The Next Hurdle in Cancer Immunotherapy: Overcoming the Non-T-Cell-Inflamed Tumor Microenvironment

Emerging role of immunotherapy in urothelial carcinoma-Immunobiology/biomarkers

Urothelial bladder cancer is one of the first cancers recognized to be immunogenic since 40 years ago when the use of bacillus Calmette-Guerin was shown to prevent recurrence. Since that time, our knowledge of immune biology of cancer has expanded tremendously, and patients with bladder cancer finally have new active immunotherapeutic drugs on the horizon. Anti-programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) therapy has shown impressively durable responses in urothelial bladder cancer (UBC), but the reported response rates warrant improvement. To outline potential strategies to overcome tumor immune resistance, herein, we summarize current models of tumor immunology with a specific focus on bladder cancer. Recognition of tumor-specific antigens through cross-presentation, T-cell priming and activation, and trafficking of immune cells to the tumor microenvironment are some of the critical steps we now understand to be necessary for an effective antitumor immune response. Many of the involved steps are important targets for therapeutic interventions. As new immunotherapies are developed, predictive biomarkers would also be important to select patients most likely to respond and to better understand tumor biology. Several potential biomarkers are reviewed including PD-L1 expression, identification of T-cell-inflamed/non-T-cell-inflamed tumors based on immune gene expression, intrinsic molecular subtyping based on luminal/basal or the cancer genome atlas (TCGA) groups, T-cell receptor sequencing, and somatic mutational density. Even within the past few years, our current knowledge of immune biology has exploded, and we are highly optimistic about the future of UBC therapy that will be available to patients.

Metastatic lymphoepithelioma-like carcinoma of the lung treated with nivolumab: a case report and focused review of literature

In recent years, significant advances have been made in cancer immunotherapy. Here, we present the first report of a patient with lymphoepithelioma-like carcinoma (LELC) of the lung, an Epstein-Barr virus (EBV)-associated lung cancer, who was treated with nivolumab, a fully human IgG4 anti-PD-1 monoclonal antibody. We also carry out a focused review to identify and examine studies of LELC of the lung in the literature. This case report highlights the need to further assess the role of immune checkpoint inhibitors in LELC of the lung.

Cisplatin selectively downregulated the frequency and immunoinhibitory function of myeloid-derived suppressor cells in a murine B16 melanoma model

The objective of this study was to investigate the immunomodulatory effect of cisplatin (DDP) on the frequency, phenotype and function of myeloid-derived suppressor cells (MDSC) in a murine B16 melanoma model. C57BL/6 mice were inoculated with B16 cells to establish the murine melanoma model and randomly received treatment with different doses of DDP. The percentages and phenotype of MDSC after DDP treatment were detected by flow cytometry. The immunoinhibitory function of MDSC was analyzed by assessing the immune responses of cocultured effector cells through CFSE-labeling assay, detection of interferon-γ production and MTT cytotoxic assay, respectively. Tumor growth and mice survival were monitored to evaluate the antitumor effect of combined DDP and adoptive cytokine-induced killer (CIK) cell therapy. DDP treatment selectively decreased the percentages, modulated the surface molecules and attenuated the immunoinhibitory effects of MDSC in murine melanoma model. The combination of DDP treatment and CIK therapy exerted synergistic antitumor effect against B16 melanoma. DDP treatment selectively downregulated the frequency and immunoinhibitory function of MDSC in B16 melanoma model, indicating the potential mechanisms mediating its immunomodulatory effect.

Is There Still Room for Cancer Vaccines at the Era of Checkpoint Inhibitors

Checkpoint inhibitor (CPI) blockade is considered to be a revolution in cancer therapy, although most patients (70%–80%) remain resistant to this therapy. It has been hypothesized that only tumors with high mutation rates generate a natural antitumor T cell response, which could be revigorated by this therapy. In patients with no pre-existing antitumor T cells, a vaccine-induced T cell response is a rational option to counteract clinical resistance. This hypothesis has been validated in preclinical models using various cancer vaccines combined with inhibitory pathway blockade (PD-1-PDL1-2, CTLA-4-CD80-CD86). Enhanced T cell infiltration of various tumors has been demonstrated following this combination therapy. The timing of this combination appears to be critical to the success of this therapy and multiple combinations of immunomodulating antibodies (CPI antagonists or costimulatory pathway agonists) have reinforced the synergy with cancer vaccines. Only limited results are available in humans and this combined approach has yet to be validated. Comprehensive monitoring of the regulation of CPI and costimulatory molecules after administration of immunomodulatory antibodies (anti-PD1/PD-L1, anti-CTLA-4, anti-OX40, etc.) and cancer vaccines should help to guide the selection of the best combination and timing of this therapy.

