Radiotherapy for Non–Small Cell Lung Cancer Induces DNA Damage Response in Both Irradiated and Out-of-field Normal Tissues

Evaluation of the Protective Effect of Compound Kushen Injection Against Radiation- induced Pneumonitis in Mice

Background Radiation-induced lung injury (RILI) via inflammation is a common adverse effect of thoracic radiation that negatively impacts patient quality of life and survival. Compound kushen injection (CKI), a botanical drug treatment, was examined for its ability to reduce RILI, and inflammatory responses and improve survival in mice exposed total lung irradiation (TLI). CKI's specific mechanisms of action were also evaluated. Methods C3H mice underwent TLI and were treated with CKI (2, 4, or 8 mL/kg) intraperitoneally once a day for 8 weeks. The effects of CKI on survival were estimated by Kaplan-Meier survival analysis and compared by log-rank test. RILI damage was evaluated by histopathology and micro-computed tomography (CT). Inflammatory cytokines and cyclooxygenase metabolites were examined by IHC staining, western blot, and ELISA. Results Pre-irradiation treatment with 4 or 8 mL/kg CKI starting 2 weeks before TLI or concurrent treatment with 8 mL/kg CKI were associated with a significantly longer survival compared with TLI vehicle-treated group ( P  < 0.05). Micro-CT images evaluations showed that concurrent treatment with 8 mL/kg CKI was associated with significantly lower incidence of RILI ( P  < 0.05). Histological evaluations revealed that concurrent TLI treatment of CKI (4 and 8 mL/kg) significantly reduced lung inflammation (p < 0.05). Mechanistic investigation showed that at 72 hours after radiation, TLI plus vehicle mice had significantly elevated serum IL6, IL17A, and TGF-β levels compared with non-irradiated, age-matched normal mice; in contrast, levels of these cytokines in mice that received TLI plus CKI treatment were lower than those in the TLI plus vehicle-treated mice ( P  < 0.05) and similar to the nonirradiated mice. IHC staining showed that the CKI treatment led to a reduction of TGF-β positive cells in the lung tissues of TLI mice (P < 0.01). The concurrent CKI with TLI treatment group had a significant reduction in COX-2 activity and COX-2 metabolites compared with the TLI vehicle-treated group ( P  < 0.05). Conclusions These data suggest that CKI treatment was associated with reduced radiation-induced inflammation in lung tissues, reduced RILI, and improved survival. Further investigation of CKI in human clinical trials as a potential radioprotector against RILI to improve patients' quality of life and survival is warranted.

The Distant Molecular Effects on the Brain by Cancer Treatment

Cancer survivors experience cancer-related cognitive impairment (CRCI) secondary to treatment. Chemotherapy and radiation therapy independently contribute to cognitive dysfunction; however, the underlying mechanisms leading to dysfunction remain unclear. We characterized brain gene expression changes in a mouse model of CRCI to identify the mechanistic underpinnings. Eleven-to-twelve-week-old SKH1 mice were treated with doxorubicin (DOX), hindlimb radiation (RT), concurrent hindlimb radiation and doxorubicin (DOX-RT), or no treatment (control). Sixteen days following treatment, gene expression was measured from murine brains using the NanoString nCounter® glial profiling panel. Gene expression was normalized and compared between groups. No two groups shared the same expression pattern, and only Gnb1 and Srpr were upregulated in multiple treatment groups. Brains from DOX-treated mice had upregulated Atf2, Atp5b, Gnb1, Rad23b, and Srpr and downregulated Sirt5 expression compared to control brains. Brains from RT-treated mice demonstrated increased Abcg2 and Fgf2 and decreased C1qa and C1qb expression compared to control brains. Brains from DOX-RT-treated mice had upregulated Adar, E2f3, Erlec1, Gnb1, Srpr, Vim, and Pdgfra expression and downregulated Rock2 and Inpp5f expression compared to control brains. The gene expression changes demonstrated here highlight roles for neuronal transmission and oxidative stress in the pathogenesis of doxorubicin-related CRCI and inflammation in RT-related CRCI.

