Radiation-induced Abscopal Effect Research Articles

Combined Radiotherapy and Hyperthermia: A Systematic Review of Immunological Synergies for Amplifying Radiation-Induced Abscopal Effects.

The abscopal effect is a systemic immune response characterized by metastases regression at sites distant from the irradiated lesion. This systematic review aims to explore the immunological mechanisms of action underlying the abscopal effect and to investigate how hyperthermia (HT) can increase the chances of radiotherapy (RT) triggering systemic anti-tumor immune responses. This review is created in accordance with the PRISMA guidelines. HT and RT have both complementary and synergistic immunological effects. Both methods trigger danger signal release, promoting cytokine and chemokine secretion, which increases T-cell infiltration and facilitates cell death. Both treatments upregulate extracellular tumor HSP70, which could amplify DAMP recognition by macrophages and DCs, leading to stronger tumor antigen presentation and CTL-mediated immune responses. Additionally, the combined increase in cell adhesion molecules (VCAM-1, ICAM-1, E-selectin, L-selectin) could enhance leukocyte adhesion to tumors, improving lymphocyte trafficking and boosting systemic anti-tumor effects. Lastly, HT causes vasodilation and improves blood flow, which might exacerbate those distant effects. We suggest the combination of local radiotherapy with fever-range whole-body hyperthermia to optimally enhance the chances of triggering the abscopal effect mediated by the immune system.

Imaging-guided companion diagnostics in radiotherapy by monitoring APE1 activity with afterglow and MRI imaging

Companion diagnostics using biomarkers have gained prominence in guiding radiotherapy. However, biopsy-based techniques fail to account for real-time variations in target response and tumor heterogeneity. Herein, we design an activated afterglow/MRI probe as a companion diagnostics tool for dynamically assessing biomarker apurinic/apyrimidinic endonuclease 1(APE1) during radiotherapy in vivo. We employ ultrabright afterglow nanoparticles and ultrasmall FeMnOx nanoparticles as dual contrast agents, significantly broadening signal change range and enhancing the sensitivity of APE1 imaging (limit of detection: 0.0092 U/mL in afterglow imaging and 0.16 U/mL in MRI). We devise longitudinally and transversely subtraction-enhanced imaging (L&T-SEI) strategy to markedly enhance MRI contrast and signal-to-noise ratio between tumor and normal tissue of living female mice. The combined afterglow and MRI facilitate both anatomical and functional imaging of APE1 activity. This probe enables correlation of afterglow and MRI signals with APE1 expression, radiation dosage, intratumor ROS, and DNA damage, enabling early prediction of radiotherapy outcomes (as early as 3 h), significantly preceding tumor size reduction (6 days). By monitoring APE1 levels, this probe allows for early and sensitive detection of liver organ injury, outperforming histopathological analysis. Furthermore, MRI evaluates APE1 expression in radiation-induced abscopal effects provides insights into underlying mechanisms, and supports the development of treatment protocols.

P-408 The ovarian tissues outside of the radiation field could be damaged by radiation-induced abscopal effects in mice: an experimental study.

