Combination approaches to immunotherapy: the radiotherapy example

Dendritic Cells and Cancer Immunotherapy: The Adjuvant Effect

Dendritic cells (DCs) are immune specialized cells playing a critical role in promoting immune response against antigens, and may represent important targets for therapeutic interventions in cancer. DCs can be stimulated ex vivo with pro-inflammatory molecules and loaded with tumor-specific antigen(s). Protocols describing the specific details of DCs vaccination manufacturing vary widely, but regardless of the employed protocol, the DCs vaccination safety and its ability to induce antitumor responses is clearly established. Many years of studies have focused on the ability of DCs to provide overall survival benefits at least for a selection of cancer patients. Lessons learned from early trials lead to the hypothesis that, to improve the efficacy of DCs-based immunotherapy, this should be combined with other treatments. Thus, the vaccine’s ultimate role may lie in the combinatorial approaches of DCs-based immunotherapy with chemotherapy and radiotherapy, more than in monotherapy. In this review, we address some key questions regarding the integration of DCs vaccination with multimodality therapy approaches for cancer treatment paradigms.

Hyperprogression After Immunotherapy for Primary Small Cell Neuroendocrine Carcinoma of the Ureter: A Case Report

Background

Primary small cell neuroendocrine carcinoma (SCNEC) in the ureter is extremely rare and has been sporadically reported in case reports. Its incidence, diagnosis, treatment, and outcomes have not yet been thoroughly understood. Here we present a patient with advanced SCNEC in the ureter who was treated by multimodal strategies. To the best of our knowledge, this is the first literature report about the clinical outcomes of the combination of programmed death ligand 1 (PD-L1) immune checkpoint inhibitors (ICIs) and radiotherapy in patient with primary ureteral SCNEC.

Case Presentation

A 71-year old male presented with right flank pain and gross hematuria. A laparoscopic right nephroureterectomy was performed. He was diagnosed with primary ureteral SCNEC, pT3N0M0. Following the surgery, 4 cycles of adjuvant chemotherapy with carboplatin and etoposide (CE) were administered, with disease-free survival (DFS) of 10.1 months. He was then offered 4 cycles of palliative first-line chemotherapy with nedaplatin and irinotecan. The disease was continuously progressed, with progression-free survival (PFS) of 3.7 months. The patient subsequently received second-line treatment with PD-L1 ICI combined with radiotherapy. Unfortunately, hyperprogressive disease was found at the end of treatment. MRI and CT scan showed bilateral pubic bones, right acetabulum, and liver metastases. Without further intervention, the patient died from extensive metastatic disease 2 months after diagnosis, with overall survival (OS) of 18.2 months.

Conclusion

Physicians must be aware of this rare and aggressive carcinoma at its initial presentation. Special attention should be paid to the potential likelihood of hyperprogression during the treatment.

Using Preclinical Data to Design Combination Clinical Trials of Radiation Therapy and Immunotherapy

Immunotherapies are rapidly entering the clinic as approved treatments for diverse cancer pathologies. Radiation therapy is an integral partner in cancer therapy, commonly as part of complicated multimodality approaches that optimize patient outcomes. Preclinical studies have demonstrated that the success of radiation therapy in tumor control is due in part to immune mechanisms, and that outcomes following radiation therapy can be improved through combination with a range of immunotherapies. However, preclinical models of cancer are very different from patient tumors, and the way these preclinical tumors are treated is often very different from standard of care treatment of patients. This review examines the preclinical and clinical data for the role of the immune system in radiation therapy outcomes, and how to integrate preclinical findings into clinical trials, using ongoing studies as examples.

Role of the immunosuppressive microenvironment in immunotherapy

Immunotherapy is reshaping cancer treatment paradigms; however, response rates to immune therapies are low and depend on the host's pre-existing antitumor immunity. The tumor microenvironment is comprised of malignant cells, stroma, and extracellular molecules and can hinder immune control of tumors. Herein, we review how anti-tumor immune responses are formed and how tumors avoid immune destruction. We also outline potential therapeutic targets in the immunosuppressive tumor microenvironment to promote immune control of tumors.

Development of immunotherapy in bladder cancer: present and future on targeting PD(L)1 and CTLA-4 pathways

PURPOSE

Over the past 3 decades, no major treatment breakthrough has been reported for advanced bladder cancer. Recent Food and Drug Administration (FDA) approval of five immune checkpoint inhibitors in the management of advanced bladder cancer represent new therapeutic opportunities. This review examines the available data of the clinical trials leading to the approval of ICIs in the management of metastatic bladder cancer and the ongoing trials in advanced and localized settings.

