Increasing the efficacy of radiotherapy by modulating the CCR2/CCR5 chemokine axes

Interactions and communications in lung tumour microenvironment: chemo/radiotherapy resistance mechanisms and therapeutic targets

The lung tumour microenvironment (TME) is composed of various cell types, including cancer cells, stromal and immune cells, as well as extracellular matrix (ECM). These cells and surrounding ECM create a stiff, hypoxic, acidic and immunosuppressive microenvironment that can augment the resistance of lung tumours to different forms of cell death and facilitate invasion and metastasis. This environment can induce chemo/radiotherapy resistance by inducing anti-apoptosis mediators such as phosphoinositide 3-kinase (PI3K)/Akt, signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa B (NF-κB), leading to the exhaustion of antitumor immunity and further resistance to chemo/radiotherapy. In addition, lung tumour cells can resist chemo/radiotherapy by boosting multidrug resistance mechanisms and antioxidant defence systems within cancer cells and other TME components. In this review, we discuss the interactions and communications between these different components of the lung TME and also the effects of hypoxia, immune evasion and ECM remodelling on lung cancer resistance. Finally, we review the current strategies in preclinical and clinical studies, including the inhibition of checkpoint molecules, chemoattractants, cytokines, growth factors and immunosuppressive mediators such as programmed death 1 (PD-1), insulin-like growth factor 2 (IGF-2) for targeting the lung TME to overcome resistance to chemotherapy and radiotherapy.

Leveraging radiotherapy to improve immunotherapy outcomes: rationale, progress and research priorities

The most successful immunotherapies for solid malignancies to date, immune checkpoint inhibitors, target the essential role of T cells in antitumor immunity. However, T-cell dysfunction presents a major hindrance to treatment efficacy, warranting research into combined treatment strategies for improving outcomes. The use of radiotherapy for this purpose has garnered much interest. Preclinical study has established that radiotherapy activates various immune mechanisms to improve T-cell activation, localisation and function within tumors, which improves response to immune checkpoint inhibitors. However, so far, these strategies have not been successfully translated into the clinic. Here, we briefly reflect on the development of immune checkpoint inhibitors and the mechanistic insights revealed by an evolving understanding of T-cell dysfunction in cancer, before providing an overview of the immunomodulatory effects of radiotherapy in the context of the T-cell-mediated antitumor immune response. We discuss the mixed results of clinical trials, comment on various factors that may preclude immuno-radiotherapy responses in the clinic, and highlight priorities for preclinical and clinical study. Finally, we discuss the role of emerging combinations of radiotherapy and immunotherapy to potentially provide additional treatment options and improve outcomes for patients.

Myeloid cells: key players in tumor microenvironments

Cancer is the result of evolving crosstalk between neoplastic cell and its immune microenvironment. In recent years, immune therapeutics targeting T lymphocytes, such as immune checkpoint blockade (ICB) and CAR-T, have made significant progress in cancer treatment and validated targeting immune cells as a promising approach to fight human cancers. However, responsiveness to the current immune therapeutic agents is limited to only a small proportion of solid cancer patients. As major components of most solid tumors, myeloid cells played critical roles in regulating the initiation and sustentation of adaptive immunity, thus determining tumor progression as well as therapeutic responses. In this review, we discuss emerging data on the diverse functions of myeloid cells in tumor progression through their direct effects or interactions with other immune cells. We explain how different metabolic reprogramming impacts the characteristics and functions of tumor myeloid cells, and discuss recent progress in revealing different mechanisms-chemotaxis, proliferation, survival, and alternative sources-involved in the infiltration and accumulation of myeloid cells within tumors. Further understanding of the function and regulation of myeloid cells is important for the development of novel strategies for therapeutic exploitation in cancer.

Regulation of ROS signaling by TIGAR induces cancer-modulating responses in the tumor microenvironment

The consequences of reactive oxygen species (ROS) in cancer cells are complex and have been shown to both promote and retard tumorigenesis in different models. In mouse models of pancreatic ductal adenocarcinoma (PDAC), loss of the antioxidant defense gene Tigar results in both a reduction in the development of early pancreatic intraepithelial neoplasia and an increase in invasive and metastatic capacity, accompanied by decreased survival of mice lacking pancreatic TIGAR. We previously demonstrated that increased ROS following loss of TIGAR promotes various cancer cell-intrinsic changes that contribute to metastatic capacity, including epithelial to mesenchymal transition, enhanced migration and invasion, and an increase in ERK signaling. In this study, we show that pancreatic overexpression of TIGAR decreases metastatic capacity and migratory phenotypes in an aggressive model of PDAC, consistent with the concept that dynamic modulation of TIGAR in PDAC contributes to the development and progression of these tumors. Using TIGAR deficient and overexpressing mouse models, we find that the impact of modulation of TIGAR and ROS in PDAC cells also has a profound effect on the normal stromal cells surrounding the tumor. Loss of TIGAR promotes the production of cytokines by cancer cells that induce changes in the surrounding fibroblasts to adopt a tumor-supportive phenotype. Furthermore, these cytokines also attract macrophages that support PDAC dissemination and metastasis. Taken together our work shows that TIGAR-modulated ROS in PDAC can control cell intrinsic and extrinsic changes to impact tumor aggression.

Cold and hot tumors: from molecular mechanisms to targeted therapy

Immunotherapy has made significant strides in cancer treatment, particularly through immune checkpoint blockade (ICB), which has shown notable clinical benefits across various tumor types. Despite the transformative impact of ICB treatment in cancer therapy, only a minority of patients exhibit a positive response to it. In patients with solid tumors, those who respond well to ICB treatment typically demonstrate an active immune profile referred to as the "hot" (immune-inflamed) phenotype. On the other hand, non-responsive patients may exhibit a distinct "cold" (immune-desert) phenotype, differing from the features of "hot" tumors. Additionally, there is a more nuanced "excluded" immune phenotype, positioned between the "cold" and "hot" categories, known as the immune "excluded" type. Effective differentiation between "cold" and "hot" tumors, and understanding tumor intrinsic factors, immune characteristics, TME, and external factors are critical for predicting tumor response and treatment results. It is widely accepted that ICB therapy exerts a more profound effect on "hot" tumors, with limited efficacy against "cold" or "altered" tumors, necessitating combinations with other therapeutic modalities to enhance immune cell infiltration into tumor tissue and convert "cold" or "altered" tumors into "hot" ones. Therefore, aligning with the traits of "cold" and "hot" tumors, this review systematically delineates the respective immune characteristics, influencing factors, and extensively discusses varied treatment approaches and drug targets based on "cold" and "hot" tumors to assess clinical efficacy.

Multiple cytokine analysis of aqueous humor in uveitis with or without secondary glaucoma

To assess the level of both pro-inflammatory and anti-inflammatory cytokines in the aqueous humor (AH) of patients suffering from uveitis, with or without coexisting glaucoma, and compare them with patients diagnosed with primary open-angle glaucoma (POAG) and those with age-related cataract (ARC). By using Luminex xMAP® multiplex assays analyses, we assessed levels of 11 cytokines and chemokines, and compared them across groups, including uveitis-secondary glaucoma (USG) (n = 16), uveitis without glaucoma (UwoG), (n = 16), POAG (n = 16), and ARC (n = 16) to explore the correlation between these cytokines and the presence of uveitis, as well as intraocular pressure (IOP). Pro-inflammatory factors MCP-1, MIP-1β, IL-6, IL-8, and transforming growth factors TGF-β1 and TGF-β2 were significantly elevated in the AH of USG eyes. In the case of enhanced anti-inflammatory in the perioperative period, the pro-inflammatory factors remained notably elevated in the USG group compared to the UwoG group (P < 0.01). The levels of IL-6, IL-8, and MCP-1 in the AH of the USG group and POAG group had the same trend, which markedly surpassed those of the ARC group (P < 0.01). Significantly increased levels of MCP-1, MIP-1β, IL-6, IL-8, TGF-β1, and TGF-β2 were found in the AH of USG patients, implying a potential role for these mediators in the progression of glaucomatous manifestations within patients with uveitis. Besides the analysis revealed no discernible statistical disparity in cytokine concentrations within the AH of USG eyes whether the preoperative baseline IOP was greater than 30 mmHg or not, indicating that the safety of antiglaucoma surgery in USG patients even with baseline high IOP.

