Tumor-specific T-cell memory: clearing the regulatory T-cell hurdle

Cytosolic Delivery of Thiolated Mn-cGAMP Nanovaccine to Enhance the Antitumor Immune Responses

As a stimulator of interferon gene (STING), cyclic dinucleotide activates a broad cellular immune response for anti-cancer immunotherapy (CIT). However, the inherent of instability of 2' 3'-cyclic-GMP-AMP (cGAMP) with poor cellular targeting, rapid clearance, and inefficient transport to the cytoplasm seriously hinders cGAMP potency. Here, a thiolated and Mn²⁺ coordinated cyclic dinucleotide nanovaccine (termed as Mn-cGAMP NVs) to enable direct cytosolic co-delivery of cGAMP and Mn²⁺ to potentiate the antitumor immune response is presented. In the NVs, the fixation cGAMP with Mn²⁺ ions not only improve its stability, but also potentiate the activation of STING. Meanwhile, the presence of polysulfides on the NVs surface allowed direct cytosolic delivery while avoiding degradation. In this way, the production of cytokines for activating T cells immunity is greatly elevated, which in turn suppressed the primary and distal tumors growth through long-term immune memory and led to long-term survival of poorly immunogenic B16F10 melanoma mice. Moreover, by further combining with anti-PD-L1 monoclonal antibody, synergistic T cells antitumor immune response is elicited. This work offers a promising strategy to enhance the potency of cGAMP, holding a considerable potential for CIT applications.

Translational Nanomedicine Boosts Anti-PD1 Therapy to Eradicate Orthotopic PTEN-Negative Glioblastoma

Glioblastoma (GBM) is resistant to immune checkpoint inhibition due to its low mutation rate, phosphatase and tensin homologue (PTEN)-deficient immunosuppressive microenvironment, and high fraction of cancer stem-like cells (CSCs). Nanomedicines fostering immunoactivating intratumoral signals could reverse GBM resistance to immune checkpoint inhibitors (ICIs) for promoting curative responses. Here, we applied pH-sensitive epirubicin-loaded micellar nanomedicines, which are under clinical evaluation, to synergize the efficacy of anti-PD1antibodies (aPD1) against PTEN-positive and PTEN-negative orthotopic GBM, the latter with a large subpopulation of CSCs. The combination of epirubicin-loaded micelles (Epi/m) with aPD1 overcame GBM resistance to ICIs by transforming cold GBM into hot tumors with high infiltration of antitumor immune cells through the induction of immunogenic cell death (ICD), elimination of immunosuppressive myeloid-derived suppressor cells (MSDCs), and reduction of PD-L1 expression on tumor cells. Thus, Epi/m plus aPD1 eradicated both PTEN-positive and PTEN-negative orthotopic GBM and provided long-term immune memory effects. Our results indicate the high translatable potential of Epi/m plus aPD1 for the treatment of GBM.

Surgical stress and cancer progression: the twisted tango

Surgical resection is an important avenue for cancer treatment, which, in most cases, can effectively alleviate the patient symptoms. However, accumulating evidence has documented that surgical resection potentially enhances metastatic seeding of tumor cells. In this review, we revisit the literature on surgical stress, and outline the mechanisms by which surgical stress, including ischemia/reperfusion injury, activation of sympathetic nervous system, inflammation, systemically hypercoagulable state, immune suppression and effects of anesthetic agents, promotes tumor metastasis. We also propose preventive strategies or resolution of tumor metastasis caused by surgical stress.

Forced co-expression of IL-21 and IL-7 in whole-cell cancer vaccines promotes antitumor immunity

Genetic modification of whole-cell cancer vaccines to augment their efficacies has a history of over two and a half decades. Various genes and gene combinations, targeting different aspects of immune responses have been tested in pursuit of potent adjuvant effects. Here we show that co-expression of two cytokine members of the common cytokine receptor γ-chain family, IL-21 and IL-7, in whole-cell cancer vaccines boosts antitumor immunity in a CD4⁺ and CD8⁺ T cell-dependent fashion. It also generates effective immune memory. The vaccine-elicited short-term effects positively correlated with enhanced infiltration of CD4⁺ and CD8⁺ effector T cells, and the long-term effects positively correlated with enhanced infiltration of effector memory T cells, especially CD8⁺ effector memory T cells. Preliminary data suggested that the vaccine exhibited good safety profile in murine models. Taken together, the combination of IL-21 and IL-7 possesses potent adjuvant efficacy in whole-cell vaccines. This finding warrants future development of IL-21 and IL-7 co-expressing whole-cell cancer vaccines and their relevant combinatorial regimens.

