The intersection of radiotherapy and immunotherapy: mechanisms and clinical implications

Antiviral Responses in Cancer: Boosting Antitumor Immunity Through Activation of Interferon Pathway in the Tumor Microenvironment

In recent years, it became apparent that cancers either associated with viral infections or aberrantly expressing endogenous retroviral elements (EREs) are more immunogenic, exhibiting an intense intra-tumor immune cell infiltration characterized by a robust cytolytic apparatus. On the other hand, epigenetic regulation of EREs is crucial to maintain steady-state conditions and cell homeostasis. In line with this, epigenetic disruptions within steady-state cells can lead to cancer development and trigger the release of EREs into the cytoplasmic compartment. As such, detection of viral molecules by intracellular innate immune sensors leads to the production of type I and type III interferons that act to induce an antiviral state, thus restraining viral replication. This knowledge has recently gained momentum due to the possibility of triggering intratumoral activation of interferon responses, which could be used as an adjuvant to elicit strong anti-tumor immune responses that ultimately lead to a cascade of cytokine production. Accordingly, several therapeutic approaches are currently being tested using this rationale to improve responses to cancer immunotherapies. In this review, we discuss the immune mechanisms operating in viral infections, show evidence that exogenous viruses and endogenous retroviruses in cancer may enhance tumor immunogenicity, dissect the epigenetic control of EREs, and point to interferon pathway activation in the tumor milieu as a promising molecular predictive marker and immunotherapy target. Finally, we briefly discuss current strategies to modulate these responses within tumor tissues, including the clinical use of innate immune receptor agonists and DNA demethylating agents.

HLA class I antigen processing machinery defects in antitumor immunity and immunotherapy

Human leukocyte antigen (HLA) class I antigen-processing machinery (APM) plays a crucial role in the synthesis and expression of HLA class I tumor antigen-derived peptide complexes; the latter mediate the recognition and elimination of malignant cells by cognate T cells. Defects in HLA class I APM component expression and/or function are frequently found in cancer cells, providing them with an immune escape mechanism that has relevance in the clinical course of the disease and in the response to T-cell-based immunotherapy. The majority of HLA class I APM defects (>75%) are caused by epigenetic mechanisms or dysregulated signaling and therefore can be corrected by strategies that counteract the underlying mechanisms. Their application in oncology is likely to improve responses to T-cell-based immunotherapies, including checkpoint inhibition.

Efficacy of single-site radiotherapy plus PD-1 inhibitors vs PD-1 inhibitors for oligometastatic non-small cell lung cancer

PURPOSE

Growing numbers of clinical trials test the efficacy of radiotherapy (RT) plus immune checkpoint inhibitors (ICIs), but the number of irradiated sites is not uniform. We aimed to evaluate the efficacy of single-site RT plus immunotherapy in oligometastatic non-small cell lung cancer (NSCLC) with smaller disease burdens and low tumor heterogeneity.

METHODS

We retrospectively identified oligometastatic NSCLC (< 4 metastatic sites) patients treated with PD-1 pathway inhibitors with or without RT to a single lesion in our institution between 2018 and 2020. The primary endpoints were the best objective response rate (ORR) and progression-free survival (PFS).

RESULTS

Of the 152 patients enrolled, 93 and 59 were identified as the ICI alone group and the ICI plus RT group, respectively. The addition of RT to ICI therapy significantly increased the best ORR from 31.2% to 50.8% (p = 0.015). The out-of-field (abscopal effect) response rate could reach 41.3% (95%CI 26.5%-56.1%) in the ICI plus RT group. Median PFS was 8.9 months (95%CI 4.7-13.1 months) with ICI alone versus 13.8 months (95%CI 9.5-18.1 months) with ICI plus radiotherapy (hazard ratio [HR] 0.556; p = 0.035). In an exploratory subgroup analysis of PFS, the addition of RT brought greater benefits in patients aged < 65 years (p = 0.016), patients with ECOG PS = 0 (p = 0.048), and patients with 1-2 metastatic sites (p = 0.024). No unexpected adverse events or significantly increased toxicities were observed in the experimental arm.

CONCLUSION

Single-site RT plus anti-PD-1 inhibitors significantly increased systemic responses and improved survival outcomes in oligometastatic NSCLC patients.

Engineered CAR-T and novel CAR-based therapies to fight the immune evasion of glioblastoma: gutta cavat lapidem

INTRODUCTION

The field of cancer immunotherapy has achieved great advancements through the application of genetically engineered T cells with chimeric antigen receptors (CAR), that have shown exciting success in eradicating hematologic malignancies and have proved to be safe with promising early signs of antitumoral activity in the treatment of glioblastoma (GBM).

AREAS COVERED

We discuss the use of CAR T cells in GBM, focusing on limitations and obstacles to advancement, mostly related to toxicities, hostile tumor microenvironment, limited CAR T cells infiltration and persistence, target antigen loss/heterogeneity and inadequate trafficking. Furthermore, we introduce the refined strategies aimed at strengthening CAR T activity and offer insights in to novel immunotherapeutic approaches, such as the potential use of CAR NK or CAR M to optimize anti-tumor effects for GBM management.

EXPERT OPINION

With the progressive wide use of CAR T cell therapy, significant challenges in treating solid tumors, including central nervous system (CNS) tumors, are emerging, highlighting early disease relapse and cancer cell resistance issues, owing to hostile immunosuppressive microenvironment and tumor antigen heterogeneity. In addition to CAR T cells, there is great interest in utilizing other types of CAR-based therapies, such as CAR natural killer (CAR NK) or CAR macrophages (CAR M) cells for CNS tumors.

Phase II, single-arm trial of preoperative short-course radiotherapy followed by chemotherapy and camrelizumab in locally advanced rectal cancer

Background

In locally advanced rectal cancer (LARC), preoperative short-course radiotherapy (SCRT) with delayed surgery has been shown to be as effective as long-course chemoradiotherapy, with only modest benefits. This study aimed to evaluate the efficacy and safety of preoperative SCRT combined with subsequent CAPOX (capecitabine and oxaliplatin) and the anti-PD-1 antibody camrelizumab in patients with LARC.

Methods

This was a prospective, single-arm, phase II trial. Treatment-naïve patients with histologically confirmed T3-4N0M0 or T1-4N+M0 rectal adenocarcinoma received 5×5 Gy SCRT with two subsequent 21-day cycles of CAPOX plus camrelizumab after 1 week, followed by radical surgery after 1 week. The primary endpoint was pathological complete response (pCR) rate. Biomarker analysis was performed to identify a potential predictor of pCR to treatment.

Results

From November 7, 2019 to September 14, 2020, 30 patients were enrolled, and 27 patients received at least one dose of CAPOX plus camrelizumab. Surgery was performed in 27 (100%) patients. The pCR (ypT0N0) rate was 48.1% (13/27), including 46.2% (12/26) for proficient mismatch repair (MMR) tumors and 100% (1/1) for deficient MMR tumors. Immune-related adverse events were all grade 1–2, with the most common being reactive cutaneous capillary endothelial proliferation (81.5%). No grade 4/5 adverse events occurred. Biomarker analysis showed patients without FGFR1–3 deletions had a better tendency for pCR.

Conclusions

SCRT combined with subsequent CAPOX plus camrelizumab followed by delayed surgery showed a favorable pCR rate with good tolerance in patients with LARC, especially in the proficient MMR setting. A randomized controlled trial is ongoing to confirm these results.

Trial registration number

ClinicalTrials.gov identifier: NCT04231552.

Head and neck tumor cells treated with hypofractionated irradiation die via apoptosis and are better taken up by M1-like macrophages

Purpose

The incidence of head and neck squamous cell carcinomas (HNSCC) is increasing worldwide, especially when triggered by the human papilloma virus (HPV). Radiotherapy has immune-modulatory properties, but the role of macrophages present in HNSCC and having contact with irradiated tumor cells remains unclear. The influence of irradiated (2 × 5Gy) HNSCC cells on the (re-)polarization and phagocytosis of human macrophages, either non-polarized or with a more M1 or M2 phenotype, was therefore investigated.

Methods

Human monocytes were differentiated with the hematopoietic growth factors M‑CSF (m) or GM-CSF (g) and additionally pre-polarized with either interleukin (IL)-4 and IL-10 or interferon (IFN)-γ and lipopolysaccharides (LPS), respectively. Subsequently, they were added to previously irradiated (2 × 5Gy) and mock-treated HPV-positive (UD-SCC-2) and HPV-negative (Cal33) HNSCC cells including their supernatants.