Mechanism of immune activation mediated by genomic instability and its implication in radiotherapy combined with immune checkpoint inhibitors

Various genetic and epigenetic changes associated with genomic instability (GI), including DNA damage repair defects, chromosomal instability, and mitochondrial GI, contribute to development and progression of cancer. These alterations not only result in DNA leakage into the cytoplasm, either directly or through micronuclei, but also trigger downstream inflammatory signals, such as the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway. Apart from directly inducing DNA damage to eliminate cancer cells, radiotherapy (RT) exerts its antitumor effects through intracellular DNA damage sensing mechanisms, leading to the activation of downstream inflammatory signaling pathways. This not only enables local tumor control but also reshapes the immune microenvironment, triggering systemic immune responses. The combination of RT and immunotherapy has emerged as a promising approach to increase the probability of abscopal effects, where distant tumors respond to treatment due to the systemic immunomodulatory effects. This review emphasizes the importance of GI in cancer biology and elucidates the mechanisms by which RT induces GI remodeling of the immune microenvironment. By elucidating the mechanisms of GI and RT-induced immune responses, we aim to emphasize the crucial importance of this approach in modern oncology. Understanding the impact of GI on tumor biological behavior and therapeutic response, as well as the possibility of activating systemic anti-tumor immunity through RT, will pave the way for the development of new treatment strategies and improve prognosis for patients.

Combining immunotherapy and radiation therapy in gastrointestinal cancers: A review

INTRODUCTION AND PURPOSE

With a significant global impact, treatment of gastrointestinal (GI) cancers still presents with challenges, despite current multimodality approaches in advanced stages. Clinical trials are expanding for checkpoint inhibition (ICI) combined with radiation therapy (RT). This review intends to offer a comprehensive image of the current data regarding the effectiveness of this association, and to reflect on possible directions to further optimize the results.

RESULTS

Several early phase studies demonstrated encouraging potential. However, translating preclinical outcomes to clinical settings proves challenging, especially in immunologically "cold" environments. GI cancers exhibit heterogeneity, requiring tailored approaches based on disease stage and patient characteristics. Current results, though promising, lack the power of evidence to influence the general practice.

CONCLUSIONS

Finding biomarkers for identifying or converting resistant cancers is essential for maximizing responses, moreover in this context strategic RT parameters need to be carefully considered. Our review emphasizes the significance of having a thorough grasp of how immunology, tumour biology, and treatment settings interact in order to propose novel research avenues and efficient GI cancer therapy.

Synergistic treatment strategy: combining CAR-NK cell therapy and radiotherapy to combat solid tumors

Immunotherapy, notably chimeric antigen receptor (CAR) modified natural killer (NK) cell therapy, has shown exciting promise in the treatment of hematologic malignancies due to its unique advantages including fewer side effects, diverse activation mechanisms, and wide availability. However, CAR-NK cell therapies have demonstrated limited efficacy against solid tumors, primarily due to challenges posed by the solid tumor microenvironment. In contrast, radiotherapy, a well-established treatment modality, has been proven to modulate the tumor microenvironment and facilitate immune cell infiltration. With these observations, we hypothesize that a novel therapeutic strategy integrating CAR-NK cell therapy with radiotherapy could enhance the ability to treat solid tumors. This hypothesis aims to address the obstacles CAR-NK cell therapies face within the solid tumor microenvironment and explore the potential efficacy of their combination with radiotherapy. By capitalizing on the synergistic advantages of CAR-NK cell therapy and radiotherapy, we posit that this could lead to improved prognoses for patients with solid tumors.

Role of chemokines in the crosstalk between tumor and tumor-associated macrophages

Tumor microenvironment (TME) consists of a dynamic network of non-tumoral stromal cells, including cancer-associated fibroblasts, endothelial cells, tumor-associated macrophages (TAMs), B and T cells. In the TME, TAMs support tumor initiation, progression, invasion and metastasis by promoting angiogenesis and immunosuppression of the tumor cells. There is close crosstalk between TAMs and tumor cells. Notably, chemokines are a significant messenger mediating the crosstalk between tumor cells and TAMs. TAMs can promote tumor progression via secretion of chemokines. Various chemokines secreted by tumors are involved in the generation and polarization of TAMs, the infiltration of TAMs in tumors, and the development of TAMs' suppressive function. This paper reviews CCL2-CCR2, CCL3/5-CCR5, CCL15-CCR1, CCL18-CCR8, CX3CL1/CCL26-CX3CR1, CXCL8-CXCR1/2, CXCL12-CXCR4/CXCR7 signaling pathways, their role in the recruitment, polarization and exertion of TAMs, and their correlation with tumor development, metastasis and prognosis. Furthermore, we present the current research progress on modulating the effects of TAMs with chemokine antagonists and discuss the prospects and potential challenges of using chemokine antagonists as therapeutic tools for cancer treatment. The TAMs targeting by chemokine receptor antagonists in combination with chemotherapy drugs, immune checkpoint inhibitors or radiotherapy appears to be a promising approach.

Vitamin D Receptor Antagonist MeTC7 Inhibits PD-L1

Small-molecule inhibitors of PD-L1 are postulated to control immune evasion in tumors similar to antibodies that target the PD-L1/PD-1 immune checkpoint axis. However, the identity of targetable PD-L1 inducers is required to develop small-molecule PD-L1 inhibitors. In this study, using chromatin immunoprecipitation (ChIP) assay and siRNA, we demonstrate that vitamin D/VDR regulates PD-L1 expression in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells. We have examined whether a VDR antagonist, MeTC7, can inhibit PD-L1. To ensure that MeTC7 inhibits VDR/PD-L1 without off-target effects, we examined competitive inhibition of VDR by MeTC7, utilizing ligand-dependent dimerization of VDR-RXR, RXR-RXR, and VDR-coactivators in a mammalian 2-hybrid (M2H) assay. MeTC7 inhibits VDR selectively, suppresses PD-L1 expression sparing PD-L2, and inhibits the cell viability, clonogenicity, and xenograft growth of AML cells. MeTC7 blocks AML/mesenchymal stem cells (MSCs) adhesion and increases the efferocytotic efficiency of THP-1 AML cells. Additionally, utilizing a syngeneic colorectal cancer model in which VDR/PD-L1 co-upregulation occurs in vivo under radiation therapy (RT), MeTC7 inhibits PD-L1 and enhances intra-tumoral CD8+T cells expressing lymphoid activation antigen-CD69. Taken together, MeTC7 is a promising small-molecule inhibitor of PD-L1 with clinical potential.

Mechanistic rationales for combining immunotherapy with radiotherapy

Immunotherapy consisted mainly of immune checkpoint inhibitors (ICIs) has led to significantly improved antitumor response. However, such response has been observed only in tumors possessing an overall responsive tumor immune micro-environment (TIME), in which the presence of functional tumor-infiltrating lymphocytes (TILs) is critical. Various mechanisms of immune escape from immunosurveillance exist, leading to different TIME phenotypes in correlation with primary or acquired resistance to ICIs. Radiotherapy has been shown to induce antitumor immunity not only in the irradiated primary tumor, but also at unirradiated distant sites of metastases. Such antitumor immunity is mainly elicited by radiation's stimulatory effects on antigenicity and adjuvanticity. Furthermore, it may be significantly augmented when irradiation is combined with immunotherapy, such as ICIs. Therefore, radiotherapy represents one potential therapeutic strategy to restore anti-tumor immunity in tumors presenting with an unresponsive TIME. In this review, the generation of anti-tumor immunity, its impairment, radiation's immunogenic properties, and the antitumor effects of combining radiation with immunotherapy will be comprehensively discussed.

Large Range Atomic Force Microscopy with High Aspect Ratio Micropipette Probe for Deep Trench Imaging

Atomic force microscopy (AFM) has been adopted in both industry and academia for high-fidelity, full-profile topographic characterization. Typically, the tiny tip of the cantilever and the limited traveling range of the scanner restrict AFM measurement to relatively flat samples (recommend 1 µm). The primary objective of this work is to address these limitations using a large-range AFM (measuring height >10 µm) system consisting of a novel repairable high aspect ratio probe (HARP) with a nested-proportional-integral-derivative (nested-PID) AFM system. The HARP is fabricated using a reliable, cost-efficient bench-top process. The tip is then fused by pulling the end of the micropipette cantilever with a length up to hundreds of micrometers and a tip diameter of 30 nm. The design, simulation, fabrication, and performance of the HARP are described herein. This instrument is then tested using polymer trenches which reveals superior image fidelity compared to standard silicon tips. Finally, a nested-PID system is developed and employed to facilitate 3D characterization of 50-µm-step samples. The results demonstrate the efficacy of the proposed bench-top technique for the fabrication of low-cost, simple HAR AFM probes that facilitate the imaging of samples with deep trenches.