METHODS

A literature search was performed on PubMed and ClinicalTrials.gov combining the MeSH terms: 'urothelial carcinoma' OR 'bladder cancer', and 'immunotherapy' OR 'CTLA-4' OR 'PD-1' OR 'PD-L1' OR 'atezolizumab' OR 'nivolumab' OR 'ipilimumab' OR 'pembrolizumab' OR 'avelumab' OR 'durvalumab' OR 'tremelimumab'. Prospectives studies evaluating anti-PD(L)1 and anti-CTLA-4 monoclonal antibodies were included.

RESULTS

Evidence-data related to early phase and phase III trials evaluating the 5 ICIs in the advanced urothelial carcinoma are detailed in this review. Anti-tumour activity of the 5 ICIs supporting the FDA approval in the second-line setting are reported. The activity of PD(L)1 inhibitors in the first-line setting in cisplatin-ineligible patients are also presented. Ongoing trials in earlier disease-states including non-muscle-invasive and muscle-invasive bladder cancer are discussed.

CONCLUSIONS

Blocking the PD-1 negative immune receptor or its ligand, PD-L1, results in unprecedented rates of anti-tumour activity in patients with metastatic urothelial cancer. However, a large majority of patients do not respond to anti-PD(L)1 drugs monotherapy. Investigations exploring the potential value of predictive biomarkers, optimal combination and sequences are ongoing to improve such treatment strategies.

The synergy between ionizing radiation and immunotherapy in the treatment of prostate cancer

There has been a surge in the use of immunotherapy for genitourinary malignancies. Immunotherapy is an established treatment for metastatic renal cell carcinoma and nonmuscle invasive bladder cancer, but its potential for treating prostate cancer (PCa) remains under investigation. Despite reported survival benefits, no published Phase III PCa trials using immunotherapy only as a treatment has demonstrated direct antitumor effects by reducing prostate-specific antigen levels. Subsequently, the thought of combining immunotherapy with other treatment modalities has gained traction as a way to achieving optimal results. Based on data from other malignancies, it is hypothesized that radiotherapy and immunotherapy can act synergistically to improve outcomes. We will discuss the clinical potential of combining immune-based treatments with radiotherapy as a treatment for advanced PCa.

Comparative analysis of the effect of different radiotherapy regimes on lymphocyte and its subpopulations in breast cancer patients

PURPOSE

The aim of this study was to determine whether different radiotherapy (RT) fractionation schemes induce disparate effects on lymphocyte and its subsets in breast cancer patients.

METHODS

60 female patients diagnosed with breast cancer were recruited in this study after receiving modified radical mastectomy and were randomly divided into two groups. One group received irradiation at a standard dose of 50 Gy in 25 fractions and the other at a dose of 40.3 Gy in 13 fractions. Both total lymphocyte count and its composition were recorded at three timepoints: right before the radiation treatment (T0), immediately after the last fraction of radiotherapy (T1) and 6 months after irradiation therapy ended (T2).

RESULTS

Both groups experienced temporal lymphopenia after finishing local radiation (T1) (13F T0 vs. T1 1570.6 ± 243.9 vs. 940.6 ± 141.8, **p < 0.01; 25F T0 vs. T1 1620.5 ± 280.2 vs. 948.5 ± 274.6, **p < 0.01), while the lymphocyte count recovered at follow-up time (T2), and the cell count in the hypofractionation group (13F) was higher than the standard fraction group (25F) (13F vs. 25F 1725.6 ± 225.6 vs. 1657.5 ± 242.4, *p < 0.05). With respect to the composition of lymphocyte, we found T cell, B cell, and NK cell reacted differently to different radiotherapy protocols.

CONCLUSIONS

Different RT protocols impose different impacts on immunity, leading us to further explore the optimal radiotherapy regimes to synergy with immunotherapy.

Mertk on tumor macrophages is a therapeutic target to prevent tumor recurrence following radiation therapy

Radiation therapy provides a means to kill large numbers of cancer cells in a controlled location resulting in the release of tumor-specific antigens and endogenous adjuvants. However, by activating pathways involved in apoptotic cell recognition and phagocytosis, irradiated cancer cells engender suppressive phenotypes in macrophages. We demonstrate that the macrophage-specific phagocytic receptor, Mertk is upregulated in macrophages in the tumor following radiation therapy. Ligation of Mertk on macrophages results in anti-inflammatory cytokine responses via NF-kB p50 upregulation, which in turn limits tumor control following radiation therapy. We demonstrate that in immunogenic tumors, loss of Mertk is sufficient to permit tumor cure following radiation therapy. However, in poorly immunogenic tumors, TGFβ inhibition is also required to result in tumor cure following radiation therapy. These data demonstrate that Mertk is a highly specific target whose absence permits tumor control in combination with radiation therapy.