Results

The HNSCC cells treated with hypofractionated irradiation died via apoptosis and were strongly phagocytosed by M0m and M2 macrophages. M0g and M1 macrophages phagocytosed the tumor cells to a lesser extent. Irradiated HNSCC cells were better phagocytosed by M1 macrophages compared to mock-treated controls. The polarization status of the macrophages was not significantly changed, except for the expression of CD206 on M2 macrophages, which was reduced after phagocytosis of irradiated HPV-negative cells. Further, a significant increase in the uptake of irradiated HPV-positive cells by M0g macrophages when compared to HPV-negative cells was observed.

Conclusion

HNSCC cells treated with hypofractionated irradiation foster phagocytosis by anti-tumorigenic M1 macrophages. The data provide the first evidence on the impact of the HPV status of HNSCC cells on the modulation of the macrophage response to irradiated tumor cells.

'Le Roi est mort, vive le Roi': New Roles of Radiotherapy in the Treatment of Lymphomas in Combination With Immunotherapy

BACKGROUND

immunotherapy (IT), including checkpoint inhibitors (CIs) and Chimeric Antigen Receptor T cell therapy (CAR-T) revolutionized the treatment of relapsing or refractory (r/r) lymphoma. Several preliminary experiences evaluated concomitant administration of radiotherapy and IT.

METHODS

we performed a systematic review of current literature as of March 30, 2020. A total of 1090 records was retrieved, 42 articles were selected on the basis of title and abstract and, after the removal of analyses with no original data or insufficient clinical information, 28 papers were included in the review.

RESULTS

previous studies were mostly represented by case reports/series or small cohorts. Nonetheless, combination of radiotherapy and CIs or CAR-T led to promising outcomes, resulting in extremely high rates of complete response and improving progression free and overall survival compared with data from recent clinical trials. Combination of RT and CIs had a fair toxicity profile with no reports of severe side effects. Within the limits of the small cohorts retrieved, RT seems a superior option compared with systemic treatment as a 'bridge' to CAR-T and could as well reduce severe complications rates. Radiotherapy could elicit immune response against lymphoma, as demonstrated by multiple cases of abscopal effect and its inclusion in anti-neoplastic vaccines protocols.

CONCLUSION

The results of this review warrant the evaluation of combination of RT and immunotherapy in larger and preferably prospective and randomized cohorts to confirm these preliminary impressive outcomes. The optimal dose, fractionation and timing of RT still have to be clarified.

The impact of bridging therapy prior to CD19-directed chimeric antigen receptor T-cell therapy in patients with large B-cell lymphoma

In the relapsed/refractory setting for treatment of large B-cell lymphoma (LBCL), chimeric antigen receptor T-cell (CAR-T) therapy has emerged as an effective treatment modality. Patients often have aggressive disease that requires prompt treatment in the form of bridging therapy (BT) for disease stabilisation while CAR-T cells are manufactured. Patients (n = 75) undergoing CAR-T therapy infusion for LBCL at our institution were identified. A total of 52 (69·3%) received BT and 23 (30·7%) received no BT (NBT). BT modalities included systemic BT (SBT) in 28 patients, radiation BT (RBT) in 14, and high-dose steroid BT (HDS) in 10. There was no difference in incidence of cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome between BT and NBT (P = 0·18 and P = 0·53 respectively). Prolonged cytopenias at Day 180 were more common in BT than NBT (50% vs. 13·3%, P = 0·04). The SBT and RBT subgroups had more cytopenias at Day 180 compared to the HDS and NBT subgroups (58·3% and 57·1% vs. 20% and 13·3% respectively, P = 0·04). Disease response at last follow-up, progression-free survival and overall survival were similar between BT, NBT, and BT subgroups. In summary, BT can be safely considered in patients undergoing CAR-T therapy. However, those undergoing BT with SBT or RBT are at higher risk of prolonged cytopenias after CAR-T therapy.

Resistance to immunotherapy in human malignancies: Mechanisms, research progresses, challenges, and opportunities

Despite remarkable advances in different types of cancer therapies, an effective therapeutic strategy is still a major and significant challenge. One of the most promising approaches in this regard is immunotherapy, which takes advantage of the patients' immune system; however, the many mechanisms that cancerous cells harbor to extend their survival make it impossible to gain perfect eradication of tumors. The response rate to cancer immunotherapies, especially checkpoint inhibitors and adoptive T cell therapy, substantially differs in various cancer types with the highest rates in advanced melanoma and non-small cell lung cancer. Indeed, the lack of response in many tumors indicates primary resistance that can originate from either tumor cells (intrinsic) or tumor microenvironment (extrinsic). On the other hand, some tumors show an initial response to immunotherapy followed by relapse in few months (acquired resistance). Understanding the underlying molecular mechanisms of immunotherapy resistance makes it possible to develop effective strategies to overcome this hurdle and boost therapy outcomes. In this review, we take a look at immunotherapy strategies and go through a number of primary and acquired resistance mechanisms. Also, we present various ongoing methods to overcoming resistance and introduce some promising fields to improve the outcome of immunotherapy in patients affected with cancer.

Effects of Radiation on the Tumor Microenvironment

A malignant tumor consists of malignant cells as well as a wide array of normal host tissues including stroma, vasculature, and immune infiltrate. The interaction between cancer and these host tissues is critical as these host tissues play a variety of roles in supporting or resisting disease progression. Radiotherapy (RT) has direct effects on malignant cells, but, also, critically important effects on these other components of the tumor microenvironment (TME). Given the growing role of immune checkpoint inhibitors and other immunotherapy strategies, understanding how RT affects the TME, particularly the immune compartment, is essential to advance RT in this new era of cancer therapy. The interactions between RT and the TME are complex, affecting the innate and adaptive arms of the immune system. RT can induce both proinflammatory effects and immune suppressive effects that can either promote or impede antitumor immunity. It is likely that the initial proinflammatory effects of RT eventually lead to rebound immune-suppression as chronic inflammation sets in. The exact kinetics and nature of how RT changes the TME likely depends on timing, dose, fractionation, site irradiated, and tumor type. With increased understanding of the effects of RT on the TME, in the future it is likely that we will be able to personalize RT by varying the dose, site, and timing of intervention to generate the desired response to partner with immunotherapy strategies.

Soluble B7-CD28 Family Inhibitory Immune Checkpoint Proteins and Anti-Cancer Immunotherapy

Co-inhibitory B7-CD28 family member proteins negatively regulate T cell responses and are extensively involved in tumor immune evasion. Blockade of classical CTLA-4 (cytotoxic T lymphocyte-associated antigen-4) and PD-1 (programmed cell death protein-1) checkpoint pathways have become the cornerstone of anti-cancer immunotherapy. New inhibitory checkpoint proteins such as B7-H3, B7-H4, and BTLA (B and T lymphocyte attenuator) are being discovered and investigated for their potential in anti-cancer immunotherapy. In addition, soluble forms of these molecules also exist in sera of healthy individuals and elevated levels are found in chronic infections, autoimmune diseases, and cancers. Soluble forms are generated by proteolytic shedding or alternative splicing. Elevated circulating levels of these inhibitory soluble checkpoint molecules in cancer have been correlated with advance stage, metastatic status, and prognosis which underscore their broader involvement in immune regulation. In addition to their potential as biomarker, understanding their mechanism of production, biological activity, and pathological interactions may also pave the way for their clinical use as a therapeutic target. Here we review these aspects of soluble checkpoint molecules and elucidate on their potential for anti-cancer immunotherapy.

Pre-treatment tumor-infiltrating T cells influence response to neoadjuvant chemoradiotherapy in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) is a disease with dismal treatment outcomes. Response to neoadjuvant chemoradiation (CRT) varies greatly. Although the underlying mechanisms of CRT resistance are not identified, accumulating evidence indicates an important role for local antitumor immunity. To explore the immune microenvironment in relation to response to CRT we performed an in-depth analysis using multiplex immunohistochemistry, flow cytometry and mRNA expression analysis (NanoString) to generate a detailed map of the immunological landscape of pretreatment biopsies as well as peripheral blood mononuclear cells (PBMCs) of EAC patients. Response to CRT was assessed by Mandard’s tumor regression grade (TRG), disease-free- and overall survival. Tumors with a complete pathological response (TRG 1) to neoadjuvant CRT had significantly higher tumor-infiltrating T cell levels compared to all other response groups (TRG 2–5). These T cells were also in closer proximity to tumor cells in complete responders compared to other response groups. Notably, immune profiles of near-complete responders (TRG 2) showed more resemblance to non-responders (TRG 3–5) than to complete responders. A high CD8:CD163 ratio in the tumor was associated with an improved disease-free survival. Gene expression analyses revealed that T cells in non-responders were Th2-skewed, while complete responders were enriched in cytotoxic immune cells. Finally, complete responders were enriched in circulating memory T cells. preexisting immune activation enhances the chance for a complete pathological response to neoadjuvant CRT. This information can potentially be used for future patient selection, but also fuels the development of immunomodulatory strategies to enhance CRT efficacy.

