Radiation-induced lung fibrosis in a tumor-bearing mouse model is associated with enhanced Type-2 immunity

Ameliorating effect of CpG-ODN (oligodeoxynucleotide) against radiation-induced lung injury in mice

While radiation-induced lung injury (RILI) is known to be progressed by Th2 skewed, pro-inflammatory immune response, there have been few therapeutic attempts through Th1 immune modulation. We investigated whether the immunostimulant CpG-oligodeoxynucleotide (CpG-ODN) would be effective against RILI by way of measuring reactive oxygen species (ROS) and nitric oxides (NO), histopathology, micro-three-dimensional computer tomography (CT), and cytokine profiling. We found that KSK CpG-ODN (K-CpG) significantly reduced histopathological fibrosis when compared to the positive control (PC) group (p < 0.01). The levels of ROS production in serum and splenocyte of PC group were significantly higher than that of K-CpG group (p < 0.01). The production of nitric oxide (NO) in CpG-ODNs group was higher than that of PC group. Last, cytokine profiling illustrated that the protein concentrations of Th1-type cytokines such as IL-12 and TNF-α as well as Th2-type cytokine IL-5 in K-CpG group inclined to be significantly (p < 0.001 or p < 0.01) higher than those of in PC group. Collectively, our study clearly indicates that K-CpG is effective against RILI in mice by modulating the innate immune response. To our knowledge, this is the first note on anti-RILI effect of human type, K-CpG, clinically implying the potential of immunotherapy for RILI control.

Radiation Exposure-Induced Changes in the Immune Cells and Immune Factors of Mice With or Without Primary Lung Tumor

Recent studies have demonstrated that radiation activates in situ antitumor immunity and consequently induced a synergistic effect of radiotherapy and immunotherapy. However, studies related to radiation-induced changes in immune system of tumor-bearing mice are limited, which are of great significance to improve the efficacy of radioimmunotherapy. In this study, we first established a primary lung tumor mouse model using urethane. Then part of the right lung of the mouse was exposed to X-ray irradiation with a computed tomography-guided small animal irradiator and the changes of immune cells in both peripheral blood and spleen were determined by flow cytometry. Besides, the levels of both cytokines and immunoglobulins in mouse serum were detected by a protein chip. We found that B lymphocytes increased while CD8⁺ T lymphocytes reduced significantly. Interleukin-3 (IL-3), IL-6, regulated upon activation, normally T-expressed, and presumably secreted factor (RANTES), and vascular endothelial growth factor (VEGF) were found to be decreased after tumor formation, and the similar results have also been observed with kappa, IgG3, IgE, IgM, and IgG2a. After irradiation, lower concentrations of IgD, kappa, and IgM were found in the serum. Our findings indicate that localized tumor irradiation caused some obvious changes like inhibiting the ability of innate immunity, and these changes may be useful in predicting prognosis.

Impact of Radiotherapy Concurrent with Anti-PD-1 Therapy on the Lung Tissue of Tumor-Bearing Mice

Pneumonitis is a common adverse effect found in non-small cell lung cancer patients after radiotherapy or immune checkpoint inhibitor treatment. We investigated the effects of these two therapies, combined, in the lung tissue of an orthotopic tumor-bearing mouse model. The mice received an 8 Gy dose three times with or without 200 µg anti-programmed death-1 (anti-PD-1) antibody intraperitoneal injection every three days. Lung tissues were H&E stained to determine histological changes. The serum levels of cytokines, such as interferon-γ, tumor necrosis factor and interleukin-5, were detected by cytometric bead array. The neutrophil infiltration was evaluated by immunohistochemical staining for myeloperoxidase. The lung injury score was higher in the treated groups than the control group, especially in the combined treatment group, in which the proportion of neutrophils in lung tissues was significantly higher compared to any other groups. Similarly, the CD4/CD8 ratio of the lung tissues in the combined treatment group, as well as the serum levels of interferon-γ, tumor necrosis factor and interleukin-5, were significantly higher than the other groups. These findings indicate that radiation combined with anti-PD-1 treatment leads to more severe lung injury in the orthotopic tumor-bearing mouse model, accompanied by increased neutrophil infiltration and increased inflammatory response.