Harnessing the Immunological Effects of Radiation to Improve Immunotherapies in Cancer

Ionizing radiation (IR) is used to treat 50% of cancers. While the cytotoxic effects related to DNA damage with IR have been known since the early 20th century, the role of the immune system in the treatment response is still yet to be fully determined. IR can induce immunogenic cell death (ICD), which activates innate and adaptive immunity against the cancer. It has also been widely reported that an intact immune system is essential to IR efficacy. However, this response is typically transient, and wound healing processes also become upregulated, dampening early immunological efforts to overcome the disease. This immune suppression involves many complex cellular and molecular mechanisms that ultimately result in the generation of radioresistance in many cases. Understanding the mechanisms behind these responses is challenging as the effects are extensive and often occur simultaneously within the tumor. Here, we describe the effects of IR on the immune landscape of tumors. ICD, along with myeloid and lymphoid responses to IR, are discussed, with the hope of shedding light on the complex immune stimulatory and immunosuppressive responses involved with this cornerstone cancer treatment. Leveraging these immunological effects can provide a platform for improving immunotherapy efficacy in the future.

The paradoxical role of radiation-induced cGAS-STING signalling network in tumour immunity

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is an essential component of the innate immune system and is central to the identification of abnormal DNA leakage caused by ionising radiation (IR) damage. Cell-intrinsic cGAS-STING initiation has been revealed to have tremendous potential for facilitating interferon synthesis and T-cell priming. Targeting the cGAS-STING axis has been proposed as a strategy to improve radiosensitivity or enhance immunosurveillance. However, due to the complex biology of the irradiated tumour microenvironment and the extensive involvement of the cGAS-STING pathway in various physiological and pathological processes, many defects in this strategy limit the therapeutic effect. Here, we outline the molecular mechanisms by which IR activates the cGAS-STING pathway and analyse the dichotomous roles of the cGAS-STING pathway in modulating cancer immunity after radiotherapy (RT). Then, based on the crosstalk between the cGAS-STING pathway and other signalling events induced by IR, such as necroptosis, autophagy and other cellular effects, we discuss the immunomodulatory actions of the broad cGAS-STING signalling network in RT and their potential therapeutic applications. Finally, recent advances in combination therapeutic strategies targeting cGAS-STING in RT are explored.

Tumors of the Digestive System: Comprehensive Review of Ancillary Testing and Biomarkers in the Era of Precision Medicine

Immunotherapy has remained at the vanguard of promising cancer therapeutic regimens due to its exceptionally high specificity for tumor cells and potential for significantly improved treatment-associated quality of life compared to other therapeutic approaches such as surgery and chemoradiation. This is especially true in the digestive system, where high rates of mutation give rise to a host of targetable tumor-specific antigens. Many patients, however, do not exhibit measurable improvements under immunotherapy due to intrinsic or acquired resistance, making predictive biomarkers necessary to determine which patients will benefit from this line of treatment. Many of these biomarkers are assessed empirically by pathologists according to nuanced scoring criteria and algorithms. This review serves to inform clinicians and pathologists of extant and promising upcoming biomarkers predictive of immunotherapeutic efficacy among digestive system malignancies and the ancillary testing required for interpretation by pathologists according to tumor site of origin.

Radiotherapy, PARP Inhibition, and Immune-Checkpoint Blockade: A Triad to Overcome the Double-Edged Effects of Each Single Player

Radiotherapy and, more recently, PARP inhibitors (PARPis) and immune-checkpoint inhibitors represent effective tools in cancer therapy. Radiotherapy exerts its effects not only by damaging DNA and inducing tumor cell death, but also stimulating anti-tumor immune responses. PARPis are known to exert their therapeutic effects by inhibiting DNA repair, and they may be used in combination with radiotherapy. Both radiotherapy and PARPis modulate inflammatory signals and stimulate type I IFN (IFN-I)-dependent immune activation. However, they can also support the development of an immunosuppressive tumor environment and upregulate PD-L1 expression on tumor cells. When provided as monotherapy, immune-checkpoint inhibitors (mainly antibodies to CTLA-4 and the PD-1/PD-L1 axis) result particularly effective only in immunogenic tumors. Combinations of immunotherapy with therapies that favor priming of the immune response to tumor-associated antigens are, therefore, suitable strategies. The widely explored association of radiotherapy and immunotherapy has confirmed this benefit for several cancers. Association with PARPis has also been investigated in clinical trials. Immunotherapy counteracts the immunosuppressive effects of radiotherapy and/or PARPis and synergies with their immunological effects, promoting and unleashing immune responses toward primary and metastatic lesions (abscopal effect). Here, we discuss the beneficial and counterproductive effects of each therapy and how they can synergize to overcome single-therapy limitations.

Cancer Immunotherapy Beyond Checkpoint Blockade: JACC: CardioOncology State-of-the-Art Review

Avoidance of immune destruction is recognized as one of the hallmarks of cancer development. Although first predicted as a potential antitumor treatment modality more than 50 years ago, the widespread clinical use of cancer immunotherapies has only recently become a reality. Cancer immunotherapy works by reactivation of a stalled pre-existing immune response or by eliciting a de novo immune response, and its toolkit comprises antibodies, vaccines, cytokines, and cell-based therapies. The treatment paradigm in some malignancies has completely changed over the past 10 to 15 years. Massive efforts in preclinical development have led to a surge of clinical trials testing innovative therapeutic approaches as monotherapy and, increasingly, in combination. Here we provide an overview of approved and emerging antitumor immune therapies, focusing on the rich landscape of therapeutic approaches beyond those that block the canonical PD-1/PD-L1 and CTLA-4 axes and placing them in the context of the latest understanding of tumor immunology.

CC Chemokine Receptor 4 (CCR4) as a Possible New Target for Therapy

Chemokines and their receptors participate in many biological processes, including the modulation of neuroimmune interactions. Approximately fifty chemokines are distinguished in humans, which are classified into four subfamilies based on the N-terminal conserved cysteine motifs: CXC, CC, C, and CX3C. Chemokines activate specific receptors localized on the surface of various immune and nervous cells. Approximately twenty chemokine receptors have been identified, and each of these receptors is a seven-transmembrane G-protein coupled receptor. Recent studies provide new evidence that CC chemokine receptor 4 (CCR4) is important in the pathogenesis of many diseases, such as diabetes, multiple sclerosis, asthma, dermatitis, and cancer. This review briefly characterizes CCR4 and its ligands (CCL17, CCL22, and CCL2), and their contributions to immunological and neoplastic diseases. The review notes a significant role of CCR4 in nociceptive transmission, especially in painful neuropathy, which accompanies many diseases. The pharmacological blockade of CCR4 seems beneficial because of its pain-relieving effects and its influence on opioid efficacy. The possibilities of using the CCL2/CCL17/CCL22/CCR4 axis as a target in new therapies for many diseases are also discussed.

Deciphering the Biological Effects of Radiotherapy in Cancer Cells

Radiotherapy remains an effective conventional method of treatment for patients with cancer. However, the clinical efficacy of radiotherapy is compromised by the development of radioresistance of the tumor cells during the treatment. Consequently, there is need for a comprehensive understanding of the regulatory mechanisms of tumor cells in response to radiation to improve radiotherapy efficacy. The current study aims to highlight new developments that illustrate various forms of cancer cell death after exposure to radiation. A summary of the cellular pathways and important target proteins that are responsible for tumor radioresistance and metastasis is also provided. Further, the study outlines several mechanistic descriptions of the interaction between ionizing radiation and the host immune system. Therefore, the current review provides a reference for future research studies on the biological effects of new radiotherapy technologies, such as ultra-high-dose-rate (FLASH) radiotherapy, proton therapy, and heavy-ion therapy.