Eradication of large established tumors in mice by combination immunotherapy that engages innate and adaptive immune responses

Checkpoint blockade with antibodies specific for cytotoxic T lymphocyte-associated protein (CTLA)-4 or programmed cell death 1 (PDCD1; also known as PD-1) elicits durable tumor regression in metastatic cancer, but these dramatic responses are confined to a minority of patients. This suboptimal outcome is probably due in part to the complex network of immunosuppressive pathways present in advanced tumors, which are unlikely to be overcome by intervention at a single signaling checkpoint. Here we describe a combination immunotherapy that recruits a variety of innate and adaptive immune cells to eliminate large tumor burdens in syngeneic tumor models and a genetically engineered mouse model of melanoma; to our knowledge tumors of this size have not previously been curable by treatments relying on endogenous immunity. Maximal antitumor efficacy required four components: a tumor-antigen-targeting antibody, a recombinant interleukin-2 with an extended half-life, anti-PD-1 and a powerful T cell vaccine. Depletion experiments revealed that CD8⁺ T cells, cross-presenting dendritic cells and several other innate immune cell subsets were required for tumor regression. Effective treatment induced infiltration of immune cells and production of inflammatory cytokines in the tumor, enhanced antibody-mediated tumor antigen uptake and promoted antigen spreading. These results demonstrate the capacity of an elicited endogenous immune response to destroy large, established tumors and elucidate essential characteristics of combination immunotherapies that are capable of curing a majority of tumors in experimental settings typically viewed as intractable.

The intersection of radiotherapy and immunotherapy: mechanisms and clinical implications

By inducing DNA damage, radiotherapy both reduces tumor burden and enhances anti-tumor immunity. Here, we will review the mechanisms by which radiation induces anti-tumor immune responses that can be augmented using immunotherapies to facilitate tumor regression. Radiotherapy increases inflammation in tumors by activating the NF-κB and the Type I interferon response pathways to induce expression of pro-inflammatory cytokines. This inflammation coupled with antigen release from irradiated cells facilitates dendritic cell maturation and cross-presentation of tumor antigens to prime tumor-specific T cell responses. Radiation also sensitizes tumors to these T cell responses by enhancing T cell infiltration into tumors and the recognition of both malignant cancer cells and non-malignant stroma that present cognate antigen. Yet, these anti-tumor immune responses may be blunted by several mechanisms including regulatory T cells and checkpoint molecules that promote T cell tolerance and exhaustion. Consequently, the combination of immunotherapy using vaccines and/or checkpoint inhibitors with radiation is demonstrating early clinical potential. Overall, this review will provide a global view for how radiation and the immune system converge to target cancers and the early attempts to exploit this synergy in clinical practice.

Nivolumab, anti-programmed death-1 (PD-1) monoclonal antibody immunotherapy: Role in advanced cancers

The development of immune checkpoint inhibitors has altered the landscape of treatment of advanced cancers. These drugs are well tolerated and have shown clinical activity against a wide variety of solid tumors and hematological malignancies. The durability of response is particularly impressive when compared to other forms of systemic therapy. Nivolumab (Opdivo) is an IgG4 antibody that causes immune checkpoint blockade by diminishing inhibitory signaling through the programmed death receptor-1 pathway. It is approved for treatment of recurrent non-small cell lung cancer, melanoma, and renal cell carcinoma. Efforts to identify biomarkers of response to nivolumab are ongoing. Clinical trials are also being conducted to determine the benefits of combining nivolumab with other forms of treatment including chemotherapy, molecular-targeted therapy, radiation therapy, and other forms of immune therapy. This review outlines the clinical trials that have led to the emergence of nivolumab as a treatment option for patients with advanced cancers.

Is all cancer therapy immunotherapy?

Researchers must renew efforts to decipher how standard chemotherapies enhance the effects of targeted immunotherapeutic agents (Müller et al., this issue).

