Effect of low dose radiation on differentiation of bone marrow cells into dendritic cells

Radiotherapy induced immunogenic cell death by remodeling tumor immune microenvironment

Emerging evidence indicates that the induction of radiotherapy(RT) on the immunogenic cell death (ICD) is not only dependent on its direct cytotoxic effect, changes in the tumor immune microenvironment also play an important role in it. Tumor immune microenvironment (TIME) refers to the immune microenvironment that tumor cells exist, including tumor cells, inflammatory cells, immune cells, various signaling molecules and extracellular matrix. TIME has a barrier effect on the anti-tumor function of immune cells, which can inhibit all stages of anti-tumor immune response. The remodeling of TIME caused by RT may affect the degree of immunogenicity, and make it change from immunosuppressive phenotype to immunostimulatory phenotype. It is of great significance to reveal the causes of immune escape of tumor cells, especially for the treatment of drug-resistant tumor. In this review, we focus on the effect of RT on the TIME, the mechanism of RT in reversing the TIME to suppress intrinsic immunity, and the sensitization effect of the remodeling of TIME caused by RT on the effectiveness of immunotherapy.

Low dose ionizing radiation and the immune response: what is the role of non-targeted effects?

OBJECTIVES

This review aims to trace the historical narrative surrounding the low dose effects of radiation on the immune system and how our understanding has changed from the beginning of the 20th century to now. The particular focus is on the non-targeted effects (NTEs) of low dose ionizing radiation (LDIR) which are effects that occur when irradiated cells emit signals that cause effects in the nearby or distant non-irradiated cells known as radiation induced bystander effect (RIBE). Moreover, radiation induced genomic instability (RIGI) and abscopal effect (AE) also regarded as NTE. This was prompted by our recent discovery that ultraviolet A (UVA) photons are emitted by the irradiated cells and that these photons can trigger NTE such as the RIBE in unirradiated recipients of these photons. Given the well-known association between UV radiation and the immune response, where these biophotons may pose as bystander signals potentiating processes in deep tissues as a consequence of LDIR, it is timely to review the field with a fresh lens. Various pathways and immune components that contribute to the beneficial and adverse types of modulation induced by LDR will also be revisited.

CONCLUSION

There is limited evidence for LDIR induced immune effects by way of a non-targeted mechanism in biological tissue. The literature examining low to medium dose effects of ionizing radiation on the immune system and its components is complex and controversial. Early work was compromised by lack of good dosimetry while later work mainly looks at the involvement of immune response in radiotherapy. There is a lack of research in the LDIR/NTE field focusing on immune response although bone marrow stem cells and lineages were critical in the identification and characterization of NTE where effects like RIGI and RIBE were heavily researched. This may be in part, a result of the difficulty of isolating NTE in whole organisms which are essential for good immune response studies. Models involving inter organism transmission of NTE are a promising route to overcome these issues.

Effect of ¹³¹I Therapy on Complete Blood Count in Patients with Differentiated Thyroid Cancer

Background

The aim of this study was to investigate the effects of ¹³¹I therapy on complete blood count (CBC) in patients with differentiated thyroid cancer (DTC).

Materia/Methods

We analyzed CBC in 542 patients with DTC who were grouped according to treatment cycles and cumulative dose and then subdivided by sex and age. The effects of ¹³¹I therapy among the different groups and subgroups were analyzed.

Results

After sorting patients by treatment cycles and doses, ¹³¹I therapy was found to have different effects on CBC depending on patient sex and age. The effect on white blood cell (WBC) counts persisted longer in women, while increases in hemoglobin (Hb) were more significant in men. The influence on red blood cell (RBC) counts was short-lived in patients aged 45 to 54 years. Monocyte counts were significantly decreased only in patients aged 55 years and older who had undergone 3 or 4 treatment cycles. In men, CBC was more affected by cumulative dose. ¹³¹I therapy only influenced platelet and monocyte counts in patients aged 55 years or older. Hb was significantly decreased and increased in the high- and low-dose groups, respectively. No significant complications were observed during follow-up.

Conclusions

¹³¹I therapy had a greater impact on WBC counts in women, while changes in RBC counts and Hb were more obvious in men. During ¹³¹I therapy, clinicians should pay attention to different CBC indicators based on a patient’s sex and age, but risks associated with an altered CBC are unlikely to outweigh the benefits of ¹³¹I. The results of the present study may help alleviate the concerns of a large proportion of patients with DTC and their families about the effects of ¹³¹I therapy on CBC.