Combination of NKG2A and PD-1 Blockade Improves Radiotherapy Response in Radioresistant Tumors

Radiotherapy (RT) is commonly employed to treat solid tumors. Immune checkpoint blockade of programmed cell death protein 1 (PD-1) and CTLA-4 improves survival in RT patients, yet many fail to respond to combination therapy. Natural killer group 2 (NKG2) family receptors, particularly inhibitory NKG2A and activating NKG2D, have emerged as promising therapeutic targets to improve antitumor T cell responses; thus, we examined how these receptors and their ligands (Qa-1b and retinoic acid early inducible 1 [Rae-1], respectively) regulate the RT response in C57BL/6 mice bearing syngeneic B16F10 melanoma and MC38 colorectal adenocarcinoma tumors. RT (15 Gy) transiently reduced B16F10 tumor burden, whereas MC38 tumors exhibited durable response to RT. Intratumoral NK and CD8 T cells expressed NKG2A and NKG2D in both models, which was unaltered by RT. In vitro/in vivo RT increased tumor/stromal cell Qa-1b and Rae-1 expression in both models, especially B16F10 tumors, but IFN-γ stimulation induced both Qa-1b and Rae-1 only in B16F10 tumors. NKG2A/Qa-1b inhibition alone did not improve RT response in either model, but combined RT and NKG2A/PD-1 blockade improved survival in the B16F10 model. Depletion experiments indicate that the triple therapy efficacy is CD8 T cell-dependent with negligible NK cell contribution. RNA sequencing of CD8 T cells from triple therapy-treated B16F10 tumors showed increased proliferative capacity compared with RT and PD-1 blockade alone. Our work demonstrates that RT modulates NKG2A ligand expression, which inhibits RT-induced T cell responses in tumors that fail to respond to combined RT and PD-1 blockade. These results provide a rationale for combining NKG2A blockade with immune checkpoint blockade therapies and RT to improve clinical response.

Synergistic effects of radiotherapy and targeted immunotherapy in improving tumor treatment efficacy: a review

Radiotherapy (RT), unlike chemotherapy, is one of the most routinely used and effective genotoxic and immune response inducing cancer therapies with an advantage of reduced side effects. However, cancer can relapse after RT owing to multiple factors, including acquired tumor resistance, immune suppressive microenvironment buildup, increased DNA repair, thus favoring tumor metastasis. Efforts to mitigate these undesirable effects have drawn interest in combining RT with immunotherapy, particularly the use of immune checkpoint inhibitors, to tilt the pre-existing tumor stromal microenvironment into long-lasting therapy-induced antitumor immunity at multiple metastatic sites (abscopal effects). This multimodal therapeutic strategy can alleviate the increased T cell priming and decrease tumor growth and metastasis, thus emerging as a significant approach to sustain as long-term antitumor immunity. To understand more about this synergism, a detailed cellular mechanism underlying the dynamic interaction between tumor and immune cells within the irradiated tumor microenvironment needs to be explored. Hence, in the present review, we have attempted to evaluate various RT-inducible immune factors, which can be targeted by immunotherapy and provide detailed explanation to optimally maximize their synergy with immunotherapy for long-lasting antitumor immunity. Moreover, we have critically assessed various combinatorial approaches along with their challenges and described strategies to modify them in addition to providing approaches for optimal synergistic effects of the combination.

Combining bempegaldesleukin (CD122-preferential IL-2 pathway agonist) and NKTR-262 (TLR7/8 agonist) improves systemic antitumor CD8+ T cell cytotoxicity over BEMPEG+RT

Background

Tumor cell death caused by radiation therapy (RT) triggers antitumor immunity in part because dying cells release adjuvant factors that amplify and sustain dendritic cell and T cell responses. We previously demonstrated that bempegaldesleukin (BEMPEG: NKTR-214, an immunostimulatory IL-2 cytokine prodrug) significantly enhanced the antitumor efficacy of RT through a T cell-dependent mechanism. Because RT can induce either immunogenic or tolerogenic cell death, depending on various factors (radiation dose, cell cycle phase), we hypothesized that providing a specific immunogenic adjuvant, like intratumoral therapy with a novel toll-like receptor (TLR) 7/8 agonist, NKTR-262, would improve systemic tumor-specific responses through the activation of local innate immunity. Therefore, we evaluated whether intratumoral NKTR-262 combined with systemic BEMPEG treatment would elicit improved tumor-specific immunity and survival compared with RT combined with BEMPEG.

Methods

Tumor-bearing mice (CT26; EMT6) received BEMPEG (0.8 mg/kg; intravenously), RT (12 Gy × 1), and/or intratumoral NKTR-262 (0.5 mg/kg). Flow cytometry was used to evaluate CD4⁺ and CD8⁺ T cell responses in the blood and tumor 7 days post-treatment. The contribution of specific immune subsets was determined by depletion of CD4⁺, CD8⁺, or NK cells. CD8⁺ T cell cytolytic activity was determined by an in vitro CTL assay. Data are representative of 1–2 independent experiments (n=5–14/group) and statistical significance was determined by 1-way analysis of variance (ANOVA) or repeated measures ANOVA (p value cut-off of 0.05).

Results

BEMPEG+NKTR-262 significantly improved survival compared with BEMPEG+RT in a CD8⁺ T cell-dependent manner. Response to BEMPEG+NKTR-262 was characterized by a significant expansion of activated CD8⁺ T cells (GzmA⁺; Ki-67⁺; ICOS⁺; PD-1⁺) in the blood, which correlated with reduced tumor size (p<0.05). In the tumor, BEMPEG+NKTR-262 induced higher frequencies of GzmA⁺ CD8⁺ T cells exhibiting reduced expression of suppressive molecules (PD-1⁺), compared with BEMPEG+RT (p<0.05). Further, BEMPEG+NKTR-262 treatment induced greater tumor-specific CD8⁺ T cell cytolytic function than BEMPEG+RT.

Conclusions

BEMPEG+NKTR-262 therapy elicited more robust expansion of activated CD8⁺ T cells compared with BEMPEG+RT, suggesting that intratumoral TLR stimulation provides superior antigen presentation and costimulatory activity compared with RT. A clinical trial of BEMPEG+NKTR-262 for patients with metastatic solid tumors is in progress (NCT03435640).

Macrophages: shapes and functions

Macrophages are cells of the innate immune system and represent an important component of the first-line defense against pathogens and tumor cells. Here, their diverse functions in inflammation and tumor defense are described, and the mechanisms, tools, and activation pathways and states applied are presented. The main focus is on the role and origin of reactive oxygen species (ROS), the important signal pathways TLR/NF-κB, and the M1/​​M2 polarization of macrophages.

Immunomodulation by radiotherapy in tumour control and normal tissue toxicity

Radiotherapy (RT) is a highly effective anticancer treatment that is delivered to more than half of all patients with cancer. In addition to the well-documented direct cytotoxic effects, RT can have immunomodulatory effects on the tumour and surrounding tissues. These effects are thought to underlie the so-called abscopal responses, whereby RT generates systemic antitumour immunity outside the irradiated tumour. The full scope of these immune changes remains unclear but is likely to involve multiple components, such as immune cells, the extracellular matrix, endothelial and epithelial cells and a myriad of chemokines and cytokines, including transforming growth factor-β (TGFβ). In normal tissues exposed to RT during cancer therapy, acute immune changes may ultimately lead to chronic inflammation and RT-induced toxicity and organ dysfunction, which limits the quality of life of survivors of cancer. Here we discuss the emerging understanding of RT-induced immune effects with particular focus on the lungs and gut and the potential immune crosstalk that occurs between these tissues.

Evaluation of the Effect of Radiotherapy on CCL5/miR-214 -3p/MALAT1 Genes Expression in Blood Samples of Breast Cancer Patients

Current cancer therapies include chemotherapy, radiation therapy, immunotherapy, and surgery. Despite these treatment methods, a major point in cancer treatment is early detection. RNAs (mRNA, miRNAs, and LncRNA) can be used as markers to improve cancer diagnosis and treatment. This research examined how radiotherapy affected CCL5, miR-214, and MALAT-1 gene expression in the immune pathway in peripheral blood samples from radiation therapy-treated breast cancer patients. Before and after radiotherapy, peripheral blood was collected from 15 patients in four steps. Blood samples were collected in an outpatient facility from 20 healthy female volunteers with no history of malignant or inflammatory conditions. RNA was extracted from the blood samples and cDNA was synthesized. CCL5, miR-214, and MALAT-1 gene expression were determined by real-time polymerase chain reaction (RT-PCR). CCL5 protein levels in the serum were determined in 80 samples (60 BC and 20 healthy controls) using Quantikine Enzyme-Linked Immunosorbent Assay (ELISA) kits (R&D Systems). The data were then statistically evaluated. There was a significant difference between CCL5 levels in tumoral and adjacent normal blood samples (p < 0.05). The results also show that the level of gene expression and serum concentration of CCL5 protein in different phases of radiotherapy is significantly different. On the other hand, the expression level of the miR-214 gene was significantly decreased in patients compared to the control group, but this decrease was not significant for the MALAT-1 gene (p< 0.05). Also, after each stage of radiotherapy, the expression level of these two genes showed a decrease, but in the fourth week after radiotherapy, this decrease was significant (p< 0.05). Radiotherapy is associated with a decrease in the expression of miR-214 and MALAT-1, as a result, an increase in the expression of CCL5. An increase in the concentration of CCL5 protein is accompanied by an increase in the level of monocytes, which ultimately causes the infiltration of macrophages and can ultimately cause cancer recurrence. It is suggested that these genes can probably be used as diagnostic and therapeutic radiotherapy markers in breast cancer.