Inflammation and tumor progression: signaling pathways and targeted intervention

Cancer development and its response to therapy are regulated by inflammation, which either promotes or suppresses tumor progression, potentially displaying opposing effects on therapeutic outcomes. Chronic inflammation facilitates tumor progression and treatment resistance, whereas induction of acute inflammatory reactions often stimulates the maturation of dendritic cells (DCs) and antigen presentation, leading to anti-tumor immune responses. In addition, multiple signaling pathways, such as nuclear factor kappa B (NF-kB), Janus kinase/signal transducers and activators of transcription (JAK-STAT), toll-like receptor (TLR) pathways, cGAS/STING, and mitogen-activated protein kinase (MAPK); inflammatory factors, including cytokines (e.g., interleukin (IL), interferon (IFN), and tumor necrosis factor (TNF)-α), chemokines (e.g., C-C motif chemokine ligands (CCLs) and C-X-C motif chemokine ligands (CXCLs)), growth factors (e.g., vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β), and inflammasome; as well as inflammatory metabolites including prostaglandins, leukotrienes, thromboxane, and specialized proresolving mediators (SPM), have been identified as pivotal regulators of the initiation and resolution of inflammation. Nowadays, local irradiation, recombinant cytokines, neutralizing antibodies, small-molecule inhibitors, DC vaccines, oncolytic viruses, TLR agonists, and SPM have been developed to specifically modulate inflammation in cancer therapy, with some of these factors already undergoing clinical trials. Herein, we discuss the initiation and resolution of inflammation, the crosstalk between tumor development and inflammatory processes. We also highlight potential targets for harnessing inflammation in the treatment of cancer.

Radiotherapy and Immunotherapy Combinations in the Treatment of Patients with Metastatic Disease: Current Status and Future Focus

Radiotherapy and immunotherapy benefit subsets of patients with metastatic cancer. Here, we review selected laboratory and clinical studies investigating the utility of combining radiotherapy and immunotherapy in metastatic patients. We examine potential approaches to increase the therapeutic ratio of radioimmunotherapy in the treatment of metastatic cancers moving forward.

Regulatory T Cells Shape the Differential Impact of Radiation Dose-Fractionation Schedules on Host Innate and Adaptive Antitumor Immune Defenses

PURPOSE

We examined how radiation dose per fraction (DPF) and total dose, as represented by biological effective dose (BED), can independently and differentially affect the immunomodulatory capacity of radiation therapy (RT).

METHODS AND MATERIALS

AT3-OVA mammary and MC38 colorectal tumors in C57BL/6 mice were irradiated with rationally selected dose-fractionation schedules, alone or with immune-modulating or -depleting agents. Tumor growth was monitored as a readout of therapeutic response. Flow cytometry and RNA sequencing of mouse tumors and analysis of transcriptomic data sets from irradiated human cancers were used to examine the immunomodulatory effects of the different radiation schedules.

RESULTS

In AT3-OVA tumors, radiation DPF rather than BED determined the ability of RT to evoke local antitumor CD8⁺ T cell responses and synergize with anti-PD-1 therapy. Natural killer cell-mediated control of irradiated tumors was more sensitive to radiation BED. Radiation-induced regulatory T cell (Treg) responses, which were detected in both mouse and human tumors, were a major factor underlying the differential activation of adaptive immunity by radiation DPF and the activity of natural killer cells during the early phase of response to RT. Targeted inhibition of Treg responses within irradiated tumors rescued and enhanced local tumor control by RT and permitted the generation of abscopal and immunologic memory responses, irrespective of radiation schedule. MC38 tumors did not support the induction of an amplified Treg response to RT and were highly vulnerable to its immunoadjuvant effects.

CONCLUSIONS

Local radiation-induced Treg responses are influenced by radiation schedule and tumor type and are a critical determinant of the immunoadjuvant potential of RT and its ability to synergize with T cell-targeted immunotherapy.

Targeting resistance to radiation-immunotherapy in cold HNSCCs by modulating the Treg-dendritic cell axis

BACKGROUND

Numerous trials combining radiation therapy (RT) and immunotherapy in head and neck squamous cell carcinoma (HNSCC) are failing. Using preclinical immune cold models of HNSCC resistant to RT-immune checkpoint inhibitors, we investigate therapeutic approaches of overcoming such resistance by examining the differential microenvironmental response to RT.

METHODS

We subjected two HPV-negative orthotopic mouse models of HNSCC to combination RT, regulatory T cells (Treg) depletion, and/or CD137 agonism. Tumor growth was measured and intratumorous and lymph node immune populations were compared among treatment groups. Human gene sets, genetically engineered mouse models DEREG and BATF3-/-, flow and time-of-flight cytometry, RNA-Seq, Treg adoptive transfer studies, and in vitro experiments were used to further evaluate the role of dendritic cells (DCs) and Tregs in these treatments.

RESULTS

In MOC2 orthotopic tumors, we find no therapeutic benefit to targeting classically defined immunosuppressive myeloids, which increase with RT. In these radioresistant tumors, supplementing combination RT and Treg depletion with anti-CD137 agonism stimulates CD103+ DC activation in tumor-draining lymph nodes as characterized by increases in CD80+ and CCR7+ DCs, resulting in a CD8 T cell-dependent response. Simultaneously, Tregs are reprogrammed to an effector phenotype demonstrated by increases in interferonγ+, tumor necrosis factorα+, PI3K+, pAKT+ and Eomes+ populations as well as decreases in CTLA4+ and NRP-1+ populations. Tumor eradication is observed when RT is increased to an 8 Gy x 5 hypofractionated regimen and combined with anti-CD25+ anti-CD137 treatment. In a human gene set from oral squamous cell carcinoma tumors, high Treg number is associated with earlier recurrence.

CONCLUSIONS

Regulating Treg functionality and DC activation status within the lymph node is critical for generating a T cell effector response in these highly radioresistant tumors. These findings underscore the plasticity of Tregs and represent a new therapeutic opportunity for reprogramming the tumor microenvironment in HNSCCs resistant to conventional radioimmunotherapy approaches.

Charged Particle and Conventional Radiotherapy: Current Implications as Partner for Immunotherapy

Radiotherapy (RT) has been shown to interfere with inflammatory signals and to enhance tumor immunogenicity via, e.g., immunogenic cell death, thereby potentially augmenting the therapeutic efficacy of immunotherapy. Conventional RT consists predominantly of high energy photon beams. Hypofractionated RT regimens administered, e.g., by stereotactic body radiation therapy (SBRT), are increasingly investigated in combination with cancer immunotherapy within clinical trials. Despite intensive preclinical studies, the optimal dose per fraction and dose schemes for elaboration of RT induced immunogenic potential remain inconclusive. Compared to the scenario of combined immune checkpoint inhibition (ICI) and RT, multimodal therapies utilizing other immunotherapy principles such as adoptive transfer of immune cells, vaccination strategies, targeted immune-cytokines and agonists are underrepresented in both preclinical and clinical settings. Despite the clinical success of ICI and RT combination, e.g., prolonging overall survival in locally advanced lung cancer, curative outcomes are still not achieved for most cancer entities studied. Charged particle RT (PRT) has gained interest as it may enhance tumor immunogenicity compared to conventional RT due to its unique biological and physical properties. However, whether PRT in combination with immune therapy will elicit superior antitumor effects both locally and systemically needs to be further investigated. In this review, the immunological effects of RT in the tumor microenvironment are summarized to understand their implications for immunotherapy combinations. Attention will be given to the various immunotherapeutic interventions that have been co-administered with RT so far. Furthermore, the theoretical basis and first evidences supporting a favorable immunogenicity profile of PRT will be examined.

Virus-specific T cells for malignancies - then, now and where to?

Purpose of Review

Virus-associated malignancies are a global health burden, constituting 10-12% of cancers worldwide. As these tumors express foreign viral antigens that can elicit specific T cell responses, virus-directed immunotherapies are a promising treatment strategy. Specifically, adoptive cell transfer of virus-specific T cells (VSTs) has demonstrated the potential to eradicate cancers associated with certain viruses.

Recent Findings

Initial studies in 1990s first showed that VSTs specific for the Epstein-Barr virus (EBVSTs) can induce complete remissions in patients with post-transplant lymphoproliferative disease. Since then, studies have validated the specificity and safety of VSTs in multiple lymphomas and solid malignancies. However, challenges remain to optimize this platform for widespread use, including enhancing potency and persistence, overcoming the immunosuppressive tumor microenvironment, and streamlining manufacturing processes that comply with regulatory requirements.

