Intratumoral dendritic cells and chemoradiation for the treatment of murine squamous cell carcinoma

The Role of Plasmacytoid Dendritic Cells in Cancers

Plasmacytoid dendritic cells (pDCs) are a special subtype of dendritic cells with the morphology of plasma cells. pDCs produce massive amounts of type I interferon (IFN-I), which was originally found to play an extremely pivotal role in antiviral immunity. Interestingly, accumulated evidence indicates that pDCs can also play an important role in tumorigenesis. In the human body, most of the IFN-α is secreted by activated pDCs mediated by toll-like receptor (TLR) stimulation. In many types of cancer, tumors are infiltrated by a large number of pDCs, however, these pDCs exhibit no response to TLR stimulation, and reduced or absent IFN-α production. In addition, tumor-infiltrating pDCs promote recruitment of regulatory T cells (Tregs) into the tumor microenvironment, leading to immunosuppression and promoting tumor growth. In this review, we discuss recent insights into the development of pDCs and their roles in a variety of malignancies, with special emphasis on the basic mechanisms.

Radiotherapy to Enhance Chimeric Antigen Receptor T-Cell Therapeutic Efficacy in Solid Tumors: A Narrative Review

Importance

Immunotherapy has emerged as a new pillar of cancer therapy over the past decade. Adoptive immunotherapy in particular has become a major area of research interest, with advances seen in the development of T-cell engineering. As a result, chimeric antigen receptor (CAR) T-cell therapy has become a new and highly effective treatment option, especially for patients with refractory or resistant blood cell cancers. However, CAR T-cell therapy has shown limited efficacy for the treatment of solid tumors thus far.

Observations

Combinatorial treatment approaches, such as addition of radiotherapy to CAR T cells, may provide a strategy to prevent resistance to CAR T-cell therapy of solid tumors. These approaches need to overcome obstacles that include abnormal vessels and adhesion molecule expression on tumor vasculature, leading to reduced transmigration of effector immune cells, including CAR T cells, and immunosuppressive cues in the tumor microenvironment, including regional hypoxia.

Conclusions and Relevance

This review provides an overview of the current developments in CAR T-cell therapy and highlights the unique opportunities and challenges in combining CAR T-cell therapy with radiotherapy.

[Radiation therapy and immunomodulation: Focus on experimental data]

The immunosuppressive effects of radiation therapy have long been the only ones considered. It has been demonstrated that exposure to ionizing radiation induces the release of tumour antigens which activates both the innate immune system and the adaptive immune response of the host. The purpose of tumour immunotherapy is based on the principle that reversal of tolerance to immunogenic tumours would be able to activate an immune response against tumour cells. Preclinical data and clinical studies early phase suggest a potential therapeutic benefit of immunotherapy combined with radiation therapy. The objective of this article is to review how tumour cells interact with the immune system and how ionizing radiation modulate this interaction and finally the combination of perspectives of immunotherapy and ionizing radiation by focusing on existing clinical data.

Modulation of radiochemoimmunotherapy-induced B16 melanoma cell death by the pan-caspase inhibitor zVAD-fmk induces anti-tumor immunity in a HMGB1-, nucleotide- and T-cell-dependent manner

One prerequisite that radiotherapy (RT) and chemotherapy (CT) result in anti-tumor immune responses is triggering of immunogenic cell death forms such as necroptosis. The latter is inducible by inhibition of apoptosis with the pan-caspase inhibitor zVAD-fmk. The design of multimodal therapies that overcome melanoma's resistance to apoptosis is a big challenge of oncoimmunology. As hints exist that immune stimulation by hyperthermia (HT) augments the efficacy of melanoma therapies and that tumors can be sensitized for RT with zVAD-fmk, we asked whether combinations of RT with dacarbazine (DTIC) and/or HT induce immunogenic melanoma cell death and how this is especially influenced by zVAD-fmk. Necroptosis was inducible in poorly immunogenic B16-F10 melanoma cells and zVAD-fmk generally increased melanoma cell necrosis concomitantly with the release of HMGB1. Supernatants (SNs) of melanoma cells whose cell death was modulated with zVAD-fmk induced an upregulation of the activation markers CD86 and MHCII on macrophages. The same was seen on dendritic cells (DCs), but only when zVAD-fmk was added to multimodal tumor treatments including DTIC. DCs of MyD88 KO mice and DCs incubated with SNs containing apyrase did not increase the expression of these activation markers on their surface. The in vivo experiments revealed that zVAD-fmk decreases the tumor growth significantly and results in a significantly reduced tumor infiltration of Tregs when added to multimodal treatment of the tumor with RT, DTIC and HT. Further, a significantly increased DC and CD8+ T-cell infiltration into the tumor and in the draining lymph nodes was induced, as well as an increased expression of IFNγ by CD8+ T cells. However, zVAD-fmk did not further reduce tumor growth in MyD88 KO mice, mice treated with apyrase or RAG KO mice. We conclude that HMGB1, nucleotides and CD8+ T cells mediate zVAD-fmk induced anti-melanoma immune reactions in multimodal therapy settings.