Abstract Study question Could irradiation-induced abscopal effects (RIAEs) induce structural and functional damage in the distal ovary in female mice, and what is its mechanism? Summary answer The RIAEs can induce an inflammatory reaction and inhibit the growth and development of ovarian follicles in mice leading to a decrease in ovarian reserve. What is known already The irradiated tumor could induce cell and tissue injury in the organs distant from the radiation site, referred to as the radiation-induced abscopal effects (RIAEs). Many pieces of research have shown out-of-field tumor regression effects of radiation therapy. However, RIAEs is a double-edged sword and may cause serious side effects on normal tissues. Premature ovarian insufficiency (POI) is one of the main side effects of radiotherapy, but the relationship between RIAE and POI has not been clarified. Study design, size, duration C57BL/6J mice were used to establish a RIAEs model by irradiating the thorax and the abdomens were shielded. Sixteen C57BL/6J female mice were randomly allocated to sham and experimental groups (n = 8/group) according to the presence or absence of irradiation with an 8 Gy X-ray on the local area of the chest every day for three days. After irradiation for twenty-one days, The effect and possible mechanism of RIAEs on non-irradiated ovarian were discussed. Participants/materials, setting, methods After irradiation, the estrous cyclicity, serum steroid hormones, and pro-inflammatory factors were compared between groups. Furthermore, RNA-seq was used to detect the expression of transcriptional levels in ovarian tissues in both groups. The differentially expressed genes (DEGs) were screened and analyzed by gene ontology-biological process (GO_BP) between irradiated and sham groups. The expression and localization of spermatogenesis-and oogenesis-specific basic helix-loop-helix-containing protein 1(SOHLH1) and neutrophil elastase (NE) in ovarian tissues were detected by immunohistochemistry(IHC). Main results and the role of chance Compared with mice in the sham group, the irradiation group had disordered estrous cycles, reduced primordial follicles (P<0.001)] and growing follicles (P<0.001), significantly increased atretic follicles (P<0.001). Levels of serum estradiol [(70.28 ± 5.27) pmol/L] and AMH [(104.00±6.98) ng/L] in the irradiation group were significantly lower than those in the sham group [estradiol (97.58±7.25) pmol/L, P=0.016; AMH [(129.70±8.39) ng/mL, P=0.046], but FSH levels in the irradiation group were not significantly different from those in the sham group (P=0.996). Compared with the sham group, Serum levels of TNF-α [(488.30±36.20) ng/L vs. (31.61±12.89) ng/L, P<0.001] and IL-1β [(62.37±2.50) ng/L vs. (52.75±2.06) ng/L, P=0.018)] in the irradiation group were significantly increased. Serum levels of IL-6 in the irradiation group were also increased compared with the sham group, but the difference was not statistically significant (P=0.301). The results of GO_BP analysis showed that down-regulated DGEs were mainly involved in the process of follicular development, and up-regulated DGEs were involved in the inflammation process. The IHC results showed that the positive expression area of SOHLH1 in the irradiation group was significantly lower than in the sham group (P=0.005). In comparison, the positive expression area of NE was significantly higher than that of the Sham group(P=0.024). Limitations, reasons for caution This study was performed using a short, 3-day irradiation treatment condition. Therefore, the results need to be cautiously interpreted concerning radiation-associated chronic toxicity. Moreover, further studies in mouse tumor models are required to determine the clinical relevance of the role of RIAE. Wider implications of the findings Although the precise molecular mechanisms of these distal effects on the genital system are still unclear, the current discovery might pave the way for establishing novel fertility preservation protocols. The research offers hope to women with POI related to cancer therapy through the modulation of abscopal effects associated with radiotherapy. Trial registration number not applicable

Injectable Oxygen Microparticles Boost Radiation–Mediated In Situ Vaccination and Systemic Antitumor Immune Responses

To determine if intratumoral injections of a liquid oxygen solution is effective at boosting radiation-induced abscopal effects. In this study, a liquid oxygen solution, comprising slow-release polymer-shelled oxygen microparticles, was fabricated and injected intratumorally to locally elevate tumor oxygen levels prior to and after treatment with radiation therapy. Changes in tumor volume were monitored. In a subset of studies, CD8 positive cells were depleted, and the experiments repeated. Histological analyses of the tumor tissues were performed to quantify the concentration of infiltrating immune cells. Here, we found that daily intratumoral injections of oxygen-filled microparticles significantly retards primary and secondary tumor growth, boosts infiltration of cytotoxic T-cells and improves overall survival when used as an adjuvant to radiotherapy. We also demonstrate that efficacy requires both radiation and oxygen, suggesting that they act synergistically to enhance in situ vaccination and systemic anti-tumor immune responses. Our findings demonstrate the potential advantages of intratumoral injections of a liquid oxygen solution as a strategy to boost radiation-induced abscopal effects and warrant future efforts into clinical translation of the injectable liquid oxygen solution.

Bioinspired immuno-radio-enhancers toward synergistic nanomedicine through radiation-induced abscopal effects and immunocheckpoint blockade therapies.