Summary

This review focuses on data from clinical trials evaluating VSTs directed against three viruses (EBV, HPV and MCPyV), as well as recent preclinical and clinical advances, and potential future directions.

Use of cardiac radiation therapy as bridging therapy to CAR-T for relapsed pediatric B-cell acute lymphoblastic leukemia

The use of radiotherapy as bridging therapy to chimeric antigen receptor T-cell therapy (CAR-T) in pre-B acute lymphoblastic leukemia (B-ALL) has been minimally explored. Here, we present a boy with B-ALL who relapsed after allogeneic bone marrow transplant with disseminated disease, including significant symptomatic cardiovascular and gastrointestinal (GI) involvement. The cardiac and GI leukemic infiltrates were successfully treated with bridging radiation therapy (BRT) prior to CAR-T infusion. Using this approach, he successfully tolerated CAR-T with no evidence of disease or sequelae on 3-month follow-up. This is the first reported case of safe and effective delivery of cardiac BRT in B-ALL.

Enhance the Immune Checkpoint Inhibitors Efficacy with Radiotherapy Induced Immunogenic Cell Death: A Comprehensive Review and Latest Developments

The immunogenic cell death (ICD) is defined as a regulated cell death able to induce an adaptive immunity. It depends on different parameters including sufficient antigenicity, adjuvanticity and favorable microenvironment conditions. Radiation therapy (RT), a pillar of modern cancer treatment, is being used in many tumor types in curative, (neo) adjuvant, as well as metastatic settings. The anti-tumor effects of RT have been traditionally attributed to the mitotic cell death resulting from the DNA damages triggered by the release of reactive oxygen species. Recent evidence suggests that RT may also exert its anti-tumor effect by recruiting tumor-specific immunity. RT is able to induce the release of tumor antigens, to act as an immune adjuvant and thus to synergize with the anti-tumor immunity. The advent of new efficient immunotherapeutic agents, such as immune checkpoint inhibitors (ICI), in multiple tumor types sheds new light on the opportunity of combining RT and ICI. Here, we will describe the biological and radiobiological rationale of the RT-induced ICD. We will then focus on the interest to combine RT and ICI, from bench to bedside, and summarize the clinical data existing with this combination. Finally, RT technical adaptations to optimize the ICD induction will be discussed.

Hypofractionated Low-Dose Radiotherapy Combined with Immune Checkpoint Inhibition in Metastatic Solid Tumors

Background

The combination of radiotherapy and immunotherapy can bring benefits to patients, especially advanced patients. However, conventional radiotherapy brings about great adverse reactions. How about the hypofractionated low-dose radiotherapy?

Materials and Methods

In this retrospective cohort study, we included 32 patients with metastatic solid tumors treated with hypofractionated radiotherapy combined with an immune checkpoint inhibitor. Patients underwent radiotherapy of 4Gy/Fx on day 1, 3, and 5, and received single-drug immunotherapy of PD-1 inhibitor on day 2. We evaluated the following outcomes: objective response rate (ORR), disease control rate (DCR), change of nonirradiated and irradiated lesions, quality of life, and symptom improvement.

Results

Among the 32 patients, the ORR was 9.4% (3/32) and the DCR was 56.25% (18/32). Hypofractionated radiotherapy combined with immunotherapy showed a remarkable efficacy of local control on metastatic tumor patients. Local masses irradiated in two patients (6.25%) were complete remission, partial response rate was 37.5% (12 patients), and 56.25% was stability (18 patients). Out of those 18 patients, 15 patients had the local masses shrank more or less. The ORR of local control reached 43.75%, and its DCR was 100%. In addition, the intratumor necrosis rate was 44.4% in the SD patients. Median progression-free survival was 3.8 months (95%Cl: 2.2–5.4). By treating the local mass, the symptoms of most patients were alleviated, and the quality of life was improved.

Conclusion

Our retrospective analysis revealed that hypofractionated radiotherapy combined with immunotherapy was effective in local control, it also relieved clinical symptoms and improved quality of life. The adverse effect rate was low. However, the incidence of abscopal effects was low either. This mode was suitable for the palliative treatment and expected to improve survival for patients with metastatic tumors.

Myeloid cell and cytokine interactions with chimeric antigen receptor-T-cell therapy: implication for future therapies

PURPOSE OF REVIEW

Chimeric antigen receptor (CAR)-T-cell therapy is a revolutionary tool in the treatment of cancer. CAR-T cells exhibit their effector functions through the recognition of their specific antigens on tumor cells and recruitment of other immune cells. However, this therapy is limited by the development of severe toxicities and modest antitumor activity in solid tumors. The host and tumor microenvironment interactions with CAR-T cells play an important role in orchestrating CAR-T-cell functions. Specifically, myeloid lineage cells and their cytokines critically influence the behavior of CAR-T cells. Here, we review the specific effects of myeloid cell interactions with CAR-T cells, their impact on CAR-T-cell response and toxicities, and potential efforts to modulate myeloid cell effects to enhance CAR-T-cell therapy efficacy and reduce toxicities.

RECENT FINDINGS

Independent studies and correlative science from clinical trials indicate that inhibitory myeloid cells and cytokines contribute to the development of CAR-T-cell-associated toxicities and impairment of their effector functions.

SUMMARY

These findings illuminate a novel way to reduce CAR-T-cell-associated toxicities and enhance their efficacy through the modulation of myeloid lineage cells and inhibitory cytokines.

Changes in peripheral immune cells after intraoperative radiation therapy in low-risk breast cancer

A detailed understanding of the interactions and the best dose-fractionation scheme of radiation to maximize antitumor immunity have not been fully established. In this study, the effect on the host immune system of a single dose of 20 Gy through intraoperative radiation therapy (IORT) on the surgical bed in low-risk breast cancer patients undergoing conserving breast cancer has been assessed. Peripheral blood samples from 13 patients were collected preoperatively and at 48 h and 3 and 10 weeks after the administration of radiation. We performed a flow cytometry analysis for lymphocyte subpopulations, natural killer cells (NK), regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSCs). We observed that the subpopulation of NK CD56+high CD16+ increased significantly at 3 weeks after IORT (0.30-0.42%, P < 0.001), while no changes were found in immunosuppressive profile, CD4+CD25+Foxp3+Helios+ Treg cells, granulocytic MDSCs (G-MDSCs) and monocytic MDSCs (Mo-MDSCs). A single dose of IORT may be an effective approach to improve antitumor immunity based on the increase in NK cells and the non-stimulation of immunosuppressive cells involved in immune escape. These findings support future combinations of IORT with immunotherapy, if they are confirmed in a large cohort of breast cancer patients.

RIG-I-Like Receptor LGP2 Is Required for Tumor Control by Radiotherapy

Dendritic cells (DC) play an essential role in innate immunity and radiation-elicited immune responses. LGP2 is a RIG-I-like receptor involved in cytoplasmic RNA recognition and antiviral responses. Although LGP2 has also been linked to cell survival of both tumor cells and T cells, the role of LGP2 in mediating DC function and antitumor immunity elicited by radiotherapy remains unclear. Here, we report that tumor DCs are linked to the clinical outcome of patients with breast cancer who received radiotherapy, and the presence of DC correlates with gene expression of LGP2 in the tumor microenvironment. In preclinical models, host LGP2 was essential for optimal antitumor control by ionizing radiation (IR). The absence of LGP2 in DC dampened type I IFN production and the priming capacity of DC. In the absence of LGP2, MDA5-mediated activation of type I IFN signaling was abrogated. The MDA5/LGP2 agonist high molecular weight poly I:C improved the antitumor effect of IR. This study reveals a previously undefined role of LGP2 in host immunity and provides a new strategy to improve the efficacy of radiotherapy. SIGNIFICANCE: These findings reveal an essential role of LGP2 in promoting antitumor immunity after radiotherapy and provide a new strategy to enhance radiotherapy.