Targeting the CCL2/CCR2 Axis in Cancer Immunotherapy: One Stone, Three Birds?

CCR2 is predominantly expressed by monocytes/macrophages with strong proinflammatory functions, prompting the development of CCR2 antagonists to dampen unwanted immune responses in inflammatory and autoimmune diseases. Paradoxically, CCR2-expressing monocytes/macrophages, particularly in tumor microenvironments, can be strongly immunosuppressive. Thus, targeting the recruitment of immunosuppressive monocytes/macrophages to tumors by CCR2 antagonism has recently been investigated as a strategy to modify the tumor microenvironment and enhance anti-tumor immunity. We present here that beneficial effects of CCR2 antagonism in the tumor setting extend beyond blocking chemotaxis of suppressive myeloid cells. Signaling within the CCL2/CCR2 axis shows underappreciated effects on myeloid cell survival and function polarization. Apart from myeloid cells, T cells are also known to express CCR2. Nevertheless, tissue homing of Treg cells among T cell populations is preferentially affected by CCR2 deficiency. Further, CCR2 signaling also directly enhances Treg functional potency. Thus, although Tregs are not the sole type of T cells expressing CCR2, the net outcome of CCR2 antagonism in T cells favors the anti-tumor arm of immune responses. Finally, the CCL2/CCR2 axis directly contributes to survival/growth and invasion/metastasis of many types of tumors bearing CCR2. Together, CCR2 links to two main types of suppressive immune cells by multiple mechanisms. Such a CCR2-assoicated immunosuppressive network is further entangled with paracrine and autocrine CCR2 signaling of tumor cells. Strategies to target CCL2/CCR2 axis as cancer therapy in the view of three types of CCR2-expessing cells in tumor microenvironment are discussed.

Rs7853346 Polymorphism in lncRNA-PTENP1 and rs1799864 Polymorphism in CCR2 are Associated with Radiotherapy-Induced Cognitive Impairment in Subjects with Glioma Via Regulating PTENP1/miR-19b/CCR2 Signaling Pathway

LncRNA-PTENP1 was reported to promote multiple myeloma cancer stem cell proliferation, and the G allele of rs7853346 polymorphism in lncRNA-PTENP1 was demonstrated to enhance the effect of lncRNA-PTENP1. In this study, we aimed to study the potential effect of lncRNA-PTENP1 and CCR2 mRNA polymorphisms on cognitive impairment in glioma patients. In this study, 279 glioma patients were recruited and grouped according to their genotypes of rs7853346 in PTENP1 and rs1799864 in CCR1. Pathogenic parameters were collected from patients before radiotherapy (month 0) or at month 1 and month 3 after radiotherapy to study the effect of rs7853346 and rs1799864 on cognitive impairment. Sequence analysis, luciferase assay, real-time PCR, and Western blot were performed to study the regulatory relationships between lncRNA-PTENP1, miR-18b, and CCR2. The glioma patient groups exhibited no significant differences concerning basic characteristics. However, the CG&GG/GG genotype alleviated radiotherapy-induced cognitive impairment by exhibiting the highest MMSE among the four groups. On the contrary, parameters including the severity of depression, bladder control, global health status, itchy skin, and weakness of legs all showed no difference among different patient groups at month 0, month 1, and month 3. Also, a long-term positive effect of CG&GG/GG genotype on role functioning and social functioning was also observed after radiotherapy. Compared with patients carrying the CC genotype of rs7853346, the expression of lncRNA-PTENP1 was reduced while the miR-19b level was elevated in patients carrying the CG&GG genotypes of rs7853346. Moreover, the expression of CCR2 mRNA was the highest in the CC/GA&AA group and the lowest in the CG&GG/GG group. Subsequent sequence analysis and luciferase assay indicated that miR-19b could bind to lncRNA-PTENP1 and 3'UTR of CCR2 mRNA, and the knockdown of lncRNA-PTENP1 led to evident up-regulation of miR-19b and down-regulation of CCR2 mRNA/protein in a cellular model, thus verifying the presence of the lncRNA-PTENP1/miR-19b/CCR2 mRNA signaling pathway. In conclusion, by studying the changes in the key parameters of glioma patients who were subjected to radiotherapy, we concluded that the rs7853346 polymorphism in lncRNA-PTENP1 and the rs1799864 polymorphism in CCR2 could independently affect cognitive impairment, while a more significant combined effect on cognitive impairment was exerted in glioma patients via the signaling pathway of PTENP1/miR-19b/CCR2.

Targeting monocytes/macrophages in fibrosis and cancer diseases: Therapeutic approaches

Over almost 140 years since their identification, the knowledge about macrophages has unbelievably evolved. The 'big eaters' from being thought of as simple phagocytic cells have been recognized as master regulators in immunity, homeostasis, healing/repair and organ development. Long considered to originate exclusively from bone marrow-derived circulating monocytes, macrophages have been also demonstrated to be the first immune cells colonizing tissues in the developing embryo and persisting in adult life by self-renewal, as long-lived tissue resident macrophages. Therefore, heterogeneous populations of macrophages with different ontogeny and functions co-exist in tissues. Macrophages act as sentinels of homeostasis and are intrinsically programmed to lead the wound healing and repair processes that occur after injury. However, in certain pathological circumstances macrophages get dysfunctional, and impaired or aberrant macrophage activities become key features of diseases. For instance, in both fibrosis and cancer, that have been defined 'wounds that do not heal', dysfunctional monocyte-derived macrophages overall play a key detrimental role. On the other hand, due to their plasticity these cells can be 're-educated' and exert anti-fibrotic and anti-cancer functions. Therefore macrophages represent an important therapeutic target in both fibrosis and cancer diseases. The current review will illustrate new insights into the role of monocytes/macrophages in these devastating diseases and summarize new therapeutic strategies and applications of macrophage-targeted drug development in their clinical setting.

Targeting Cbx3/HP1γ Induces LEF-1 and IL-21R to Promote Tumor-Infiltrating CD8 T-Cell Persistence

Immune checkpoint blockade (ICB) relieves CD8⁺ T-cell exhaustion in most mutated tumors, and TCF-1 is implicated in converting progenitor exhausted cells to functional effector cells. However, identifying mechanisms that can prevent functional senescence and potentiate CD8⁺ T-cell persistence for ICB non-responsive and resistant tumors remains elusive. We demonstrate that targeting Cbx3/HP1γ in CD8⁺ T cells augments transcription initiation and chromatin remodeling leading to increased transcriptional activity at Lef1 and Il21r. LEF-1 and IL-21R are necessary for Cbx3/HP1γ-deficient CD8⁺ effector T cells to persist and control ovarian cancer, melanoma, and neuroblastoma in preclinical models. The enhanced persistence of Cbx3/HP1γ-deficient CD8⁺ T cells facilitates remodeling of the tumor chemokine/receptor landscape ensuring their optimal invasion at the expense of CD4⁺ Tregs. Thus, CD8⁺ T cells heightened effector function consequent to Cbx3/HP1γ deficiency may be distinct from functional reactivation by ICB, implicating Cbx3/HP1γ as a viable cancer T-cell-based therapy target for ICB resistant, non-responsive solid tumors.

