Beyond checkpoint inhibition - Immunotherapeutical strategies in combination with radiation

Neoadjuvant chemoradiotherapy up-regulates PD-L1 in radioresistant colorectal cancer

Background

Combining radiotherapy (RT) with immune checkpoint inhibitors (ICIs) is a promising strategy that can enhance the therapeutic efficacy of ICIs. However, little is known about RT-induced changes in the expression of immune checkpoints, such as PD-L1, and their clinical implications in colorectal cancer (CRC). This study aimed to investigate the association between responsiveness to RT and changes in PD-L1 expression in human CRC tissue and cell lines.

Methods

Tissue specimens from preoperative biopsy via sigmoidoscopy and surgical resection were obtained from 24 patients with locally advanced rectal cancer (LARC) who underwent neoadjuvant chemoradiation therapy (CRT) between August 2016 and December 2017. Immunohistochemistry for PD-L1 in formalin-fixed paraffin-embedded tissue was performed from the endoscopic biopsy and surgical specimens. RNA sequencing was performed using 11 pairs of human LARC tissues before and after irradiation. After exposing human CRC cells to radiation, we investigated changes in the expression levels of PD-L1 and its regulatory signaling pathways.

Results

Patients were classified by tumor regression grade into responders (grade 2; 9 patients, 37.5 %) and non-responders (grades 3, 4, or 5; 15 patients, 62.5 %). In the non-responder group, 13 patients had low PD-L1 expression, but neoadjuvant CRT increased PD-L1 expression in 7 patients (53.9 %) (McNemar's test, p=0.034). CRT up-regulated PD-L1 in non-responder LARC tissues. Similarly, radiation increased PD-L1 in radioresistant DLD-1 cells more than in radiosensitive HCT116 cells, also affecting PD-L1-regulating genes and immune checkpoints in CRC cells. Conventional fractionated radiation treatment further increased PD-L1 in DLD-1 cells compared to HCT116 cells.

Conclusions

This study demonstrated that radiation induces an increase in PD-L1 expression, which is more pronounced in radioresistant CRC, proving the theoretical framework for a combined treatment strategy with a PD-L1 blockade for locally advanced rectal cancer.

Case report: Interstitial implantation radiotherapy combined with immunotherapy and GM-CSF in oligometastatic platinum-resistant ovarian cancer

Background

Treatment for platinum-resistant ovarian cancer is challenging. Currently, platinum-resistant ovarian cancer is typically treated with non-platinum single-agent chemotherapy ± bevacizumab, but the prognosis is often extremely poor. In the treatment of platinum-resistant ovarian cancer patients, reports of triple therapy with interstitial implantation radiotherapy combined with immunotherapy and granulocyte-macrophage colony-stimulating factor (GM-CSF) (PRaG for short) are relatively rare.

Case description

Here, we report a patient with oligometastatic platinum-resistant ovarian cancer. The patient achieved partial response (PR) of the lesion and sustained benefit for more than six months after receiving interstitial implantation radiotherapy combined with immunotherapy along with GM-CSF.

Conclusion

This triple therapy may provide additional options for these patients.

Biological Bases of Immune-Related Adverse Events and Potential Crosslinks With Immunogenic Effects of Radiation

Immune checkpoint inhibitors have gained an established role in the treatment of different tumors. Indeed, their use has dramatically changed the landscape of cancer care, especially for tumor types traditionally known to have poor outcomes. However, stimulating anticancer immune responses may also elicit an unusual pattern of immune-related adverse events (irAEs), different from those of conventional chemotherapy, likely due to a self-tolerance impairment featuring the production of autoreactive lymphocytes and autoantibodies, or a non-specific autoinflammatory reaction. Ionizing radiation has proven to promote both positive pro-inflammatory and immunostimolatory activities, and negative anti-inflammatory and immunosuppressive mechanisms, as a result of cross-linked interactions among radiation dose, the tumor microenvironment and the host genetic predisposition. Several publications argue in favor of combining immunotherapy and a broad range of radiation schedules, based on the recent evidence of superior treatment responses and patient survival. The synergistic modulation of the immune response by radiation therapy and immunotherapeutics, particularly those manipulating T-cell activation, may also affect the type and severity of irAEs, suggesting a relationship between the positive antitumor and adverse autoimmune effects of these agents. As yet, information on factors that may help to predict immune toxicity is still lacking. The aim of our work is to provide an overview of the biological mechanisms underlying irAEs and possible crosslinks with radiation-induced anticancer immune responses. We believe such an overview may support the optimization of immunotherapy and radiotherapy as essential components of multimodal anticancer therapeutic approaches. Challenges in translating these to clinical practice are discussed.