Local radio-therapy combined with immunotherapy has attracted great interest in controlling local tumors. In this study, we have developed membrane-cloaked manganese dioxide nanoparticles displaying anti-PD-L1 antibodies as targeted immuno-radio-enhancers. Mediated by anti-PD-L1 antibodies (aPD-L1) expressed on cell membranes, this kind of membrane-coated nanosystem can selectively deliver cytosine-phosphate-guanine (CpG)-loaded MnO2 nanoparticles (NPs) and induce systemic anti-tumor immunities, thereby achieving favorable immuno/radio-therapeutic outcomes. Through expressing various functional proteins onto cellular membranes, the new class of membrane-camouflaged nanovehicles can be endowed with a wide variety of artificial functionalities such as enzymatic catalytic capabilities and specific targeting. This versatile nanoplatform, in general, enables the targeted delivery of theranostics, opening a new avenue for personalized nanomedicine.

Necroptosis-dependent Immunogenicity of Cisplatin: Implications for Enhancing the Radiation-induced Abscopal Effect.

Cisplatin is increasingly used in chemoimmunotherapy and may enhance the T cell-dependent radiation-induced abscopal effect, but how it promotes antitumor immunity is poorly understood. We investigated whether and why cisplatin is immunogenic, and the implications for the cisplatin-enhanced abscopal effect. Cisplatin, carboplatin, and the well-known immunogenic cell death (ICD) inducer oxaliplatin were compared for their potency to enhance the abscopal effect and induce type I IFN (IFN-I) and extracellular ATP, danger signals of ICD. The hypothetical role of necroptosis and associated damage-associated molecular patterns for cisplatin-induced ICD was investigated by inhibitors and knockout cells in vitro and in two tumor models in mice. A novel necroptosis signature for tumor immune cell infiltration and therapy response was developed. Cisplatin enhanced the abscopal effect more strongly than oxaliplatin or carboplatin. This correlated with higher induction of IFN-I and extracellular ATP by cisplatin, in a necroptosis-dependent manner. Cisplatin triggered receptor-interacting protein kinase 3 (RIPK3)-dependent tumor cell necroptosis causing cytosolic mitochondrial DNA (mtDNA) release, initiating the cyclic GMP-AMP synthase-stimulator of interferon genes pathway and IFN-I secretion promoting T-cell cross-priming by dendritic cells (DC). Accordingly, tumor cell RIPK3 or mtDNA deficiency and loss of IFN-I or ATP signaling diminished the cisplatin-enhanced abscopal effect. Cisplatin-treated tumor cells were immunogenic in vaccination experiments, depending on RIPK3 and mtDNA. In human tumor transcriptome analysis, necroptotic features correlated with abundant CD8+ T cells/DCs, sparse immunosuppressive cells, and immunotherapy response. Cisplatin induces antitumor immunity through necroptosis-mediated ICD. Our findings may help explain the benefits of cisplatin in chemo(radio)immunotherapies and develop clinical trials to investigate whether cisplatin enhances the abscopal effect in patients.

Modification of protein secondary structure as an indicator of radiation-induced abscopal effect: A spectroscopic investigation

In this study, we investigate the abscopal effect induced in the brain, lung and kidney as a result of partial irradiation of experimental animals with 2 Gy γ-rays. Modifications in the protein secondary structure were used as indicator for the abscopal effect. FTIR spectroscopy and analysis of the amide I and amide II absorption bands suggested possible modifications in the protein secondary structure in the brain and kidney following irradiation. Significant shift in the amide I band was recorded only in the brain. However, the amide I/amide II band area ratio for the three organs examined varied differentially in the irradiated groups as compared with the sham-irradiated group.Employing the lorentzian model to analyze the amide I band of the FTIR spectra, we dissected the amide I band into its components, each component represents one form of the protein secondary structure. Calculation of the weight percentage contribution of each of the protein secondary structure revealed decrease in the α-helix contribution associated with equivalent increase in β-sheets and turns/random coils contributions in the brain and kidney, however the response was more evident in the brain. No change in the α-helix or β-sheets contributions was reported in the lung following irradiation. The data suggest the induction of abscopal effect in the brain and kidney rather than the lung in the form of protein conformation modification. The data also indicate that the abscopal effect is comparable to the effect of direct irradiation in both of the brain and kidney.