The use of interferon in melanoma patients: a systematic review

Interferon (IFN) and PEG-IFN are the only drugs approved as adjuvant therapy in patients with melanoma at high-risk of recurrence after surgical resection. Several clinical trials of adjuvant IFN, using different doses and durations of therapy, have been conducted in these patients. Results generally suggest relapse-free survival and overall survival benefits; however, questions over the optimal dose and duration of treatment and concerns over toxicity have limited its use. IFN exerts its biological activity in melanoma via multiple mechanisms of action, most of which can be considered as indirect immunomodulatory effects. As such, IFN may also be of benefit in the neoadjuvant setting, where it may have a role in melanoma patients with locally advanced disease for whom immediate surgical excision is not possible. However, this has not been well studied. The use of IFN in patients with metastatic melanoma is controversial, with limited data and no convincing evidence of a survival benefit. However, IFN therapy combined with novel biological and immunotherapies offers the potential for a synergistic effect and improved clinical outcomes. Predictive and prognostic factors to better select melanoma patients for IFN treatment have been identified (e.g. disease stage, ulceration, various cytokines) and may also enhance its therapeutic efficacy, but their incorporation into the clinical decision-making process requires validation in prospective trials. In conclusion, the modest efficacy of IFN shown in clinical trials is largely a reflection of differences in response between patients. Despite advancements in the understanding of its biological mechanisms of action, the huge potential of IFN remains to be fully explored and utilized in patients with melanoma.

Foxp3+ T cells inhibit antitumor immune memory modulated by mTOR inhibition

Inhibition of mTOR signaling enhances antitumor memory lymphocytes. However, pharmacologic mTOR inhibition also enhances regulatory T-cell (Treg) activity. To counter this effect, Treg control was added to mTOR inhibition in preclinical models. Tregs were controlled with CD4-depleting antibodies because CD4 depletion has high translational potential and already has a well-established safety profile in patients. The antitumor activity of the combination therapy was CD8 dependent and controlled growth of syngeneic tumors even when an adoptive immunotherapy was not used. Lymphocytes resulting from the combination therapy could be transferred into naïve mice to inhibit aggressive growth of lung metastases. The combination therapy enhanced CD8 memory formation as determined by memory markers and functional studies of immune recall. Removal of FoxP3-expressing T lymphocytes was the mechanism underlying immunologic memory formation following CD4 depletion. This was confirmed using transgenic DEREG (depletion of regulatory T cells) mice to specifically remove Foxp3(+) T cells. It was further confirmed with reciprocal studies where stimulation of immunologic memory because of CD4 depletion was completely neutralized by adoptively transferring tumor-specific Foxp3(+) T cells. Also contributing to tumor control, Tregs that eventually recovered following CD4 depletion were less immunosuppressive. These results provide a rationale for further study of mTOR inhibition and CD4 depletion in patients.

Myeloid-derived suppressor cells are associated with disease progression and decreased overall survival in advanced-stage melanoma patients

Myeloid-derived suppressor cells are increased in the peripheral blood of advanced-stage cancer patients; however, no studies have shown a correlation of these immunosuppressive cells with clinical outcomes in melanoma patients. We characterized the frequency and suppressive function of multiple subsets of myeloid-derived suppressor cells in the peripheral blood of 34 patients with Stage IV melanoma, 20 patients with Stage I melanoma, and 15 healthy donors. The frequency of CD14+ MDSCs (Lin- CD11b+ HLA-DR- CD14+ CD33+) and CD14- MDSCs (Lin- CD11b+ HLA-DR- CD14- CD33+) was increased in the peripheral blood of Stage IV melanoma patients relative to healthy donors. The frequency of CD14+ and CD14- MDSCs correlated with each other and with the increased frequency of regulatory T cells, but not with classically defined monocytes. CD14- MDSCs isolated from the peripheral blood of Stage IV melanoma patients suppressed T cell activation more than those isolated from healthy donors, and the frequency of these cells correlated with disease progression and decreased overall survival. Our study provides the first evidence that the frequency of CD14- MDSCs negatively correlates with clinical outcomes in advanced-stage melanoma patients. These data indicate that suppressive MDSCs should be considered as targets for future immunotherapies.