Changes in Blood Biomarkers of Angiogenesis and Immune Modulation after Radiation Therapy and Their Association with Outcomes in Thoracic Malignancies

The effects of radiotherapy on systemic immunity remain to be fully characterized in a disease-specific manner. The aim of the study was to examine potential biomarkers of systemic immunomodulation when using radiotherapy for thoracic malignancies. Serial blood samples were collected from 56 patients with thoracic malignancies prior (RTbaseline), during (RTduring) and at the end of radiotherapy (RTend), as well as at the first (FU1) and second follow-up (FU2). The changes in serum levels of IL-10, IFN-γ, IL-12p70, IL-13, IL-1β, IL-4, IL-6, IL-8, TNF-α, bFGF, sFlt-1, PlGF, VEGF, VEGF-C, VEGF-D and HGF were measured by multiplexed array and tested for associations with clinical outcomes. We observed an increase in the levels of IL-10, IFN-γ, PlGF and VEGF-D and a decrease in those of IL-8, VEGF, VEGF-C and sFlt-1 during and at the end of radiotherapy. Furthermore, baseline concentration of TNF-α significantly correlated with OS. IL-6 level at RTend and FU1,2 correlated with OS (RTend: p = 0.039, HR: 1.041, 95% CI: 1.002-1.082, FU1: p = 0.001, HR: 1.139, 95% CI: 1.056-1.228, FU2: p = 0.017, HR: 1.101 95% CI: 1.018-1.192), while IL-8 level correlated with OS at RTduring and RTend (RTduring: p = 0.017, HR: 1.014, 95% CI: 1.002-1.026, RTend: p = 0.004, HR: 1.007, 95% CI: 1.061-1.686). In conclusion, serum levels of TNF-α, IL-6 and IL-8 are potential biomarkers of response to radiotherapy. Given the recent implementation of immunotherapy in lung and esophageal cancer, these putative blood biomarkers should be further validated and evaluated in the combination or sequential therapy setting.

Radiotherapy planning parameters correlate with changes in the peripheral immune status of patients undergoing curative radiotherapy for localized prostate cancer

Purpose

The influence of radiotherapy on patient immune cell subsets has been established by several groups. Following a previously published analysis of immune changes during and after curative radiotherapy for prostate cancer, this analysis focused on describing correlations of changes of immune cell subsets with radiation treatment parameters.

Patients and methods

For 13 patients treated in a prospective trial with radiotherapy to the prostate region (primary analysis) and five patients treated with radiotherapy to prostate and pelvic nodal regions (exploratory analysis), already published immune monitoring data were correlated with clinical data as well as radiation planning parameters such as clinical target volume (CTV) and volumes receiving 20 Gy (V20) for newly contoured volumes of pelvic blood vessels and bone marrow.

Results

Most significant changes among immune cell subsets were observed at the end of radiotherapy. In contrast, correlations of age and CD8⁺ subsets (effector and memory cells) were observed early during and 3 months after radiotherapy. Ratios of T cells and T cell proliferation compared to baseline correlated with CTV. Early changes in regulatory T cells (Treg cells) and CD8⁺ effector T cells correlated with V20 of blood vessels and bone volumes.

Conclusions

Patient age as well as radiotherapy planning parameters correlated with immune changes during radiotherapy. Larger irradiated volumes seem to correlate with early suppression of anti-cancer immunity. For immune cell analysis during normofractionated radiotherapy and correlations with treatment planning parameters, different time points should be looked at in future projects.

Trial registration number:

NCT01376674, 20.06.2011

Supplementary Information

The online version contains supplementary material available at 10.1007/s00262-021-03002-6.

