The importance of the vascular endothelial barrier in the immune-inflammatory response induced by radiotherapy

Genetic Upregulation of Activated Protein C Mitigates Delayed Effects of Acute Radiation Exposure in the Mouse Plasma

Exposure to ionizing radiation, accidental or intentional, may lead to delayed effects of acute radiation exposure (DEARE) that manifest as injury to organ systems, including the kidney, heart, and brain. This study examines the role of activated protein C (APC), a known mitigator of radiation-induced early toxicity, in long-term plasma metabolite and lipid panels that may be associated with DEARE in APCHi mice. The APCHi mouse model used in the study was developed in a C57BL/6N background, expressing the D168F/N173K mouse analog of the hyper-activatable human D167F/D172K protein C variant. This modification enables increased circulating APC levels throughout the mouse's lifetime. Male and female cohorts of C57BL/6N wild-type and APCHi transgenic mice were exposed to 9.5 Gy γ-rays with their hind legs shielded to allow long-term survival that is necessary to monitor DEARE, and plasma was collected at 6 months for LC-MS-based metabolomics and lipidomics. We observed significant dyslipidemia, indicative of inflammatory phenotype, upon radiation exposure. Additionally, observance of several other metabolic dysregulations was suggestive of gut damage, perturbations in TriCarboxylic Acid (TCA) and urea cycles, and arginine metabolism. We also observed gender- and genotype-modulated metabolic perturbations post radiation exposure. The APCHi mice showed near-normal abundance for several lipids. Moreover, restoration of plasma levels of some metabolites, including amino acids, citric acid, and hypoxanthine, in APCHi mice is indicative of APC-mediated protection from radiation injuries. With the help of these findings, the role of APC in plasma molecular events after acute γ-radiation exposure in a gender-specific manner can be established for the first time.

Eight weeks of exercise intervention improves visuomotor and functional capacity, performance, and physiological profile in a patient with choroidal melanoma

The aim of this case study was to investigate the effects of an 8-wk combined exercise intervention, consisting of visual-coordinative and high-intensity interval training (HIIT), on the physical and visuomotor-functional capacity, performance, and physiological profile of a moderately active 29-yr-old man diagnosed with choroidal melanoma of the left eye. Data were collected on three occasions: at the initial diagnosis (T0), after hospitalization and radiotherapy treatment (T1), and following the recovery through the exercise intervention (T2), spanning a total of 17 wk. The primary outcome variables consisted of visuomotor and functional tests (VFTs), cardiorespiratory fitness (CRF), and microvascular circulation measured via flicker light-induced dilation (FiD). For visuomotor tests in general, a significant decline was observed between baseline T0 and T1 (by 6%-22%), followed by significant improvements at T2 (by 11%-36%), surpassing the initially observed T0 values. The cardiopulmonary exercise testing (CPET)-derived parameters exhibited a similar pattern, declining from T0 to T1 [by 8%-12% for peak V̇o2, peak power output (PO), and CPET duration, respectively], with a subsequent recovery observed in response to 8 wk of exercise training (T2), resulting in increases of 11%-25% for V̇o2, peak PO, and CPET duration. Interestingly, the dilation of both arteries and veins in response to the FiD stimulus exhibited a twofold increase compared with baseline levels. Our results suggest that the 8-wk exercise intervention improved patients' VFT and CRF profiles and exceeded baseline values. Additional investigation, particularly through randomized controlled trials, is needed to comprehensively explain changes in FiD.NEW & NOTEWORTHY Results presented here suggest that combined visual-coordinative and HIIT training improves the visual-functional capacity, performance, and physiological profile of choroidal melanoma patients during treatment recovery. This case study lays the groundwork for further research concerning exercise therapy in this unique patient population. In addition, further investigation is required to fully comprehend the combined effects of exercise and radiation therapy on vasculature and oxygenation in patients with choroidal melanoma.

Regenerating murine CD8+ lung tissue resident memory T cells after targeted radiation exposure

Radiation exposure occurs during medical procedures, nuclear accidents, or spaceflight, making effective medical countermeasures a public health priority. Naïve T cells are highly sensitive to radiation-induced depletion, although their numbers recover with time. Circulating memory CD8+ T cells are also depleted by radiation; however, their numbers do not recover. Critically, the impact of radiation exposure on tissue-resident memory T cells (TRM) remains unknown. Here, we found that sublethal thorax-targeted radiation resulted in the rapid and prolonged numerical decline of influenza A virus (IAV)-specific lung TRM in mice, but no decline in antigen-matched circulating memory T cells. Prolonged loss of lung TRM was associated with decreased heterosubtypic immunity. Importantly, boosting with IAV-epitope expressing pathogens that replicate in the lungs or peripheral tissues or with a peripherally administered mRNA vaccine regenerated lung TRM that was derived largely from circulating memory CD8+ T cells. Designing effective vaccination strategies to regenerate TRM will be important in combating the immunological effects of radiation exposure.

Endothelial marker profiles in cerebral radiation-induced vasculopathy: A comparative immunohistochemical analysis

Radiation therapy results in radiation-induced vasculopathy, characterized by alterations in the vascular architecture stemming from radiation exposure. The exact molecular pathways and associated pathologies of this condition have yet to be comprehensively understood. This study aimed to identify specific markers' roles in cerebral vascular endothelial injury pathogenesis after radiosurgery and explore their unique expression patterns in diverse pathologies post-stereotactic radiosurgery. A retrospective cohort study was conducted to assess the expression profiles of endothelial markers via immunohistochemical analysis in 25 adult patients (13 males and 12 females) who had undergone neurosurgical resection for various central nervous system pathologies following stereotactic radiosurgery or radiotherapy from 2001 to 2015. Our findings revealed strong immunohistochemical expression of ICAM-1 and E-selectin across various disease states, while MMP-9, PAI-1, and eNOS exhibited moderate expression levels. In contrast, VCAM-1 and P-Selectin had the weakest expression across all groups. Notably, while individual markers showed significant variations in expression levels when comparing different diseases (P < .001), no substantial differences were found in the overall immunohistochemical expression patterns across the 5 distinct pathologies studied (P = .407, via 2-way ANOVA). Despite the varied long-term effects of radiotherapy on the vascular endothelium, a common thread of inflammation runs through the pathology of these conditions. The distinct patterns of marker expression identified in our study suggest that different markers play unique roles in the development of radiation-induced vasculopathy. These findings offer insights that could lead to the development of novel preventive strategies and treatments.

Combination of phytochemicals, including ginsenoside and curcumin, shows a synergistic effect on the recovery of radiation-induced toxicity

Radiotherapy is commonly used to treat solid cancers located in the pelvis. A considerable number of patients experience proctitis of varying severity, even for a considerable period after radiotherapy. These side effects are often long-lasting or progressively worsen despite multiple therapeutic efforts and are a primary cause of an unexpectedly low quality of life, even after successful cancer treatment. Therefore, this study evaluated the individual and combined efficacy of ginsenoside, curcumin, butyric acid, and sucralfate compounds in treating radiation-induced proctitis. While the candidate compounds did not affect the proliferation and migration of cancer cells, they promoted the recovery of cell activity, including motility. They exhibited anti-inflammatory effects on human dermal fibroblasts or human umbilical vein endothelial cells within in vitro disease models. When each compound was tested, curcumin and ginsenoside were the most effective in cell recovery and promoted the migration of human dermal fibroblasts and cell restoration of human umbilical vein endothelial cells. The combination of ginsenoside and curcumin resulted in cell migration recovery of approximately 54%. In addition, there was a significant improvement in the length of the endothelial tube, with an increase of approximately 25%, suggesting that the ginsenoside-curcumin-containing combination was the most effective against radiation-induced damage. Furthermore, studies evaluating the effects of combined treatments on activated macrophages indicated that the compounds effectively reduced the secretion of inflammatory cytokines, including chemokines, and alleviated radiation-induced inflammation. In conclusion, our study provides valuable insights into using curcumin and ginsenoside as potential compounds for the effective treatment of radiation-induced injuries and highlights the promising therapeutic benefits of combining these two compounds.