Stereotactic Radiotherapy Increases Functionally Suppressive Regulatory T Cells in the Tumor Microenvironment

Radiotherapy (RT) enhances innate and adaptive antitumor immunity; however, the effects of radiation on suppressive immune cells, such as regulatory T cells (Treg), in the tumor microenvironment (TME) are not fully elucidated. Although previous reports suggest an increased Treg infiltration after radiation, whether these Tregs are functionally suppressive remains undetermined. To test the hypothesis that RT enhances the suppressive function of Treg in the TME, we selectively irradiated implanted tumors using the small animal radiation research platform (SARRP), which models stereotactic radiotherapy in human patients. We then analyzed tumor-infiltrating lymphocytes (TIL) with flow-cytometry and functional assays. Our data showed that RT significantly increased tumor-infiltrating Tregs (TIL-Treg), which had higher expression of CTLA-4, 4-1BB, and Helios compared with Tregs in nonirradiated tumors. This observation held true across several tumor models (B16/F10, RENCA, and MC38). We found that TIL-Tregs from irradiated tumors had equal or improved suppressive capacity compared with nonirradiated tumors. Our data also indicated that after RT, Tregs proliferated more robustly than other T-cell subsets in the TME. In addition, after RT, expansion of Tregs occurred when T-cell migration was inhibited using Fingolimod, suggesting that the increased Treg frequency was likely due to preferential proliferation of intratumoral Treg after radiation. Our data also suggested that Treg expansion after irradiation was independent of TGFβ and IL33 signaling. These data demonstrate that RT increased phenotypically and functionally suppressive Tregs in the TME. Our results suggest that RT might be combined effectively with Treg-targeting agents to maximize antitumor efficacy. Cancer Immunol Res; 5(11); 992-1004. ©2017 AACR.

Dose-dependent enhancement of T-lymphocyte priming and CTL lysis following ionizing radiation in an engineered model of oral cancer

OBJECTIVES

Determine if direct tumor cell cytotoxicity, antigen release, and susceptibility to T-lymphocyte killing following radiation treatment is dose-dependent.

MATERIALS AND METHODS

Mouse oral cancer cells were engineered to express full-length ovalbumin as a model antigen. Tumor antigen release with uptake and cross presentation of antigen by antigen presenting cells with subsequent priming and expansion of antigen-specific T-lymphocytes following radiation was modeled in vitro and in vivo. T-lymphocyte mediated killing was measured following radiation treatment using a novel impedance-based cytotoxicity assay.

RESULTS

Radiation treatment induced dose-dependent induction of executioner caspase activity and apoptosis in MOC1 cells. In vitro modeling of antigen release and T-lymphocyte priming demonstrated enhanced proliferation of OT-1 T-lymphocytes with 8Gy treatment of MOC1ova cells compared to 2Gy. This was validated in vivo following treatment of established MOC1ova tumors and adoptive transfer of antigen-specific T-lymphocytes. Using a novel impedance-based cytotoxicity assay, 8Gy enhanced tumor cell susceptibility to T-lymphocyte killing to a greater degree than 2Gy.

CONCLUSION

In the context of using clinically-relevant doses of radiation treatment as an adjuvant for immunotherapy, 8Gy is superior to 2Gy for induction of antigen-specific immune responses and enhancing tumor cell susceptibility to T-lymphocyte killing. These findings have significant implications for the design of trials combining radiation and immunotherapy.

Immune Checkpoint Modulators: An Emerging Antiglioma Armamentarium

Immune checkpoints have come to the forefront of cancer therapies as a powerful and promising strategy to stimulate antitumor T cell activity. Results from recent preclinical and clinical studies demonstrate how checkpoint inhibition can be utilized to prevent tumor immune evasion and both local and systemic immune suppression. This review encompasses the key immune checkpoints that have been found to play a role in tumorigenesis and, more specifically, gliomagenesis. The review will provide an overview of the existing preclinical and clinical data, antitumor efficacy, and clinical applications for each checkpoint with respect to GBM, as well as a summary of combination therapies with chemotherapy and radiation.