Highlighting the Potential for Chronic Stress to Minimize Therapeutic Responses to Radiotherapy through Increased Immunosuppression and Radiation Resistance

Ionizing radiation has been used in the treatment of cancer for more than 100 years. While often very effective, there is still a great effort in place to improve the efficacy of radiation therapy for controlling the progression and recurrence of tumors. Recent research has revealed the close interaction between nerves and tumor progression, especially nerves of the autonomic nervous system that are activated by a variety of stressful stimuli including anxiety, pain, sleep loss or depression, each of which is likely to be increased in cancer patients. A growing literature now points to a negative effect of chronic stressful stimuli in tumor progression. In this review article, we present data on the potential for adrenergic stress to influence the efficacy of radiation and in particular, its potential to influence the anti-tumor immune response, and the frequency of an "abscopal effect" or the shrinkage of tumors which are outside an irradiated field. We conclude that chronic stress can be a major impediment to more effective radiation therapy through mechanisms involving immunosuppression and increased resistance to radiation-induced tumor cell death. Overall, these data highlight the potential value of stress reduction strategies to improve the outcome of radiation therapy. At the same time, objective biomarkers that can accurately and objectively reflect the degree of stress in patients over prolonged periods of time, and whether it is influencing immunosuppression and radiation resistance, are also critically needed.

Single High-Dose Radiation Enhances Dendritic Cell Homing and T Cell Priming by Promoting Reactive Oxygen Species-Induced Cytoskeletal Reorganization

PURPOSE

Radiation therapy (RT) affects tumor-infiltrating immune cells, cooperatively driving tumor growth inhibition. However, there is still no absolute consensus on whether the homing ability of dendritic cells (DCs) is affected by direct x-ray irradiation. Most importantly, the underlying mechanisms are poorly understood.

METHODS AND MATERIALS

Using noninvasive imaging, we systematically examined the dose effect of RT on the in vivo homing and distribution of bone marrow-derived DCs and elucidated the detailed mechanisms underlying these events. After exposure to 2, 5, 10, 15, and 20 Gy, DCs were analyzed for maturation, in vivo homing ability, and T cell priming.

RESULTS

At ranges of 2 to 20 Gy, irradiation did not cause direct cellular apoptosis or necrosis, but it induced mitochondrial damage in DCs independent of dose. In addition, upregulation of CD40, CD80, CD86, CXCR4, and CCR7 were detected on irradiated DCs. Secretion of IL-1β and IL-12p70 remained unchanged, whereas decreased secretion of IL-6 and promotion of tumor necrosis factor α secretion were observed. In particular, the homing ability of both the local residual and blood circulating DCs to lymphoid tissues was significantly higher in groups that received ≥5 Gy radiation than in the group that received 2 Gy. Furthermore, improved homing ability was associated with rearrangement of the cytoskeleton, which was regulated by reactive oxygen species accumulation through the RhoA/ROCK1 signaling pathway. Finally, more robust T cell activation was observed in mice inoculated with 20 Gy-treated DCs than in those inoculated with 2 Gy-irradiated DCs, and T cell activation also correlated with reactive oxygen species production.

CONCLUSIONS

An RT dose ≥5 Gy has distinct advantages over 2 Gy in facilitating DC homing to lymph nodes and cross-priming T cells.

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.

Low concentrations of FA exhibits the Hormesis effect by affecting cell division and the Warburg effect

Formaldehyde (FA), a ubiquitous indoor environmental pollutant, has been classified as a carcinogen. There are many studies showed that low levels of FA could promote cell proliferation, however, little is known about the signal pathways. To determine the potential molecular mechanisms, human chronic myeloid leukemia cells (K562 cells) and human bronchial epithelial cells (16HBE cells) were exposed to different concentrations of FA. The data showed that FA at 0-125 μM or 0-60 μM promoted the proliferation of K562 cells or 16HBE cells respectively, indicating that FA did have the Hormesis effect. FA at 75 μM (K562 cells) and 40 μM (16HBE cells) significantly promoted cell proliferation, increased intracellular reactive oxygen species (ROS) levels, and decreased glutathione (GSH) content. At the same time, FA treatment induced a marked increase in the key molecules of cell division like CyclinD-cdk4 and E2F1. In addition, pyruvate kinase isozyme M2 (PKM2), glucose, glucose transporter 1 (GLUT1), lactic acid and lactate dehydrogenase A (LDHA) content in the Warburg effect were increased. Administering Vitamin E (VE), significantly disrupted cell division and disturbed the Warburg effect, effectively indicating the decrease of cell activity. Conclusively, these findings suggested that low concentrations of FA could promote cell proliferation by accelerating cell division process or enhancing the Warburg effect to embody the Hormesis effect.