Tumor-Associated Macrophages in Bladder Cancer: Biological Role, Impact on Therapeutic Response and Perspectives for Immunotherapy

Tumor-associated macrophages (TAMs) are one of the most abundant infiltrating immune cells of solid tumors. Despite their possible dual role, i.e., pro- or anti-tumoral, there is considerable evidence showing that the accumulation of TAMs promotes tumor progression rather than slowing it. Several strategies are being developed and clinically tested to target these cells. Bladder cancer (BCa) is one of the most common cancers, and despite heavy treatments, including immune checkpoint inhibitors (ICIs), the overall patient survival for advanced BCa is still poor. TAMs are present in bladder tumors and play a significant role in BCa development. However, few investigations have analyzed the effect of targeting TAMs in BCa. In this review, we focus on the importance of TAMs in a cancerous bladder, their association with patient outcome and treatment efficiency as well as on how current BCa treatments impact these cells. We also report different strategies used in other cancer types to develop new immunotherapeutic strategies with the aim of improving BCa management through TAMs targeting.

TAp73 represses NF-κB-mediated recruitment of tumor-associated macrophages in breast cancer

Breast cancer is one of the most prevalent cancers worldwide. Understanding this complex disease is therefore of great importance. Here, we report that loss of TAp73, a known tumor suppressor and member of the p53 protein family, leads to increased activation of the NF-κB pathway, secretion of the chemokine CCL2, and an increase in protumoral macrophage infiltration in human breast cancer. Both high levels of CCL2 and high macrophage infiltration are known to correlate with poor prognosis in breast cancer patients. This study identifies TAp73 as a regulator of macrophage recruitment and highlights a role for TAp73 in immune cell regulation in cancer.

Infiltration of tumor-promoting immune cells is a strong driver of tumor progression. Especially the accumulation of macrophages in the tumor microenvironment is known to facilitate tumor growth and to correlate with poor prognosis in many tumor types. TAp73, a member of the p53/p63/p73 family, acts as a tumor suppressor and has been shown to suppress tumor angiogenesis. However, what role TAp73 has in regulating immune cell infiltration is unknown. Here, we report that low levels of TAp73 correlate with an increased NF-κB–regulated inflammatory signature in breast cancer. Furthermore, we show that loss of TAp73 results in NF-κB hyperactivation and secretion of Ccl2, a known NF-κB target and chemoattractant for monocytes and macrophages. Importantly, TAp73-deficient tumors display an increased accumulation of protumoral macrophages that express the mannose receptor (CD206) and scavenger receptor A (CD204) compared to controls. The relevance of TAp73 expression in human breast carcinoma was further accentuated by revealing that TAp73 expression correlates negatively with the accumulation of protumoral CD163⁺ macrophages in breast cancer patient samples. Taken together, our findings suggest that TAp73 regulates macrophage accumulation and phenotype in breast cancer through inhibition of the NF-κB pathway.

Chemokines and the immune response to cancer

Chemokines are chemotactic cytokines that regulate the migration of immune cells. Chemokines function as cues for the coordinated recruitment of immune cells into and out of tissue and also guide the spatial organization and cellular interactions of immune cells within tissues. Chemokines are critical in directing immune cell migration necessary to mount and then deliver an effective anti-tumor immune response; however, chemokines also participate in the generation and recruitment of immune cells that contribute to a pro-tumorigenic microenvironment. Here, we review the role of the chemokine system in anti-tumor and pro-tumor immune responses and discuss how malignant cells and the tumor microenvironment regulate the overall chemokine landscape to shape the type and outcome of immune responses to cancer and cancer treatment.

Coadministration of a Clinically Relevant Dexamethasone Dosage With Ablative Radiation Therapy Reduces Peripheral Lymphocytes But Does Not Alter In Vivo Intratumoral Lymphocyte Phenotype or Inhibit Efficacy of Radiation Therapy in a Murine Colorectal Tumor Model

PURPOSE

Dexamethasone is commonly given during radiation therapy (RT) to manage toxicities. Our study examines if dexamethasone coadministration with RT inhibits the RT-induced antitumor T cell response in mouse.

METHODS AND MATERIALS

Intramuscularly implanted MC38 tumors were irradiated with 15 Gy after establishing for 7 days. Tumor bearing mice were administered dexamethasone using multiple schedules and doses. Peripheral lymphocyte reduction was monitored by complete blood count and intratumoral and tumor draining lymph node (tdLN) populations by flow cytometry. Effector phenotype and function of ex vivo stimulated tumor-infiltrating lymphocytes (TILs) and naïve splenocytes as well as in vivo TILs with or without dexamethasone were monitored by flow cytometry and ELISA.

RESULTS

Long course high dose, short course high dose, and short course human equivalent dose dexamethasone reduced peripheral lymphocytes yet did not inhibit survival after irradiation. Short course high dose administration decreased TIL and tdLN lymphocyte activation as well as tdLN mass but did not affect TIL frequencies or change tdLN cell population composition. Dexamethasone inhibited effector function of ex vivo stimulated naïve splenocytes and TILs, but magnitude of IFN-γ secretion was consistently higher in TILs regardless of dexamethasone dose. In vivo analysis of TILs after irradiation and HE dexamethasone treatment showed that TILs had a similar effector phenotype compared with vehicle controls.

CONCLUSIONS

Dexamethasone reduces blood and tdLN lymphocytes. Dexamethasone also suppresses TIL activation/effector function yet does not affect survival in irradiated MC38 tumor bearing mice, which depend on RT-induced immune responses for therapy efficacy. Additional study in human subjects is warranted.

Immune Response: A Missed Opportunity Between Vitamin D and Radiotherapy

Radiotherapy (RT) is a mainstay treatment in several types of cancer and acts by mediating various forms of cancer cell death, although it is still a large challenge to enhance therapy efficacy. Radiation resistance represents the main cause of cancer progression, therefore, overcoming treatment resistance is now the greatest challenge for clinicians. Increasing evidence indicates that immune response plays a role in reprogramming the radiation-induced tumor microenvironment (TME). Intriguingly, radiation-induced immunosuppression possibly overwhelms the ability of immune system to ablate tumor cells. This induces an immune equilibrium, which, we hypothesize, is an opportunity for radiosensitizers to make actions. Vitamin D has been reported to act in synergistic with RT by potentiating antiproliferative effect induced by therapeutics. Additionally, vitamin D can also regulate the TME and may even lead to immunostimulation by blocking immunosuppression following radiation. Previous reviews have focused on vitamin D metabolism and epidemiological trials, however, the synergistic effect of vitamin D and existing therapies remains unknown. This review summarizes vitamin D mediated radiosensitization, radiation immunity, and vitamin D-regulated TME, which may contribute to more successful vitamin D-adjuvant radiotherapy.

NKTR-214 immunotherapy synergizes with radiotherapy to stimulate systemic CD8+ T cell responses capable of curing multi-focal cancer

Background

High-dose radiotherapy (RT) is known to be immunogenic, but is rarely capable of driving clinically relevant abscopal antitumor immunity as monotherapy. RT is known to increase antigen presentation, type I/II interferon responses, and immune cell trafficking to irradiated tumors. Bempegaldesleukin (NKTR-214) is a CD122-preferential interleukin 2 (IL-2) pathway agonist that has been shown to increase tumor-infiltrating lymphocytes, T cell clonality, and increase PD-1 expression. NKTR-214 has increased drug half-life, decreased toxicity, and increased CD8⁺ T cell and natural killer cell stimulation compared with IL-2.

Methods

Animals bearing bilateral subcutaneous MCA-205 fibrosarcoma or CT26 colorectal tumors were treated with NKTR-214, RT, or combination therapy, and tumor growth of irradiated and abscopal lesions was assessed. Focal RT was delivered using a small animal radiation research platform. Peripheral and tumor-infiltrating immune phenotype and functional analyses were performed by flow cytometry. RNA expression profiling from both irradiated and abscopal lesions was performed using microarray.

Results

We demonstrate synergy between RT of a single tumor and NKTR-214 systemic therapy resulting in dramatically increased cure rates of mice bearing bilateral tumors compared with RT or NKTR-214 therapy alone. Combination therapy resulted in increased magnitude and effector function of tumor-specific CD8⁺ T cell responses and increased trafficking of these T cells to both irradiated and distant, unirradiated, tumors.

Conclusions

Given the increasing role of hypofractionated and stereotactic body RT as standard of care treatments in the management of locally advanced and metastatic cancer, these data have important implications for future clinical trial development. The combination of RT and NKTR-214 therapy potently stimulates systemic antitumor immunity and should be evaluated for the treatment of patients with locally advanced and metastatic solid tumors.