Advances in Molecular Mechanisms and Treatment of Radiation-Induced Pulmonary Fibrosis

Radiation-induced pulmonary fibrosis (RIPF) is a common complication in patients with lung cancer and breast cancer after receiving thoracic radiotherapy. The average incidence of RIPF is 16%-28% after radiotherapy. RIPF includes a heterogeneous group of lung disorders characterized by progressive and irreversible destruction of lung architecture and disruption of gas exchange. The clinical signs of RIPF include increasing dyspnea, deteriorating lung function, and accumulation of interstitial fluid, eventually leading to respiratory failure. No medical therapy for RIPF has been approved for routine clinical use despite the apparent need for an effective treatment. Numerous signaling pathways are involved in the initiation and progression of RIPF. Also, various approaches for RIPF treatments have focused on several aspects of the current understanding of the molecular pathology of RIPF. This review used the mechanistic categories of associated cell signaling pathways, epithelial cell dysfunction and senescence, abnormal lung remodeling, and aberrant innate and adaptive immunity to review the published literature on RIPF to date and then to identify potential areas for the effective treatment of RIPF.

Longitudinal microcomputed tomography-derived biomarkers for lung metastasis detection in a syngeneic mouse model: added value to bioluminescence imaging

With more patients dying from metastasis than from primary cancers, metastasis is a very important area in cancer research. Investigators thereby heavily rely on animal models of metastasis to common organs such as the lung to improve our insight into the pathogenesis and to research novel therapeutic approaches to combat metastasis. In this experimental context, novel tools that allow longitudinal monitoring of lung metastasis in individual animals are highly needed. We have therefore evaluated for the first time microcomputed tomography (μCT) as a very efficient and crossvalidated means to noninvasively and repeatedly monitor metastasis to the lung in individual, free-breathing syngeneic mice. Two individual clones of KLN205 cancer cells were intravenously injected in syngeneic DBA/2 mice and lung metastasis was monitored weekly during 3 weeks using μCT, and was compared with the current gold standard histology and bioluminescence imaging (BLI). μCT enabled us to visualize diffuse tumor morphology and also to extract four different biomarkers that quantify not only tumor load but also aerated space in the lung as a marker of vital lung capacity and potential compensatory mechanisms. Complementary to BLI, applying this novel μCT-based approach enabled us to unravel sensitively and efficiently differences in metastatic potential between two cellular clones. In conclusion, μCT and BLI offer biomarkers that describe different and complementary aspects of lung metastasis, underlining the importance of multimodality follow-up. The added value of μCT findings is important to better assess lung metastasis and host/lung response in preclinical studies, which will be valuable for translational applications.

The Role of Lymphocytes in Radiotherapy-Induced Adverse Late Effects in the Lung

Radiation-induced pneumonitis and fibrosis are dose-limiting side effects of thoracic irradiation. Thoracic irradiation triggers acute and chronic environmental lung changes that are shaped by the damage response of resident cells, by the resulting reaction of the immune system, and by repair processes. Although considerable progress has been made during the last decade in defining involved effector cells and soluble mediators, the network of pathophysiological events and the cellular cross talk linking acute tissue damage to chronic inflammation and fibrosis still require further definition. Infiltration of cells from the innate and adaptive immune systems is a common response of normal tissues to ionizing radiation. Herein, lymphocytes represent a versatile and wide-ranged group of cells of the immune system that can react under specific conditions in various ways and participate in modulating the lung environment by adopting pro-inflammatory, anti-inflammatory, or even pro- or anti-fibrotic phenotypes. The present review provides an overview on published data about the role of lymphocytes in radiation-induced lung disease and related damage-associated pulmonary diseases with a focus on T lymphocytes and B lymphocytes. We also discuss the suspected dual role of specific lymphocyte subsets during the pneumonitic phase and fibrotic phase that is shaped by the environmental conditions as well as the interaction and the intercellular cross talk between cells from the innate and adaptive immune systems and (damaged) resident epithelial cells and stromal cells (e.g., endothelial cells, mesenchymal stem cells, and fibroblasts). Finally, we highlight potential therapeutic targets suited to counteract pathological lymphocyte responses to prevent or treat radiation-induced lung disease.

