse input-reconstruction approach to calculate the unknown drug stimulus input, when one desires a known output tissue-response (full tumour cell elimination, no excess toxicity). The asymptotic extremity is taken care of using a bias shift of tumour-cell distribution and guided control of drug administration, with toxicity limits enforced, during mutually-synchronized chemotherapy (as Temozolomide) and immunotherapy (Interleukin-2 and Cytotoxic T-lymphocyte).

RESULTS

Quantitative modeling is done using representative characteristics of rapidly and slowly-growing tumours. Both were fully eliminated within 2 months with checks for recurrence and toxicity over a two-year time-line. The dose-time profile of the therapeutic agents has similar features across tumours: biphasic (lymphocytes), monophasic (chemotherapy) and stationary (interleukin), with terminal pulses of the three agents together ensuring elimination of all malignant cells. The model is then justified with clinical case studies and animal models of different neurooncological tumours like glioma, meningioma and glioblastoma.

CONCLUSION

The conflicting oncological objectives of tumour-cell extinction and host protection can be simultaneously accommodated using the techniques of drug input reconstruction by enforcing a bias shift and guided control over the drug dose-time profile. For translational applicability, the procedure can be adapted to accommodate varying patient parameters, and for corrective clinical monitoring, to implement full tumour extinction, while maintaining the health profile of the patient.

Inhibitory Receptor Expression Depends More Dominantly on Differentiation and Activation than "Exhaustion" of Human CD8 T Cells

Under conditions of chronic antigen stimulation, such as persistent viral infection and cancer, CD8 T cells may diminish effector function, which has been termed "exhaustion." Expression of inhibitory Receptors (iRs) is often regarded as a hallmark of "exhaustion." Here we studied the expression of eight different iRs by CD8 T cells of healthy humans, including CTLA-4, PD1, TIM3, LAG3, 2B4, BTLA, CD160, and KLRG1. We show that many iRs are expressed upon activation, and with progressive differentiation to effector cells, even in absence of long-term ("chronic") antigenic stimulation. In particular, we evaluated the direct relationship between iR expression and functionality in CD8 T cells by using anti-CD3 and anti-CD28 stimulation to stimulate all cells and differentiation subsets. We observed a striking up-regulation of certain iRs following the cytokine production wave, in agreement with the notion that iRs function as a negative feedback mechanism. Intriguingly, we found no major impairment of cytokine production in cells positive for a broad array of iRs, as previously shown for PD1 in healthy donors. Rather, the expression of the various iRs strongly correlated with T cell differentiation or activation states, or both. Furthermore, we analyzed CD8 T cells from lymph nodes (LNs) of melanoma patients. Interestingly, we found altered iR expression and lower cytokine production by T cells from metastatic LNs, but also from non-metastatic LNs, likely due to mechanisms which are not related to exhaustion. Together, our data shows that expression of iRs per se does not mark dysfunctional cells, but is rather tightly linked to activation and differentiation. This study highlights the importance of considering the status of activation and differentiation for the study and the clinical monitoring of CD8 T cells.

Reversal of in situ T-cell exhaustion during effective human antileukemia responses to donor lymphocyte infusion

Increasing evidence across malignancies suggests that infiltrating T cells at the site of disease are crucial to tumor control. We hypothesized that marrow-infiltrating immune populations play a critical role in response to donor lymphocyte infusion (DLI), an established and potentially curative immune therapy whose precise mechanism remains unknown. We therefore analyzed marrow-infiltrating immune populations in 29 patients (22 responders, 7 nonresponders) with relapsed chronic myelogenous leukemia who received CD4(+) DLI in the pre-tyrosine kinase inhibitor era. Immunohistochemical analysis of pretreatment marrow revealed that the presence of >4% marrow-infiltrating CD8(+) (but not CD4(+)) T cells predicted DLI response, even in the setting of high leukemia burden. Furthermore, mRNA expression profiling of marrow-infiltrating T cells of a subset of responders compared with nonresponders revealed enrichment of T-cell exhaustion-specific genes in pretreatment T cells of DLI responders and significant downregulation of gene components in the same pathway in responders in conjunction with clinical response. Our data demonstrate that response to DLI is associated with quantity of preexisting marrow CD8(+) T cells and local reversal of T-cell exhaustion. Our studies implicate T-cell exhaustion as a therapeutic target of DLI and support the potential use of novel anti-PD1/PDL1 agents in lieu of DLI.