Stimuli-Responsive Nanoradiosensitizers for Enhanced Cancer Radiotherapy

Radiotherapy (RT) has been a classical therapeutic method of cancer for several decades. It attracts tremendous attention for the precise and efficient treatment of local tumors with stimuli-responsive nanomaterials, which enhance RT. However, there are few systematic reviews summarizing the newly emerging stimuli-responsive mechanisms and strategies used for tumor radio-sensitization. Hence, this review provides a comprehensive overview of recently reported studies on stimuli-responsive nanomaterials for radio-sensitization. It includes four different approaches for sensitized RT, namely endogenous response, exogenous response, dual stimuli-response, and multi stimuli-response. Endogenous response involves various stimuli such as pH, hypoxia, GSH, and reactive oxygen species (ROS), and enzymes. On the other hand, exogenous response encompasses X-ray, light, and ultrasound. Dual stimuli-response combines pH/enzyme, pH/ultrasound, and ROS/light. Lastly, multi stimuli-response involves the combination of pH/ROS/GSH and X-ray/ROS/GSH. By elaborating on these responsive mechanisms and applying them to clinical RT diagnosis and treatment, these methods can enhance radiosensitive efficiency and minimize damage to surrounding normal tissues. Finally, this review discusses the additional challenges and perspectives related to stimuli-responsive nanomaterials for tumor radio-sensitization.

Ultra-Hypofractionated Re-Irradiation with Anti-PD-1 Immunotherapy for Locoregionally Recurrent (after Radical Chemo-Radiotherapy) Non-Small Cell Lung Cancer

Large fractions of radiotherapy of 8 Gy (ultra-hypofractionated RT, ultra-hypoRT) promote anti-tumor immune responses that have been clinically substantiated in combination trials with immune checkpoint inhibitors (ICIs). In the current study, we postulated that ultra-hypoRT in combination with ICIs may enhance tumor clearance in NSCLC patients with locoregional relapse after radical chemo-RT. Between 2019 and 2021, eleven patients received re-irradiation with one or two fractions of 8 Gy concurrently with anti-PD1 immunotherapy (nivolumab or pembrolizumab). RT-related toxicities were negligible, while immune-related adverse events enforced immunotherapy interruption in 36% of patients. The overall response rate was 81.8%. Tumor reduction between 80 and 100% was noted in 63.5% of patients. Within a median follow-up of 22 months, the locoregional relapse-free rate was 54.5%, while the projected 2-year disease-specific overall survival was 62%. The results were independent of PD-L1 status. The current report provides encouraging evidence that a relatively low biological dose of RT delivered with 8 Gy fractions is feasible and can be safely combined with anti-PD-1 immunotherapy. Despite the low number of patients, the significant tumor regression achieved and the long-lasting locoregional control and overall progression-free intervals provide a basis to pursue immuno-RT trials with U-hypoRT schemes in this group of NSCLC patients of poor prognosis.

[Interactions between vascular endothelium and immune cells: A key control point of radiation-induced digestive lesions]

Radiation-induced toxicity of the digestive tract is a major clinical concern as many cancer survivors have received radiotherapy for tumours of the abdominopelvic area. The coordination and orchestration of a tissue's response to stress depend not only on the phenotype of the cells that make up the tissue but also on cell-cell interactions. The digestive system, i.e., the intestine/colon/rectum, is made up of a range of different cell populations: epithelial cells, stromal cells, i.e. endothelial cells and mesenchymal lineages, immune cells and nerve cells. Moreover, each of these populations is heterogeneous and presents very significant plasticity and differentiation states. The pathogenesis of radiation-induced digestive lesions is an integrated process that involves multiple cellular compartments interacting in a complex sequence of events. Understanding all the cellular events and communication networks that contribute to the tissue's response to stress is therefore a major conceptual and methodological scientific challenge. The study of heterogeneous populations of cells in a tissue is now possible thanks to "single cell' RNA sequencing and spatial transcriptomics techniques, which enable a comprehensive study of the transcriptomic profiles of individual cells in an integrated system. In addition, the mathematical and bioinformatics tools that are now available for the large-scale analysis of data allow the inference of cell-cell communication networks. Such approaches have become possible through advances in bioinformatics algorithms for the analysis and deciphering of interaction networks. Interactions influence the tissue regeneration process through expression of various molecules, including metabolites, integrins, junction proteins, ligands, receptors and proteins secreted into the extracellular space. The vascular network is viewed as a key player in the progression of digestive lesions, which are characterised by infiltration of a range of immune cells. A better characterisation of endothelium/immune cell interactions in suitable preclinical models, as well as in humans, may help to identify some promising therapeutic targets for the prediction, prevention or treatment of digestive toxicity after radiotherapy.

Ultrasound-stimulated microbubbles enhancement of fractionated radiation for tumor treatment

BACKGROUND

Radiation therapy (XRT) causes numerous biological changes in tumor microenvironment. Radiation vascular response, due to endothelial disruption, can influence treatment outcomes in a dose-dependent manner. Ultrasound-stimulated microbubbles (USMB) have also been demonstrated to create a vascular response in the tumor microenvironment and enhance tumor response when used in combination with XRT. Single doses of 8-10 Gy are known to induce activation of acid sphingomyelinase (ASMase)-induced ceramide production, causing vascular damage. Destruction of vasculature results in endothelial apoptosis followed by tumor cell death. The effect of tumor response is known to be synergistic by 10-fold higher cell kill observed when USMB is combined with radiation.

METHODS

In this study, we used an USMB approach in combination with conventional low dose fractionated radiation to enhance endothelial cell responses to XRT in human PC3 prostate cancer xenograft model. Mice were divided into untreated, USMB therapy, fractionated XRT, and combined USMB therapy followed by XRT (USMB + XRT) groups. USMB therapy was delivered twice per week in the USMB-alone and combined USMB + XRT treatment groups over four weeks. Radiation treatments were delivered in fractions of 2 Gy/day (total 40 Gy in 20 fractions, BED₁₀ = 48 Gy) in the XRT-alone and combined USMB + XRT groups. The treatment outcome was evaluated using histopathology, power Doppler, and immunohistochemistry assays.

RESULTS

Tumor growth assessment showed that sizes of tumors increased in the control and the single treatment groups over a treatment period of four weeks, but significantly decreased with the combined treatments of USMB + XRT. Immunohistochemical analysis indicated a statistically significant vascular disruption in mice that received treatment involving a full 4-week schedule of combined (USMB + XRT) treatments. A statistically significant increase in vascular disruption was demonstrated through CD68 and trichrome fibrosis staining. Changes in local perfusion assessed using high-frequency power Doppler imaging demonstrated attenuated blood flow in the combined group.

DISCUSSION AND CONCLUSIONS

This work demonstrates the efficacy of using USMB as a radiation sensitizer in a mouse model of human PC3 tumor xenograft. This radiation treatment enhancement modality has the advantage of targeting tumor vasculature with ultrasound stimulation that can be implemented prior to radiation treatment.

Nanoparticle-Mediated Radiotherapy Remodels the Tumor Microenvironment to Enhance Antitumor Efficacy

Radiotherapy (RT) uses ionizing radiation to eradicate localized tumors and, in rare cases, control tumors outside of the irradiated fields via stimulating an antitumor immune response (abscopal effect). However, the therapeutic effect of RT is often limited by inherent physiological barriers of the tumor microenvironment (TME), such as hypoxia, abnormal vasculature, dense extracellular matrix (ECM), and an immunosuppressive TME. Thus, it is critical to develop new RT strategies that can remodel the TME to overcome radio-resistance and immune suppression. In the past decade, high-Z-element nanoparticles have been developed to increase radiotherapeutic indices of localized tumors by reducing X-ray doses and side effects to normal tissues and enhance abscopal effects by activating the TME to elicit systemic antitumor immunity. In this review, the principles of RT and radiosensitization, the mechanisms of radio-resistance and immune suppression, and the use of various nanoparticles to sensitize RT and remodel TMEs for enhanced antitumor efficacy are discussed. The challenges in clinical translation of multifunctional TME-remodeling nanoradiosensitizers are also highlighted.

Melatonin and TGF-β-Mediated Release of Extracellular Vesicles

The immune system, unlike other systems, must be flexible and able to "adapt" to fully cope with lurking dangers. The transition from intracorporeal balance to homeostasis disruption is associated with activation of inflammatory signaling pathways, which causes modulation of the immunology response. Chemotactic cytokines, signaling molecules, and extracellular vesicles act as critical mediators of inflammation and participate in intercellular communication, conditioning the immune system's proper response. Among the well-known cytokines allowing for the development and proper functioning of the immune system by mediating cell survival and cell-death-inducing signaling, the tumor necrosis factor α (TNF-α) and transforming growth factor β (TGF-β) are noteworthy. The high bloodstream concentration of those pleiotropic cytokines can be characterized by anti- and pro-inflammatory activity, considering the powerful anti-inflammatory and anti-oxidative stress capabilities of TGF-β known from the literature. Together with the chemokines, the immune system response is also influenced by biologically active chemicals, such as melatonin. The enhanced cellular communication shows the relationship between the TGF-β signaling pathway and the extracellular vesicles (EVs) secreted under the influence of melatonin. This review outlines the findings on melatonin activity on TGF-β-dependent inflammatory response regulation in cell-to-cell communication leading to secretion of the different EV populations.