Theranostics in Nuclear Medicine: Emerging and Re-emerging Integrated Imaging and Therapies in the Era of Precision Oncology

Theranostics refers to the pairing of diagnostic biomarkers with therapeutic agents that share a specific target in diseased cells or tissues. Nuclear medicine, particularly with regard to applications in oncology, is currently one of the greatest components of the theranostic concept in clinical and research scenarios. Theranostics in nuclear medicine, or nuclear theranostics, refers to the use of radioactive compounds to image biologic phenomena by means of expression of specific disease targets such as cell surface receptors or membrane transporters, and then to use specifically designed agents to deliver ionizing radiation to the tissues that express these targets. The nuclear theranostic approach has sparked increasing interest and gained importance in parallel to the growth in molecular imaging and personalized medicine, helping to provide customized management for various diseases; improving patient selection, prediction of response and toxicity, and determination of prognosis; and avoiding futile and costly diagnostic examinations and treatment of many diseases. The authors provide an overview of theranostic approaches in nuclear medicine, starting with a review of the main concepts and unique features of nuclear theranostics and aided by a retrospective discussion of the progress of theranostic agents since early applications, with illustrative cases emphasizing the imaging features. Advanced concepts regarding the role of fluorine 18-fluorodeoxyglucose PET in theranostics, as well as developments in and future directions of theranostics, are discussed. ^©RSNA, 2020 See discussion on this article by Greenspan and Jadvar.

Biomarkers of Radiotherapy-Induced Immunogenic Cell Death

Radiation therapy (RT) can induce an immunogenic variant of regulated cell death that can initiate clinically relevant tumor-targeting immune responses. Immunogenic cell death (ICD) is accompanied by the exposure and release of damage-associated molecular patterns (DAMPs), chemokine release, and stimulation of type I interferon (IFN-I) responses. In recent years, intensive research has unraveled major mechanistic aspects of RT-induced ICD and has resulted in the identification of immunogenic factors that are released by irradiated tumor cells. However, so far, only a limited number of studies have searched for potential biomarkers that can be used to predict if irradiated tumor cells undergo ICD that can elicit an effective immunogenic anti-tumor response. In this article, we summarize the available literature on potential biomarkers of RT-induced ICD that have been evaluated in cancer patients. Additionally, we discuss the clinical relevance of these findings and important aspects that should be considered in future studies.

Efficacy of Stereotactic Body Radiotherapy in Patients With Hepatocellular Carcinoma Not Suitable for Transarterial Chemoembolization (HERACLES: HEpatocellular Carcinoma Stereotactic RAdiotherapy CLinical Efficacy Study)

The aim of this prospective observational trial was to evaluate the efficacy, toxicity and quality of life after stereotactic body radiation therapy (SBRT) in patients with hepatocellular carcinoma (HCC) and to assess the results of this treatment in comparison to trans-arterial chemoembolization (TACE). Patients with HCC, treated with TACE or SBRT, over a period of 12 months, enrolled in the study. The primary endpoint was feasibility; secondary endpoints were toxicity, quality of life (QOL), local progression (LP) and overall survival (OS). Between 06/2016 and 06/2017, 19 patients received TACE and 20 SBRT, 2 of whom were excluded due to progression. The median follow-up was 31 months. The QOL remained stable before and after treatment and was comparable in both treatment groups. Five patients developed grade ≥ 3 toxicities in the TACE group and 3 in the SBRT group. The cumulative incidence of LP after 1-, 2- and 3-years was 6, 6, 6% in the SBRT group and 28, 39, and 65% in the TACE group (p = 0.02). The 1- and 2- years OS rates were 84% and 47% in the TACE group and 44% and 39% in the SBRT group (p = 0.20). In conclusion, SBRT is a well-tolerated local treatment with a high local control rates and can be safely delivered, while preserving the QOL of HCC patients.

Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches

Anticytotoxic T lymphocyte-associated protein 4 (CTLA4) antibodies have shown potent antitumor activity, but systemic immune activation leads to severe immune-related adverse events, limiting clinical usage. We developed novel, conditionally active biologic (CAB) anti-CTLA4 antibodies that are active only in the acidic tumor microenvironment. In healthy tissue, this binding is reversibly inhibited by a novel mechanism using physiological chemicals as protein-associated chemical switches (PaCS). No enzymes or potentially immunogenic covalent modifications to the antibody are required for activation in the tumor. The novel anti-CTLA4 antibodies show similar efficacy in animal models compared to an analog of a marketed anti-CTLA4 biologic, but have markedly reduced toxicity in nonhuman primates (in combination with an anti-PD1 checkpoint inhibitor), indicating a widened therapeutic index (TI). The PaCS encompass mechanisms that are applicable to a wide array of antibody formats (e.g., ADC, bispecifics) and antigens. Examples shown here include antibodies to EpCAM, Her2, Nectin4, CD73, and CD3. Existing antibodies can be engineered readily to be made sensitive to PaCS, and the inhibitory activity can be optimized for each antigen's varying expression level and tissue distribution. PaCS can modulate diverse physiological molecular interactions and are applicable to various pathologic conditions, enabling differential CAB antibody activities in normal versus disease microenvironments.