Lymphatic vessels regulate immune microenvironments in human and murine melanoma

Lymphatic remodeling in tumor microenvironments correlates with progression and metastasis, and local lymphatic vessels play complex and poorly understood roles in tumor immunity. Tumor lymphangiogenesis is associated with increased immune suppression, yet lymphatic vessels are required for fluid drainage and immune cell trafficking to lymph nodes, where adaptive immune responses are mounted. Here, we examined the contribution of lymphatic drainage to tumor inflammation and immunity using a mouse model that lacks dermal lymphatic vessels (K14-VEGFR3-Ig mice). Melanomas implanted in these mice grew robustly, but exhibited drastically reduced cytokine expression and leukocyte infiltration compared with those implanted in control animals. In the absence of local immune suppression, transferred cytotoxic T cells more effectively controlled tumors in K14-VEGFR3-Ig mice than in control mice. Furthermore, gene expression analysis of human melanoma samples revealed that patient immune parameters are markedly stratified by levels of lymphatic markers. This work suggests that the establishment of tumor-associated inflammation and immunity critically depends on lymphatic vessel remodeling and drainage. Moreover, these results have implications for immunotherapies, the efficacies of which are regulated by the tumor immune microenvironment.

The promise of immunotherapy in head and neck squamous cell carcinoma

Squamous cell cancers of the head and neck (HNSCC) comprise a diverse group of malignancies that includes tobacco-related tumors in addition to an increasing number of human papillomavirus-associated cancers. Independently of cause, there is a growing body of evidence supporting that the immune system plays a pivotal role in HNSCC development, as tumor cells evade immunosurveillance by exploiting inhibitory checkpoint pathways that suppress anti-tumor T-cell responses. HNSCC cells have the ability to manipulate the immune system through a variety of different mechanisms, forcing it to promote tumor growth and spread. Over the last decade, discoveries in immunologic research resulted in increased understanding of complex interactions between HNSCC and the host immune system as well as T-cell regulatory mechanisms, promoting the development of a variety of novel immunotherapies. Following the availability of novel immunotherapeutic strategies, the challenge for clinicians is to understand how and in which clinical setting to use these agents in order to provide greater clinical benefit for patients. Combination of immunotherapies with standard treatment approaches also represents an evolving field of research. Herein, we provide a comprehensive review of immune escape mechanisms in HNSCC, as well as current immunotherapy approaches under investigation.

Profiling networks of distinct immune-cells in tumors

Background

It is now clearly evident that cancer outcome and response to therapy is guided by diverse immune-cell activity in tumors. Presently, a key challenge is to comprehensively identify networks of distinct immune-cell signatures present in complex tissue, at higher-resolution and at various stages of differentiation, activation or function. This is particularly so for closely related immune-cells with diminutive, yet critical, differences.

Results

To predict networks of infiltrated distinct immune-cell phenotypes at higher resolution, we explored an integrated knowledge-based approach to select immune-cell signature genes integrating not only expression enrichment across immune-cells, but also an automatic capture of relevant immune-cell signature genes from the literature. This knowledge-based approach was integrated with resources of immune-cell specific protein networks, to define signature genes of distinct immune-cell phenotypes. We demonstrate the utility of this approach by profiling signatures of distinct immune-cells, and networks of immune-cells, from metastatic melanoma patients who had undergone chemotherapy. The resultant bioinformatics strategy complements immunohistochemistry from these tumors, and predicts both tumor-killing and immunosuppressive networks of distinct immune-cells in responders and non-responders, respectively. The approach is also shown to capture differences in the immune-cell networks of BRAF versus NRAS mutated metastatic melanomas, and the dynamic changes in resistance to targeted kinase inhibitors in MAPK signalling.

Conclusions

This integrative bioinformatics approach demonstrates that capturing the protein network signatures and ratios of distinct immune-cell in the tumor microenvironment maybe an important factor in predicting response to therapy. This may serve as a computational strategy to define network signatures of distinct immune-cells to guide immuno-pathological discovery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1141-3) contains supplementary material, which is available to authorized users.

Molecular Drivers of the Non-T-cell-Inflamed Tumor Microenvironment in Urothelial Bladder Cancer

Muscle-invasive urothelial bladder cancer is a common malignancy with poor outcomes for which immune checkpoint blockade is now showing promise. Despite clinical activity of PD-1/PD-L1-targeted therapy in this disease, most patients do not benefit and resistance mechanisms remain unknown. The non-T-cell-inflamed tumor microenvironment correlates with poor prognosis and resistance to immunotherapies. In this study, we determined tumor-oncogenic pathways correlating with T-cell exclusion. We first establish in this report that T-cell-inflamed bladder tumors can be identified by immune gene expression profiling with concordance with CD8(+) T-cell infiltration. Upregulation of genes encoding immune checkpoint proteins PD-L1, IDO, FOXP3, TIM3, and LAG3 was associated with T-cell-inflamed tumors, suggesting potential for sensitivity to checkpoint blockade. β-Catenin, PPAR-γ, and FGFR3 pathways were activated in non-T-cell-inflamed tumors. No difference was seen in overall somatic mutational density between groups. The three pathways identified represent targetable potential pathways of tumor-intrinsic immunotherapy resistance. Cancer Immunol Res; 4(7); 563-8. ©2016 AACR.