Antigen-specific memory regulatory CD4+Foxp3+ T cells control memory responses to influenza virus infection

Regulatory CD4(+)Foxp3(+) T cells (Tregs) are key regulators of inflammatory responses and control the magnitude of cellular immune responses to viral infections. However, little is known about how Tregs contribute to immune regulation during memory responses to previously encountered pathogens. In this study, we used MHC class II tetramers specific for the 311-325 peptide from influenza nucleoprotein (NP311-325/IA(b)) to track the Ag-specific Treg response to primary and secondary influenza virus infections. During secondary infections, Ag-specific memory Tregs showed accelerated accumulation in the lung-draining lymph node and lung parenchyma relative to a primary infection. Memory Tregs effectively controlled the in vitro proliferation of memory CD8(+) cells in an Ag-specific fashion that was MHC class II dependent. When memory Tregs were depleted before secondary infection, the magnitude of the Ag-specific memory CD8(+) T cell response was increased, as was pulmonary inflammation and airway cytokine/chemokine expression. Replacement of memory Tregs with naive Tregs failed to restore the regulation of the memory CD8 T cell response during secondary infection. Together, these data demonstrate the existence of a previously undescribed population of Ag-specific memory Tregs that shape the cellular immune response to secondary influenza virus challenges and offer an additional parameter to consider when determining the efficacy of vaccinations.

Induction of antitumor immunity ex vivo using dendritic cells transduced with fowl pox vector expressing MUC1, CEA, and a triad of costimulatory molecules (rF-PANVAC)

The fowl pox vector expressing the tumor-associated antigens, mucin-1 and carcinoembryonic antigen in the context of costimulatory molecules (rF-PANVAC) has shown promise as a tumor vaccine. However, vaccine-mediated expansion of suppressor T-cell populations may blunt clinical efficacy. We characterized the cellular immune response induced by ex vivo dendritic cells (DCs) transduced with (rF)-PANVAC. Consistent with the functional characteristics of potent antigen-presenting cells, rF-PANVAC-DCs demonstrated strong expression of mucin-1 and carcinoembryonic antigen and costimulatory molecules, CD80, CD86, and CD83; decreased levels of phosphorylated STAT3, and increased levels of Tyk2, Janus kinase 2, and STAT1. rF-PANVAC-DCs stimulated expansion of tumor antigen-specific T cells with potent cytolytic capacity. However, rF-PANVAC-transduced DCs also induced the concurrent expansion of FOXP3 expressing CD4CD25 regulatory T cells (Tregs) that inhibited T-cell activation. Moreover, Tregs expressed high levels of Th2 cytokines [interleukin (IL)-10, IL-4, IL-5, and IL-13] together with phosphorylated STAT3 and STAT6. In contrast, the vaccine-expanded Treg population expressed high levels of Th1 cytokines IL-2 and interferon-γ and the proinflammatory receptor-related orphan receptor γt (RORγt) and IL-17A suggesting that these cells may share effector functions with conventional TH17 T cells. These data suggest that Tregs expanded by rF-PANVAC-DCs, exhibit immunosuppressive properties potentially mediated by Th2 cytokines, but simultaneous expression of Th1 and Th17-associated factors suggests a high degree of plasticity.

Regional lymphatic immunity in melanoma

Melanoma is an immunogenic tumor that has developed methods to successfully evade immune recognition, while paradoxically spreading through the lymphatic system. Increasing evidence supports that melanoma-derived factors suppress regional immunity within the host. At a very early stage, melanoma communicates with the tumor-draining lymph nodes, and prepares them for seeding of metastatic disease by stimulating lymphangiogenesis and downregulation of the sentinel lymph node immunity well before the malignant cells arrive. Investigations have demonstrated that the induction of suppressor cells, peripheral tolerance, and a less tumor-responsive Th2 cytokine environment may provide a hospitable environment for subsequent lymphatic metastasis. Patients with early-stage disease may benefit from the restoration of the regional immune function to a level that controls the progression of residual occult metastases and ensures a durable clinical response. Herein we provide a succinct summary of the current progress in this field in order to guide future investigations.

Characterization of surgical models of postoperative tumor recurrence for preclinical adjuvant therapy assessment

PURPOSE

Nearly 30% of cancer patients undergoing curative surgery succumb to distant recurrent disease. Despite large implications and known differences between primary and recurrent tumors, preclinical adjuvant therapy evaluation frequently occurs only in primary tumors and not recurrent tumors. We hypothesized that well characterized and reproducible models of postoperative systemic recurrences should be used for preclinical evaluation of adjuvant approaches.