Radioimmunotherapy combined with maintenance anti-CD20 antibody may trigger long-term protective T cell immunity in follicular lymphoma patients

Growing evidence suggests that the patient's immune response may play a major role in the long-term efficacy of antibody therapies of follicular lymphoma (FL). Particular long-lasting recurrence free survivals have been observed after first line, single agent rituximab or after radioimmunotherapy (RIT). Rituximab maintenance, furthermore, has a major efficacy in prolonging recurrence free survival after chemotherapy. On the other hand, RIT as a single step treatment showed a remarkable capacity to induce complete and partial remissions when applied in recurrence and as initial treatment of FL or given for consolidation. These clinical results strongly suggest that RIT combined with rituximab maintenance could stabilize the high percentages of patients with CR and PR induced by RIT. While the precise mechanisms of the long-term efficacy of these 2 treatments are not elucidated, different observations suggest that the patient's T cell immune response could be decisive. With this review, we discuss the potential role of the patient's immune system under rituximab and RIT and argue that the T cell immunity might be particularly promoted when combining the 2 antibody treatments in the early therapy of FL.

Strategies to reverse melanoma-induced T-cell dysfunction

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.

Tolerance and exhaustion: defining mechanisms of T cell dysfunction

CD8 T cell activation and differentiation are tightly controlled, and dependent on the context in which naïve T cells encounter antigen, can either result in functional memory or T cell dysfunction, including exhaustion, tolerance, anergy, or senescence. With the identification of phenotypic and functional traits shared in different settings of T cell dysfunction, distinctions between such dysfunctional states have become blurred. Here, we discuss distinct states of CD8 T cell dysfunction, with an emphasis on: (i) T cell tolerance to self-antigens (self-tolerance); (ii) T cell exhaustion during chronic infections; and (iii) tumor-induced T cell dysfunction. We highlight recent findings on cellular and molecular characteristics defining these states, cell-intrinsic regulatory mechanisms that induce and maintain them, and strategies that can lead to their reversal.

Adoptive T cell transfer for cancer immunotherapy in the era of synthetic biology

Adoptive T cell transfer for cancer and chronic infection is an emerging field that shows promise in recent trials. Synthetic-biology-based engineering of T lymphocytes to express high-affinity antigen receptors can overcome immune tolerance, which has been a major limitation of immunotherapy-based strategies. Advances in cell engineering and culture approaches to enable efficient gene transfer and ex vivo cell expansion have facilitated broader evaluation of this technology, moving adoptive transfer from a "boutique" application to the cusp of a mainstream technology. The major challenge currently facing the field is to increase the specificity of engineered T cells for tumors, because targeting shared antigens has the potential to lead to on-target off-tumor toxicities, as observed in recent trials. As the field of adoptive transfer technology matures, the major engineering challenge is the development of automated cell culture systems, so that the approach can extend beyond specialized academic centers and become widely available.

Immunotherapy-induced CD8+ T cells instigate immune suppression in the tumor

Despite clear evidence of immunogenicity, cancer vaccines only provide a modest clinical benefit. To evaluate the mechanisms that limit tumor regression following vaccination, we have investigated the weak efficacy of a highly immunogenic experimental vaccine using a murine melanoma model. We discovered that the tumor adapts rapidly to the immune attack instigated by tumor-specific CD8+ T cells in the first few days following vaccination, resulting in the upregulation of a complex set of biological networks, including multiple immunosuppressive processes. This rapid adaptation acts to prevent sustained local immune attack, despite continued infiltration by increasing numbers of tumor-specific T cells. Combining vaccination with adoptive transfer of tumor-specific T cells produced complete regression of the treated tumors but did not prevent the adaptive immunosuppression. In fact, the adaptive immunosuppressive pathways were more highly induced in regressing tumors, commensurate with the enhanced level of immune attack. Examination of tumor infiltrating T-cell functionality revealed that the adaptive immunosuppression leads to a progressive loss in T-cell function, even in tumors that are regressing. These novel observations that T cells produced by therapeutic intervention can instigate a rapid adaptive immunosuppressive response within the tumor have important implications for clinical implementation of immunotherapies.