Immune-priming of the tumor microenvironment by radiotherapy: rationale for combination with immunotherapy to improve anticancer efficacy

A clear contribution of the immune system to eradication of tumors has been supported by recent developments in the field of immunotherapy. Durable clinical responses obtained after treatment with immunomodulatory agents such as ipilimumab (Yervoy) and anti-PD-1 antibody (BMS-936558), have established that harnessing the immune response against chemoresistant tumors can result in their complete eradication. However, only a subset of patients benefit from these therapeutic approaches. Accumulating evidence suggests that tumors with a preexisting active immune microenvironment might have a better response to immunotherapy. In a number of preclinical and clinical studies, many cytotoxic agents elicit changes within tumors and their microenvironment that may make these malignant cells more sensitive to an efficient immune cell attack. Therefore, it is plausible that combining immunotherapy with standard anticancer therapies such as chemotherapy or radiotherapy will provide synergistic antitumor effects. Despite a large collection of preclinical data, the immune mechanisms that might contribute to the efficacy of conventional cytotoxic therapies and their combinations with immunotherapeutic approaches have not yet been extensively studied in the clinical setting and warrant further investigation. This review will focus on current knowledge of the immunomodulatory effects of one such cytotoxic treatment, radiotherapy, and explore different pathways by which its combination with immunomodulatory antibodies might contribute toward more efficacious antitumor immunity.

Using chemo-drugs or irradiation to break immune tolerance and facilitate immunotherapy in solid cancer

The immunity is dual host-protective and tumor-promoting in cancer development and progression. Many immune suppressive cells and cytokines in microenvironment can prevent cytotoxic T lymphocytes (CTL) and natural killer cells (NK) from killing tumor cells. Chemotherapy drugs and irradiation have been reported helpful in breaking immune tolerance and creating microenvironment for adoptive cell therapy. Low-dose cyclophosphamide or gemcitabine therapy can selectively deplete T regulatory cells (Treg). Paclitaxel can alter cytokine network at the tumor site, and 5-fluorouracil shows a pronounced effect on myeloid-derived suppressor cells (MDSC) depletion. Local tumor irradiation and total body irradiation (TBI) can also affect tumor microenvironment and facilitate immunotherapy. In this review, we summarize the particular effects of these agents and methods on immunomodulation, as well as their potential values in immunotherapy. The combination with immunotherapy represents a novel therapeutic strategy.

Immunotherapy for head and neck squamous cell carcinoma

OBJECTIVES

To review the current state of immunotherapy of head and neck squamous cell carcinoma.

MATERIALS AND METHODS

Review of the literature with emphasis on clinical trial data.

RESULTS

Patients with head and neck squamous cell carcinoma (HNSCC) have long been known to be immunosuppressed. This impairment of the immune system is believed, at least in part, to underlie the poor outcomes in this patient population. Modulating the immune system to improve cancer outcomes is an attractive concept in this difficult to treat population.

CONCLUSION

New studies have started to unravel the mechanisms of immunosuppression and new therapies are being developed to exploit this new information.