Non-Targeted Effects of Synchrotron Radiation: Lessons from Experiments at the Australian and European Synchrotrons

Studies have been conducted at synchrotron facilities in Europe and Australia to explore a variety of applications of synchrotron X-rays in medicine and biology. We discuss the major technical aspects of the synchrotron irradiation setups, paying specific attention to the Australian Synchrotron (AS) and the European Synchrotron Radiation Facility (ESRF) as those best configured for a wide range of biomedical research involving animals and future cancer patients. Due to ultra-high dose rates, treatment doses can be delivered within milliseconds, abiding by FLASH radiotherapy principles. In addition, a homogeneous radiation field can be spatially fractionated into a geometric pattern called microbeam radiotherapy (MRT); a coplanar array of thin beams of microscopic dimensions. Both are clinically promising radiotherapy modalities because they trigger a cascade of biological effects that improve tumor control, while increasing normal tissue tolerance compared to conventional radiation. Synchrotrons can deliver high doses to a very small volume with low beam divergence, thus facilitating the study of non-targeted effects of these novel radiation modalities in both in-vitro and in-vivo models. Non-targeted radiation effects studied at the AS and ESRF include monitoring cell–cell communication after partial irradiation of a cell population (radiation-induced bystander effect, RIBE), the response of tissues outside the irradiated field (radiation-induced abscopal effect, RIAE), and the influence of irradiated animals on non-irradiated ones in close proximity (inter-animal RIBE). Here we provide a summary of these experiments and perspectives on their implications for non-targeted effects in biomedical fields.

Theoretical Bases of the Influence of Radiation-induced Abscopal Effects on the Cardiovascular System

Theoretical Bases of the Influence of Radiation-induced Abscopal Effects on the Cardiovascular System

Fractionated Irradiation of Right Thorax Induces Abscopal Damage on Bone Marrow Cells via TNF-α and SAA.

Radiation-induced abscopal effect (RIAE) outside of radiation field is becoming more attractive. However, the underlying mechanisms are still obscure. This work investigated the deleterious effect of thoracic irradiation (Th-IR) on distant bone marrow and associated signaling factors by irradiating the right thorax of mice with fractionated doses (8 Gy × 3). It was found that this localized Th-IR increased apoptosis of bone marrow cells and micronucleus formation of bone marrow polychromatic erythrocytes after irradiation. Tandem mass tagging (TMT) analysis and ELISA assay showed that the concentrations of TNF-α and serum amyloid A (SAA) in the mice were significantly increased after Th-IR. An immunohistochemistry assay revealed a robust increase in SAA expression in the liver rather than in the lungs after Th-IR. In vitro experiments demonstrated that TNF-α induced SAA expression in mouse hepatoma Hepa1–6 cells, and these two signaling factors induced DNA damage in bone marrow mesenchymal stem cells (BMSCs) by increasing reactive oxygen species (ROS). On the other hand, injection with TNF-α inhibitor before Th-IR reduced the secretion of SAA and attenuated the abscopal damage in bone marrow. ROS scavenger NAC could also mitigated Th-IR/SAA-induced bone marrow damage in mice. Our findings indicated that Th-IR triggered TNF-α release from lung, which further promoted SAA secretion from liver in a manner of cascade reaction. Consequently, these signaling factors resulted in induction of abscopal damage on bone marrow of mice.

Valproic acid triggers radiation-induced abscopal effect by modulating the unirradiated tumor immune microenvironment in a rat model of breast cancer.