In Vivo Irradiation of Mice Induces Activation of Dendritic Cells

It is becoming clear that ionizing radiation positively influences certain immune parameters, which opens the possibility for combining radio- and immunotherapies in cancer treatment. The presence of functionally competent dendritic cells (DCs) is crucial in mounting a successful antitumor immune response. While it has been shown that DCs are relatively radioresistant, few and contradictory data are available on how ionizing radiation alters the functional integrity of these cells. Therefore, our objective was to investigate the effect of whole-body irradiation on the function of splenic DCs. C57Bl/6 mice were irradiated with 0.1, 0.25, and 2 Gy X-rays and changes in the phenotype of splenic DCs were compared to unirradiated controls. An increase was seen in DC surface markers influencing DC-T cell interactions. In vivo cytokine production was determined by direct intracellular cytokine staining. Irradiation with 2 Gy induced a 1.6-fold increase in IL-1α production, while the combination of irradiation and lipopolysaccharide (LPS) treatment induced a 3.9-fold increase, indicating a strong synergism between irradiation and LPS stimulation. Interaction of DCs with effector and regulatory T cells was investigated in a mixed lymphocyte reaction. While DCs from control animals induced stronger proliferation of regulatory T cells, DCs from animals irradiated with 2 Gy induced stronger proliferation of effector T cells. Antigen uptake and presentation was investigated by measuring the capacity of DCs to internalize and present ovalbumine (OVA)-derived peptides on their major histocompatibility complex (MHCI) molecules. Irradiation with 2 Gy did not influence antigen uptake or presentation, while low doses stimulated antigen uptake and reduced the level of antigen presentation. In conclusion, high-dose in vivo irradiation induced increased expression of T cell costimulatory markers, enhanced production of proinflammatory cytokines and a stronger stimulation of effector T cell proliferation than that of regulatory T cells. However, it did not influence DC antigen uptake or presentation. On the other hand, low-dose irradiation increased antigen uptake and lowered antigen presentation of DCs, indicating that low- and high-dose irradiation act on different pathways in DCs.

Radiation-Induced Transformation of Immunoregulatory Networks in the Tumor Stroma

The implementation of novel cancer immunotherapies in the form of immune checkpoint blockers represents a major advancement in the treatment of cancer, and has renewed enthusiasm for identifying new ways to induce antitumor immune responses in patients. Despite the proven efficacy of neutralizing antibodies that target immune checkpoints in some refractory cancers, many patients do not experience therapeutic benefit, possibly owing to a lack of antitumor immune recognition, or to the presence of dominant immunosuppressive mechanisms in the tumor microenvironment (TME). Recent developments in this field have revealed that local radiotherapy (RT) can transform tumors into in situ vaccines, and may help to overcome some of the barriers to tumor-specific immune rejection. RT has the potential to ignite tumor immune recognition by generating immunogenic signals and releasing neoantigens, but the multiple immunosuppressive forces in the TME continue to represent important barriers to successful tumor rejection. In this article, we review the radiation-induced changes in the stromal compartments of tumors that could have an impact on tumor immune attack. Since different RT regimens are known to mediate strikingly different effects on the multifarious elements of the tumor stroma, special emphasis is given to different RT schedules, and the time after treatment at which the effects are measured. A better understanding of TME remodeling following specific RT regimens and the window of opportunity offered by RT will enable optimization of the design of novel treatment combinations.

Low-Dose Radiation Promotes Dendritic Cell Migration and IL-12 Production via the ATM/NF-KappaB Pathway

For dendritic cells (DCs) to initiate an immune response, their ability to migrate and to produce interleukin-12 (IL-12) is crucial. It has been previously shown that low-dose radiation (LDR) promoted IL-12 production by DCs, resulting in increased DC activity that contributed to LDR hormesis in the immune system. However, the molecular mechanism of LDR-induced IL-12 production, as well as the effect of LDR on DC migration capacity require further elucidation. Using the JAWSII immortalized mouse dendritic cell line, we showed that in vitro X-ray irradiation (0.2 Gy) of DCs significantly increased DC migration and IL-12 production, and upregulated CCR7. The neutralizing antibody against CCR7 has been shown to abolish LDR-enhanced DC migration, demonstrating that CCR7 mediates LDR-promoting DC migration. We identified nuclear factor kappaB (NF-κB) as the central signaling pathway that mediated LDR-enhanced expression of IL-12 and CCR7 based on findings that 0.2 Gy X-ray irradiation activated NF-κB, showing increased nuclear p65 translocation and NF-κB DNA-binding activity, while an NF-κB inhibitor blocked LDR-enhanced expression of IL-12 and CCR7, as well as DC migration. Finally, we demonstrated that 0.2 Gy X-ray irradiation promoted ATM phosphorylation and reactive oxygen species generation; however, only the ATM inhibitor abolished the LDR-induced NF-κB-mediated expression of IL-12 and CCR7. Altogether, our data show that exposure to LDR resulted in a hormetic effect on DCs regarding CCR7-mediated migration and IL-12 production by activating the ATM/NF-κB pathway.