Concepts of immunotherapy for glioma

Immunotherapy is coming to the fore as a viable anti-cancer treatment modality, even in poorly immunogenic cancers such as glioblastoma (GBM). Accumulating evidence suggests that the central nervous system may not be impervious to tumor-specific immune cells and could be an adequate substrate for immunologic anti-cancer therapies. Recent advances in antigen-specific cancer vaccines and checkpoint blockade in GBM provide promise for future immunotherapy in glioma. As anti-GBM immunotherapeutics enter clinical trials, it is important to understand the interactions, if any, between immune-based treatment modalities and the current standard of care for GBM involving chemoradiation and steroid therapy. Current data suggests that chemoradiation may not preclude the success of immunotherapeutics, as their effects may be synergistic. The future of therapy for GBM lies in the power of combination modalities, involving immunotherapy and the current standard of care.

The future of glioblastoma therapy: synergism of standard of care and immunotherapy

The current standard of care for glioblastoma (GBM) is maximal surgical resection with adjuvant radiotherapy and temozolomide (TMZ). As the 5-year survival with GBM remains at a dismal <10%, novel therapies are needed. Immunotherapies such as the dendritic cell (DC) vaccine, heat shock protein vaccines, and epidermal growth factor receptor (EGFRvIII) vaccines have shown encouraging results in clinical trials, and have demonstrated synergistic effects with conventional therapeutics resulting in ongoing phase III trials. Chemoradiation has been shown to have synergistic effects when used in combination with immunotherapy. Cytotoxic ionizing radiation is known to trigger pro-inflammatory signaling cascades and immune activation secondary to cell death, which can then be exploited by immunotherapies. The future of GBM therapeutics will involve finding the place for immunotherapy in the current treatment regimen with a focus on developing strategies. Here, we review current GBM therapy and the evidence for combination of immune checkpoint inhibitors, DC and peptide vaccines with the current standard of care.

Radiation-induced autophagy potentiates immunotherapy of cancer via up-regulation of mannose 6-phosphate receptor on tumor cells in mice

There is a significant body of evidence demonstrating that radiation therapy (XRT) enhances the effect of immune therapy. However, the precise mechanisms by which XRT potentiates the immunotherapy of cancer remain elusive. Here, we report that XRT potentiates the effect of immune therapy via induction of autophagy and resultant trafficking of mannose-6-phopsphate receptor (MPR) to the cell surface. Irradiation of different tumor cells caused substantial up-regulation of MPR on the cell surface in vitro and in vivo. Down-regulation of MPR in tumor cells with shRNA completely abrogated the combined effect of XRT and immunotherapy (CTLA4 antibody) in B16F10-bearing mice without changes in the tumor-specific responses of T cells. Radiation-induced MPR up-regulation was the result of redistribution of the receptor to the cell surface. This effect was caused by autophagy with redirection of MPR to autophagosomes in a clathrin-dependent manner. In autophagosomes, MPR lost its natural ligands, which resulted in subsequent trafficking of empty receptor(s) back to the surface. Together, our data demonstrated a novel mechanism by which XRT can enhance the effect of immunotherapy and the molecular mechanism of this process.

Strategies for optimizing the response of cancer and normal tissues to radiation

Approximately 50% of all patients with cancer receive radiation therapy at some point during the course of their treatment, and the majority of these patients are treated with curative intent. Despite recent advances in the planning of radiation treatment and the delivery of image-guided radiation therapy, acute toxicity and potential long-term side effects often limit the ability to deliver a sufficient dose of radiation to control tumours locally. In the past two decades, a better understanding of the hallmarks of cancer and the discovery of specific signalling pathways by which cells respond to radiation have provided new opportunities to design molecularly targeted therapies to increase the therapeutic window of radiation therapy. Here, we review efforts to develop approaches that could improve outcomes with radiation therapy by increasing the probability of tumour cure or by decreasing normal tissue toxicity.