An abscopal effect occurs when localized radiotherapy causes the regression of tumors distant from the irradiated site. However, such a clinically detectable abscopal effect from radiotherapy alone is rare. This study investigated whether valproic acid ([VPA], a histone deacetylase inhibitor [HDACi]) treatment can stimulate radiation-induced abscopal effect. We used 7,12-dimethylbenz[a]anthracene, a typical environmental carcinogen, to establish a rat model with multiple breast tumors. Only one tumor received 8 Gy fractionated doses of X-rays (2 Gy daily fractions over four days) and 200mg/kg VPA was administered intraperitoneally. We monitored the growth of both irradiated and unirradiated tumors after treatments. The unirradiated tumor was collected for hematoxylin and eosin (HE) staining, immunohistochemistry (IHC) (CD8, Granzyme B, Cleaved Caspase-3, BrdU, Ki67, F4/80 and CD68), double immunofluorescence (F4/80 and CD86), Western blot (Cleaved Caspase-3) and qRT-PCR (CD86, CD163, IL-1β, IL-6, IL-12, IL-23, IL-10, TGF-β) analysis. We found ionizing radiation (IR) + VPA treatment inhibited both irradiated and unirradiated tumor growth as compared to IR alone. Such observe abscopal effect was mediated by the recruitment of activated CD8+ T cells into the unirradiated tumor sites, which released Granzyme B to cause tumor cell apoptosis. Furthermore, IR + VPA treatment led to macrophages infiltration into the unirradiated tumor sites and polarization to M1 phenotype, resulted in increased levels of pro-inflammatory cytokines such as IL-1β and IL-12, and decreased levels of anti-inflammatory cytokines such as IL-10 and TGF-β. Our data supports the proposition that VPA may be a potential therapeutic candidate to trigger radiation-induced abscopal effect by modulating the unirradiated tumor immune microenvironment.

TP53 drives abscopal effect by secretion of senescence-associated molecular signals in non-small cell lung cancer

BackgroundRecent developments in abscopal effect strongly support the use of radiotherapy for the treatment of metastatic disease. However, deeper understanding of the molecular mechanisms underlying the abscopal effect are required to best benefit a larger proportion of patients with metastasis. Several groups including ours, reported the involvement of wild-type (wt) p53 in radiation-induced abscopal effects, however very little is known on the role of wtp53 dependent molecular mechanisms.MethodsWe investigated through in vivo and in vitro approaches how wtp53 orchestrates radiation-induced abscopal effects. Wtp53 bearing (A549) and p53-null (H1299) NSCLC lines were xenotransplanted in nude mice, and cultured in 2D monolayers and 3D tumor spheroids. Extracellular vesicles (EVs) were isolated from medium cell culture by ultracentrifugation protocol followed by Nanoparticle Tracking Analysis. Gene expression was evaluated by RT-Real Time, digital qRT-PCR, and dot blot technique. Protein levels were determined by immunohistochemistry, confocal anlysis, western blot techniques, and immunoassay.ResultsWe demonstrated that single high-dose irradiation (20 Gy) induces significant tumor growth inhibition in contralateral non-irradiated (NIR) A549 xenograft tumors but not in NIR p53-null H1299 or p53-silenced A549 (A549sh/p53) xenografts. We further demonstrates that irradiation of A549 cells in vitro induces a senescence-associated secretory phenotype (SASP) producing extracellular vesicles (EVs) expressing CD63 and carrying DNA:RNA hybrids and LINE-1 retrotransposon. IR-A549 EVs also hamper the colony-forming capability of recipient NIR A549 cells, induce senescent phenotype, nuclear expression of DNA:RNA hybrids, and M1 macrophage polarization.ConclusionsIn our models, we demonstrate that high radiation dose in wtp53 tumors induce the onset of SASP and secretion of CD63+ EVs loaded with DNA:RNA hybrids and LINE-1 retrotransposons that convey senescence messages out of the irradiation field triggering abscopal effect in NIR tumors.

Radiation-induced abscopal reproductive effect is driven by TNF-α/p38 MAPK/Rac1 axis in Sertoli cells.