Effect of radiotherapy on T cell and PD-1 / PD-L1 blocking therapy in tumor microenvironment

Cancer is a worldwide problem that threatens human health. Radiotherapy plays an important role in a variety of cancer treatment methods. The administration of radiotherapy can alter the differentiation pathways and functions of T cells, which in turn improves the immune response of T cells. Radiotherapy can also induce up-regulation of PD-L1 expression, which means that it has great potential for enhancing the therapeutic effect of anti-PD-1/PD-L1 inhibitors and reducing the risk of drug resistance toward them. At present, the combination of radiotherapy and anti-PD-1/PD-L1 inhibitors has shown significant therapeutic effects in clinical tumor research. This review focuses on the mechanism of radiotherapy on T cells reported in recent years, as well as related research progress in the application of PD-1/PD-L1 blockers. It will provide a theoretical basis for the rational clinical application of radiotherapy combined with PD-1/PD-L1 inhibitors.

The Evolving Role of Radiation Therapy in the Treatment of Biliary Tract Cancer

Biliary tract cancers (BTC) are a disease entity comprising diverse epithelial tumors, which are categorized according to their anatomical location as intrahepatic (iCCA), perihilar (pCCA), distal (dCCA) cholangiocarcinomas, and gallbladder carcinomas (GBC), with distinct epidemiology, biology, and prognosis. Complete surgical resection is the mainstay in operable BTC as it is the only potentially curative treatment option. Nevertheless, even after curative (R0) resection, the 5-year survival rate ranges between 20 and 40% and the disease free survival rates (DFS) is approximately 48–65% after one year and 23–35% after three years without adjuvant treatment. Improvements in adjuvant chemotherapy have improved the DFS, but the role of adjuvant radiotherapy is unclear. On the other hand, more than 50% of the patients present with unresectable disease at the time of diagnosis, which limits the prognosis to a few months without treatment. Herein, we review the role of radiotherapy in the treatment of cholangiocarcinoma in the curative and palliative setting.

UniCAR T cell immunotherapy enables efficient elimination of radioresistant cancer cells

Induction or selection of radioresistant cancer (stem) cells following standard radiotherapy is presumably one of the major causes for recurrence of metastatic disease. One possibility to prevent tumor relapse is the application of targeted immunotherapies including, e.g., chimeric antigen receptor (CAR) T cells. In light of long-term remissions, it is highly relevant to clarify whether radioresistant cancer cells are susceptible to CAR T cell-mediated killing. To answer this question, we evaluated the anti-tumor activity of the switchable universal chimeric antigen receptor (UniCAR) system against highly radioresistant head and neck squamous cell carcinoma cells both in vitro and in vivo. Following specific UniCAR T cell engagement via EGFR or CD98 target modules, T cell effector mechanisms were induced including secretion of pro-inflammatory cytokines, up-regulation of granzyme B and perforin, as well as T cell proliferation. CD98- or EGFR-redirected UniCAR T cells further possess the capability to efficiently lyse radioresistant tumor cells. Observed anti-tumor effects were comparable to those against the radiosensitive parental cell lines. Finally, redirected UniCAR T cells significantly inhibited the growth of radioresistant cancer cells in immunodeficient mice. Taken together, our obtained data underline that the UniCAR system is able to overcome radioresistance. Thus, it represents an attractive technology for the development of combined radioimmunotherapeutic approaches that might improve the outcome of patients with metastatic radioresistant tumor diseases.