Role of Orai3-Mediated Store-Operated Calcium Entry in Radiation-Induced Brain Microvascular Endothelial Cell Injury

Radiation-induced brain injury is a serious complication with complex pathogenesis that may accompany radiotherapy of head and neck tumors. Although studies have shown that calcium (Ca²⁺) signaling may be involved in the occurrence and development of radiation-induced brain injury, the underlying molecular mechanisms are not well understood. In this study, we used real-time quantitative polymerase chain reaction and Western blotting assays to verify our previous finding using next-generation sequencing that the mRNA and protein expression levels of Orai3 in rat brain microvascular endothelial cells (rBMECs) increased after X-ray irradiation. We next explored the role of Orai3 and Orai3-mediated store-operated Ca²⁺ entry (SOCE) in radiation-induced brain injury. Primary cultured rBMECs derived from wild-type and Orai3 knockout (Orai3^(-/-)) Sprague-Dawley rats were used for in vitro experiments. Orai3-mediated SOCE was significantly increased in rBMECs after X-ray irradiation. However, X-ray irradiation-induced SOCE increase was markedly reduced in Orai3 knockout rBMECs, and the percentage of BTP2 (a nonselective inhibitor of Orai channels)-inhibited SOCE was significantly decreased in Orai3 knockout rBMECs. Functional studies indicated that X-ray irradiation decreased rBMEC proliferation, migration, and tube formation (a model for assessing angiogenesis) but increased rBMEC apoptosis, all of which were ameliorated by BTP2. In addition, occurrences of all four functional deficits were suppressed in X-ray irradiation-exposed rBMECs derived from Orai3^(-/-) rats. Cerebrovascular damage caused by whole-brain X-ray irradiation was much less in Orai3^(-/-) rats than in wild-type rats. These findings provide evidence that Orai3-mediated SOCE plays an important role in radiation-induced rBMEC damage and brain injury and suggest that Orai3 may warrant development as a potential therapeutic target for reducing or preventing radiation-induced brain injury.

Application of injectable hydrogels in cancer immunotherapy

Immunotherapy is a revolutionary and promising approach to cancer treatment. However, traditional cancer immunotherapy often has the disadvantages of limited immune response rate, poor targeting, and low treatment index due to systemic administration. Hydrogels are drug carriers with many advantages. They can be loaded and transported with immunotherapeutic agents, chemical anticancer drugs, radiopharmaceuticals, photothermal agents, photosensitizers, and other therapeutic agents to achieve controlled release of drugs, extend the retention time of drugs, and thus successfully trigger anti-tumor effects and maintain long-term therapeutic effects after administration. This paper reviews recent advances in injectable hydrogel-based cancer immunotherapy, including immunotherapy alone, immunotherapy with combination chemotherapy, radiotherapy, phototherapy, and DNA hydrogel-based immunotherapy. Finally, we review the potential and limitations of injectable hydrogels in cancer immunotherapy.

Clinical Radiobiology for Radiation Oncology

This chapter is focused on radiobiological aspects at the molecular, cellular, and tissue level which are relevant for the clinical use of ionizing radiation (IR) in cancer therapy. For radiation oncology, it is critical to find a balance, i.e., the therapeutic window, between the probability of tumor control and the probability of side effects caused by radiation injury to the healthy tissues and organs. An overview is given about modern precision radiotherapy (RT) techniques, which allow optimal sparing of healthy tissues. Biological factors determining the width of the therapeutic window are explained. The role of the six typical radiobiological phenomena determining the response of both malignant and normal tissues in the clinic, the 6R’s, which are Reoxygenation, Redistribution, Repopulation, Repair, Radiosensitivity, and Reactivation of the immune system, is discussed. Information is provided on tumor characteristics, for example, tumor type, growth kinetics, hypoxia, aberrant molecular signaling pathways, cancer stem cells and their impact on the response to RT. The role of the tumor microenvironment and microbiota is described and the effects of radiation on the immune system including the abscopal effect phenomenon are outlined. A summary is given on tumor diagnosis, response prediction via biomarkers, genetics, and radiomics, and ways to selectively enhance the RT response in tumors. Furthermore, we describe acute and late normal tissue reactions following exposure to radiation: cellular aspects, tissue kinetics, latency periods, permanent or transient injury, and histopathology. Details are also given on the differential effect on tumor and late responding healthy tissues following fractionated and low dose rate irradiation as well as the effect of whole-body exposure.

Sex Differences in X-ray-Induced Endothelial Damage: Effect of Taurine and N-Acetylcysteine

Ionizing radiation (IR) can induce some associated pathological conditions due to numerous cell damages. The influence of sex is scarcely known, and even less known is whether the effect of antioxidants is sex-dependent. Given the increased use of IR, we investigated whether male human umbilical vein endothelial cells (MHUVECs) and female human umbilical vein endothelial cells (FHUVECs) respond differently to IR exposure and whether the antioxidants 10 mM taurine (TAU) and 5 mM N-acetylcysteine (NAC) can prevent IR-induced damage in a sex-dependent way. In untreated cells, sex differences were observed only during autophagy, which was higher in FHUVECs. In non-irradiated cells, preincubation with TAU and NAC did not modify viability, lactate dehydrogenase (LDH) release, migration, or autophagy, whereas only NAC increased malondialdehyde (MDA) levels in FHUVECs. X-ray irradiation increased LDH release and reduced viability and migration in a sex-independent manner. TAU and NAC did not affect viability while reduced LDH release in irradiated cells: they have the same protective effect in FHUVECs, while, TAU was more protective than NAC in male cells.. Moreover, TAU and NAC significantly promoted the closure of wounds in both sexes in irradiated cells, but NAC was more effective at doing this in FHUVECs. In irradiated cells, TAU did not change autophagy, while NAC attenuated the differences between the sexes. Finally, NAC significantly decreased MDA in MHUVECs and increased MDA in FHUVECs. In conclusion, FHUVECs appear to be more susceptible to IR damage, and the effects of the two antioxidants present some sex differences, suggesting the need to study the influence of sex in radiation mitigators.

The Lymphatic Endothelium in the Context of Radioimmuno-Oncology

The study of lymphatic tumor vasculature has been gaining interest in the context of cancer immunotherapy. These vessels constitute conduits for immune cells' transit toward the lymph nodes, and they endow tumors with routes to metastasize to the lymph nodes and, from them, toward distant sites. In addition, this vasculature participates in the modulation of the immune response directly through the interaction with tumor-infiltrating leukocytes and indirectly through the secretion of cytokines and chemokines that attract leukocytes and tumor cells. Radiotherapy constitutes the therapeutic option for more than 50% of solid tumors. Besides impacting transformed cells, RT affects stromal cells such as endothelial and immune cells. Mature lymphatic endothelial cells are resistant to RT, but we do not know to what extent RT may affect tumor-aberrant lymphatics. RT compromises lymphatic integrity and functionality, and it is a risk factor to the onset of lymphedema, a condition characterized by deficient lymphatic drainage and compromised tissue homeostasis. This review aims to provide evidence of RT's effects on tumor vessels, particularly on lymphatic endothelial cell physiology and immune properties. We will also explore the therapeutic options available so far to modulate signaling through lymphatic endothelial cell receptors and their repercussions on tumor immune cells in the context of cancer. There is a need for careful consideration of the RT dosage to come to terms with the participation of the lymphatic vasculature in anti-tumor response. Here, we provide new approaches to enhance the contribution of the lymphatic endothelium to radioimmuno-oncology.