Radiation and Immunotherapy in Upper Gastrointestinal Cancers: The Current State of Play

Radiotherapy remains one of the contemporary cornerstones of cancer treatment in the neoadjuvant, curative, adjuvant and palliative settings, either in isolation or as a multimodal approach. Moreover, recent advances in targeted immune checkpoint therapy have firmly established immunotherapy as the fourth pillar in cancer therapy alongside surgery, chemotherapy and notably radiotherapy. There is emerging evidence to suggest both radioresistance and reduced efficacy of immune checkpoint blockade (ICB) are potentiated by the tumour microenvironment (TME) and in fact modulating aspects of this immunosuppressive milieu is instrumental to unlocking anti-tumour immunity. The response rates of Upper Gastrointestinal (UGI) malignancies to ICB remains modest at 10-15%, compared to melanoma at 20-40%. Harnessing the effects of radiotherapy through remodelling of the TME using ICB as a radiosensitisor is an avenue showing promise. Here we explore the rationale behind combining radiotherapy with ICB, as a symbiotic relationship in shifting the balance in favour of anti-tumour immunity. We discuss the effects of radiotherapy on immunogenic cell death, the concept of the abscopal effect, the importance of the cGAS STING pathway, and their relevance in the context of the tumour microenvironment. Furthermore, dosing and timing of radiotherapy and ICB is now being evaluated for its synergistic effects on host tumour immunity, and we review the ongoing efforts and current available literature for single agent and dual agent ICB in combination multimodal therapy for both locally advanced operable and metastatic disease of the upper gastrointestinal tract.

Radiotherapy, immunotherapy, and the tumour microenvironment: Turning an immunosuppressive milieu into a therapeutic opportunity

Immune checkpoint blockade (ICB) has revolutionised the treatment of solid tumours, yet most patients do not derive a clinical benefit. Resistance to ICB is often contingent on the tumour microenvironment (TME) and modulating aspects of this immunosuppressive milieu is a goal of combination treatment approaches. Radiation has been used for over a century in the management of cancer with more than half of all cancer patients receiving radiotherapy. Here, we outline the rationale behind combining radiotherapy with ICB, a potential synergy through mutually beneficial remodelling of the TME. We discuss the pleiotropic effects radiation has on the TME including immunogenic cell death, activation of cytosolic DNA sensors, remodelling the stroma and vasculature, and paradoxical infiltration of both anti-tumour and suppressive immune cell populations. These events depend on the radiation dose and fractionation and optimising these parameters will be key to develop safe and effective combination regimens. Finally, we highlight ongoing efforts that combine radiation, immunotherapy and inhibitors of DNA damage response, which can help achieve a favourable equilibrium between the immunogenic and tolerogenic effects of radiation on the immune microenvironment.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of the Ligands of Receptors CCR1, CCR2, CCR3, and CCR4

CC chemokines, a subfamily of 27 chemotactic cytokines, are a component of intercellular communication, which is crucial for the functioning of the tumor microenvironment. Although many individual chemokines have been well researched, there has been no comprehensive review presenting the role of all known human CC chemokines in the hallmarks of cancer, and this paper aims at filling this gap. The first part of this review discusses the importance of CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 in cancer. Here, we discuss the significance of CCL2 (MCP-1), CCL7, CCL8, CCL11, CCL13, CCL14, CCL15, CCL16, CCL17, CCL22, CCL23, CCL24, and CCL26. The presentation of each chemokine includes its physiological function and then the role in tumor, including proliferation, drug resistance, migration, invasion, and organ-specific metastasis of tumor cells, as well as the effects on angiogenesis and lymphangiogenesis. We also discuss the effects of each CC chemokine on the recruitment of cancer-associated cells to the tumor niche (eosinophils, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), tumor-associated neutrophils (TAN), regulatory T cells (T_reg)). On the other hand, we also present the anti-cancer properties of CC chemokines, consisting in the recruitment of tumor-infiltrating lymphocytes (TIL).

Immunotherapy Targeting Tumor-Associated Macrophages

Macrophages are phagocytic cells that play a broad role in maintaining body homeostasis and defense against foreign pathogens; whereas tumor-associated macrophages (TAMs) support tumor growth and metastasis by promoting cancer cell proliferation and invasion, immunosuppression, and angiogenesis, which is closely related to the poor prognosis in almost all solid tumors. Hence, deep-insight knowledge into TAMs can provide an opportunity to discover more effective strategies for cancer therapeutics. So far, a large number of therapeutic agents targeting TAMs are in clinical trials. In this review, we introduce an extensive overview about macrophages and macrophage-targeting agents.

Reprogramming the tumour microenvironment by radiotherapy: implications for radiotherapy and immunotherapy combinations

Radiotherapy (RT) is a highly effective anti-cancer therapy delivered to around 50-60% of patients. It is part of therapy for around 40% of cancer patients who are cured of their disease. Until recently, the focus of this anti-tumour efficacy has been on the direct tumour cytotoxicity and RT-induced DNA damage. Recently, the immunomodulatory effects of RT on the tumour microenvironment have increasingly been recognized. There is now intense interest in potentially using RT to induce an anti-tumour immune response, which has led to rethinking into how the efficacy of RT could be further enhanced. Following the breakthrough of immune check point inhibitors (ICIs), a new era of immuno-oncology (IO) agents has emerged and established immunotherapy as a routine part of cancer treatment. Despite ICI improving outcomes in many cancer types, overall durable responses occur in only a minority of patients. The immunostimulatory effects of RT make combinations with ICI attractive to potentially amplify anti-tumour immunity resulting in increased tumour responses and improved outcomes. In contrast, tumours with profoundly immunosuppressive tumour microenvironments, dominated by myeloid-derived cell populations, remain a greater clinical challenge and RT may potentially further enhance the immunosuppression. To harness the full potential of RT and IO agent combinations, further insights are required to enhance our understanding of the role these immunosuppressive myeloid populations play, how RT influences these populations and how they may be therapeutically manipulated in combination with RT to improve outcomes further. These are exciting times with increasing numbers of IO targets being discovered and IO agents undergoing clinical evaluation. Multidisciplinary research collaborations will be required to establish the optimal parameters for delivering RT (target volume, dose and fractionation) in combination with IO agents, including scheduling to achieve maximal therapeutic efficacy.

Immunotherapy as sensitizer for local radiotherapy

The purpose of this report was to systematically review the radiation enhancement factor (REF) effects of immunotherapy on radiotherapy (RT) to the local tumor in comparison with other traditional radiation sensitizers such as cisplatin. PubMed and Medline databases were searched until February 2019. Reports with abscopal effect in the results were excluded. Graphs of the selected papers were digitized using Plot Digitizer (Sourceforge.net) in order to calculate the tumor growth delay (TGD) caused by immunotherapy. To enable comparison between different studies,the TGD were used to define the REF between RT versus the RT/immunotherapy combination. Thirty-two preclinical papers, and nine clinical series were selected. Different mouse models were exposed to RT doses ranging from 1 to 10 fractions of 1.8 to 20 Gray (Gy) per fraction. Endpoints were heterogeneous, ranging from regression to complete local response. No randomized clinical studies were identified. The median preclinical REF effect of different immunotherapy was varying from 1.7 to 9.1. There was no relationship observed either with subclasses of immunotherapy orRT doses. In the clinical studies, RT doses ranged from 1 to 37 fractions of 1.8 to 24 Gy per fraction. Most clinical trials used ipilimumab and interleukin-2. Local control rate in the clinical series ranged from 66% to 100%. A strong REF of immunotherapy (1.7 to 9.1) was observed, this being higher than traditionally sensitizers such as cisplatin (1.1). This result implies that for the same RT dose, a higher local control was achieved with a combination of immunotherapy and RT in preclinical settings. This study therefore supports the use of combined RT and immunotherapy to improve local tumor control in clinical settings without exacerbation of toxicities.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of Receptors CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 Ligands

CC chemokines (or β-chemokines) are 28 chemotactic cytokines with an N-terminal CC domain that play an important role in immune system cells, such as CD4⁺ and CD8⁺ lymphocytes, dendritic cells, eosinophils, macrophages, monocytes, and NK cells, as well in neoplasia. In this review, we discuss human CC motif chemokine ligands: CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 (CC motif chemokine receptor CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 ligands). We present their functioning in human physiology and in neoplasia, including their role in the proliferation, apoptosis resistance, drug resistance, migration, and invasion of cancer cells. We discuss the significance of chemokine receptors in organ-specific metastasis, as well as the influence of each chemokine on the recruitment of various cells to the tumor niche, such as cancer-associated fibroblasts (CAF), Kupffer cells, myeloid-derived suppressor cells (MDSC), osteoclasts, tumor-associated macrophages (TAM), tumor-infiltrating lymphocytes (TIL), and regulatory T cells (T_reg). Finally, we show how the effect of the chemokines on vascular endothelial cells and lymphatic endothelial cells leads to angiogenesis and lymphangiogenesis.