Combination of Gas Plasma and Radiotherapy Has Immunostimulatory Potential and Additive Toxicity in Murine Melanoma Cells in Vitro

Despite continuous advances in therapy, malignant melanoma is still among the deadliest types of cancer. At the same time, owing to its high plasticity and immunogenicity, melanoma is regarded as a model tumor entity when testing new treatment approaches. Cold physical plasma is a novel anticancer tool that utilizes a plethora of reactive oxygen species (ROS) being deposited on the target cells and tissues. To test whether plasma treatment would enhance the toxicity of an established antitumor therapy, ionizing radiation, we combined both physical treatment modalities targeting B16F10 murine melanoma cell in vitro. Repeated rather than single radiotherapy, in combination with gas plasma-introduced ROS, induced apoptosis and cell cycle arrest in an additive fashion. In tendency, gas plasma treatment sensitized the cells to subsequent radiotherapy rather than the other way around. This was concomitant with increased levels of TNFα, IL6, and GM-CSF in supernatants. Murine JAWS dendritic cells cultured in these supernatants showed an increased expression of cell surface activation markers, such as MHCII and CD83. For PD-L1 and PD-L2, increased expression was observed. Our results are the first to suggest an additive therapeutic effect of gas plasma and radiotherapy, and translational tumor models are needed to develop this concept further.

A theranostic PSMA ligand for PET imaging and retargeting of T cells expressing the universal chimeric antigen receptor UniCAR

Chimeric antigen receptor (CAR) T cells have shown impressive therapeutic potential. Due to the lack of direct control mechanisms, therapy-related adverse reactions including cytokine release- and tumor lysis syndrome can even become life-threatening. In case of target antigen expression on non-malignant cells, CAR T cells can also attack healthy tissues. To overcome such side effects, we have established a modular CAR platform termed UniCAR: UniCAR T cells per se are inert as they recognize a peptide epitope (UniCAR epitope) that is not accessible on the surface of living cells. Bifunctional adapter molecules termed target modules (TM) can cross-link UniCAR T cells with target cells. In the absence of TMs, UniCAR T cells automatically turn off. Until now, all UniCAR TMs were constructed by fusion of the UniCAR epitope to an antibody domain. To open up the wide field of low-molecular-weight compounds for retargeting of UniCAR T cells to tumor cells, and to follow in parallel the progress of UniCAR T cell therapy by PET imaging we challenged the idea to convert a PET tracer into a UniCAR-TM. For proof of concept, we selected the clinically used PET tracer PSMA-11, which binds to the prostate-specific membrane antigen overexpressed in prostate carcinoma. Here we show that fusion of the UniCAR epitope to PSMA-11 results in a low-molecular-weight theranostic compound that can be used for both retargeting of UniCAR T cells to tumor cells, and for non-invasive PET imaging and thus represents a member of a novel class of theranostics.

Risk Assessment of kINPen Plasma Treatment of Four Human Pancreatic Cancer Cell Lines with Respect to Metastasis

Cold physical plasma has limited tumor growth in many preclinical models and is, therefore, suggested as a putative therapeutic option against cancer. Yet, studies investigating the cells' metastatic behavior following plasma treatment are scarce, although being of prime importance to evaluate the safety of this technology. Therefore, we investigated four human pancreatic cancer cell lines for their metastatic behavior in vitro and in chicken embryos (in ovo). Pancreatic cancer was chosen as it is particularly metastatic to the peritoneum and systemically, which is most predictive for outcome. In vitro, treatment with the kINPen plasma jet reduced pancreatic cancer cell activity and viability, along with unchanged or decreased motility. Additionally, the expression of adhesion markers relevant for metastasis was down-regulated, except for increased CD49d. Analysis of 3D tumor spheroid outgrowth showed a lack of plasma-spurred metastatic behavior. Finally, analysis of tumor tissue grown on chicken embryos validated the absence of an increase of metabolically active cells physically or chemically detached with plasma treatment. We conclude that plasma treatment is a safe and promising therapeutic option and that it does not promote metastatic behavior in pancreatic cancer cells in vitro and in ovo.

IFN-γ: A cytokine at the right time, is in the right place

Interferon gamma has long been studied as a critical mediator of tumor immunity. In recent years, the complexity of cellular interactions that take place in the tumor microenvironment has become better appreciated in the context of immunotherapy. While checkpoint inhibitors have dramatically improved remission rates in cancer treatment, IFN-γ and related effectors continue to be identified as strong predictors of treatment success. In this review, we provide an overview of the multiple immunosuppressive barriers that IFN-γ has to overcome to eliminate tumors, and potential avenues for modulating the immune response in favor of tumor rejection.