Hunting down NLRP3 inflammasome: An executioner of radiation-induced injury

Radiotherapy is one of the mainstream treatment modalities for several malignancies. However, radiation-induced injury to surrounding normal tissues limits its efficacy. The NLRP3 inflammasome is an essential mechanism of innate immunity that reacts to challenges from endogenous danger signals and pathological microbes. A growing body of evidence has demonstrated a key role of NLRP3 inflammasome in the pathogenesis of radiation-induced tissue injury. Despite accumulating evidence, the potential value of the NLRP3 inflammasome in the management of radiation-induced tissue injury is not adequately recognized. We conducted a literature review to characterize the relationship between NLRP3 inflammasome and radiation injury. By analyzing recent evidence, we identify NLRP3 inflammasome as one of the executioners of radiation-induced injury, since it responds to the challenges of radiation, induces cell pyroptosis and tissue dysfunction, and initiates non-resolving inflammation and fibrosis. Based on these concepts, we propose early intervention/prevention strategies targeting NLRP3 inflammasome in a radiation context, which may help resolve imperative clinical problems.

Preclinical models of radiation-induced cardiac toxicity: Potential mechanisms and biomarkers

Radiation therapy (RT) is an important modality in cancer treatment with >50% of cancer patients undergoing RT for curative or palliative intent. In patients with breast, lung, and esophageal cancer, as well as mediastinal malignancies, incidental RT dose to heart or vascular structures has been linked to the development of Radiation-Induced Heart Disease (RIHD) which manifests as ischemic heart disease, cardiomyopathy, cardiac dysfunction, and heart failure. Despite the remarkable progress in the delivery of radiotherapy treatment, off-target cardiac toxicities are unavoidable. One of the best-studied pathological consequences of incidental exposure of the heart to RT is collagen deposition and fibrosis, leading to the development of radiation-induced myocardial fibrosis (RIMF). However, the pathogenesis of RIMF is still largely unknown. Moreover, there are no available clinical approaches to reverse RIMF once it occurs and it continues to impair the quality of life of long-term cancer survivors. Hence, there is an increasing need for more clinically relevant preclinical models to elucidate the molecular and cellular mechanisms involved in the development of RIMF. This review offers an insight into the existing preclinical models to study RIHD and the suggested mechanisms of RIMF, as well as available multi-modality treatments and outcomes. Moreover, we summarize the valuable detection methods of RIHD/RIMF, and the clinical use of sensitive radiographic and circulating biomarkers.

Vascular Protective Effect and Its Possible Mechanism of Action on Selected Active Phytocompounds: A Review

Vascular endothelial dysfunction is characterized by an imbalance of vasodilation and vasoconstriction, deficiency of nitric oxide (NO) bioavailability and elevated reactive oxygen species (ROS), and proinflammatory factors. This dysfunction is a key to the early pathological development of major cardiovascular diseases including hypertension, atherosclerosis, and diabetes. Therefore, modulation of the vascular endothelium is considered an important therapeutic strategy to maintain the health of the cardiovascular system. Epidemiological studies have shown that regular consumption of medicinal plants, fruits, and vegetables promotes vascular health, lowering the risk of cardiovascular diseases. This is mainly attributed to the phytochemical compounds contained in these resources. Various databases, including Google Scholar, MEDLINE, PubMed, and the Directory of Open Access Journals, were searched to identify studies demonstrating the vascular protective effects of phytochemical compounds. The literature had revealed abundant data on phytochemical compounds protecting and improving the vascular system. Of the numerous compounds reported, curcumin, resveratrol, cyanidin-3-glucoside, berberine, epigallocatechin-3-gallate, and quercetin are discussed in this review to provide recent information on their vascular protective mechanisms in vivo and in vitro. Phytochemical compounds are promising therapeutic agents for vascular dysfunction due to their antioxidative mechanisms. However, future human studies will be necessary to confirm the clinical effects of these vascular protective mechanisms.

Paeoniflorin Inhibits ASK1-TF Axis by Up-Regulating SOCS3 to Alleviate Radiation Enteritis

Radiation enteritis is one of the main adverse effects of radiotherapy, presenting with a poorly understood etiology and limited options for therapy. Intestinal inflammation and ischemia are the core mechanisms of radiation enteritis. Suppressor of cytokine signaling 3 (SOCS3) is an endogenous “inflammation brake.” We hypothesized that paeoniflorin, a pinane monoterpene bitter glycoside, could increase SOCS3 expression to reduce inflammation and ischemia and improve enteritis in mice. Laser Doppler flowmetry was used to detect changes in intestinal blood flow. RAW264.7 and human umbilical vein endothelial cells were used to investigate the mechanism of action of paeoniflorin. It was observed that radiation caused high mortality, intestinal inflammatory responses, and low blood flow in mice. Paeoniflorin effectively alleviated intestinal atrophy, prevented thrombosis, improved radiation enteritis, and reduced mortality in mice undergoing radiotherapy. In addition, paeoniflorin increased the release of growth arrest-specific gene 6 (Gas6) and phosphorylation of the Axl receptor, subsequently inducing the expression of SOCS3 and inhibiting the expression of p-apoptosis signal-regulating kinase 1 and tissue factor in vivo and in vitro. Based on our findings, we suggest that paeoniflorin is potentially effective in alleviating radiation enteritis via the activation of the Gas6/Axl/SOCS3 axis and subsequent reduction in intestinal inflammation and ischemia.

Understanding Molecular Mechanisms and Identifying Key Processes in Chronic Radiation Cystitis

Chronic radiation cystitis (CRC) is a consequence of pelvic radiotherapy and affects 5–10% of patients. The pathology of CRC is without curative treatment and is characterized by incontinence, pelvic pain and hematuria, which severely degrades patients’ quality of life. Current management strategies rely primarily on symptomatic measures and have certain limitations. Thanks to a better understanding of the pathophysiology of radiation cystitis, studies targeting key manifestations such as inflammation, neovascularization and cell atrophy have emerged and are promising avenues for future treatment. However, the mechanisms of CRC are still better described in animal models than in human models. Preclinical studies conducted to elucidate the pathophysiology of CRC use distinct models and are most often limited to specific processes, such as fibrosis, vascular damage and inflammation. This review presents a synthesis of experimental studies aimed at improving our understanding of the molecular mechanisms at play and identifying key processes in CRC.

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.

Deep models of integrated multiscale molecular data decipher the endothelial cell response to ionizing radiation

The vascular endothelium is a hot spot in the response to radiation therapy for both tumors and normal tissues. To improve patient outcomes, interpretable systemic hypotheses are needed to help radiobiologists and radiation oncologists propose endothelial targets that could protect normal tissues from the adverse effects of radiation therapy and/or enhance its antitumor potential. To this end, we captured the kinetics of multi-omics layers-i.e. miRNome, targeted transcriptome, proteome, and metabolome-in irradiated primary human endothelial cells cultured in vitro. We then designed a strategy of deep learning as in convolutional graph networks that facilitates unsupervised high-level feature extraction of important omics data to learn how ionizing radiation-induced endothelial dysfunction may evolve over time. Last, we present experimental data showing that some of the features identified using our approach are involved in the alteration of angiogenesis by ionizing radiation.

Transcriptomic profiling and pathway analysis of cultured human lung microvascular endothelial cells following ionizing radiation exposure

The vascular system is sensitive to radiation injury, and vascular damage is believed to play a key role in delayed tissue injury such as pulmonary fibrosis. However, the response of endothelial cells to radiation is not completely understood. We examined the response of primary human lung microvascular endothelial cells (HLMVEC) to 10 Gy (1.15 Gy/min) X-irradiation. HLMVEC underwent senescence (80-85%) with no significant necrosis or apoptosis. Targeted RT-qPCR showed increased expression of genes CDKN1A and MDM2 (10-120 min). Western blotting showed upregulation of p2/waf1, MDM2, ATM, and Akt phosphorylation (15 min-72 h). Low levels of apoptosis at 24-72 h were identified using nuclear morphology. To identify novel pathway regulation, RNA-seq was performed on mRNA using time points from 2 to 24 h post-irradiation. Gene ontology and pathway analysis revealed increased cell cycle inhibition, DNA damage response, pro- and anti- apoptosis, and pro-senescence gene expression. Based on published literature on inflammation and endothelial-to-mesenchymal transition (EndMT) pathway genes, we identified increased expression of pro-inflammatory genes and EndMT-associated genes by 24 h. Together our data reveal a time course of integrated gene expression and protein activation leading from early DNA damage response and cell cycle arrest to senescence, pro-inflammatory gene expression, and endothelial-to-mesenchymal transition.