T-cell agonists in cancer immunotherapy

Cancer cells can evade immune surveillance in the body. However, immune checkpoint inhibitors can interrupt this evasion and enhance the antitumor activity of T cells. Other mechanisms for promoting antitumor T-cell function are the targeting of costimulatory molecules expressed on the surface of T cells, such as 4-1BB, OX40, inducible T-cell costimulator and glucocorticoid-induced tumor necrosis factor receptor. In addition, CD40 targets the modulation of the activation of antigen-presenting cells, which ultimately leads to T-cell activation. Agonists of these costimulatory molecules have demonstrated promising results in preclinical and early-phase trials and are now being tested in ongoing clinical trials. In addition, researchers are conducting trials of combinations of such immune modulators with checkpoint blockade, radiotherapy and cytotoxic chemotherapeutic drugs in patients with advanced tumors. This review gives a comprehensive picture of the current knowledge of T-cell agonists based on their use in recent and ongoing clinical trials.

Cytokines Explored in Saliva and Tears from Radiated Cancer Patients Correlate with Clinical Manifestations, Influencing Important Immunoregulatory Cellular Pathways

Although radiotherapy is a common form of treatment for head and neck cancer, it may lead to tissue damage in the salivary and lacrimal glands, possibly affecting cytokine expression in the gland fluid of treated individuals. Cytokine profiles in saliva and tear fluid of 29 radiated head and neck cancer patients and 20 controls were screened using a multiplex assay. Correlations between cytokine expression and clinical oral and ocular manifestations were examined, and cellular pathways influenced by these cytokines were assessed using the Functional Enrichment Analysis Tool. Significantly elevated cytokines identified in patient saliva were CCL21, IL-4, CX3CL1, CCL2, CXCL1 and CCL15. Many of these cytokines correlated positively with objective signs of oral dryness, and reduced saliva production in the patients. Although CCL21 and IL-4 levels were significantly lower in patient tear fluid, they correlated with subjective ocular symptoms. These increased salivary cytokines affected pro-inflammatory and apoptotic cellular pathways, including T cell signalling, several interleukin signalling pathways, TNF and TGF-β receptor signalling, and the apoptotic p53 pathway. In conclusion, the upregulated salivary cytokines identified suggest an interplay between innate and adaptive immunity, affecting immunoregulatory cellular pathways. Whether this is due to late effects of radiotherapy or tissue repair remains to be investigated.

Inflammatory microenvironment remodelling by tumour cells after radiotherapy

The development of immune checkpoint inhibitors (ICIs) is revolutionizing the way we think about cancer treatment. Even so, for most types of cancer, only a minority of patients currently benefit from ICI therapies. Intrinsic and acquired resistance to ICIs has focused research towards new combination therapy approaches that seek to increase response rates, the depth of remission and the durability of benefit. In this Review, we describe how radiotherapy, through its immunomodulating effects, represents a promising combination partner with ICIs. We describe how recent research on DNA damage response (DDR) inhibitors in combination with radiotherapy may be used to augment this approach. Radiotherapy can kill cancer cells while simultaneously triggering the release of pro-inflammatory mediators and increasing tumour-infiltrating immune cells - phenomena often described colloquially as turning immunologically 'cold' tumours 'hot'. Here, we focus on new developments illustrating the key role of tumour cell-autonomous signalling after radiotherapy. Radiotherapy-induced tumour cell micronuclei activate cytosolic nucleic acid sensor pathways, such as cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING), and propagation of the resulting inflammatory signals remodels the immune contexture of the tumour microenvironment. In parallel, radiation can impact immunosurveillance by modulating neoantigen expression. Finally, we highlight how tumour cell-autonomous mechanisms might be exploited by combining DDR inhibitors, ICIs and radiotherapy.

Extracellular Hsp70 Reduces the Pro-Tumor Capacity of Monocytes/Macrophages Co-Cultivated with Cancer Cells

Cancer cells are known to contain high levels of the heat shock protein 70 kDa (Hsp70), which mediates increased cell proliferation, escape from programmed cell death, enhanced invasion, and metastasis. A part of Hsp70 molecules may release from cancer cells and affect the behavior of adjacent stromal cells. To explore the effects of Hsp70 on the status of monocytes/macrophages in the tumor locale, we incubated human carcinoma cells of three distinct lines with normal and reduced content of Hsp70 with THP1 monocytes. Using two methods, we showed that the cells with knock-down of Hsp70 released a lower amount of protein in the extracellular medium. Three cycles of the co-cultivation of cancer and monocytic cells led to the secretion of several cytokines typical of the tumor microenvironment (TME) and to pro-cancer activation of the monocytes/macrophages as established by elevation of F4/80 and arginase-1 markers. Unexpectedly, the efficacy of epithelial–mesenchymal transition and resistance of carcinoma cells to anticancer drugs after incubation with monocytic cells were more pronounced in cells with lower Hsp70, e.g., releasing less Hsp70 into the extracellular milieu. These data suggest that Hsp70 released from tumor cells into the TME is able, together with the development of an anti-cancer immune response, to limit the conversion of a considerable part of monocytic cells to the pro-tumor phenotype.

Stereotactic Body Radiation and Interleukin-12 Combination Therapy Eradicates Pancreatic Tumors by Repolarizing the Immune Microenvironment

Over 80% of pancreatic ductal adenocarcinoma (PDA) patients are diagnosed with non-resectable late-stage disease that lacks effective neoadjuvant therapies. Stereotactic body radiation therapy (SBRT) has shown promise as an emerging neoadjuvant approach for treating PDA, and here, we report that its combination with local interleukin-12 (IL-12) microsphere (MS) immunotherapy results in marked tumor reduction and cures in multiple preclinical mouse models of PDA. Our findings demonstrate an increase of intratumoral interferon gamma (IFNγ) production following SBRT/IL-12 MS administration that initiates suppressor cell reprogramming and a subsequent increase in CD8 T cell activation. Furthermore, SBRT/IL-12 MS therapy results in the generation of systemic tumor immunity that is capable of eliminating established liver metastases, providing a rationale for follow-up studies in advanced metastatic disease.

Accelerated, but not conventional, radiotherapy of murine B-cell lymphoma induces potent T cell-mediated remissions

Conventional local tumor irradiation (LTI), delivered in small daily doses over several weeks, is used clinically as a palliative, rather than curative, treatment for chemotherapy-resistant diffuse large B-cell lymphoma (DLBCL) for patients who are ineligible for hematopoietic cell transplantation. Our goal was to test the hypothesis that accelerated, but not conventional, LTI would be more curative by inducing T cell-mediated durable remissions. We irradiated subcutaneous A20 and BL3750 lymphoma tumors in mice with a clinically relevant total radiation dose of 30 Gy LTI, delivered in 10 doses of 3 Gy over 4 days (accelerated irradiation) or as 10 doses of 3 Gy over 12 days (conventional irradiation). Compared with conventional LTI, accelerated LTI resulted in more complete and durable tumor remissions. The majority of these mice were resistant to rechallenge with lymphoma cells, demonstrating the induction of memory antitumor immunity. The increased efficacy of accelerated LTI correlated with higher levels of tumor cell necrosis vs apoptosis and expression of "immunogenic cell death" markers, including calreticulin, heat shock protein 70 (Hsp70), and Hsp90. Accelerated LTI-induced remissions were not seen in immunodeficient Rag-2 ^-/- mice, CD8⁺ T-cell-depleted mice, or Batf-3 ^-/- mice lacking CD8α⁺ and CD103⁺ dendritic cells. Accelerated, but not conventional, LTI in immunocompetent hosts induced marked increases in tumor-infiltrating CD4⁺ and CD8⁺ T cells and MHCII⁺CD103⁺CD11c⁺ dendritic cells and corresponding reductions in exhausted PD-1⁺Eomes⁺CD8⁺ T cells and CD4⁺CD25⁺FOXP3⁺ regulatory T cells. These findings raise the possibility that accelerated LTI can provide effective immune control of human DLBCL.