Targeting the tumor-draining lymph node with adjuvanted nanoparticles reshapes the anti-tumor immune response

Accumulating evidence implicates the tumor-draining lymph node (TDLN) in tumor-induced immune escape, as it drains regulatory molecules and leukocytes from the tumor microenvironment. We asked whether targeted delivery of adjuvant to the TDLN, presumably already bathed in tumor antigens, could promote anti-tumor immunity and hinder tumor growth. To this end, we used 30 nm polymeric nanoparticles (NPs) that effectively target dendritic cells (DCs, CD11c(+)) within the lymph node (LN) after intradermal administration. These NPs accumulated within the TDLN when administered in the limb ipsilateral (i.l.) to the tumor or in the non-TDLN when administered in the contralateral (c.l.) limb. Incorporating the adjuvants CpG or paclitaxel into the NPs (CpG-NP and PXL-NP) induced DC maturation in vitro. When administered daily i.l. and thus targeting the TDLN of a B16-F10 melanoma, adjuvanted NPs induced DC maturation within the TDLN and reshaped the CD4(+) T cell distribution within the tumor towards a Th1 (CXCR3(+)) phenotype. Importantly, this also led to an increase in the frequency of antigen-specific CD8(+) T cells within the tumor. This correlated with slowed tumor growth, in contrast to unhindered tumor growth after c.l. delivery of adjuvanted NPs (targeting a non-TDLN) or i.l. delivery of free adjuvant. CpG-NP treatment in the i.l. limb also was associated with an increase in CD8(+)/CD4(+) T cell ratios and frequencies of activated (CD25(+)) CD8(+) T cells within the TDLN whereas PXL-NP treatment reduced the frequency of regulatory T (FoxP3(+) CD4(+)) cells in the TDLN. Together, these data implicate the TDLN as a delivery target for adjuvant therapy of solid tumors.

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.

Hypoxia-inducible factors enhance the effector responses of CD8(+) T cells to persistent antigen

Cytolytic activity by CD8(+) cytotoxic T lymphocytes (CTLs) is a powerful strategy for the elimination of intracellular pathogens and tumor cells. The destructive capacity of CTLs is progressively dampened during chronic infection, yet the environmental cues and molecular pathways that influence immunological 'exhaustion' remain unclear. Here we found that CTL immunity was regulated by the central transcriptional response to hypoxia, which is controlled in part by hypoxia-inducible factors (HIFs) and the von Hippel-Lindau tumor suppressor VHL. Loss of VHL, the main negative regulator of HIFs, led to lethal CTL-mediated immunopathology during chronic infection, and VHL-deficient CTLs displayed enhanced control of persistent viral infection and neoplastic growth. We found that HIFs and oxygen influenced the expression of pivotal transcription, effector and costimulatory-inhibitory molecules of CTLs, which was relevant to strategies that promote the clearance of viruses and tumors.

Antibodies targeting human OX40 expand effector T cells and block inducible and natural regulatory T cell function

Current cancer vaccines induce tumor-specific T cell responses without sustained tumor regression because immunosuppressive elements within the tumor induce exhaustion of effector T cells and infiltration of immune-suppressive regulatory T cells (Tregs). Therefore, much effort has been made to generate agonistic Abs targeting members of the TNFR superfamily, such as OX40, 4-1BB, and GITR, expressed on effector T cells and Tregs, to reinvigorate T cell effector function and block Treg-suppressive function. In this article, we describe the development of a panel of anti-human OX40 agonistic mouse mAbs that could promote effector CD4(+) and CD8(+) T cell proliferation, inhibit the induction of CD4(+) IL-10 -producing type 1 regulatory T cells, inhibit the expansion of ICOS(+)IL-10(+) Tregs, inhibit TGF-β-induced FOXP3 expression on naive CD4(+) T cells, and block natural Treg-suppressive function. We humanized two anti-human OX40 mAb clones, and they retained the potency of their parental clones. These Abs should provide broad opportunities for potential combination therapy to treat a wide realm of cancers and preventative vaccines against infectious diseases.