Refining the mandibular osteoradionecrosis rat model by in vivo longitudinal µCT analysis

Osteoradionecrosis (ORN) is one of the most feared side effects of radiotherapy following cancers of the upper aero-digestive tract and leading to severe functional defects in patients. Today, our lack of knowledge about the physiopathology restricts the development of new treatments. In this study, we refined the ORN rat model and quantitatively studied the progression of the disease. We tested the impact of radiation doses from 20 to 40 Gy, delivered with incident 4MV X-ray beams on the left mandible of the inbred Lewis Rat. We used micro-computed tomography (µCT) to obtain in vivo images for longitudinal bone imaging and ex vivo images after animal perfusion with barium sulphate contrast agent for vessel imaging. We compared quantification methods by analyzing 3D images and 2D measurements to determine the most appropriate and precise method according to the degree of damage. We defined 25 Gy as the minimum irradiation dose combined with the median molar extraction necessary to develop non-regenerative bone necrosis. µCT image analyses were correlated with clinical and histological analyses. This refined model and accurate methods for bone and vessel quantification will improve our knowledge of the progression of ORN pathology and allow us to test the efficacy of new regenerative medicine procedures.

Variation of 4 MV X-ray dose rate in fractionated irradiation strongly impacts biological endothelial cell response in vitro

PURPOSE

Even though X-ray beams are widely used in medical diagnosis or radiotherapy, the comparisons of their dose rates are scarce. We have recently demonstrated in vitro (clonogenic assay, cell viability, cell cycle, senescence) and in vivo (weight follow-up of animals and bordering epithelium staining of lesion), that for a single dose of irradiation, the relative biological effectiveness (RBE) deviates from 1 (up to twofold greater severe damage at the highest dose rate depending on the assay) when increasing the dose rate of high energy X-ray beams.

MATERIAL AND METHODS

To further investigate the impact of the dose rate on RBE, in this study, we performed in vitro fractionated irradiations by using the same two dose rates (0.63 and 2.5 Gy.min^-1) of high-energy X-rays (both at 4 MV) on normal endothelial cells (HUVECs). We investigated the viability/mortality, characterized radiation-induced senescence by using flow cytometry and measured gene analysis deregulations on custom arrays.

RESULTS

The overall results enlighten that, in fractionated irradiations when varying the dose rate of high-energy X-rays, the RBE of photons deviates from 1 (up to 2.86 for viability/mortality experiments performed 21 days postirradiation).

CONCLUSION

These results strengthen the interest of multiparametric analysis approaches in providing an accurate evaluation of the outcomes of irradiated cells in support of clonogenic assays, especially when such assays are not feasible.

Interaction Between Modern Radiotherapy and Immunotherapy for Metastatic Prostate Cancer

Prostate cancer is the most frequently diagnosed cancer in men and a leading cause of cancer-related death. In recent decades, the development of immunotherapies has resulted in great promise to cure metastatic disease. However, prostate cancer has failed to show any significant response, presumably due to its immunosuppressive microenvironment. There is therefore growing interest in combining immunotherapy with other therapies able to relieve the immunosuppressive microenvironment. Radiation therapy remains the mainstay treatment for prostate cancer patients, is known to exhibit immunomodulatory effects, depending on the dose, and is a potent inducer of immunogenic tumor cell death. Optimal doses of radiotherapy are thus expected to unleash the full potential of immunotherapy, improving primary target destruction with further hope of inducing immune-cell-mediated elimination of metastases at distance from the irradiated site. In this review, we summarize the current knowledge on both the tumor immune microenvironment in prostate cancer and the effects of radiotherapy on it, as well as on the use of immunotherapy. In addition, we discuss the utility to combine immunotherapy and radiotherapy to treat oligometastatic metastatic prostate cancer.

[Combination radiotherapy-immunotherapy in genitourinary cancer]

Immunotherapy occupies a growing place in urologic oncology, mainly for kidney and bladder cancers. On the basis of encouraging preclinical work, the combination of immunotherapy with radiotherapy aims to increase the tumor response, including in metastatic tumors, which raises many hopes, which this article reviews.

Radiation dose and fraction in immunotherapy: one-size regimen does not fit all settings, so how does one choose?

Recent evidence indicates that ionizing radiation can enhance immune responses to tumors. Advances in radiation delivery techniques allow hypofractionated delivery of conformal radiotherapy. Hypofractionation or other modifications of standard fractionation may improve radiation’s ability to promote immune responses to tumors. Other novel delivery options may also affect immune responses, including T-cell activation and tumor-antigen presentation changes. However, there is limited understanding of the immunological impact of hypofractionated and unique multifractionated radiotherapy regimens, as these observations are relatively recent. Hence, these differences in radiotherapy fractionation result in distinct immune-modulatory effects. Radiation oncologists and immunologists convened a virtual consensus discussion to identify current deficiencies, challenges, pitfalls and critical gaps when combining radiotherapy with immunotherapy and making recommendations to the field and advise National Cancer Institute on new directions and initiatives that will help further development of these two fields.

This commentary aims to raise the awareness of this complexity so that the need to study radiation dose, fractionation, type and volume is understood and valued by the immuno-oncology research community. Divergence of approaches and findings between preclinical studies and clinical trials highlights the need for evaluating the design of future clinical studies with particular emphasis on radiation dose and fractionation, immune biomarkers and selecting appropriate end points for combination radiation/immune modulator trials, recognizing that direct effect on the tumor and potential abscopal effect may well be different. Similarly, preclinical studies should be designed as much as possible to model the intended clinical setting. This article describes a conceptual framework for testing different radiation therapy regimens as separate models of how radiation itself functions as an immunomodulatory ‘drug’ to provide alternatives to the widely adopted ‘one-size-fits-all’ strategy of frequently used 8 Gy×3 regimens immunomodulation.

RGD-Binding Integrins Revisited: How Recently Discovered Functions and Novel Synthetic Ligands (Re-)Shape an Ever-Evolving Field

Simple Summary

Integrins, a superfamily of cell adhesion receptors, were extensively investigated as therapeutic targets over the last decades, motivated by their multiple functions, e.g., in cancer (progression, metastasis, angiogenesis), sepsis, fibrosis, and viral infections. Although integrin-targeting clinical trials, especially in cancer, did not meet the high expectations yet, integrins remain highly interesting therapeutic targets. In this article, we analyze the state-of-the-art knowledge on the roles of a subfamily of integrins, which require binding of the tripeptide motif Arg-Gly-Asp (RGD) for cell adhesion and signal transduction, in cancer, in tumor-associated exosomes, in fibrosis and SARS-CoV-2 infection. Furthermore, we outline the latest achievements in the design and development of synthetic ligands, which are highly selective and affine to single integrin subtypes, i.e., αvβ3, αvβ5, α5β1, αvβ6, αvβ8, and αvβ1. Lastly, we present the substantial progress in the field of nuclear and optical molecular imaging of integrins, including first-in-human and clinical studies.

Abstract

Integrins have been extensively investigated as therapeutic targets over the last decades, which has been inspired by their multiple functions in cancer progression, metastasis, and angiogenesis as well as a continuously expanding number of other diseases, e.g., sepsis, fibrosis, and viral infections, possibly also Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). Although integrin-targeted (cancer) therapy trials did not meet the high expectations yet, integrins are still valid and promising targets due to their elevated expression and surface accessibility on diseased cells. Thus, for the future successful clinical translation of integrin-targeted compounds, revisited and innovative treatment strategies have to be explored based on accumulated knowledge of integrin biology. For this, refined approaches are demanded aiming at alternative and improved preclinical models, optimized selectivity and pharmacological properties of integrin ligands, as well as more sophisticated treatment protocols considering dose fine-tuning of compounds. Moreover, integrin ligands exert high accuracy in disease monitoring as diagnostic molecular imaging tools, enabling patient selection for individualized integrin-targeted therapy. The present review comprehensively analyzes the state-of-the-art knowledge on the roles of RGD-binding integrin subtypes in cancer and non-cancerous diseases and outlines the latest achievements in the design and development of synthetic ligands and their application in biomedical, translational, and molecular imaging approaches. Indeed, substantial progress has already been made, including advanced ligand designs, numerous elaborated pre-clinical and first-in-human studies, while the discovery of novel applications for integrin ligands remains to be explored.