Rationale: Radiotherapy has become a mainstay for tumor management, and more than 50% of patients with thoracic tumor need to be treated with radiotherapy. However, the potential adverse effects of thoracic radiotherapy on the reproductive system remain elusive.Methods: Western blot analysis, immunofluorescence assay and transmission electron microscopy (TEM) analysis were performed to investigate the integrity of blood-testis barrier (BTB) in male mice after hypofractionated irradiation (IR) on the right thorax. RNA sequencing, co-immunoprecipitation (IP), Duolink PLA and inhibitor experiments were carried out to demonstrate the molecular mechanisms of the BTB dynamics changes and the subsequent reproductive effect.Results: It was found that the hypofractionated IR on right thorax evoked ultrastructural destruction in distant testes, and thus caused radiation-induced abscopal reproductive effect (RIARE) in male mice. Mechanistically, thoracic IR induced significant nuclear translocation of Rac Family Small GTPase 1 (Rac1) in abscopal Sertoli cells, which closely correlated with the activation of TNF-α/p38 mitogen activated protein kinase (MAPK) pathway. Of note, YWHAZ, a critical polarity protein, was found to be co-localized with Rac1 in Sertoli cells, and this interaction was indispensable for thoracic IR-induced Rac1 nuclear translocation and subsequent degradation of BTB-associated proteins.Conclusions: Our findings imply for the first time that YWHAZ-mediated Rac1 nuclear translocation plays central roles in RIARE, and TNF-α/p38 MAPK/Rac1 axis can be employed as a therapeutic target against RIARE for young male patients receiving hypofractionated radiotherapy.

Radiation-induced abscopal effect and its enhancement by programmed cell death 1 blockade in the hepatocellular carcinoma: A murine model study.

Background/AimsThe abscopal effect, a rare phenomenon induced by radiation, can be reinforced by immunotherapy. Although radiation therapy and immunotherapy are increasingly being utilized for the treatment of hepatocellular carcinoma (HCC), whether immunotherapy could boost the abscopal effect remains unclear. In this study, we aimed to elucidate the immunological mechanisms underlying the abscopal effect induced by the combination of irradiation and immunotherapy in a murine HCC model.MethodsA syngeneic HCC mouse model was established by transplanting murine Hepa 1–6 HCC cells into both hind legs of immunocompetent C57BL/6 mice. The tumors on the right hind legs were irradiated, and abscopal effects were observed in the non-irradiated tumors on the left hind leg with or without the coadministration of anti-programmed cell death 1 (PD-1) antibodies. Flow cytometric analyses were performed to analyze the distributions of immune cells infiltrating both irradiated and non-irradiated tumors and the tumor-draining lymph nodes (TDLNs).ResultsAdministration of 16 Gy in two fractions more effectively inhibited the growth of both irradiated and non-irradiated tumors with higher tumor infiltration of cytotoxic T cells than 8 Gy did in a single fraction. The higher dose also increased activated dendritic cells in TDLNs, which had higher expression of the programmed cell death ligand 1. Coadministration of anti-PD-1 antibodies significantly enhanced the abscopal effect and increased infiltration of activated cytotoxic T cells in both irradiated and non-irradiated tumors.ConclusionsOur findings show that adding anti-PD-1 therapy to radiation enhanced the abscopal effect in a syngeneic murine model of HCC.

Biological Guided Carbon-Ion Microporous Radiation to Tumor Hypoxia Area Triggers Robust Abscopal Effects as Open Field Radiation.

Recently, a growing number of studies focus on partial tumor irradiation to induce the stronger non-target effects. However, the value of partial volume carbon ion radiotherapy (CIRT) targeting hypoxic region of a tumor under imaging guidance as well as its effect of inducing radiation induced abscopal effects (RIAEs) have not been well investigated. Herein, we developed a technique of carbon ion microporous radiation (CI-MPR), guided by 18F-FMISO PET/computerized tomography (CT), for partial volume radiation targeting the hypoxia area of a tumor and investigated its capability of inducing abscopal effects. Tumor-bearing mice were inoculated subcutaneously with breast cancer 4T1 cells into the flanks of both hind legs of mouse. Mice were assigned to three groups: group I: control group with no treatment; group II: carbon ion open field radiation (CI-OFR group) targeting the entire tumor; group III: partial volume carbon ion microporous radiation (CI-MPR group) targeting the hypoxia region. The tumors on the left hind legs of mice were irradiated with single fraction of 20 Gy of CIRT. Mice treated with CI-MPR or CI-OFR showed that significant growth delay on both the irradiated and unirradiated of tumor as compared to the control groups. Tumor regression of left tumor irradiated with CI-OFR was more prominent as compared to the tumor treated with CI-MPR, while the regression of the unirradiated tumor in both CI-MPR and CI-OFR group was similar. Biological-guided CIRT using the newly developed microporous technique targeting tumor hypoxia region could induce robust abscopal effects similar to CIRT covering the entire tumor.