Rationale for Combining Radiotherapy and Immune Checkpoint Inhibition for Patients With Hypoxic Tumors

In order to compensate for the increased oxygen consumption in growing tumors, tumors need angiogenesis and vasculogenesis to increase the supply. Insufficiency in this process or in the microcirculation leads to hypoxic tumor areas with a significantly reduced pO2, which in turn leads to alterations in the biology of cancer cells as well as in the tumor microenvironment. Cancer cells develop more aggressive phenotypes, stem cell features and are more prone to metastasis formation and migration. In addition, intratumoral hypoxia confers therapy resistance, specifically radioresistance. Reactive oxygen species are crucial in fixing DNA breaks after ionizing radiation. Thus, hypoxic tumor cells show a two- to threefold increase in radioresistance. The microenvironment is enriched with chemokines (e.g., SDF-1) and growth factors (e.g., TGFβ) additionally reducing radiosensitivity. During recent years hypoxia has also been identified as a major factor for immune suppression in the tumor microenvironment. Hypoxic tumors show increased numbers of myeloid derived suppressor cells (MDSCs) as well as regulatory T cells (Tregs) and decreased infiltration and activation of cytotoxic T cells. The combination of radiotherapy with immune checkpoint inhibition is on the rise in the treatment of metastatic cancer patients, but is also tested in multiple curative treatment settings. There is a strong rationale for synergistic effects, such as increased T cell infiltration in irradiated tumors and mitigation of radiation-induced immunosuppressive mechanisms such as PD-L1 upregulation by immune checkpoint inhibition. Given the worse prognosis of patients with hypoxic tumors due to local therapy resistance but also increased rate of distant metastases and the strong immune suppression induced by hypoxia, we hypothesize that the subgroup of patients with hypoxic tumors might be of special interest for combining immune checkpoint inhibition with radiotherapy.

Potential Role of CXCR4 Targeting in the Context of Radiotherapy and Immunotherapy of Cancer

Cancer immunotherapy has been established as standard of care in different tumor entities. After the first reports on synergistic effects with radiotherapy and the induction of abscopal effects-tumor shrinkage outside the irradiated volume attributed to immunological effects of radiotherapy-several treatment combinations have been evaluated. Different immunotherapy strategies (e.g., immune checkpoint inhibition, vaccination, cytokine based therapies) have been combined with local tumor irradiation in preclinical models. Clinical trials are ongoing in different cancer entities with a broad range of immunotherapeutics and radiation schedules. SDF-1 (CXCL12)/CXCR4 signaling has been described to play a major role in tumor biology, especially in hypoxia adaptation, metastasis and migration. Local tumor irradiation is a known inducer of SDF-1 expression and release. CXCR4 also plays a major role in immunological processes. CXCR4 antagonists have been approved for the use of hematopoietic stem cell mobilization from the bone marrow. In addition, several groups reported an influence of the SDF-1/CXCR4 axis on intratumoral immune cell subsets and anti-tumor immune response. The aim of this review is to merge the knowledge on the role of SDF-1/CXCR4 in tumor biology, radiotherapy and immunotherapy of cancer and in combinatorial approaches.

Trial watch: Peptide-based vaccines in anticancer therapy

Peptide-based anticancer vaccination aims at stimulating an immune response against one or multiple tumor-associated antigens (TAAs) following immunization with purified, recombinant or synthetically engineered epitopes. Despite high expectations, the peptide-based vaccines that have been explored in the clinic so far had limited therapeutic activity, largely due to cancer cell-intrinsic alterations that minimize antigenicity and/or changes in the tumor microenvironment that foster immunosuppression. Several strategies have been developed to overcome such limitations, including the use of immunostimulatory adjuvants, the co-treatment with cytotoxic anticancer therapies that enable the coordinated release of damage-associated molecular patterns, and the concomitant blockade of immune checkpoints. Personalized peptide-based vaccines are also being explored for therapeutic activity in the clinic. Here, we review recent preclinical and clinical progress in the use of peptide-based vaccines as anticancer therapeutics.Abbreviations: CMP: carbohydrate-mimetic peptide; CMV: cytomegalovirus; DC: dendritic cell; FDA: Food and Drug Administration; HPV: human papillomavirus; MDS: myelodysplastic syndrome; MHP: melanoma helper vaccine; NSCLC: non-small cell lung carcinoma; ODD: orphan drug designation; PPV: personalized peptide vaccination; SLP: synthetic long peptide; TAA: tumor-associated antigen; TNA: tumor neoantigen