Exosomes derived from plasma: promising immunomodulatory agents for promoting angiogenesis to treat radiation-induced vascular dysfunction

Ionizing radiation (IR)-induced vascular disorders slow down tissue regeneration. Exosomes derived from plasma exhibit potential to promote angiogenesis; meanwhile, the immune microenvironment plays a significant role in the process. This study aimed to test the hypothesis that plasma exosomes promote angiogenesis in irradiated tissue by mediating the immune microenvironment. First, we explored the impact of IR on macrophages. We found that cell viability and capacity for promoting angiogenesis were decreased in irradiated macrophages compared to control macrophages. Then, we isolated and characterized rat plasma-derived exosomes (RP-Exos) which were defined as 40-160 nm extracellular vesicles extracted from rat plasma. Afterward, we evaluated the effects of RP-Exos on the behaviors of irradiated macrophages. Our results show that RP-Exos promoted cell proliferation. More importantly, we found that RP-Exos stimulated the immune microenvironment in a manner that improved the angiogenesis-related genes and proteins of irradiated macrophages. The supernatant of macrophage cell cultures was used as conditioned medium to treat human primary umbilical vein endothelial cells, further confirming the pro-angiogenic ability of macrophages receiving RP-Exo intervention. RP-Exos were used in vivo to treat irradiated skin or calvarial defects in irradiated Sprague-Dawley male rats. The results indicated the ability of RP-Exos to enhance angiogenesis and promote tissue regeneration. Our research suggested the potential of plasma exosomes to be used as immunomodulatory agents with angiogenic capacity to treat radiation-associated vascular disorders and facilitate tissue repair.

Atorvastatin Inhibits Endothelial PAI-1-Mediated Monocyte Migration and Alleviates Radiation-Induced Enteropathy

Intestinal injury is observed in cancer patients after radiotherapy and in individuals exposed to radiation after a nuclear accident. Radiation disrupts normal vascular homeostasis in the gastrointestinal system by inducing endothelial damage and senescence. Despite advances in medical technology, the toxicity of radiation to healthy tissue remains an issue. To address this issue, we investigated the effect of atorvastatin, a commonly prescribed hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor of cholesterol synthesis, on radiation-induced enteropathy and inflammatory responses. We selected atorvastatin based on its pleiotropic anti-fibrotic and anti-inflammatory effects. We found that atorvastatin mitigated radiation-induced endothelial damage by regulating plasminogen activator inhibitor-1 (PAI-1) using human umbilical vein endothelial cells (HUVECs) and mouse model. PAI-1 secreted by HUVECs contributed to endothelial dysfunction and trans-endothelial monocyte migration after radiation exposure. We observed that PAI-1 production and secretion was inhibited by atorvastatin in irradiated HUVECs and radiation-induced enteropathy mouse model. More specifically, atorvastatin inhibited PAI-1 production following radiation through the JNK/c-Jun signaling pathway. Together, our findings suggest that atorvastatin alleviates radiation-induced enteropathy and supports the investigation of atorvastatin as a radio-mitigator in patients receiving radiotherapy.

CircRNA-016901 silencing attenuates irradiation-induced injury in bone mesenchymal stem cells via regulating the miR-1249-5p/HIPK2 axis

Currently, bone marrow transplantation remains the basic treatment for various hematological tumors and irradiation is one of the most important pretreatment methods. However, irradiation pretreatment may result in damage to bone mesenchymal stem cells (BMSCs). The present study aimed to investigate the effect of circular RNA-016901 (circ-016901) on the injury of irradiation-induced BMSCs and the underlying mechanism. The expression levels of circ-016901, microRNA-1249-5p (miR-1249-5p) and homeodomain interacting protein kinase 2 (HIPK2) in irradiation-induced mouse BMSCs at various irradiation doses were detected via reverse transcription-quantitative PCR (RT-qPCR). The effect of circ-016901 on cell proliferation was examined using Cell Counting Kit-8 assays following silencing or overexpression of circ-016901. Cell apoptosis was detected by flow cytometry and caspase-3/7 activity. The expression of autophagy-related markers, including Beclin-1 and LC3-II/I, was detected at the mRNA and protein levels by RT-qPCR and western blotting, respectively. Irradiation treatment upregulated the expression of circ-016901 and HIPK2 and downregulated miR-1249-5p expression. The expression levels of LC3-II/I and Beclin-1 in BMSCs were downregulated in a dose-dependent manner. Silencing of circ-016901 promoted proliferation of irradiation-induced BMSCs and attenuated irradiation-induced apoptosis. Moreover, silencing of circ-016901 elevated the expressions of LC3-II/I and Beclin-1 in irradiation-induced BMSCs. Similar results were obtained with miR-1249-5p overexpression and HIPK2 silencing. These results demonstrated that circ-016901 silencing attenuated injury in irradiation-induced mouse BMSCs by regulating the miR-1249-5p/HIPK2 axis, providing a novel target for future research on the mechanism of radiation resistance in BMSCs.

Effect of fractionated whole-brain irradiation on brain and plasma in a rat model: Metabolic, volumetric and histopathological changes

In the present study, we investigated the correlation between histopathological, metabolic, and volumetric changes in the brain and plasma under experimental conditions. Adult male Wistar rats received fractionated whole-brain irradiation (fWBI) with a total dose of 32 Gy delivered in 4 fractions (dose 8 Gy per fraction) once a week on the same day for 4 consecutive weeks. Proton magnetic resonance spectroscopy (¹H MRS) and imaging were used to detect metabolic and volumetric changes in the brain and plasma. Histopathological changes in the brain were determined by image analysis of immunofluorescent stained sections. Metabolic changes in the brain measured by ¹H MRS before, 48 h, and 9 weeks after the end of fWBI showed a significant decrease in the ratio of total N-acetylaspartate to total creatine (tNAA/tCr) in the corpus striatum. We found a significant decrease in glutamine + glutamate/tCr (Glx/tCr) and, conversely, an increase in gamma-aminobutyric acid to tCr (GABA/tCr) in olfactory bulb (OB). The ratio of astrocyte marker myoinositol/tCr (mIns/tCr) significantly increased in almost all evaluated areas. Magnetic resonance imaging (MRI)-based brain volumetry showed a significant increase in volume, and a concomitant increase in the T₂ relaxation time of the hippocampus. Proton nuclear magnetic resonance (¹H NMR) plasma metabolomics displayed a significant decrease in the level of glucose and glycolytic intermediates and an increase in ketone bodies. The histomorphological analysis showed a decrease to elimination of neuroblasts, increased astrocyte proliferation, and a mild microglia response. The results of the study clearly reflect early subacute changes 9-11 weeks after fWBI with strong manifestations of brain edema, astrogliosis, and ongoing ketosis.

Mechanisms of radiation-induced endothelium damage: Emerging models and technologies

Radiation-induced endothelial/vascular injury is a major complicating factor in radiotherapy and a leading cause of morbidity and mortality in nuclear or radiological catastrophes. Exposure of tissue to ionizing radiation (IR) leads to the release of oxygen radicals and proteases that result in loss of endothelial barrier function and leukocyte dysfunction leading to tissue injury and organ damage. Microvascular endothelial cells are particularly sensitive to IR and radiation-induced alterations in endothelial cell function are thought to be a critical factor in organ damage through endothelial cell activation, enhanced leukocyte-endothelial cell interactions, increased barrier permeability and initiation of apoptotic pathways. These radiation-induced inflammatory responses are important in early and late radiation pathologies in various organs. A better understanding of mechanisms of radiation-induced endothelium dysfunction is therefore vital, as radiobiological response of endothelium is of major importance for medical management and therapeutic development for radiation injuries. In this review, we summarize the current knowledge of cellular and molecular mechanisms of radiation-induced endothelium damage and their impact on early and late radiation injury. Furthermore, we review established and emerging in vivo and in vitro models that have been developed to study the mechanisms of radiation-induced endothelium damage and to design, develop and rapidly screen therapeutics for treatment of radiation-induced vascular damage. Currently there are no specific therapeutics available to protect against radiation-induced loss of endothelial barrier function, leukocyte dysfunction and resulting organ damage. Developing therapeutics to prevent endothelium dysfunction and normal tissue damage during radiotherapy can serve as the urgently needed medical countermeasures.