Soluble PD-1: Predictive, Prognostic, and Therapeutic Value for Cancer Immunotherapy

Programmed death protein 1 (PD-1) interaction with PD-L1 deliver immunosuppressive environment for tumor growth, and its blockade with directed monoclonal antibodies (anti-PD-1/anti-PD-L1) has shown remarkable clinical outcome. Lately, their soluble counterparts, sPD-1 and sPD-L1, have been detected in plasma, and elevated levels have been associated with advanced disease, clinical stages, and worst prognosis for cancer patients. Elevated plasma levels of sPD-L1 have been correlated with worst prognosis in several studies and has displayed a persistent outlook. On the other hand, sPD-1 levels have been inconsistent in their predictive and prognostic ability. Pretherapeutic higher sPD-1 plasma levels have shown to predict advanced disease state and to a lesser extent worst prognosis. Any increase in sPD-1 plasma level post therapeutically have been correlated with improved survival for various cancers. In vitro and in vivo studies have shown sPD-1 ability to bind PD-L1 and PD-L2 and block PD-1/PD-L1 interaction. Local delivery of sPD-1 in cancer tumor microenvironment through local gene therapy have demonstrated an increase in tumor specific CD8+ T cell immunity and tumor growth reduction. It had also exhibited enhancement of T cell immunity induced by vaccination and other gene therapeutic agents. Furthermore, it may also lessen the inhibitory effect of circulating sPD-L1 and enhance the effects of mAb-based immunotherapy. In this review, we highlight various aspects of sPD-1 role in cancer prediction, prognosis, and anti-cancer immunity, as well as, its therapeutic value for local gene therapy or systemic immunotherapy in blocking the PD-1 and PD-L1 checkpoint interactions.

Gene signature based on B cell predicts clinical outcome of radiotherapy and immunotherapy for patients with lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most common and lethal cancer worldwide. Radiotherapy (RT) is widely used at all stages of LUAD, and the development of immunotherapy substantially enhances the survival of LUAD patients. Although the emerging treatments for LUAD have improved prognosis, only a small fraction of patients can benefit from clinical therapies. Thereby, approaches assessing responses to RT and immunotherapy in LUAD patients are essential. After integrating the analysis of RT, immunization, mRNA, and clinical information, we constructed a signature based on 308 tumor‐infiltrating B lymphocyte‐specific genes (TILBSig) using a machine learning method. TILBSig was composed of 6 B cell‐specific genes (PARP15, BIRC3, RUBCNL, SP110, TLE1, and FADS3), which were highly associated with the overall survival as independent factors. TILBSig was able to differentiate better survival compared with worse survival among different patients, and served as an independent factor for clinical characteristics. The low‐risk TILBSig group was correlated with more immune cell infiltration (especially B lineages) and lower cancer stem cell characteristics than the high‐risk group. The patients with lower risk scores were more likely to respond to RT and immunotherapy. TILBSig served as an excellent predicator for prognosis and response to immunotherapy and RT in LUAD patients.

Nanoscale metal-organic frameworks for x-ray activated in situ cancer vaccination

Cancer vaccines have been actively pursued to bolster antitumor immunity. Here, we designed nanoscale metal-organic frameworks (nMOFs) as locally activable immunotherapeutics to release danger-associated molecular patterns (DAMPs) and tumor antigens and deliver pathogen-associated molecular patterns (PAMPs) for in situ personalized cancer vaccination. When activated by x-rays, nMOFs effectively generate reactive oxygen species to release DAMPs and tumor antigens while delivering CpG oligodeoxynucleotides as PAMPs to facilitate the maturation of antigen-presenting cells. Together, DAMPs, tumor antigens, and PAMPs expand cytotoxic T cells in tumor-draining lymph nodes to reinvigorate the adaptive immune system for local tumor regression. When treated in combination with an immune checkpoint inhibitor, the local therapeutic effects of nMOF-based vaccines were extended to distant tumors via attenuating T cell exhaustion. Our work demonstrates the potential of nMOFs as x-ray-activable in situ cancer vaccines to awaken the host's innate and adaptive immune systems for systemic antitumor immunity.

Dual blockade of CD47 and HER2 eliminates radioresistant breast cancer cells

Although the efficacy of cancer radiotherapy (RT) can be enhanced by targeted immunotherapy, the immunosuppressive factors induced by radiation on tumor cells remain to be identified. Here, we report that CD47-mediated anti-phagocytosis is concurrently upregulated with HER2 in radioresistant breast cancer (BC) cells and RT-treated mouse syngeneic BC. Co-expression of both receptors is more frequently detected in recurrent BC patients with poor prognosis. CD47 is upregulated preferentially in HER2-expressing cells, and blocking CD47 or HER2 reduces both receptors with diminished clonogenicity and augmented phagocytosis. CRISPR-mediated CD47 and HER2 dual knockouts not only inhibit clonogenicity but also enhance macrophage-mediated attack. Dual antibody of both receptors synergizes with RT in control of syngeneic mouse breast tumor. These results provide the evidence that aggressive behavior of radioresistant BC is caused by CD47-mediated anti-phagocytosis conjugated with HER2-prompted proliferation. Dual blockade of CD47 and HER2 is suggested to eliminate resistant cancer cells in BC radiotherapy.

Advances in engineering local drug delivery systems for cancer immunotherapy

Cancer immunotherapy aims to leverage the immune system to suppress the growth of tumors and to inhibit metastasis. The recent promising clinical outcomes associated with cancer immunotherapy have prompted research and development efforts towards enhancing the efficacy of immune checkpoint blockade, cancer vaccines, cytokine therapy, and adoptive T cell therapy. Advancements in biomaterials, nanomedicine, and micro-/nano-technology have facilitated the development of enhanced local delivery systems for cancer immunotherapy, which can enhance treatment efficacy while minimizing toxicity. Furthermore, locally administered cancer therapies that combine immunotherapy with chemotherapy, radiotherapy, or phototherapy have the potential to achieve synergistic antitumor effects. Herein, the latest studies on local delivery systems for cancer immunotherapy are surveyed, with an emphasis on the therapeutic benefits associated with the design of biomaterials and nanomedicines. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

In-vivo and in-vitro impact of high-dose rate radiotherapy using flattening-filter-free beams on the anti-tumor immune response

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Effect of RT dose rate modulation on immune response has never been evaluated.

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Preclinical study using FFF RT technique in vivo and in vitro.

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RT dose rate did not influence radio-immune response parameters.

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We may modulate RT dose rate in association with immunotherapy without efficacy modification.

Introduction

Modern accelerators have the “flattening filter-free” (FFF) technique to deliver RT with a moderate high-dose rate, currently used in limited clinical indications. No scientifically established data are currently available on the possible effects of this high dose rate on the anti-tumor immune response. We therefore propose here to study these effects in a preclinical CT26 murine colorectal tumor model.

Material and methods

In-vitro, CT26 cells were irradiated on a Varian TrueBeam® linac at 3 different dose rates (4; 12 or 24 Gy/min) using the FFF mode. Activation of the anti-tumor immune response was evaluated by the analysis of induction of genes of the type I interferon pathway by RT-qPCR, and by the study of the induction of immunogenic death biomarkers. In-vivo, an efficacy study of RT delivering 16.5 Gy at 2 different dose rates was performed in immunocompetent Balb/c mice carrying CT26 syngeneic tumors, as well as an immunomonitoring analysed by flow cytometry and a transcriptomic analysis using RNA sequencing. Statistical analyzes were performed using non-parametric tests.

Results

In-vitro, no significant influence of an increase in FFF dose rate was shown for the induction of genes of the type I interferon pathway as well as for the studied immunogenic death markers (HMGB1 secretion). In-vivo, no difference in terms of tumor growth retardation between the 2 dose rates used was demonstrated, as well as for the composition of immune cell infiltrates within tumor microenvironment and the expression of immune checkpoints in immunomonitoring and RNAseq.

Conclusion

In this study involving the CT26 model, no influence of a moderate high dose rate in FFF technique on the anti-tumor immune response was demonstrated, which would make studies of associations between RT and checkpoint inhibitors fit with this technique of RT. However, further explorations using other cellular models seem to be of interest.

SBRT combined with PD-1/PD-L1 inhibitors in NSCLC treatment: a focus on the mechanisms, advances, and future challenges

Immune checkpoint inhibitors targeting programmed cell death 1 (PD-1), programmed cell death ligand-1 (PD-L1), and others have shown potent clinical efficacy and have revolutionized the treatment protocols of a broad spectrum of tumor types, especially non–small-cell lung cancer (NSCLC). Despite the substantial optimism of treatment with PD-1/PD-L1 inhibitors, there is still a large proportion of patients with advanced NSCLC who are resistant to the inhibitors. Preclinical and clinical trials have demonstrated that radiotherapy can induce a systemic antitumor immune response and have a great potential to sensitize refractory “cold” tumors to immunotherapy. Stereotactic body radiation therapy (SBRT), as a novel radiotherapy modality that delivers higher doses to smaller target lesions, has shown favorable antitumor effects with significantly improved local and distant control as well as better survival benefits in various solid tumors. Notably, research has revealed that SBRT is superior to conventional radiotherapy, possibly because of its more powerful immune activation effects. Thus, PD-1/PD-L1 inhibitors combined with SBRT instead of conventional radiotherapy might be more promising to fight against NSCLC, further achieving more favorable survival outcomes. In this review, we focus on the underlying mechanisms and recent advances of SBRT combined with PD-1/PD-L1 inhibitors with an emphasis on some future challenges and directions that warrant further investigation.