Cisplatin Facilitates Radiation-Induced Abscopal Effects in Conjunction with PD-1 Checkpoint Blockade Through CXCR3/CXCL10-Mediated T-cell Recruitment.

Localized radiotherapy can cause T-cell-mediated abscopal effects on nonirradiated metastases, particularly in combination with immune checkpoint blockade (ICB). However, results of prospective clinical trials have not met the expectations. We therefore investigated whether additional chemotherapy can enhance radiotherapy-induced abscopal effects in conjunction with ICB. In three different two-tumor mouse models, triple therapy with radiotherapy, anti-PD-1, and cisplatin (one of the most widely used antineoplastic agents) was compared with double or single therapies. In these mouse models, the response of the nonirradiated tumor and the survival of the mice were much better upon triple therapy than upon radiotherapy + anti-PD-1 or cisplatin + anti-PD-1 or the monotherapies; complete regression of the nonirradiated tumor was usually only observed in triple-treated mice. Mechanistically, the enhanced abscopal effect required CD8+T cells and relied on the CXCR3/CXCL10 axis. Moreover, CXCL10 was found to be directly induced by cisplatin in the tumor cells. Furthermore, cisplatin-induced CD8+T cells and direct cytoreductive effects of cisplatin also seem to contribute to the enhanced systemic effect. Finally, the results show that the abscopal effect is not precluded by the observed transient radiotherapy-induced lymphopenia. This is the first report showing that chemotherapy can enhance radiotherapy-induced abscopal effects in conjunction with ICB. This even applies to cisplatin, which is not classically immunogenic. Whereas previous studies have focused on how to effectively induce tumor-specific T cells, this study highlights that successful attraction of the induced T cells to nonirradiated tumors is also crucial for potent abscopal effects.

Fractionated irradiation of right thorax induces abscopal damage on testes leading to decline in fertility

Radiation-induced abscopal effect (RIAE) may influence radiotherapy efficiency. However, it is unknown whether RIAE triggers abnormal genetic consequence. We present a novel evidence that, when mice were given fractionated irradiation on right thorax, the ultrastructure of blood-testis barrier was damaged in company with apoptosis induction in testes, and the sperm number and vitality were drastically decreased so that both the fertility and the survival of their offspring were reduced. Protein microarray assay and hormone detection showed that some cytokines especially TNF-α, TGF-β and estradiol in the serum of irradiated mice increased to higher levels in consistent with abscopal damage, and this conditioned serum had toxic effect on TM4 cells in vitro. When the mice were fed with cimetidine, the above abscopal responses were significantly attenuated. This study demonstrates in the first time that the thoracic irradiation (Th-IR) induces structural and functional damage in the distal testes and further cause fertility decline of irradiated male mice, which may have important implications in the strategy development of radiotherapy in avoiding abnormal genetic consequence.

Bioactive Polysaccharide Nanoparticles Improve Radiation-Induced Abscopal Effect through Manipulation of Dendritic Cells.

Radiotherapy was considered to induce an abscopal effect initiated through antigen release and presented by dendritic cells (DC), while the immunosuppressive tumor microenvironment (TEM) attenuated the effects. Herein, we utilized bioactive polysaccharides extracted from the natural herb Astragalus membranaceus and developed polysaccharide nanoparticles (ANPs) that can reverse TEM and, accordingly, enhance the radiation-induced abscopal effect. ANP showed ability to prolong the survival rate of tumor-bearing mice. In addition, ANP dramatically inhibited the growth of the primary tumor subjected to radiation as well as the secondary tumor distant from the primary lesion. Mechanistic study demonstrated that an ANP-induced immune response was mainly reflected by DC activation, represented by phenotypic maturation and enhanced antigen presentation through the TLR4 signaling pathway. Mature DC induced by ANP migrated to the tumor-draining lymph node and initiated T-cell expansion. Specifically, DC activation was successfully translated into an increase in CD4+ T/Treg and CD8+ T/Treg ratios within both primary (irradiated) and secondary (unirradiated) tumors. Our results also indicated that the systemic antitumor immune response and immune memory were enhanced with the increase in IFN-γ production and effector memory T-cell population. Our work provided a novel strategy to facilitate the incorporation of immunoactive macromolecules purified from natural herbs into modern nanotechnology in the era of immunotherapy.