The use of dendritic cells for peptide-based vaccination in cancer immunotherapy

Effective antitumor immunity requires the generation and persistence of functional tumor-specific T-cell responses. Among the critical factors that often control these responses is how the antigen is delivered and presented to T cells. The use of peptide-based vaccination has been found to be a promising means to induce antitumor T-cell responses but with limited effects even if the peptide is co-delivered with a potent adjuvant. This limited response could be due to cancer-induced dysfunction in dendritic cells (DC), which play a central role in shaping the quantity and quality of antitumor immunity. Therefore, DC-based peptide delivery of tumor antigen is becoming a potential approach in cancer immunotherapy. In this approach, autologous DC are generated from their precursors in bone marrow or peripheral blood mononuclear cells, loaded with tumor antigen(s) and then infused back to the tumor-bearing host in about 7 days. This DC-based vaccination can act as an antigen delivery vehicle as well as a potent adjuvant, resulting in measurable antitumor immunity in several cancer settings in preclinical and clinical studies. This chapter focuses on DC-based vaccination and how this approach can be more efficacious in cancer immunotherapy.Effective antitumor immunity requires the generation and persistence of functional tumor-specific T-cell responses. Among the critical factors that often control these responses is how the antigen is delivered and presented to T cells. The use of peptide-based vaccination has been found to be a promising means to induce antitumor T-cell responses but with limited effects even if the peptide is co-delivered with a potent adjuvant. This limited response could be due to cancer-induced dysfunction in dendritic cells (DC), which play a central role in shaping the quantity and quality of antitumor immunity. Therefore, DC-based peptide delivery of tumor antigen is becoming a potential approach in cancer immunotherapy. In this approach, autologous DC are generated from their precursors in bone marrow or peripheral blood mononuclear cells, loaded with tumor antigen(s) and then infused back to the tumor-bearing host in about 7 days. This DC-based vaccination can act as an antigen delivery vehicle as well as a potent adjuvant, resulting in measurable antitumor immunity in several cancer settings in preclinical and clinical studies. This chapter focuses on DC-based vaccination and how this approach can be more efficacious in cancer immunotherapy.

The impact of radiation therapy on the antitumor immunity: local effects and systemic consequences

The main antitumor efficacy of irradiation relies in its direct cytotoxic effect. Increasing evidence indicates a systemic effect of radiation though, mediated mainly by the immune system. In this review we wish to focus on the radiotherapy induced modifications of the soluble and cellular mediators of the antitumor immune response and summarize some of the mechanisms by which radiation driven local and systemic bystander effects can influence tumor immunogenicity. In different tumor types due to the intrinsic immunogenicity of the tumor cells and the immunological characteristics of the tumor microenvironment, different radiation induced immune modulatory mechanisms are predominant. Radiation most probably can only amplify or augment a pro-immunogenic phenotype and can hardly change by itself a net immune suppressing environment into an immune stimulating one. This immune modulatory potential of radiotherapy could be exploited in tumor treatment by developing combined radiotherapeutic and immunotherapeutic approaches. The last few years showed a dramatic increase in the knowledge of radiation induced out-of field and systemic effects, which foresees a rapid progress in the development and clinical application of these new, combined therapies for cancer cure.

The application of radiation therapy to the Pediatric Preclinical Testing Program (PPTP): results of a pilot study in rhabdomyosarcoma

BACKGROUND

The Pediatric Preclinical Testing Program (PPTP) has been successfully used to determine the efficacy of novel agents against solid tumors by testing them within a mouse-flank in vivo model. To date, radiation therapy has not been applied to this system. We report on the feasibility and biologic outcomes of a pilot study using alveolar and embryonal rhabdomyosarcoma xenograft lines.

PROCEDURES

We developed a high-throughput mouse-flank irradiation device that allows the safe delivery of radiotherapy in clinically relevant doses. For our pilot study, two rhabdomyosarcoma xenograft lines from the PPTP, Rh30 (alveolar) and Rh18 (embryonal) were selected. Using established methods, xenografts were implanted, grown to appropriate volumes, and were subjected to fractionated radiotherapy. Tumor response-rates, growth kinetics, and event-free survival time were measured.

RESULTS

Once optimized, the rate of acute toxicity requiring early removal from study in 93 mice was only 3%. During the optimization phase, it was observed that the alveolar Rh30 xenograft line demonstrated a significantly greater radiation resistance than embryonal Rh18 in vivo. This finding was validated within the standardized 30 Gy treatment phase, resulting in overall treatment failure rates of 10% versus 60% for the embryonal versus alveolar subtype, respectively.

CONCLUSIONS

Our pilot study demonstrated the feasibility of our device which enables safe, clinically relevant focal radiation delivery to immunocompromised mice. It further recapitulated the expected clinical radiobiology.