Low-frequency ultrasound-induced VEGF suppression and synergy with dendritic cell-mediated anti-tumor immunity in murine prostate cancer cells in vitro

High tumor vascular endothelial growth factor (VEGF) levels are associated with poor treatment outcomes in prostate cancer (PCa), and immune deficiency in the PCa microenvironment, especially suppression of dendritic cell (DC) proliferation, has been confirmed. In this study, we (1) investigated whether VEGF participates in DC suppression in murine PCa cells (RM-1), (2) down-regulated VEGF expression using low-frequency ultrasound and microbubbles (UM), and (3) further explored any synergistic effect on immunological activation. DCs from the bone marrow of BALB/c mice were stimulated by the addition of cytokines (granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4)), and we analyzed their proliferation status via flow cytometric recognition of the surface antigen markers CD11c and CD83. The results demonstrated that co-culture with RM-1 cells markedly inhibited expression of the general marker CD11c and the mature marker CD83; UM weakened this inhibition by down-regulating VEGF expression. T lymphocytes were extracted from murine spleens, and CD4 and CD8a were identified as the biomarkers of activated cells participating in the anti-tumor immune response. When DCs, T lymphocytes and RM-1 cells were co-cultured, cell migration and invasion assays and cytoactive detection showed that UM could not only directly suppress PCa cell evolution but also promote activation of anti-tumor immunocytes in the VEGF-inhibited microenvironment.

Modulating Both Tumor Cell Death and Innate Immunity Is Essential for Improving Radiation Therapy Effectiveness

Radiation therapy is one of the cornerstones of cancer treatment. In tumor cells, exposure to ionizing radiation (IR) provokes DNA damages that trigger various forms of cell death such as apoptosis, necrosis, autophagic cell death, and mitotic catastrophe. IR can also induce cellular senescence that could serve as an additional antitumor barrier in a context-dependent manner. Moreover, accumulating evidence has demonstrated that IR interacts profoundly with tumor-infiltrating immune cells, which cooperatively drive treatment outcomes. Recent preclinical and clinical successes due to the combination of radiation therapy and immune checkpoint blockade have underscored the need for a better understanding of the interplay between radiation therapy and the immune system. In this review, we will present an overview of cell death modalities induced by IR, summarize the immunogenic properties of irradiated cancer cells, and discuss the biological consequences of IR on innate immune cell functions, with a particular attention on dendritic cells, macrophages, and NK cells. Finally, we will discuss their potential applications in cancer treatment.

Influence of the first radioactive iodine ablation on peripheral complete blood count in patients with differentiated thyroid cancer

Radioactive iodine (RAI) is considered to be related with hematologic changes. This study aimed to evaluate influence of the first RAI ablation on peripheral complete blood count (CBC) in patients with differentiated thyroid cancer (DTC).Data of CBC at baseline and 6 months after RAI were obtained in 385 patients with DTC with approximately 3700 MBq I (ranging 2220-7585 MBq). Further comparison was done in 196 patients with 1-month postablation data available. Routine blood examinations were performed to determine impact of RAI on white blood cell (WBC), red blood cell (RBC), hemoglobin, platelet, neutrophil, lymphocyte, and monocyte in both sexes. Continuous variables were compared by paired t tests and independent samples t test, and categorical variables were compared by chi-square analysis. Data with repeated measurements were analyzed by analysis of variance.The first RAI after thyroidectomy was associated with mild, yet significant declines in WBC, platelet, and lymphocyte, which persisted for 6 months. One month after RAI, significant declines were found in all CBC, including RBC and hemoglobin (all P < 0.05). While CBC partly recovered 6 months after RAI, this follow-up CBC still demonstrated significant declines in WBC, platelet, and lymphocyte (all P < 0.05) without gender differences. Significant rises in RBC and hemoglobin in males and females were found. The decline of platelet in females was more obvious than in males at 3700 to 4440 MBq of RAI. On the contrary, the rises of RBC and hemoglobin in males were higher than in females. There were no significant complications during the follow-up.WBC and platelet decreased obviously 1 month after RAI. While they partly recovered 6 months after RAI, they were still lower than the baseline. However, RBC and hemoglobin transiently decreased at 1 month and then increased to levels even higher than baseline 6 months later. At 3700 to 4440 MBq of RAI, the decline of platelet in females was more obvious than in males. Yet, rises of RBC and hemoglobin in males were higher than in females. The risks associated with these changes are unlikely to outweigh the potential benefits of RAI in patients with DTC.