Immuno-pharmacodynamics for evaluating mechanism of action and developing immunotherapy combinations

Immunotherapy has become a major modality of cancer treatment, with multiple new classes of immunotherapeutics recently entering the clinic and obtaining market approval from regulatory agencies. While the promise of these therapies is great, so is the number of possible combinations not only with each other but also with small molecule therapeutics. Furthermore, the observation of unusual dose-response relationships suggests a critical dependency of drug effectiveness on the dosage regimen (dose and schedule). Clinical pharmacodynamic (PD) biomarkers will be useful endpoints for confirming drug mechanism of action, evaluating combination therapies for synergy or antagonism, and identifying optimal dosage regimens. In contrast to conventional PD in which drug action occurs entirely within a single target cell (ie, is self-contained within the malignant cell), immunotherapy involves a complex mechanism of action with sequential steps that propagate through multiple cell types, both normal and malignant. Its intercellular pharmacology begins with molecular target engagement either on an immune effector cell or a malignant cell, followed by stimulatory biochemical and biological signals in immune effector cells, and then finally ends with activation of cell death mechanisms in malignant cells lying within a certain distance from the activated effector cells (immune cell-tumor cell proximity). Evaluating such "trans-cellular pharmacology," in which different steps of drug action are distributed across multiple cell types, requires novel microscopy and image analysis tools capable of quantifying PD-biomarker responses, mapping the responses onto the cellular geography of the tumor using phenotypic biomarkers to identify specific cell types, and finally analyzing the spatial relationships between biomarkers in the context of each cell's biological role. We have termed this form of nearest neighbor image analysis of drug action "proximity PD microscopy," to indicate the importance of the location of the PD-biomarker response within the cellular landscape of a tumor specimen. We discuss herein the major modes of immunotherapy, and lay out a blueprint for using PD assessment to optimize dosage regimens of single agents and guide development of combination immunotherapy regimens, using PD1/PD-L1 immune checkpoint inhibition as a case study.

The emerging role of immunotherapy in head and neck squamous cell carcinoma (HNSCC): anti-tumor immunity and clinical applications

Head and neck squamous cell carcinoma (HNSCC) carries a poor prognosis, with low survival rates for advanced stage tumors and minimal improvement in survival trends through the past decades. It is becoming increasingly clear that HNSCC oncogenesis and evolution is characterized by profound immune defects, as cancer cells evade immunosurveillance due to accumulation of genetic mutations and tumor heterogeneity. Improved understanding of the role of the immune system in cancer has led to the identification of novel therapeutic targets, which are being investigated for their potential to provide durable responses. In this review, we will summarize the role of the immune system in HNSCC, the rationale behind immunotherapy strategies and their clinical applications.

Immunoregulatory roles of versican proteolysis in the myeloma microenvironment

Myeloma immunosurveillance remains incompletely understood. We have demonstrated proteolytic processing of the matrix proteoglycan, versican (VCAN), in myeloma tumors. Whereas intact VCAN exerts tolerogenic activities through Toll-like receptor 2 (TLR2) binding, the immunoregulatory consequences of VCAN proteolysis remain unknown. Here we show that human myeloma tumors displaying CD8(+) infiltration/aggregates underwent VCAN proteolysis at a site predicted to generate a glycosaminoglycan-bereft N-terminal fragment, versikine Myeloma-associated macrophages (MAMs), rather than tumor cells, chiefly produced V1-VCAN, the precursor to versikine, whereas stromal cell-derived ADAMTS1 was the most robustly expressed VCAN-degrading protease. Purified versikine induced early expression of inflammatory cytokines interleukin 1β (IL-1β) and IL-6 by human myeloma marrow-derived MAMs. We show that versikine signals through pathways both dependent and independent of Tpl2 kinase, a key regulator of nuclear factor κB1-mediated MAPK activation in macrophages. Unlike intact VCAN, versikine-induced Il-6 production was partially independent of Tlr2. In a model of macrophage-myeloma cell crosstalk, versikine induced components of "T-cell inflammation," including IRF8-dependent type I interferon transcriptional signatures and T-cell chemoattractant CCL2. Thus the interplay between stromal cells and myeloid cells in the myeloma microenvironment generates versikine, a novel bioactive damage-associated molecular pattern that may facilitate immune sensing of myeloma tumors and modulate the tolerogenic consequences of intact VCAN accumulation. Therapeutic versikine administration may potentiate T-cell-activating immunotherapies.