A Randomized Feasibility Trial of Stereotactic Prostate Radiation Therapy With or Without Elective Nodal Irradiation in High-Risk Localized Prostate Cancer (SPORT Trial)

PURPOSE

The aim of this study was to establish the feasibility of a randomized clinical trial comparing SABR with prostate-only (P-SABR) or with prostate plus pelvic lymph nodes (PPN-SABR) in patients with unfavorable intermediate- or high-risk localized prostate cancer and to explore potential toxicity biomarkers.

METHODS AND MATERIALS

Thirty adult men with at least 1 of the following features were randomized 1:1 to P-SABR or PPN-SABR: clinical magnetic resonance imaging stage T3a N0 M0, Gleason score ≥7 (4+3), and prostate-specific antigen >20 ng/mL. P-SABR patients received 36.25 Gy/5 fractions/29 days, and PPN-SABR patients received 25 Gy/5 fractions to pelvic nodes, with the final cohort receiving a boost to the dominant intraprostatic lesion of 45 to 50 Gy. Phosphorylated gamma-H2AX (γH2AX) foci numbers, citrulline levels, and circulating lymphocyte counts were quantified. Acute toxicity information (Common Terminology Criteria for Adverse Events, version 4.03) was collected weekly at each treatment and at 6 weeks and 3 months. Physician-reported late Radiation Therapy Oncology Group (RTOG) toxicity was recorded from 90 days to 36 months postcompletion of SABR. Patient-reported quality of life (Expanded Prostate Cancer Index Composite and International Prostate Symptom Score) scores were recorded with each toxicity time point.

RESULTS

The target recruitment was achieved, and treatment was successfully delivered in all patients. A total of 0% and 6.7% (P-SABR) and 6.7% and 20.0% (PPN-SABR) experienced acute grade ≥2 gastrointestinal (GI) and genitourinary (GU) toxicity, respectively. At 3 years, 6.7% and 6.7% (P-SABR) and 13.3% and 33.3% (PPN-SABR) had experienced late grade ≥2 GI and GU toxicity, respectively. One patient (PPN-SABR) had late grade 3 GU toxicity (cystitis and hematuria). No other grade ≥3 toxicity was observed. In addition, 33.3% and 60% (P-SABR) and 64.3% and 92.9% (PPN-SABR) experienced a minimally clinically important change in late Expanded Prostate Cancer Index Composite bowel and urinary summary scores, respectively. γH2AX foci numbers at 1 hour after the first fraction were significantly higher in the PPN-SABR arm compared with the P-SABR arm (P = .04). Patients with late grade ≥1 GI toxicity had significantly greater falls in circulating lymphocytes (12 weeks post-radiation therapy, P = .01) and a trend toward higher γH2AX foci numbers (P = .09) than patients with no late toxicity. Patients with late grade ≥1 bowel toxicity and late diarrhea experienced greater falls in citrulline levels (P = .05).

CONCLUSIONS

A randomized trial comparing P-SABR with PPN-SABR is feasible with acceptable toxicity. Correlations of γH2AX foci, lymphocyte counts, and citrulline levels with irradiated volume and toxicity suggest potential as predictive biomarkers. This study has informed a multicenter, randomized, phase 3 clinical trial in the United Kingdom.

Assessment of Individual Radiosensitivity in Breast Cancer Patients Using a Combination of Biomolecular Markers

About 5% of patients undergoing radiotherapy (RT) develop RT-related side effects. To assess individual radiosensitivity, we collected peripheral blood from breast cancer patients before, during and after the RT, and γH2AX/53BP1 foci, apoptosis, chromosomal aberrations (CAs) and micronuclei (MN) were analyzed and correlated with the healthy tissue side effects assessed by the RTOG/EORTC criteria. The results showed a significantly higher level of γH2AX/53BP1 foci before the RT in radiosensitive (RS) patients in comparison to normal responding patients (NOR). Analysis of apoptosis did not reveal any correlation with side effects. CA and MN assays displayed an increase in genomic instability during and after RT and a higher frequency of MN in the lymphocytes of RS patients. We also studied time kinetics of γH2AX/53BP1 foci and apoptosis after in vitro irradiation of lymphocytes. Higher levels of primary 53BP1 and co-localizing γH2AX/53BP1 foci were detected in cells from RS patients as compared to NOR patients, while no difference in the residual foci or apoptotic response was found. The data suggested impaired DNA damage response in cells from RS patients. We suggest γH2AX/53BP1 foci and MN as potential biomarkers of individual radiosensitivity, but they need to be evaluated with a larger cohort of patients for clinics.