EXPERIMENTAL DESIGN

We examined traditional animal models of cancer surgery that generate systemic cancer recurrences. We also investigated models of systemic cancer recurrences that incorporate spontaneously metastatic cell lines and surgical resection. For each model, we critiqued feasibility, reproducibility and similarity to human recurrence biology. Using our novel model, we then tested the adjuvant use of a novel systemic inhibitor of TGF-β, 1D11.

RESULTS

Traditional surgical models are confounded by immunologic factors including concomitant immunity and perioperative immunosuppression. A superior preclinical model of postoperative systemic recurrences incorporates spontaneously metastatic cell lines and primary tumor excision. This approach is biologically relevant and readily feasible. Using this model, we discovered that "perioperative" TGF-β blockade has strong anti-tumor effects in the setting of advanced disease that would not be appreciated in primary tumor cell lines or other surgical models.

CONCLUSIONS

There are multiple immunologic effects that rendered previous models of postoperative cancer recurrences inadequate. Use of spontaneously metastatic cell lines followed by surgical resection eliminates these confounders, and best resembles the clinical scenario. This preclinical model provides more reliable preclinical information when evaluating new adjuvant therapies.

Protective CD8 memory T cell responses to mouse melanoma are generated in the absence of CD4 T cell help

BACKGROUND

We have previously demonstrated that temporary depletion of CD4 T cells in mice with progressive B16 melanoma, followed by surgical tumor excision, induces protective memory CD8 T cell responses to melanoma/melanocyte antigens. We also showed that persistence of these CD8 T cells is supported, in an antigen-dependent fashion, by concurrent autoimmune melanocyte destruction. Herein we explore the requirement of CD4 T cell help in priming and maintaining this protective CD8 T cell response to melanoma.

METHODOLOGY AND PRINCIPAL FINDINGS

To induce melanoma/melanocyte antigen-specific CD8 T cells, B16 tumor bearing mice were depleted of regulatory T cells (T(reg)) by either temporary, or long-term continuous treatment with anti-CD4 (mAb clone GK1.5). Total depletion of CD4 T cells led to significant priming of IFN-γ-producing CD8 T cell responses to TRP-2 and gp100. Surprisingly, treatment with anti-CD25 (mAb clone PC61), to specifically deplete T(reg) cells while leaving help intact, was ineffective at priming CD8 T cells. Thirty to sixty days after primary tumors were surgically excised, mice completely lacking CD4 T cell help developed autoimmune vitiligo, and maintained antigen-specific memory CD8 T cell responses that were highly effective at producing cytokines (IFN-γ, TNF-α, and IL-2). Mice lacking total CD4 T cell help also mounted protection against re-challenge with B16 melanoma sixty days after primary tumor excision.

CONCLUSIONS AND SIGNIFICANCE

This work establishes that CD4 T cell help is dispensable for the generation of protective memory T cell responses to melanoma. Our findings support further use of CD4 T cell depletion therapy for inducing long-lived immunity to cancer.

Control of established melanoma by CD27 stimulation is associated with enhanced effector function and persistence, and reduced PD-1 expression of tumor infiltrating CD8(+) T cells

The immune response to the tumor can be enhanced by targeting costimulatory molecules on T cells. As the CD70-CD27 costimulatory axis plays an important role in the activation, survival, and differentiation of lymphocytes, we have examined the efficacy of agonistic anti-CD27 antibodies as monotherapies for established melanoma in a murine model. We show that this approach leads to a substantial reduction in the outgrowth of both experimental lung metastases and subcutaneous tumors. Anti-CD27 treatment supports the maintenance of tumor-specific CD8(+) T cells within the tumor, reduces the frequency of FoxP3-expressing CD4(+) T cells within tumors, and potentiates the ability of NK1.1(+) and CD8(+) tumor infiltrating cells to secrete IFNγ upon coculture with tumor cells. The enhanced effector function correlated with lower levels of PD-1 expression on CD8(+) T cells from anti-CD27-treated mice. Despite the modulating effect of anti-CD27 on multiple cell types, only CD8(+) T cells were absolutely required for tumor control. The CD4(+) T cells were dispensable, whereas NK1.1(+) cells were needed during early stages of tumor growth but not for the effectiveness of anti-CD27. Thus, CD27-mediated costimulation provides a potent boost to multiple aspects of the endogenous responses to tumor, and may be exploited to enhance tumor immunity.