Biology of iatrogenic sexual dysfunction in men and women survivors of cancer

Sexual dysfunction (SD) is widely reported by cancer survivors. However, this is an issue underestimated by doctors and the contribution of anticancer therapies for the development of SD in cancer survivors is understudied and poorly understood. Sexual function involves the activation of a neurovascular system that leads to penile erection in males and clitoral engorgement in females. Anticancer therapies can cause damage to the neurovascular circuit responsible for normal sexual function and thus, individual or combined therapies could play a role in the development of SD in all types of cancer survivors and not only those affected by genital cancers. In this review, the pathophysiology of SD and possible mechanisms underlying SD induced by anticancer therapies will be discussed. The effects of chemotherapy, radiotherapy and surgical interventions on the vasculature and nerves as well as their effects on sex hormones and inflammatory processes could link the biological effects of these interventions with SD. In conclusion, this review reports evidence that, despite psychological aspects and the disease itself, anticancer therapies are able to induce direct and indirect effects in males and females that could lead to SD in cancer survivors even after the end of the treatment.

3,3'-Diindolylmethane Enhances Tumor Regression After Radiation Through Protecting Normal Cells to Modulate Antitumor Immunity

Purpose

Preclinical and clinical data indicate that radiation therapy acts as an immune modifier, having both immune-stimulatory and immunosuppressive effects on the tumor-immune microenvironment (TIME). 3.3’-diindolylmethane (DIM) sensitizes tumor cells to radiation and protects mice from lethal doses of total body irradiation. We hypothesize that protecting nontumoral cells from the adverse effects of radiation treatment (RT) may help to correct immunosuppression resulting from radiation.

Methods and Materials

We generated tumor graft models using immune-competent and immune-deficient mouse strains. Narrow-beamed radiation was targeted to tumor sites using shielding. Tumor regression was monitored after DIM and RT versus RT alone. The effects of DIM on the efficacy of RT were assessed using immunohistochemistry staining and gene expression profiling. Complete blood counts, clonogenic cell survival assays, and global gene expression profiling of cultured cells were performed to study DIM’s radioprotective effects on normal cells.

Results

DIM enhanced tumor regression after RT in immune-competent but not immune-deficient mice. Data indicated that DIM increased intratumoral immune cells after RT, contributing to enhanced immunologic responses such as adhesion and antigen processing. DIM protected normal cells from radiation-induced immediate injuries in vitro and in vivo. Transcriptomic profiling of cultured cells showed that DIM treatment mildly increased expression of some genes that are normally induced after radiation, such as genes involved in cell cycle arrest and apoptosis.

Conclusions

In this study, using cultured cells and preclinical breast cancer models, we show that DIM protects normal cells from radiation-induced immediate cellular injury and combination treatment of DIM and radiation potentiates antitumor immune responses and enhances the efficacy of RT.

Host CD39 Deficiency Affects Radiation-Induced Tumor Growth Delay and Aggravates Radiation-Induced Normal Tissue Toxicity

The ectonucleoside triphosphate diphosphohydrolase (CD39)/5′ ectonuclotidase (CD73)-dependent purinergic pathway emerges as promising cancer target. Yet, except for own previous work revealing a pathogenic role of CD73 and adenosine in radiation-induced lung fibrosis, the role of purinergic signaling for radiotherapy outcome remained elusive. Here we used C57BL/6 wild-type (WT), CD39 knockout (CD39^−/−), and CD73 knockout (CD73^−/−) mice and hind-leg tumors of syngeneic murine Lewis lung carcinoma cells (LLC1) to elucidate how host purinergic signaling shapes the growth of LLC1 tumors to a single high-dose irradiation with 10 Gy in vivo. In complementary in vitro experiments, we examined the radiation response of LLC1 cells in combination with exogenously added ATP or adenosine, the proinflammatory and anti-inflammatory arms of purinergic signaling. Finally, we analyzed the impact of genetic loss of CD39 on pathophysiologic lung changes associated with lung fibrosis induced by a single-dose whole-thorax irradiation (WTI) with 15 Gy. Loss of CD73 in the tumor host did neither significantly affect tumor growth nor the radiation response of the CD39/CD73-negative LLC1 tumors. In contrast, LLC1 tumors exhibited a tendency to grow faster in CD39^−/− mice compared to WT mice. Even more important, tumors grown in the CD39-deficient background displayed a significantly reduced tumor growth delay upon irradiation when compared to irradiated tumors grown on WT mice. CD39 deficiency caused only subtle differences in the immune compartment of irradiated LLC1 tumors compared to WT mice. Instead, we could associate the tumor growth and radioresistance-promoting effects of host CD39 deficiency to alterations in the tumor endothelial compartment. Importantly, genetic deficiency of CD39 also augmented the expression level of fibrosis-associated osteopontin in irradiated normal lungs and exacerbated radiation-induced lung fibrosis at 25 weeks after irradiation. We conclude that genetic loss of host CD39 alters the tumor microenvironment, particularly the tumor microvasculature, and thereby promotes growth and radioresistance of murine LLC1 tumors. In the normal tissue loss of host, CD39 exacerbates radiation-induced adverse late effects. The suggested beneficial roles of host CD39 on the therapeutic ratio of radiotherapy suggest that therapeutic strategies targeting CD39 in combination with radiotherapy have to be considered with caution.

Radiation-induced Adaptive Response: New Potential for Cancer Treatment

Radiotherapy is highly effective due to its ability to physically focus the treatment to target the tumor while sparing normal tissue and its ability to be combined with systemic therapy. This systemic therapy can be utilized before radiotherapy as an adjuvant or induction treatment, during radiotherapy as a radiation "sensitizer," or following radiotherapy as a part of combined modality therapy. As part of a unique concept of using radiation as "focused biology," we investigated how tumors and normal tissues adapt to clinically relevant multifraction (MF) and single-dose (SD) radiation to observe whether the adaptations can induce susceptibility to cell killing by available drugs or by immune enhancement. We identified an adaptation occurring after MF (3 × 2 Gy) that induced cell killing when AKT-mTOR inhibitors were delivered following cessation of radiotherapy. In addition, we identified inducible changes in integrin expression 2 months following cessation of radiotherapy that differ between MF (1 Gy × 10) and SD (10 Gy) that remain targetable compared with preradiotherapy. Adaptation is reflected across different "omics" studies, and thus the range of possible molecular targets is not only broad but also time, dose, and schedule dependent. While much remains to be studied about the radiation adaptive response, radiation should be characterized by its molecular perturbations in addition to physical dose. Consideration of the adaptive effects should result in the design of a tailored radiotherapy treatment plan that accounts for specific molecular changes to be targeted as part of precision multimodality cancer treatment.

Radioprotection and Radiomitigation: From the Bench to Clinical Practice

The development of protective agents against harmful radiations has been a subject of investigation for decades. However, effective (ideal) radioprotectors and radiomitigators remain an unsolved problem. Because ionizing radiation-induced cellular damage is primarily attributed to free radicals, radical scavengers are promising as potential radioprotectors. Early development of such agents focused on thiol synthetic compounds, e.g., amifostine (2-(3-aminopropylamino) ethylsulfanylphosphonic acid), approved as a radioprotector by the Food and Drug Administration (FDA, USA) but for limited clinical indications and not for nonclinical uses. To date, no new chemical entity has been approved by the FDA as a radiation countermeasure for acute radiation syndrome (ARS). All FDA-approved radiation countermeasures (filgrastim, a recombinant DNA form of the naturally occurring granulocyte colony-stimulating factor, G-CSF; pegfilgrastim, a PEGylated form of the recombinant human G-CSF; sargramostim, a recombinant granulocyte macrophage colony-stimulating factor, GM-CSF) are classified as radiomitigators. No radioprotector that can be administered prior to exposure has been approved for ARS. This differentiates radioprotectors (reduce direct damage caused by radiation) and radiomitigators (minimize toxicity even after radiation has been delivered). Molecules under development with the aim of reaching clinical practice and other nonclinical applications are discussed. Assays to evaluate the biological effects of ionizing radiations are also analyzed.

Radiation Response of Human Cardiac Endothelial Cells Reveals a Central Role of the cGAS-STING Pathway in the Development of Inflammation

Radiation-induced inflammation leading to the permeability of the endothelial barrier may increase the risk of cardiovascular disease. The aim of this study was to investigate potential mechanisms in vitro at the level of the proteome in human coronary artery endothelial cells (HCECest2) that were exposed to radiation doses of 0, 0.25, 0.5, 2.0 and 10 Gy (60Co-γ). Proteomics analysis was performed using mass spectrometry in a label-free data-independent acquisition mode. The data were validated using bioinformatics and immunoblotting. The low- and moderate-dose-irradiated samples (0.25 Gy, 0.5 Gy) showed only scarce proteome changes. In contrast, an activation of DNA-damage repair, inflammation, and oxidative stress pathways was seen after the high-dose treatments (2 and 10 Gy). The level of the DNA damage response protein DDB2 was enhanced early at the 10 Gy dose. The expression of proteins belonging to the inflammatory response or cGAS-STING pathway (STING, STAT1, ICAM1, ISG15) increased in a dose-dependent manner, showing the strongest effects at 10 Gy after one week. This study suggests a connection between the radiation-induced DNA damage and the induction of inflammation which supports the inhibition of the cGAS-STING pathway in the prevention of radiation-induced cardiovascular disease.