Abstract 3742: Exosome-mediated EGR1 transportation controls the radiation-induced abscopal effect in head and neck cancer

Abstract Head and neck cancer (HNC) are one of the vital types of metastatic cancer, and radiotherapy (RT) is the convincing treatment regarding its location. RT can regulate cancer growth in not only directly irradiated cells but also non-irradiated remote cells by abscopal or bystander effects. It is evident that radiation-induced Early Growth Response 1 (EGR1) is involved in the control of such type cancer progression. Also, exosomes are established carriers for biological factors basically in cell communication. In this study, we would like to identify the EGR1 as a functional molecule that carried by the radiation-induced exosome to control the HNC growth to disclose the molecular mechanism of the abscopal effect. In this case, we used FaDu cell, a hypopharyngeal cancer, for in vitro experiments. Irradiation was given to the cells in a dose-dependent manner from 0 to 12 Gy followed by exosome isolation using miRCURY Exosome Cell Kit. Characterization of the isolated exosomes was performed by Nanoparticle Tracking Analysis (NTA) for vesicle sizes and concentration, and by transmembrane markers CD63 and CD9 through western blot. We treated unirradiated FaDu cells with isolated exosomes to address the phenotypic changes. MTT assay and colony-forming assay observed the cell viability and survival. Moreover, the expression of EGR1 in both radiation-induced exosome and the exosome-treated cells were determined by western blot. To validate the causal effect of exosomal transportation of EGR1, we assessed the viability changes in EGR1-silenced FaDu cells with exosome treatment. Our results indicated that the number of exosomes was increased while the amounts of protein in each isolated exosome were also increased in a radiation dose-dependent manner. CD63 and CD9 had been identified through western blotting. Moreover, the enhanced expression of EGR1 was observed in both radiation-induced exosomes and the cells treated with isolated exosomes. The possible abscopal effect was evident by the significant decrease of the viability of unirradiated FaDu cells treated with radiation-induced exosomes. Besides, elevated expression of EGR1 was noticed in the radiation-induced exosomes comparing to non-irradiated cohorts. Notably, EGR1-containing exosomes can suppress the proliferation of the unirradiated FaDu cells. Alternatively, radiation-induced EGR1-containing exosome failed to inhibit the proliferation of EGR1 knockdown FaDu cells. In conclusion, radiation-induced EGR1 via exosome transportation contributes to the mechanism of the abscopal effect for metastatic head and neck cancer. Citation Format: Mohammady Akbor, Liang-Ting Lin. Exosome-mediated EGR1 transportation controls the radiation-induced abscopal effect in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3742.

TGF-β mediates thoracic radiation-induced abscopal effects of testis injury in rat

To investigate the thoracic irradiation induced abscopal effect on distal testes and the underlying inflammatory factors, the rats were irradiated on right thorax with fractionated doses. It was found the testes structures were damaged including disorder of spermatogenic cell arrangement and decrease of sperm number. Moreover, the expressions of caspase-3 and caspase-8 in testis tissue were enhanced, and the concentrations of TGF-β and TNF-α in the rat serum were increased. When TM4 cells were treated with the conditioned medium (CS) collected from irradiated rat, the cellular ROS and apoptosis was significantly increased. When the CS was neutralized with anti-TGF-β, its toxic effects were reduced. These results suggest that the thoracic irradiation-induced TGF-β was involved in the above abscopal damage of testes, which reinforces the necessity of new prevention strategy development of radiotherapy in avoiding any abnormal genetic consequence.