Immune alterations in malignant melanoma and current immunotherapy concepts

INTRODUCTION

Malignant melanoma is a highly aggressive, immunogenic tumor that has the ability to modulate the immune system to its own advantage. Patients with melanoma present numerous cellular immune defects and cytokine abnormalities, all leading to suppression of the host anti-tumor immune response. Innovative treatment strategies can be achieved through employing our knowledge of the melanoma-induced immune alterations.

AREAS COVERED

The authors review comprehensively the immune abnormalities in individuals with melanoma, and provide a summary of currently available melanoma immunotherapy agents that are currently on the market or undergoing clinical trials.

EXPERT OPINION

Ipilimumab, a monoclonal antibody directed against the CTLA-4, is one of the current forefront treatment strategies in malignant melanoma. Novel immunomodulating agents have shown clear activity in patients with malignant melanoma. These include anti-PD-1 and anti-PD-1 ligand antibodies that may soon become important items in the anti-melanoma armamentarium. Combinations of different immunotherapy agents, between themselves or with other agents, are currently being studied in an attempt to further enhance the antineoplastic effect in patients with malignant melanoma.

Novel antibodies targeting immune regulatory checkpoints for cancer therapy

Cancers must evade or suppress the immune system in order to develop. Better understanding of the molecular regulation governing tumour detection and effective activation of the immune system (so called immune regulatory checkpoints) has provided new targets for cancer immunotherapy. Therapeutic monoclonal antibodies against these targets are currently undergoing clinical evaluation with more in pre-clinical development; buoyed by the recent licence approval of the anti-CTLA-4 antibody, ipilumumab, for use in melanoma. This article will review the current status of the various antibodies and target molecules being investigated.

Mucosal imprinting of vaccine-induced CD8⁺ T cells is crucial to inhibit the growth of mucosal tumors

Although many human cancers are located in mucosal sites, most cancer vaccines are tested against subcutaneous tumors in preclinical models. We therefore wondered whether mucosa-specific homing instructions to the immune system might influence mucosal tumor outgrowth. We showed that the growth of orthotopic head and neck or lung cancers was inhibited when a cancer vaccine was delivered by the intranasal mucosal route but not the intramuscular route. This antitumor effect was dependent on CD8⁺ T cells. Indeed, only intranasal vaccination elicited mucosal-specific CD8⁺ T cells expressing the mucosal integrin CD49a. Blockade of CD49a decreased intratumoral CD8⁺ T cell infiltration and the efficacy of cancer vaccine on mucosal tumor. We then showed that after intranasal vaccination, dendritic cells from lung parenchyma, but not those from spleen, induced the expression of CD49a on cocultured specific CD8⁺ T cells. Tumor-infiltrating lymphocytes from human mucosal lung cancer also expressed CD49a, which supports the relevance and possible extrapolation of these results in humans. We thus identified a link between the route of vaccination and the induction of a mucosal homing program on induced CD8⁺ T cells that controlled their trafficking. Immunization route directly affected the efficacy of the cancer vaccine to control mucosal tumors.

Expression profiling of TCR-engineered T cells demonstrates overexpression of multiple inhibitory receptors in persisting lymphocytes

Despite significant progress in the development of adoptive cell-transfer therapies (ACTs) using gene-engineered T cells, little is known about the fate of cells following infusion. To address that, we performed a comparative analysis of gene expression between T-cell receptor-engineered lymphocytes persisting in the circulation 1 month after administration and the product that was infused. We observed that 156 genes related to immune function were differentially expressed, including underexpression of stimulators of lymphocyte function and overexpression of inhibitory genes in postinfusion cells. Of genes overexpressed postinfusion, the product of programmed cell death 1 (PDCD1), coinhibitory receptor PD-1, was expressed at a higher percentage in postinfusion lymphocytes than in the infusion product. This was associated with a higher sensitivity to inhibition of cytokine production by interaction with its ligand PD-L1. Coinhibitory receptor CD160 was also overexpressed in persisting cells, and its expression was associated with decreased reactivity, which surprisingly was found to be ligand-independent. These results contribute to a deeper understanding of the properties of transgenic lymphocytes used to treat human malignancies and may provide a rationale for the development of combination therapies as a method to improve ACT.