Trial Watch: Anticancer radioimmunotherapy

Radiotherapy has extensively been employed as a curative or palliative intervention against cancer throughout the last century, with a varying degree of success. For a long time, the antineoplastic activity of X- and γ-rays was entirely ascribed to their capacity of damaging macromolecules, in particular DNA, and hence triggering the (apoptotic) demise of malignant cells. However, accumulating evidence indicates that (at least part of) the clinical potential of radiotherapy stems from cancer cell-extrinsic mechanisms, including the normalization of tumor vasculature as well as short- and long-range bystander effects. Local bystander effects involve either the direct transmission of lethal signals between cells connected by gap junctions or the production of diffusible cytotoxic mediators, including reactive oxygen species, nitric oxide and cytokines. Conversely, long-range bystander effects, also known as out-of-field or abscopal effects, presumably reflect the elicitation of tumor-specific adaptive immune responses. Ionizing rays have indeed been shown to promote the immunogenic demise of malignant cells, a process that relies on the spatiotemporally defined emanation of specific damage-associated molecular patterns (DAMPs). Thus, irradiation reportedly improves the clinical efficacy of other treatment modalities such as surgery (both in neo-adjuvant and adjuvant settings) or chemotherapy. Moreover, at least under some circumstances, radiotherapy may potentiate anticancer immune responses as elicited by various immunotherapeutic agents, including (but presumably not limited to) immunomodulatory monoclonal antibodies, cancer-specific vaccines, dendritic cell-based interventions and Toll-like receptor agonists. Here, we review the rationale of using radiotherapy, alone or combined with immunomodulatory agents, as a means to elicit or boost anticancer immune responses, and present recent clinical trials investigating the therapeutic potential of this approach in cancer patients.

Multimodality therapy for patients with high-risk prostate cancer: current status and future directions

Prostate cancer is the most commonly diagnosed cancer and second most common cause of cancer death in American men. Although high-risk disease accounts for less than 15% of diagnoses, high-risk prostate cancer patients have a cancer-specific mortality rate of 15% at 10 years. There is currently no consensus on the optimal management of high-risk disease because (1) there are different primary modalities available (ie, surgery, radiation), for which there are no randomized trials comparing efficacy; and (2) unstandardized timing of different therapies (ie, neoadjuvant v concurrent v adjuvant), which makes comparisons of efficacy problematic. Increased understanding into the mechanisms leading to the formation of advanced metastatic disease has spurred the development of agents to target these pathways. However, new questions regarding optimal management of disease arise with regard to the role of these therapies in combination with "conventional" primary modalities for earlier stage, high-risk prostate cancer patients. In this article, we review the transforming world of multimodality therapy in high-risk prostate cancer.

Combining radiotherapy and cancer immunotherapy: a paradigm shift

The therapeutic application of ionizing radiation has been largely based on its cytocidal power combined with the ability to selectively target tumors. Radiotherapy effects on survival of cancer patients are generally interpreted as the consequence of improved local control of the tumor, directly decreasing systemic spread. Experimental data from multiple cancer models have provided sufficient evidence to propose a paradigm shift, whereby some of the effects of ionizing radiation are recognized as contributing to systemic antitumor immunity. Recent examples of objective responses achieved by adding radiotherapy to immunotherapy in metastatic cancer patients support this view. Therefore, the traditional palliative role of radiotherapy in metastatic disease is evolving into that of a powerful adjuvant for immunotherapy. This combination strategy adds to the current anticancer arsenal and offers opportunities to harness the immune system to extend survival, even among metastatic and heavily pretreated cancer patients. We briefly summarize key evidence supporting the role of radiotherapy as an immune adjuvant. A critical appraisal of the current status of knowledge must include potential immunosuppressive effects of radiation that can hamper its capacity to convert the irradiated tumor into an in situ, individualized vaccine. Moreover, we discuss some of the current challenges to translate this knowledge to the clinic as more trials testing radiation with different immunotherapies are proposed.

Targeting the tumor microenvironment by immunotherapy: part 2

Cancer therapy was traditionally centered on the neoplastic cells. This included mainly surgery, radiation, and chemotherapy, in some cases hormone therapy and to a lesser extent immunotherapy – all traditionally targeted to the highly proliferating mutated tumor cells. In view of our present understanding of the powerfull influence of the tumor microenvironment (TME) on cancer behavior and response – and lack of response – to treatment, this previously ignored constituent of cancer now has to be considered as an important, even indispensable target for therapy. The TME may be targeted both to its immune and to its nonimmune components. The various immune evasion elements of the TME should be targeted as well.

On the selectivity and efficacy of defense peptides with respect to cancer cells

Here, we review potential determinants of the anticancer efficacy of innate immune peptides (ACPs) for cancer cells. These determinants include membrane-based factors, such as receptors, phosphatidylserine, sialic acid residues, and sulfated glycans, and peptide-based factors, such as residue composition, sequence length, net charge, hydrophobic arc size, hydrophobicity, and amphiphilicity. Each of these factors may contribute to the anticancer action of ACPs, but no single factor(s) makes an overriding contribution to their overall selectivity and toxicity. Differences between the anticancer actions of ACPs seem to relate to different levels of interplay between these peptide and membrane-based factors.