Surmounting the obstacles that impede effective CAR T cell trafficking to solid tumors

Innovative immunotherapies based on immune checkpoint targeting antibodies and engineered T cells are transforming the way we approach cancer treatment. However, although these T cell centered strategies result in marked and durable responses in patients across many different tumor types, they provide therapeutic efficacy only in a proportion of patients. A major challenge of immuno‐oncology is thereby to identify mechanisms responsible for resistance to cancer immunotherapy in order to overcome them via adapted strategies that will ultimately improve intrinsic efficacy and response rates. Here, we focus on the barriers that restrain the trafficking of chimeric antigen receptor (CAR)‐expressing T cells to solid tumors. Upon infusion, CAR T cells need to home into malignant sites, navigate within complex tumor environments, form productive interactions with cancer cells, deliver their cytotoxic activities, and finally persist. We review the accumulating evidence that the microenvironment of solid tumors contains multiple obstacles that hinder CAR T cells in the dynamic steps underlying their trafficking. We focus on how these hurdles may in part account for the failure of CAR T cell clinical trials in human carcinomas. Given the engineered nature of CAR T cells and possibilities to modify the tumor environment, there are ample opportunities to augment CAR T cell ability to efficiently find and combat tumors. We present some of these strategies, which represent a dynamic field of research with high potential for clinical applicability.

Radiation-induced myocardial fibrosis: Mechanisms underlying its pathogenesis and therapeutic strategies

Radiation-induced myocardial fibrosis (RIMF) is a potentially lethal clinical complication of chest radiotherapy (RT) and a final stage of radiation-induced heart disease (RIHD). RIMF is characterized by decreased ventricular elasticity and distensibility, which can result in decreased ejection fraction, heart failure and even sudden cardiac death. Together, these conditions impair the long-term health of post-RT survivors and limit the dose and intensity of RT required to effectively kill tumour cells. Although the exact mechanisms involving in RIMF are unclear, increasing evidence indicates that the occurrence of RIMF is related to various cells, regulatory molecules and cytokines. However, accurately diagnosing and identifying patients who may progress to RIMF has been challenging. Despite the urgent need for an effective treatment, there is currently no medical therapy for RIMF approved for routine clinical application. In this review, we investigated the underlying pathophysiology involved in the initiation and progression of RIMF before outlining potential preventative and therapeutic strategies to counter this toxicity.

Bi-Directional interactions between microbiota and ionizing radiation in head and neck and pelvic radiotherapy - clinical relevance

Purpose: Rapid developments in high throughput screening technology for the detection and identification of the human microbiota have helped in understanding its influence on human health and disease. In the recent past, several seminal studies have demonstrated the influence of microbiota on outcomes of therapy-associated radiation exposure. In this review, we highlight the concepts related to the mechanisms by which radiation alters the microbiota composition linked with radiation-associated toxicity in head and neck and pelvic regions. We further discuss specific microbial changes that can be employed as a biomarker for radiation and tumor response.Conclusion: Knowledge of the influence of microbiota in radiation response and advances in microbiota manipulation techniques would help to design personalized treatment augmenting the efficacy of radiotherapy.

Variation of 4 MV X-ray dose rate strongly impacts biological response both in vitro and in vivo

Whereas an RBE > 1 is described for very low-energy X-ray beams (in the range of 25–50 kV), there is a consensus that the RBE of X-rays (from 0.1 to 3 MeV) is equal to 1, whatever the energy or dose rate of the beam. Comparisons of X-ray beam dose rates are scarce even though these beams are widely used in medical diagnosis or radiotherapy. By using two dose rates (0.63 and 2.5 Gy.min⁻¹) of high-energy X-rays on normal endothelial cells (HUVECs), we have studied the clonogenic assay, but also viability/mortality, cell cycle analysis and measured cellular senescence by flow cytometry, and have performed gene analysis on custom arrays. In order to consolidate these data, we performed localized irradiation of exteriorized small intestine at 0.63 and 2.5 Gy.min⁻¹. Interestingly, in vivo validation has shown a significantly higher loss of weight at the higher dose when irradiating to 19 Gy a small fragment of exteriorized small intestine of C57Bl6J mice. Nevertheless, no significant differences were observed in lesioned scores between the two dose rates, while bordering epithelium staining indicated twofold greater severe damage at 2.5 Gy.min⁻¹ compared to 0.63 Gy.min⁻¹ at one week post-irradiation. Taken together, these experiments systematically show that the relative biological effectiveness of photons is different from 1 when varying the dose rate of high-energy X-rays. Moreover, these results strongly suggest that, in support of clonogenic assay, multiparametric analysis should be considered to provide an accurate evaluation of the outcome of irradiated cells.

microRNAs identified in prostate cancer: Correlative studies on response to ionizing radiation

As the most frequently diagnosed non-skin cancer in men and a leading cause of cancer-related death, understanding the molecular mechanisms that drive treatment resistance in prostate cancer poses a significant clinical need. Radiotherapy is one of the most widely used treatments for prostate cancer, along with surgery, hormone therapy, and chemotherapy. However, inherent radioresistance of tumor cells can reduce local control and ultimately lead to poor patient outcomes, such as recurrence, metastasis and death. The underlying mechanisms of radioresistance have not been fully elucidated, but it has been suggested that miRNAs play a critical role. miRNAs are small non-coding RNAs that regulate gene expression in every signaling pathway of the cell, with one miRNA often having multiple targets. By fine-tuning gene expression, miRNAs are important players in modulating DNA damage response, cell death, tumor aggression and the tumor microenvironment, and can ultimately affect a tumor’s response to radiotherapy. Furthermore, much interest has focused on miRNAs found in biofluids and their potential utility in various clinical applications. In this review, we summarize the current knowledge on miRNA deregulation after irradiation and the associated functional outcomes, with a focus on prostate cancer. In addition, we discuss the utility of circulating miRNAs as non-invasive biomarkers to diagnose, predict response to treatment, and prognosticate patient outcomes.

Immunological impact of cell death signaling driven by radiation on the tumor microenvironment

Therapeutic irradiation of the tumor microenvironment causes differential activation of pro-survival and pro-death pathways in malignant, stromal, endothelial and immune cells, hence causing a profound cellular and biological reconfiguration via multiple, non-redundant mechanisms. Such mechanisms include the selective elimination of particularly radiosensitive cell types and consequent loss of specific cellular functions, the local release of cytokines and danger signals by dying radiosensitive cells, and altered cytokine secretion by surviving radioresistant cells. Altogether, these processes create chemotactic and immunomodulatory cues for incoming and resident immune cells. Here we discuss how cytoprotective and cytotoxic signaling modules activated by radiation in specific cell populations reshape the immunological tumor microenvironment.

Stereotactic Lung Irradiation in Mice Promotes Long-Term Senescence and Lung Injury

PURPOSE

Lung cancer will be treated more frequently using stereotactic body radiation therapy, and preclinical research to model long-term toxicity of ablative doses of radiation is crucial. Stereotactic lung irradiation of a small volume can induce radiation pneumonitis and fibrosis in normal tissues.

METHODS AND MATERIALS

Senescence has been reported to contribute to lung fibrosis, and we investigated in vivo the effects of ablative doses of ionizing radiation on senescence-associated processes. The left lung of p16^INK4a-LUC knock-in mice was exposed to a single dose or fractionated radiation doses in a millimetric volume using a small animal radiation research platform.

RESULTS

Single or fractionated ablative radiation induces acute and very long-term p16^INK4a activation in the irradiated lung target volume associated with lung injury. We observed a panel of heterogeneous senescent cells including pneumocytes, macrophages, and endothelial cells that accumulated around the radiation-induced lung focal lesion, suggesting that different senescent cell types may contribute to radiation injury.

CONCLUSIONS

This work provides important information on the long-term effects of ablative radiation doses in the normal lung and strongly suggests that stress-induced senescence is involved in stereotactic body radiation therapy-induced late fibrosis.