Evaluating biomarkers to model cancer risk post cosmic ray exposure

Robust predictive models are essential to manage the risk of radiation-induced carcinogenesis. Chronic exposure to cosmic rays in the context of the complex deep space environment may place astronauts at high cancer risk. To estimate this risk, it is critical to understand how radiation-induced cellular stress impacts cell fate decisions and how this in turn alters the risk of carcinogenesis. Exposure to the heavy ion component of cosmic rays triggers a multitude of cellular changes, depending on the rate of exposure, the type of damage incurred and individual susceptibility. Heterogeneity in dose, dose rate, radiation quality, energy and particle flux contribute to the complexity of risk assessment. To unravel the impact of each of these factors, it is critical to identify sensitive biomarkers that can serve as inputs for robust modeling of individual risk of cancer or other long-term health consequences of exposure. Limitations in sensitivity of biomarkers to dose and dose rate, and the complexity of longitudinal monitoring, are some of the factors that increase uncertainties in the output from risk prediction models. Here, we critically evaluate candidate early and late biomarkers of radiation exposure and discuss their usefulness in predicting cell fate decisions. Some of the biomarkers we have reviewed include complex clustered DNA damage, persistent DNA repair foci, reactive oxygen species, chromosome aberrations and inflammation. Other biomarkers discussed, often assayed for at longer points post exposure, include mutations, chromosome aberrations, reactive oxygen species and telomere length changes. We discuss the relationship of biomarkers to different potential cell fates, including proliferation, apoptosis, senescence, and loss of stemness, which can propagate genomic instability and alter tissue composition and the underlying mRNA signatures that contribute to cell fate decisions. Our goal is to highlight factors that are important in choosing biomarkers and to evaluate the potential for biomarkers to inform models of post exposure cancer risk. Because cellular stress response pathways to space radiation and environmental carcinogens share common nodes, biomarker-driven risk models may be broadly applicable for estimating risks for other carcinogens.

Radiation triggering immune response and inflammation

Radiation therapy (RT) is a well-established but still under optimization branch of Cancer Therapy (CT). RT uses electromagnetic waves or charged particles in order to kill malignant cells, by accumulating the energy onto these cells. The issue at stake for RT, as well as for any other Cancer Therapy technique, is always to kill only cancer cells, without affecting the surrounding healthy ones. This perspective of CT is usually described under the terms "specificity" and "selectivity". Specificity and selectivity are the ideal goal, but the ideal is never entirely achieved. Thus, in addition to killing healthy cells, changes and effects are observed in the immune system after irradiation. In this review, we mainly focus on the effects of ionizing radiation on the immune system and its components like bone marrow. Additionally, we are interested in the effects and benefits of low-dose ionizing radiation on the hematopoiesis and immune response. Low dose radiation has been shown to induce biological responses like inflammatory responses, innate immune system activation and DNA repair (adaptive response). This review reveals the fact that there are many unanswered questions regarding the role of radiation as either an immune-activating (low dose) or immunosuppressive (high dose) agent.

Sam68 is cleaved by caspases under apoptotic cell death induced by ionizing radiation

The RNA-binding protein Sam68, a mitotic substrate of tyrosine kinases, has been reported to participate in the cell cycle, apoptosis, and signaling. In particular, overexpression of Sam68 protein is known to suppress cell growth and cell cycle progression in NIH3T3 cells. Although Sam68 is involved in many cellular activities, the function of Sam68, especially in response to apoptotic stimulation, is not well understood. In this study, we found that Sam68 protein is cleaved in immune cells undergoing apoptosis induced by γ-radiation. Moreover, we found that Sam68 cleavage was induced by apoptotic stimuli containing γ-radiation in a caspase-dependent manner. In particular, we showed that activated casepase-3, 7, 8 and 9 can directly cleave Sam68 protein through in vitro protease cleavage assay. Finally, we found that the knockdown of Sam68 attenuated γ-radiation-induced cell death and growth suppression. Conclusively, the cleavage of Sam68 is a new indicator for the cell damaging effects of ionizing radiation.