Partial depletion of regulatory T cells does not influence the inflammation caused by high dose hemi-body irradiation

There is clinical interest in the modulation of regulatory T cells for cancer therapy. The safety of these therapies in combination with conventional anti-cancer therapies, including radiation therapy, can be studied in animal models. The effects of partial depletion of regulatory T (Treg) cells with an anti-CD25 antibody in conjunction with ionizing radiation on inflammation and tissue injury were analyzed in C57BL/6 mice. An anti-CD25 antibody (PC61) was administered 3 days prior to 13 Gy lower-half hemi-body irradiation (HBI). The blood, spleen, mesenteric lymph nodes (mLNs) and inguinal lymph nodes (iLNs) were harvested at various times thereafter. Alterations in the proportion of leukocyte subsets including CD4⁺ T cells, CD8⁺ T cells, Treg cells, B cells, NK cells, NK1.1⁺ T cells, macrophages and granulocytes were analyzed by FACS. The lungs, liver, pancreas, stomach, jejunum, duodenum, ileum, colon and kidney were harvested and studied by H&E staining. Expression of inflammatory mediators in plasma and tissue were investigated by ELISA. HBI significantly decreased the leukocyte pool though the various leukocyte subsets had different sensitivities to HBI. The administration of PC61 significantly decreased the proportion of Treg cells in spleen, iLN, mLN and blood (reduction of approximately 60%). Irradiation significantly increased the proportion of Treg cells in the spleen, iLN and mLN. HBI induced a systemic inflammatory reaction as demonstrated by increased plasma levels of IL-6, KC/CXCL1 and circulating granulocytes in the blood. Neutrophils also infiltrated the small bowel. The same general patterns were observed whether or not Treg cells were partially depleted with PC61 prior to HBI. These data demonstrate that partial depletion of Treg cells in these mice does not influence HBI-induced inflammatory response and tissue injury, and that combining anti-CD25 therapy with radiation may be safe and well tolerated in a clinical setting.

In vivo screening of S100B inhibitors for melanoma therapy

S100 proteins are markers for numerous cancers, and in many cases high S100 protein levels are a prognostic indicator for poor survival. One such case is S100B, which is overproduced in a very large percentage of malignant melanoma cases. Elevated S100B protein was more recently validated to have causative effects towards cancer progression via down-regulating the tumor suppressor protein, p53. Towards eliminating this problem in melanoma, targeting S100B with small molecule inhibitors was initiated. This work relies on numerous chemical biology technologies including structural biology, computer-aided drug design, compound screening, and medicinal chemistry approaches. Another important component of drug development is the ability to test compounds and various molecular scaffolds for their efficacy in vivo. This chapter briefly describes the development of S100B inhibitors, termed SBiXs, for melanoma therapy with a focus on the inclusion of in vivo screening at an early stage in the drug discovery process.

Radiation therapy and immunotherapy: implications for a combined cancer treatment

Ionizing radiation (IR) is used as primary treatment for numerous localized cancers. Although it is usually described as an immunosuppressive modality, there are new preclinical evidences suggesting that IR could have also generated substantial changes in the tumor microenvironment, including triggering an inflammatory process. This finding implies that radiotherapy could both modulate tumor immunity and have out-of-field activity by recruiting biological effectors. There are numerous uncertainties regarding the true biological impact of radiation on tumor immunogenicity, but some preclinical studies established the proof of concept that combining IR with strategies modifying immunology could enhance antitumor effects. From these findings, clinical trials are now analyzing how immunotherapy and radiation work while given together, with promising preliminary results. This review aims at summarizing the recent developments regarding the impact of IR on tumor immunity, with focus on potential therapeutic targets.

Cancer stem cell vaccination confers significant antitumor immunity

Most studies of cancer stem cells (CSC) involve the inoculation of cells from human tumors into immunosuppressed mice, preventing an assessment on the immunologic interactions and effects of CSCs. In this study, we examined the vaccination effects produced by CSC-enriched populations from histologically distinct murine tumors after their inoculation into different syngeneic immunocompetent hosts. Enriched CSCs were immunogenic and more effective as an antigen source than unselected tumor cells in inducing protective antitumor immunity. Immune sera from CSC-vaccinated hosts contained high levels of IgG which bound to CSCs, resulting in CSC lysis in the presence of complement. CTLs generated from peripheral blood mononuclear cells or splenocytes harvested from CSC-vaccinated hosts were capable of killing CSCs in vitro. Mechanistic investigations established that CSC-primed antibodies and T cells were capable of selective targeting CSCs and conferring antitumor immunity. Together, these proof-of-concept results provide a rationale for a new type of cancer immunotherapy based on the development of CSC vaccines that can specifically target CSCs.