Impact of curative radiotherapy on the immune status of patients with localized prostate cancer

Combination of radiotherapy with immunotherapy has become an attractive concept for the treatment of cancer. The objective of this study was to assess the effect of curative, normofractionated radiotherapy on peripheral immune lymphocytes in prostate cancer patients, in order to propose a rationale for scheduling of normofractionated radiotherapy with T-cell based immunotherapy. In a prospective study (clinicaltrials.gov: NCT01376674), eighteen patients with localized prostate cancer were treated with radiotherapy with or without hormonal therapy. Irradiation volumes encompassed prostate and, in select cases, elective pelvic nodal regions. Blood samples were collected from all patients before, during, and after radiotherapy, as well as from 6 healthy individuals as control. Normofractionated radiotherapy of prostate cancer over eight weeks had a significant influence on the systemic immune status of patients compared to healthy controls. Absolute leukocyte and lymphocyte counts decreased during treatment as did peripheral blood immune subsets (T cells, CD8+ and naïve CD4+ T cells, B cells). Regulatory T cells and NK cells increased. Proliferation of all immune cells except regulatory T cells increased during RT. Most of these changes were transient. Importantly, the functionality of T lymphocytes and the frequency of antigen-specific CD8+ T cells were not affected during therapy. Our data indicate that combination of normofractionated radiotherapy with immunotherapy might be feasible for patients with prostate cancer. Conceptually, beginning with immunotherapy early during the course of radiotherapy could be beneficial, as the percentage of T cells is highest, the percentage of regulatory T cells is lowest, and as the effects of radiotherapy did not completely subside 3 months after end of radiotherapy.

Abscopal effects of radiotherapy and combined mRNA-based immunotherapy in a syngeneic, OVA-expressing thymoma mouse model

BACKGROUND

Tumor metastasis and immune evasion present major challenges of cancer treatment. Radiotherapy can overcome immunosuppressive tumor microenvironments. Anecdotal reports suggest abscopal anti-tumor immune responses. This study assesses abscopal effects of radiotherapy in combination with mRNA-based cancer vaccination (RNActive®).

METHODS

C57BL/6 mice were injected with ovalbumin-expressing thymoma cells into the right hind leg (primary tumor) and left flank (secondary tumor) with a delay of 4 days. Primary tumors were irradiated with 3 × 2 Gy, while secondary tumors were shielded. RNA and combined treatment groups received mRNA-based RNActive® vaccination.

RESULTS

Radiotherapy and combined radioimmunotherapy significantly delayed primary tumor growth with a tumor control in 15 and 53% of mice, respectively. In small secondary tumors, radioimmunotherapy significantly slowed growth rate compared to vaccination (p = 0.002) and control groups (p = 0.01). Cytokine microarray analysis of secondary tumors showed changes in the cytokine microenvironment, even in the non-irradiated contralateral tumors after combination treatment.

CONCLUSION

Combined irradiation and immunotherapy is able to induce abscopal responses, even with low, normofractionated radiation doses. Thus, the combination of mRNA-based vaccination with irradiation might be an effective regimen to induce systemic anti-tumor immunity.

Optimizing tumor immune response through combination of radiation and immunotherapy

Radiation therapy and immunotherapy are two highly evolving modalities for the treatment of solid tumors. Immunotherapeutic drugs can either stimulate the immune system via immunogenic pathways or target co-inhibitory checkpoints. An augmented tumor cell recognition by host immune cells can be achieved post-irradiation, as irradiated tissues can release chemical signals which are sensed by the immune system resulting in its activation. Different strategies combining both treatment modalities were tested in order to achieve a better therapeutic response and longer tumor control. Both regimens act synergistically to one another with complimentary mechanisms. In this review, we explore the scientific basis behind such a combination, starting initially with a brief historical overview behind utilizing radiation and immunotherapies for solid tumors, followed by the different types of these two modalities, and the biological concept behind their synergistic effect. We also shed light on the common side effects and toxicities associated with radiation and immunotherapy. Finally, we discuss previous clinical trials tackling this multimodality combination and highlight future ongoing research.