Immunomodulatory cytokines as therapeutic agents for melanoma

Melanoma is the most aggressive form of skin cancer whose worldwide incidence is rising faster than any other cancer. Few treatment options are available to patients with metastatic disease, and standard chemotherapeutic agents are generally ineffective. Cytokines such as IFN-α or IL-2 can promote immune recognition of melanoma, occasionally inducing dramatic and durable clinical responses. Here, we discuss several immunomodulatory agents, the safety of which are being evaluated in clinical trials. Challenges include an incomplete understanding of signaling pathways, appropriate clinical dose and route, and systemic immunosuppression in advanced melanoma patients. We consider how targeted cytokine therapy will integrate into the clinical arena, as well as the low likelihood of success of single cytokine therapies. Evidence supports a synergy between cytokine immunotherapy and other therapeutic approaches in melanoma, and strengthening this area of research will improve our understanding of how to use cytokine therapy better.

Autoimmune melanocyte destruction is required for robust CD8+ memory T cell responses to mouse melanoma

A link between autoimmunity and improved antitumor immunity has long been recognized, although the exact mechanistic relationship between these two phenomena remains unclear. In the present study we have found that vitiligo, the autoimmune destruction of melanocytes, generates self antigen required for mounting persistent and protective memory CD8+ T cell responses to melanoma. Vitiligo developed in approximately 60% of mice that were depleted of regulatory CD4+ T cells and then subjected to surgical excision of large established B16 melanomas. Mice with vitiligo generated 10-fold larger populations of CD8+ memory T cells specific for shared melanoma/melanocyte antigens. CD8+ T cells in mice with vitiligo acquired phenotypic and functional characteristics of effector memory, suggesting that they were supported by ongoing antigen stimulation. Such responses were not generated in melanocyte-deficient mice, indicating a requirement for melanocyte destruction in maintaining CD8+ T cell immunity to melanoma. Vitiligo-associated memory CD8+ T cells provided durable tumor protection, were capable of mounting a rapid recall response to melanoma, and did not demonstrate phenotypic or functional signs of exhaustion even after many months of exposure to antigen. This work establishes melanocyte destruction as a key determinant of lasting melanoma-reactive immune responses, thus illustrating that immune-mediated destruction of normal tissues can perpetuate adaptive immune responses to cancer.

Targeting a mimotope vaccine to activating Fcgamma receptors empowers dendritic cells to prime specific CD8+ T cell responses in tumor-bearing mice

A major challenge for inducing antitumor immune responses with native or modified tumor/self-Ags in tumor-bearing hosts relates to achieving efficient uptake and processing by dendritic cells (DCs) to activate immune effector cells and limit the generation of regulatory T cell activity. We analyzed the ability of therapeutic DC vaccines expressing a CD166 cross-reactive mimotope of the GD2 ganglioside, 47-LDA, to selectively expand adoptively transferred, tumor-specific T cells in NXS2 neuroblastoma tumor-bearing syngeneic mice. Before the adoptive cell transfer and DC vaccination, the tumor-bearing mice were lymphodepleted by nonmyeloablative total body irradiation or a myeloablative regimen that required bone marrow transplantation. The 47-LDA mimotope was presented to DCs either as a linear polypeptide in conjunction with universal Th epitopes or as a fusion protein with the murine IgG2a Fc fragment (47-LDA-Fcgamma2a) to deliver the antigenic cassette to the activating Fcgamma receptors. We demonstrate that immunization of adoptively transferred T cells in tumor-bearing mice with the 47-LDA mimotope expressed in the context of the activating Fc fusion protein induced higher levels of antitumor immune responses and protection than the 47-LDA polypeptide-DC vaccine. The antitumor efficacy of the therapeutic 47-LDA-Fcgamma2a-DC vaccine was comparable to that achieved by a virotherapy-associated cancer vaccine using a recombinant oncolytic vaccinia virus expressing the 47-LDA-Fcgamma2a fusion protein. The latter treatment, however, did not require total body irradiation or adoptive cell transfer and resulted in induction of antitumor immune responses in the setting of established tolerance, paving the way for testing novel anticancer treatment strategies.

Active specific immunotherapy and cell-transfer therapy for the treatment of non-small cell lung cancer

Lung cancer is an intractable disease urgently requiring more effective treatment approaches. The potential of immunotherapy in this context remains promising, although presently there are no satisfactory protocols available for lung cancer. However, encouraging evidence of clinical benefits from immunotherapy is beginning to accumulate in several lung cancer trials. Better understanding of tumor-specific immune responses, identifying tumor-associated antigens, and manipulating the immunoregulatory environment of the tumor is likely to further increase the efficacy of immune-mediated cancer therapies. Here, we review recent advances in cellular immunotherapy and vaccines for lung cancer, emphasizing an important paradigm shift in the analysis of clinical benefit away from "tumor response" towards "patient response".