Interferon-γ and Tumor Necrosis Factor-α Polarize Bone Marrow Stromal Cells Uniformly to a Th1 Phenotype

Activated T cells polarize mesenchymal stromal cells (MSCs) to a proinflammatory Th1 phenotype which likely has an important role in amplifying the immune response in the tumor microenvironment. We investigated the role of interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), two factors produced by activated T cells, in MSC polarization. Gene expression and culture supernatant analysis showed that TNF-α and IFN-γ stimulated MSCs expressed distinct sets of proinflammatory factors. The combination of IFN-γ and TNF-α was synergistic and induced a transcriptome most similar to that found in MSCs stimulated with activated T cells and similar to that found in the inflamed tumor microenvironment; a Th1 phenotype with the expression of the immunosuppressive factors IL-4, IL-10, CD274/PD-L1 and indoleamine 2,3 dioxygenase (IDO). Single cell qRT-PCR analysis showed that the combination of IFN-γ and TNF-α polarized uniformly to this phenotype. The combination of IFN-γ and TNF-α results in the synergist uniform polarization of MSCs toward a primarily Th1 phenotype. The stimulation of MSCs by IFN-γ and TNF-α released from activated tumor infiltrating T cells is likely responsible for the production of many factors that characterize the tumor microenvironment.

Immune escape to PD-L1/PD-1 blockade: seven steps to success (or failure)

The emergence of programmed death-ligand 1 (PD-L1)/programmed death-1 (PD-1)-targeted therapy has demonstrated the importance of the PD-L1 : PD-1 interaction in inhibiting anticancer T-cell immunity in multiple human cancers, generating durable responses and extended overall survival. However, not all patients treated with PD-L1/PD-1-targeted therapy experience tumor shrinkage, durable responses, or prolonged survival. To extend such benefits to more cancer patients, it is necessary to understand why some patients experience primary or secondary immune escape, in which the immune response is incapable of eradicating all cancer cells. Understanding immune escape from PD-L1/PD-1-targeted therapy will be important to the development of rational immune-combination therapy and predictive diagnostics and to the identification of novel immune targets. Factors that likely relate to immune escape include the lack of strong cancer antigens or epitopes recognized by T cells, minimal activation of cancer-specific T cells, poor infiltration of T cells into tumors, downregulation of the major histocompatibility complex on cancer cells, and immunosuppressive factors and cells in the tumor microenvironment. Precisely identifying and understanding these mechanisms of immune escape in individual cancer patients will allow for personalized cancer immunotherapy, in which monotherapy and combination immunotherapy are chosen based on the presence of specific immune biology. This approach may enable treatment with immunotherapy without inducing immune escape, resulting in a larger proportion of patients obtaining clinical benefit.

Molecular Drivers of the Non-T-cell-Inflamed Tumor Microenvironment in Urothelial Bladder Cancer

Muscle-invasive urothelial bladder cancer is a common malignancy with poor outcomes for which immune checkpoint blockade is now showing promise. Despite clinical activity of PD-1/PD-L1-targeted therapy in this disease, most patients do not benefit and resistance mechanisms remain unknown. The non-T-cell-inflamed tumor microenvironment correlates with poor prognosis and resistance to immunotherapies. In this study, we determined tumor-oncogenic pathways correlating with T-cell exclusion. We first establish in this report that T-cell-inflamed bladder tumors can be identified by immune gene expression profiling with concordance with CD8(+) T-cell infiltration. Upregulation of genes encoding immune checkpoint proteins PD-L1, IDO, FOXP3, TIM3, and LAG3 was associated with T-cell-inflamed tumors, suggesting potential for sensitivity to checkpoint blockade. β-Catenin, PPAR-γ, and FGFR3 pathways were activated in non-T-cell-inflamed tumors. No difference was seen in overall somatic mutational density between groups. The three pathways identified represent targetable potential pathways of tumor-intrinsic immunotherapy resistance. Cancer Immunol Res; 4(7); 563-8. ©2016 AACR.