Mechanisms of the alternative activation of macrophages and non-coding RNAs in the development of radiation-induced lung fibrosis

Radiation-induced lung fibrosis (RILF) is a common side effect of thoracic irradiation therapy and leads to high mortality rates after cancer treatment. Radiation injury induces inflammatory M1 macrophage polarization leading to radiation pneumonitis, the first stage of RILF progression. Fibrosis occurs due to the transition of M1 macrophages to the anti-inflammatory pro-fibrotic M2 phenotype, and the resulting imbalance of macrophage regulated inflammatory signaling. Non-coding RNA signaling has been shown to play a large role in the regulation of the M2 mediated signaling pathways that are associated with the development and progression of fibrosis. While many studies show the link between M2 macrophages and fibrosis, there are only a few that explore their distinct role and the regulation of their signaling by non-coding RNA in RILF. In this review we summarize the current body of knowledge describing the roles of M2 macrophages in RILF, with an emphasis on the expression and functions of non-coding RNAs.

The effect of the TLR9 ligand CpG-oligodeoxynucleotide on the protective immune response to radiation-induced lung fibrosis in mice

CpG-oligodeoxynucleotide (CpG-ODN) is not only reported to protect against airway hyper responsiveness but is also known as a potent vaccine adjuvant for anti-tumor therapy. Little is known about the effect of CpG-ODN in mice with radiation-induced lung fibrosis (RILF), a common late stage form of tissue damage that occurs after thorax radiotherapy (RT). Here, we evaluated the immunomodulatory effects of CpG-ODN on the development of RILF. Mice were divided into four groups: (1) RT, single dose of 12Gy to the whole thorax; (2) CpG, only intraperitoneal injection of CpG-ODN for total 5 weeks; (3) RT+CpG, irradiation plus CpG-ODN treatment before and after irradiation for total 5 weeks; and (4) control (CTL): No RT or CpG-ODN treatment. In this study, we found that CpG-ODN treatment attenuated lung fibrosis and collagen deposition by increasing the number of M1 macrophagocytes, levels of Type-2 cytokines and TGF-β. CpG-ODN administration up-regulated the expression of TLR9 and STAT1 phosphorylation and reversed the expression of Type-2 immune response key transcription factor GATA-3. Activation of the JAK-STAT1 signaling pathway further enhanced M1 macrophage differentiation and Type-1 cytokine production. This study reveals the mitigating effect of early exposure to CpG-ODN on lung injury caused by irradiation in mice. The potential mechanism of action may be related to enhancement of Type-1 immunity. In conclusion, CpG-ODN may be a potential therapeutic target to treat RILF.

Novel concepts in radiation-induced cardiovascular disease

Radiation-induced cardiovascular disease (RICVD) is the most common nonmalignant cause of morbidity and mortality among cancer survivors who have undergone mediastinal radiation therapy (RT). Cardiovascular complications include effusive or constrictive pericarditis, cardiomyopathy, valvular heart disease, and coronary/vascular disease. These are pathophysiologically distinct disease entities whose prevalence varies depending on the timing and extent of radiation exposure to the heart and great vessels. Although refinements in RT dosimetry and shielding will inevitably limit future cases of RICVD, the increasing number of long-term cancer survivors, including those treated with older higher-dose RT regimens, will ensure a steady flow of afflicted patients for the foreseeable future. Thus, there is a pressing need for enhanced understanding of the disease mechanisms, and improved detection methods and treatment strategies. Newly characterized mechanisms responsible for the establishment of chronic fibrosis, such as oxidative stress, inflammation and epigenetic modifications, are discussed and linked to potential treatments currently under study. Novel imaging modalities may serve as powerful screening tools in RICVD, and recent research and expert opinion advocating their use is introduced. Data arguing for the aggressive use of percutaneous interventions, such as transcutaneous valve replacement and drug-eluting stents, are examined and considered in the context of prior therapeutic approaches. RICVD and its treatment options are the subject of a rich and dynamic body of research, and patients who are at risk or suffering from this disease will benefit from the care of physicians with specialty expertise in the emerging field of cardio-oncology.