Combination of external beam radiotherapy (EBRT) with intratumoral injection of dendritic cells as neo-adjuvant treatment of high-risk soft tissue sarcoma patients

PURPOSE

The goal of this study was to determine the effect of combination of intratumoral administration of dendritic cells (DC) and fractionated external beam radiation (EBRT) on tumor-specific immune responses in patients with soft-tissue sarcoma (STS).

METHODS AND MATERIAL

Seventeen patients with large (>5 cm) high-grade STS were enrolled in the study. They were treated in the neoadjuvant setting with 5,040 cGy of EBRT, split into 28 fractions and delivered 5 days per week, combined with intratumoral injection of 10(7) DCs followed by complete resection. DCs were injected on the second, third, and fourth Friday of the treatment cycle. Clinical evaluation and immunological assessments were performed.

RESULTS

The treatment was well tolerated. No patient had tumor-specific immune responses before combined EBRT/DC therapy; 9 patients (52.9%) developed tumor-specific immune responses, which lasted from 11 to 42 weeks. Twelve of 17 patients (70.6%) were progression free after 1 year. Treatment caused a dramatic accumulation of T cells in the tumor. The presence of CD4(+) T cells in the tumor positively correlated with tumor-specific immune responses that developed following combined therapy. Accumulation of myeloid-derived suppressor cells but not regulatory T cells negatively correlated with the development of tumor-specific immune responses. Experiments with (111)In labeled DCs demonstrated that these antigen presenting cells need at least 48 h to start migrating from tumor site.

CONCLUSIONS

Combination of intratumoral DC administration with EBRT was safe and resulted in induction of antitumor immune responses. This suggests that this therapy is promising and needs further testing in clinical trials design to assess clinical efficacy.

Combination approaches to immunotherapy: the radiotherapy example

The marquee cell of the immune response, the T lymphocyte, is exquisitely sensitive to ionizing radiation. Moreover, the majority of cells of the hematopoietic lineage, with their high turnover and radiation sensitivity, are effectively ablated by relatively low radiation doses, such that total-body irradiation is an effective immunosuppressive therapy. Despite and sometimes because of these facts, the immune system may underlie some portion of the therapeutic effects of radiation. In this review, we will discuss these processes, and go on to discuss current therapies combining radiation therapy with immunotherapy for the treatment of cancer.

The tumor-immune microenvironment and response to radiation therapy

Chemotherapy and radiation therapy (RT) are standard therapeutic modalities for patients with cancer, including breast cancer. Historic studies examining tissue and cellular responses to RT have predominantly focused on damage caused to proliferating malignant cells leading to their death. However, there is increasing evidence that RT also leads to significant alterations in the tumor microenvironment, particularly with respect to effects on immune cells infiltrating tumors. This review focuses on tumor-associated immune cell responses following RT and discusses how immune responses may be modified to enhance durability and efficacy of RT.

Immunotherapy of head and neck cancer: current and future considerations

Patients with head and neck squamous cell carcinoma (HNSCC) are at considerable risk for death, with 5-year relative survival rates of approximately 60%. The profound multifaceted deficiencies in cell-mediated immunity that persist in most patients after treatment may be related to the high rates of treatment failure and second primary malignancies. Radiotherapy and chemoradiotherapy commonly have severe acute and long-term side effects on immune responses. The development of immunotherapies reflects growing awareness that certain immune system deficiencies specific to HNSCC and some other cancers may contribute to the poor long-term outcomes. Systemic cell-mediated immunotherapy is intended to activate the entire immune system and mount a systemic and/or locoregional antitumor response. The delivery of cytokines, either by single cytokines, for example, interleukin-2, interleukin-12, interferon-γ, interferon-α, or by a biologic mix of multiple cytokines, such as IRX-2, may result in tumor rejection and durable immune responses. Targeted immunotherapy makes use of monoclonal antibodies or vaccines. All immunotherapies for HNSCC except cetuximab remain investigational, but a number of agents whose efficacy and tolerability are promising have entered phase 2 or phase 3 development.