A tumor-immune interaction model for hepatocellular carcinoma based on measured lymphocyte counts in patients undergoing radiotherapy

PURPOSE

The impact of radiation therapy on the immune system has recently gained attention particularly when delivered in combination with immunotherapy. However, it is unclear how different treatment fractionation regimens influence the interaction between the immune system and radiation. The goal of this work was to develop a mathematical model that quantifies both the immune stimulating as well as the immunosuppressive effects of radiotherapy and simulates the effects of different fractionation regimens based on patient data.

METHODS AND MATERIALS

The framework describes the temporal evolution of tumor cells, lymphocytes, and inactivated dying tumor cells releasing antigens during radiation therapy, specifically modeling how recruited lymphocytes inhibit tumor progression. The parameters of the model were partly taken from the literature and in part extracted from blood samples (circulating lymphocytes: CLs) collected from hepatocellular carcinoma patients undergoing radiotherapy and their outcomes. The dose volume histograms to circulating lymphocytes were calculated with a probability-based model.

RESULTS

Based on the fitted parameters, the model enabled a study into the depletion and recovery of CLs in patients as a function of fractionation regimen. Our results quantify the ability of short fractionation regimens to lead to shorter periods of lymphocyte depletion and predict faster recovery after the end of treatment. The model shows that treatment breaks between fractions can prolong the period of lymphocyte depletion and should be avoided.

CONCLUSIONS

This study introduces a mathematical model for tumor-immune interactions using clinically extracted radiotherapy patient data, which can be applied to design trials aimed at minimizing lymphocyte depleting effects in radiation therapy.

Radiation-induced bystander and abscopal effects: important lessons from preclinical models

Radiotherapy is a pivotal component in the curative treatment of patients with localised cancer and isolated metastasis, as well as being used as a palliative strategy for patients with disseminated disease. The clinical efficacy of radiotherapy has traditionally been attributed to the local effects of ionising radiation, which induces cell death by directly and indirectly inducing DNA damage, but substantial work has uncovered an unexpected and dual relationship between tumour irradiation and the host immune system. In clinical practice, it is, therefore, tempting to tailor immunotherapies with radiotherapy in order to synergise innate and adaptive immunity against cancer cells, as well as to bypass immune tolerance and exhaustion, with the aim of facilitating tumour regression. However, our understanding of how radiation impacts on immune system activation is still in its early stages, and concerns and challenges regarding therapeutic applications still need to be overcome. With the increasing use of immunotherapy and its common combination with ionising radiation, this review briefly delineates current knowledge about the non-targeted effects of radiotherapy, and aims to provide insights, at the preclinical level, into the mechanisms that are involved with the potential to yield clinically relevant combinatorial approaches of radiotherapy and immunotherapy.

Radiosensitising Cancer Using Phosphatidylinositol-3-Kinase (PI3K), Protein Kinase B (AKT) or Mammalian Target of Rapamycin (mTOR) Inhibitors

Radiotherapy is routinely used as a neoadjuvant, adjuvant or palliative treatment in various cancers. There is significant variation in clinical response to radiotherapy with or without traditional chemotherapy. Patients with a good response to radiotherapy demonstrate better clinical outcomes universally across different cancers. The PI3K/AKT/mTOR pathway upregulation has been linked to radiotherapy resistance. We reviewed the current literature exploring the role of inhibiting targets along this pathway, in enhancing radiotherapy response. We identified several studies using in vitro cancer cell lines, in vivo tumour xenografts and a few Phase I/II clinical trials. Most of the current evidence in this area comes from glioblastoma multiforme, non-small cell lung cancer, head and neck cancer, colorectal cancer, and prostate cancer. The biological basis for radiosensitivity following pathway inhibition was through inhibited DNA double strand break repair, inhibited cell proliferation, enhanced apoptosis and autophagy as well as tumour microenvironment changes. Dual PI3K/mTOR inhibition consistently demonstrated radiosensitisation of all types of cancer cells. Single pathway component inhibitors and other inhibitor combinations yielded variable outcomes especially within early clinical trials. There is ample evidence from preclinical studies to suggest that direct pharmacological inhibition of the PI3K/AKT/mTOR pathway components can radiosensitise different types of cancer cells. We recommend that future in vitro and in vivo research in this field should focus on dual PI3K/mTOR inhibitors. Early clinical trials are needed to assess the feasibility and efficacy of these dual inhibitors in combination with radiotherapy in brain, lung, head and neck, breast, prostate and rectal cancer patients.

Killers 2.0: NK cell therapies at the forefront of cancer control

Natural killer (NK) cells are innate cytotoxic lymphocytes involved in the surveillance and elimination of cancer. As we have learned more and more about the mechanisms NK cells employ to recognize and eliminate tumor cells, and how, in turn, cancer evades NK cell responses, we have gained a clear appreciation that NK cells can be harnessed in cancer immunotherapy. Here, we review the evidence for NK cells' critical role in combating transformed and malignant cells, and how cancer immunotherapies potentiate NK cell responses for therapeutic purposes. We highlight cutting-edge immunotherapeutic strategies in preclinical and clinical development such as adoptive NK cell transfer, chimeric antigen receptor-expressing NK cells (CAR-NKs), bispecific and trispecific killer cell engagers (BiKEs and TriKEs), checkpoint blockade, and oncolytic virotherapy. Further, we describe the challenges that NK cells face (e.g., postsurgical dysfunction) that must be overcome by these therapeutic modalities to achieve cancer clearance.

The future of radiation-induced abscopal response: beyond conventional radiotherapy approaches

Advances in the immunological pharmaceuticals, such as checkpoint inhibitors and agonists, have positive implications for the future of the radiotherapy abscopal response. A once rare phenomenon, whereby distant nonirradiated tumor sites regressed after radiotherapy alone, may become more common when combined with the immune modulating agents. Radiotherapy can increase neoantigen expression, increased tumor PD-L1 expression, increase MHC class I expression, reverse exhausted CD8 T cells and increase tumor-infiltrating tumors within the tumor microenvironment. These changes in the tumor and the tumor microenvironment after radiotherapy could potentiate responses to anti-CTL-4, anti-PD-L1/PD-1 and other immunotherapy agents. Thus, advances in checkpoint inhibitors have increased interest in re-evaluation of the role of conventional radiotherapy approaches on the immune system. We reviewed newer nonconventional approaches such as SBRT-PATHY, GRID, FLASH, carbon ion and proton therapy and their role in eliciting immune responses. We believe that combining these novel radiation methods may enhance the outcome with the newly US FDA approved immune modulating agents.

Impact of Neoadjuvant Chemoradiation on Pathologic Response in Patients With Localized Pancreatic Cancer

Introduction/Background: Multimodal neoadjuvant therapy has resulted in increased rates of histologic response in pancreatic tumors and adjacent lymph nodes. The biologic significance of the collective response in the primary tumor and lymph nodes is not understood.

Methods: Patients with localized PC who received neoadjuvant therapy and surgery with histologic assessment of the primary tumor and local-regional lymph nodes were included. Histopathologic response was classified using the modified Ryan score as follows: no viable cancer cells (CR), rare groups of cancer cells (nCR), residual cancer with evident tumor regression (PR), and extensive residual cancer with no evident tumor regression (NR). Nodal status was defined by number of lymph nodes (LN) with tumor metastases: N0 (0 LN), N1 (1–3), N2 (≥4).

Results: Of 341 patients with localized PC who received neoadjuvant therapy and surgery, 107 (31%) received chemoradiation alone, 44 (13%) received chemotherapy alone, and 190 (56%) received chemotherapy and chemoradiation. Histopathologic response consisted of 15 (4%) CRs, 59 (17%) nCRs, 188 (55%) PRs, and 79 (23%) NRs. Patients who received chemotherapy alone had the worst responses (n = 21 for NR, 48%) as compared to patients who received chemoradiation alone (n = 25 for NR, 24%) or patients who received both therapies (n = 33 for NR, 17%) (Table 1; p = 0.001). Median overall survival for all 341 patients was 39 months; OS by histopathologic subtype was not reached (CR), 49 months (nCR), 38 months (PR), and 34 months (NR), respectively (p = 0.004). Of the 341 patients, 208 (61%) had N0 disease, 97 (28%) had N1 disease, and 36 (11%) had N2 disease. In an adjusted hazards model, modified Ryan score of PR or NR (HR: 1.71; 95% CI: 1.15–2.54; p = 0.008) and N1 (HR: 1.42; 95% CI: 1.1.02–2.01; p = 0.04), or N2 disease (HR: 2.54, 95% CI: 1.64–3.93; p < 0.001) were associated with increased risk of death.

Conclusions: Neoadjuvant chemotherapy alone is associated with lower rates of pathologic response. Patients with CR or nCR have a significantly improved OS as compared to patients with PR or NR. Nodal status is the most important pathologic prognostic factor. Neoadjuvant chemoradiation may be an important driver of pathologic response.

Adrenergic stress constrains the development of anti-tumor immunity and abscopal responses following local radiation

The abscopal effect following ionizing radiation therapy (RT) is considered to be a rare event. This effect does occur more frequently when combined with other therapies, including immunotherapy. Here we demonstrate that the frequency of abscopal events following RT alone is highly dependent upon the degree of adrenergic stress in the tumor-bearing host. Using a combination of physiologic, pharmacologic and genetic strategies, we observe improvements in the control of both irradiated and non-irradiated distant tumors, including metastatic tumors, when adrenergic stress or signaling through β-adrenergic receptor is reduced. Further, we observe cellular and molecular evidence of improved, antigen-specific, anti-tumor immune responses which also depend upon T cell egress from draining lymph nodes. These data suggest that blockade of β2 adrenergic stress signaling could be a useful, safe, and feasible strategy to improve efficacy in cancer patients undergoing radiation therapy.

Sublethal Radiation Affects Antigen Processing and Presentation Genes to Enhance Immunogenicity of Cancer Cells

While immunotherapy in cancer is designed to stimulate effector T cell response, tumor-associated antigens have to be presented on malignant cells at a sufficient level for recognition of cancer by T cells. Recent studies suggest that radiotherapy enhances the anti-cancer immune response and also improves the efficacy of immunotherapy. To understand the molecular basis of such observations, we examined the effect of ionizing X-rays on tumor antigens and their presentation in a set of nine human cell lines representing cancers of the esophagus, lung, and head and neck. A single dose of 7.5 or 15 Gy radiation enhanced the New York esophageal squamous cell carcinoma 1 (NY-ESO-1) tumor-antigen-mediated recognition of cancer cells by NY-ESO-1-specific CD8⁺ T cells. Irradiation led to significant enlargement of live cells after four days, and microscopy and flow cytometry revealed multinucleation and polyploidy in the cells because of dysregulated mitosis, which was also revealed in RNA-sequencing-based transcriptome profiles of cells. Transcriptome analyses also showed that while radiation had no universal effect on genes encoding tumor antigens, it upregulated the expression of numerous genes involved in antigen processing and presentation pathways in all cell lines. This effect may explain the immunostimulatory role of cancer radiotherapy.

Interferon-Induced IDO1 Mediates Radiation Resistance and Is a Therapeutic Target in Colorectal Cancer

Colorectal cancer is a major cause of mortality worldwide. Chemotherapy and radiation remain standard treatment for locally advanced disease, with current immune-targeting therapies applying to only a small subset of patients. Expression of the immuno-oncology target indoleamine 2,3 dioxygenase 1 (IDO1) is associated with poor colorectal cancer clinical outcomes but is understudied as a potential treatment target. In this study, we examined the interaction between the IDO1 pathway and radiotherapy in colorectal cancer. We used human and mouse colorectal cancer cell lines, organoids, mouse syngeneic colorectal cancer tumor graft models, and colorectal cancer tissues from patients who received radiotherapy. IDO1 activity was blocked using the clinical IDO1 inhibitor epacadostat and by genetic disruption. We found that radiation induced IDO1 overexpression in colorectal cancer through type I and II IFN signaling. IDO1 enzymatic activity directly influenced colorectal cancer radiation sensitivity. IDO1 inhibition sensitized colorectal cancer to radiation-induced cell death, whereas the IDO1 metabolite kynurenine promoted radioprotection. IDO1 inhibition also potentiated Th1 cytokines and myeloid cell-modulating factors in the tumor microenvironment and promoted an abscopal effect on tumors outside the radiation field. Conversely, IDO1 blockade protected the normal small intestinal epithelium from radiation toxicity and accelerated recovery from radiation-induced weight loss, indicating a role in limiting side effects. These data demonstrated that IDO1 inhibition potentiates radiotherapy effectiveness in colorectal cancer. The findings also provide rationale and mechanistic insight for the study of IDO1 inhibitors as adjuvant therapy to radiation in patients with locally advanced sporadic and colitis-associated colorectal cancer.

Chemoradiation and granulocyte-colony or granulocyte macrophage-colony stimulating factors (G-CSF or GM-CSF): time to think out of the box?

Concerns have been raised about potential toxic interactions when colony-stimulating factors (CSFs) and chemoradiation are concurrently performed. In 2006, the ASCO guidelines advised against their concomitant use. Nevertheless, with the development of modern radiotherapy techniques and supportive care, the therapeutic index of combined chemotherapy, radiotherapy, and CSFs is worth reassessing. Recent clinical trials testing chemoradiation in lung cancer let investigators free to decide the use of concomitant CSFs or not. No abnormal infield event was reported after the use of modern radiotherapy techniques and concomitant chemotherapy regimens. These elements call for further investigation to set new recommendations in favour of the association of chemoradiation and CSFs. Moreover, radiotherapy could induce anticancer systemic effects mediated by the immune system in vitro and in vivo. With combined CSFs, this effect was reinforced in preclinical and clinical trials introducing innovative radioimmunotherapy models. So far, the association of radiation with CSFs has not been combined with immunotherapy. However, it might play a major role in triggering an immune response against cancer cells, leading to abscopal effects. The present article reassesses the therapeutic index of the combination CSFs-chemoradiation through an updated review on its safety and efficacy. It also provides a special focus on radioimmunotherapy.

Preclinical Activity of Embryonic Annexin A2-Specific Chimeric Antigen Receptor T Cells Against Ovarian Cancer

Chimeric antigen receptors (CARs) have found clinical success in B cell malignancies, but a dearth of potential targets limits their wider clinical application, especially in solid tumours. Here, we describe the development of an anti-annexin A2 CAR, CAR(2448), derived from an antibody found to have activity against epithelial ovarian cancer cell lines. The spacer length of CAR(2448) was optimised based on in vitro cytotoxic activity against ovarian cancer (OC) cell lines via a real-time cytotoxicity assay. The longer spacer CAR(2448)L T cells exhibit significant effector activity, inducing inflammatory cytokine release and cytotoxicity against OC cell lines. Furthermore, CAR(2448)L-BBz T cells induced enhanced survival in an in vivo OC xenograft model and reduced tumour volume by 76.6%. Our preclinical studies of CAR(2448) suggest its potential for the unmet need of novel strategies for the treatment of ovarian cancer.

Integration of stereotactic radiosurgery or whole brain radiation therapy with immunotherapy for treatment of brain metastases

The prognosis of brain metastases (BM) is traditionally poor. BM are mainly treated by local radiotherapy, including stereotactic radiosurgery (SRS) or whole brain radiation therapy (WBRT). Recently, immunotherapy (i.e., immune checkpoint inhibitors, ICI) has demonstrated a survival advantage in multiple malignancies commonly associated with BM. Individually, radiotherapy and ICI both treat BM efficiently; hence, their combination seems logical. In this review, we summarize the existing preclinical and clinical evidence that supports the applicability of radiotherapy as a sensitizer of ICI for BM. Further, we discuss the optimal timing at which radiotherapy and ICI should be administered and review the safety of the combination therapy. Data from a few clinical studies suggest that combining SRS or WBRT with ICI simultaneously rather than consecutively potentially enhances brain abscopal-like responses and survival. However, there is a lack of conclusion about the definition of "simultaneous"; the cumulative toxic effect of the combined therapies also requires further study. Thus, ongoing and planned prospective trials are needed to further explore and validate the effect, safety, and optimal timing of the combination of immunotherapy with radiotherapy for patients with BM.

Enhanced Radiation Sensitivity of Human Papillomavirus-Driven Head and Neck Cancer: Focus on Immunological Aspects

Head and neck squamous cell carcinomas (HNSCC), emerging in the mucosa of the upper aerodigestive tract, are associated with either the classical risk factors, tobacco and alcohol consumption, or with infections with high-risk types of the human papillomavirus (HPV). Depending on the involvement of HPV, HNSCC follow different pathways of carcinogenesis and show distinct clinical presentations regarding survival, prognosis and treatment response. For instance, HPV-driven HNSCC exhibit an enhanced radiation response compared to their typically radioresistant HPV-negative counterparts. Although radiosensitivity of HNSCC has been studied by many research groups, the major causes for the difference in radiation responses between HPV-driven and HPV-negative HNSCC are still an open question. In this mini review, we discuss the reported cellular and immunological factors involved in the enhanced radiation response in HPV-driven HNSCC, focusing on the vital role of the immune response in the outcome of HNSCC radiotherapy.

A Novel Anti-PD-L1 Vaccine for Cancer Immunotherapy and Immunoprevention

Dendritic cells (DCs) are potent antigen-presenting cells that play a critical role in activating cellular and humoral immune responses. DC-based tumor vaccines targeting tumor-associated antigens (TAAs) have been extensively tested and demonstrated to be safe and potent in inducing anti-TAA immune responses in cancer patients. Sipuleucel-T (Provenge), a cancer vaccine of autologous DCs loaded with TAA, was approved by the United States Food and Drug Administration (FDA) for the treatment of castration-resistant prostate cancer. Sipuleucel-T prolongs patient survival, but has little or no effect on clinical disease progression or biomarker kinetics. Due to the overall limited clinical efficacy of tumor vaccines, there is a need to enhance their potency. PD-L1 is a key immune checkpoint molecule and is frequently overexpressed on tumor cells to evade antitumor immune destruction. Repeated administrations of PD-L1 or PD-1 antibodies have induced sustained tumor regression in a fraction of cancer patients. In this study, we tested whether vaccinations with DCs, loaded with a PD-L1 immunogen (PDL1-Vax), are able to induce anti-PD-L1 immune responses. We found that DCs loaded with PDL1-Vax induced anti-PD-L1 antibody and T cell responses in immunized mice and that PD-L1-specific CTLs had cytolytic activities against PD-L1⁺ tumor cells. We demonstrated that vaccination with PDL1-Vax DCs potently inhibited the growth of PD-L1⁺ tumor cells. In summary, this study demonstrates for the first time the principle and feasibility of DC vaccination (PDL1-Vax) to actively induce anti-PD-L1 antibody and T cell responses capable of inhibiting PD-L1⁺ tumor growth. This novel anti-PD-L1 vaccination strategy could be used for cancer treatment and prevention.

Interferons α and β in cancer: therapeutic opportunities from new insights

Over the past decade, preclinical and clinical research have confirmed the essential role of interferons for effective host immunological responses to malignant cells. Type I interferons (IFNα and IFNβ) directly regulate transcription of >100 downstream genes, which results in a myriad of direct (on cancer cells) and indirect (through immune effector cells and vasculature) effects on the tumour. New insights into endogenous and exogenous activation of type I interferons in the tumour and its microenvironment have given impetus to drug discovery and patient evaluation of interferon-directed strategies. When combined with prior observations or with other effective modalities for cancer treatment, modulation of the interferon system could contribute to further reductions in cancer morbidity and mortality. This Review discusses new interferon-directed therapeutic opportunities, ranging from cyclic dinucleotides to genome methylation inhibitors, angiogenesis inhibitors, chemoradiation, complexes with neoantigen-targeted monoclonal antibodies, combinations with other emerging therapeutic interventions and associations of interferon-stimulated gene expression with patient prognosis - all of which are strategies that have or will soon enter translational clinical evaluation.

Oncolytic Newcastle disease virus expressing a checkpoint inhibitor as a radioenhancing agent for murine melanoma

BACKGROUND

Monoclonal antibodies (mAbs) targeting negative regulators, or checkpoint molecules (e.g. PD1/PD-L1 & CTLA4), of anti-tumoural T cells have demonstrated clinical efficacy in treating several neoplastic diseases. While many patients enjoy remarkable responses to checkpoint inhibitors, a majority show adverse effects. Understanding how checkpoint inhibitors may augment established chemotherapy or radiotherapy regimens or other immunotherapies like oncolytic viruses may lead to better clinical outcomes measured by improved efficacy with reduced toxicity. Here, we assess how Newcastle disease virus (NDV), an oncolytic virus in clinical testing, may interact with radiotherapy to enhance checkpoint inhibitor blockade.

METHODS

An immunocompetent B16-F10 murine melanoma model, generally considered to be a poorly immunogenic or "cold" tumour, was utilised to query whether combining localised radiotherapy with NDV may be more effective than either therapy alone in controlling tumours in mice treated with anti-PD1 or anti-CTLA4 monoclonal antibodies. We also investigated whether localised administration of a checkpoint inhibitor through an intratumoural injection of NDV that expresses anti-CTLA4 single-chain variable fragment (scFv) is comparable to systemic administration of anti-CTLA4 when combined with radiation in mediating its anti-tumour efficacy. Response rates were characterised by measuring tumour size over time, observation of complete tumour regression, and overall survival.

FINDINGS

Our results show that combining NDV plus radiotherapy with checkpoint inhibitors (PD1 or CTLA4 targeted mAbs) results in significantly better complete tumour regression rates with an abscopal effect in a murine model of melanoma than either single therapy combined with checkpoint inhibitors. Finally, we also show that localised administration of a recombinant NDV expressing anti-CTLA4 plus radiation is comparable to systemic anti-CTLA4 plus radiation in mediating its anti-tumour effect as assayed by survival benefit.

INTERPRETATION

Our results show that oncolytic NDV plus radiotherapy work together with checkpoint inhibitors to enhance tumour clearance of murine melanoma. NDV is an effective radiotherapy dose-sparing and immunotherapeutic agent capable of transgenic, in vivo expression of an anti-CTLA4 targeted scFv antibody with the potential to spare systemic exposure.

FUNDING

The National Institutes of Health grant HHSN272201400008C supported the work. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Combining alpha radiation-based brachytherapy with immunomodulators promotes complete tumor regression in mice via tumor-specific long-term immune response

Diffusing alpha-emitters radiation therapy (DaRT) is the only known method for treating solid tumors with highly destructive alpha radiation. More importantly, as a monotherapy, DaRT has been shown to induce a systemic antitumor immune response following tumor ablation. Here, immunomodulatory strategies to boost the antitumor immune response induced by DaRT, and the response specificity, were investigated in the colon cancer CT26 mouse model. Local treatment prior to DaRT, with the TLR3 agonist poly I:C, was sufficient to inhibit tumor growth relative to poly I:C or DaRT alone. DaRT used in combination with the TLR9 agonist CpG, or with the TLR1/2 agonist XS15 retarded tumor growth and increased tumor-rejection rates, compared to DaRT alone, curing 41% and 20% of the mice, respectively. DaRT in combination with CpG, the Treg inhibitor cyclophosphamide, and the MDSC inhibitor sildenafil, cured 51% of the animals, compared to only 6% and 0% cure when immunomodulation or DaRT was used alone, respectively. Challenge and Winn assays revealed that these high cure rates involved a specific immunological memory against CT26 antigens. We suggest that DaRT acts in synergy with immunomodulation to induce a specific and systemic antitumor immune response. This strategy may serve as a safe and efficient method not only for tumor ablation, but also for in situ vaccination of cancer patients.

Two may be better than one: PD-1/PD-L1 blockade combination approaches in metastatic breast cancer

Antibodies blocking programmed death 1 (anti-PD-1) or its ligand (anti-PD-L1) are associated with modest response rates as monotherapy in metastatic breast cancer, but are generally well tolerated and capable of generating dramatic and durable benefit in a minority of patients. Anti-PD-1/L1 antibodies are also safe when administered in combination with a variety of systemic therapies (chemotherapy, targeted therapies), as well as with radiotherapy. We summarize preclinical, translational, and preliminary clinical data in support of combination approaches with anti-PD-1/L1 in metastatic breast cancer, focusing on potential mechanisms of synergy, and considerations for clinical practice and future investigation.

Tumor-reprogrammed resident T cells resist radiation to control tumors

Successful combinations of radiotherapy and immunotherapy depend on the presence of live T cells within the tumor; however, radiotherapy is believed to damage T cells. Here, based on longitudinal in vivo imaging and functional analysis, we report that a large proportion of T cells survive clinically relevant doses of radiation and show increased motility, and higher production of interferon gamma, compared with T cells from unirradiated tumors. Irradiated intratumoral T cells can mediate tumor control without newly-infiltrating T cells. Transcriptomic analysis suggests T cell reprogramming in the tumor microenvironment and similarities with tissue-resident memory T cells, which are more radio-resistant than circulating/lymphoid tissue T cells. TGFβ is a key upstream regulator of T cell reprogramming and contributes to intratumoral Tcell radio-resistance. These findings have implications for the design of radio-immunotherapy trials in that local irradiation is not inherently immunosuppressive, and irradiation of multiple tumors might optimize systemic effects of radiotherapy.