Prognostic value of proliferation, PD-L1 and nuclear size in patients with superior sulcus tumours treated with chemoradiotherapy and surgery

AIMS

The aim of this study was to determine the relationship between proliferative activity, PD-L1 status and nuclear size changes after preoperative chemoradiotherapy (CRT) and the clinical outcome in patients with superior sulcus tumours.

METHODS

Proliferative activity (MIB-1) and PD-L1 status were estimated by immunohistochemistry in the tumour cells of resection specimen in a series of 33 patients with residual tumour after trimodality therapy for a sulcus superior tumour between 2005 and 2014. A morphometric analysis of both pretreatment and post-treatment tumour materials was also performed. Results were related to disease-free survival and overall survival.

RESULTS

Low proliferative activity (<20% MIB-1) was associated with better overall survival: 2-year overall survival of 73% compared with 43% and 25%, respectively, for moderate (MIB-1 20%-50%) and high (MIB-1 >50%) proliferative activity (p=0.016). A negative PD-L1 status (<1% positive tumour cells) was also associated with better overall survival (p=0.021). The mean nuclear size of normal lung tissue pneumocytes was significantly smaller compared with the mean nuclear size of tumour cells of the resection specimens (median difference -38.1; range -115.2 to 16.0; p<0.001). The mean nuclear size of tumour cells did not differ between pretreatment biopsies and resection specimens (median difference -4.6; range -75.2 to 86.7; p=0.14). Nuclear size was not associated with survival (p=0.82).

CONCLUSIONS

Low proliferative activity determined by MIB-1 as well as a negative PD-L1 expression are significantly associated with better overall survival in patients with residual tumour after CRT for superior sulcus tumour.

Cancer treatment induces neuroinflammation and behavioral deficits in mice

Introduction: Cancer survivors are increasingly diagnosed with a syndrome of neurocognitive dysfunction termed cancer-related cognitive impairment (CRCI). Chemotherapy and radiation therapy have been implicated in CRCI; however, its underlying pathogenesis remains unclear, hindering effective prevention or treatment. Methods: We used the hairless strain SKH1 (11-12-week-old) and treated the mice with radiation to the right hindlimb, doxorubicin (a chemotherapy agent), concurrent radiation, and doxorubicin, or no treatment (control). Neurocognition was evaluated via standardized behavioral testing following treatment. Mice were subsequently humanely euthanized, and plasma and brains were collected to identify inflammatory changes. Results: Mice treated with radiation, doxorubicin, or both radiation and doxorubicin demonstrated equivalent hippocampal dependent memory deficits and significant increases in activated microglia and astrocytes compared to control mice. Doxorubicin-treated mice had significantly increased plasma IL-6 and failed to gain weight compared to control mice over the study period. Discussion: This study demonstrates that non-brain directed radiation induces both gliosis and neurocognitive deficits. Moreover, this work presents the first characterization of SKH1 mice as a relevant and facile animal model of CRCI. This study provides a platform from which to build further studies to identify potential key targets that contribute to CRCI such that strategies can be developed to mitigate unintended neuropathologic consequences associated with anticancer treatment.

Mechanisms of radioresistance and the underlying signaling pathways in colorectal cancer cells

Radiotherapy is one of the most common modalities for the treatment of a wide range of tumors, including colorectal cancer (CRC); however, radioresistance of cancer cells remains a major limitation for this treatment. Following radiotherapy, the activities of various cellular mechanisms and cell signaling pathways are altered, resulting in the development of radioresistance, which leads to therapeutic failure and poor prognosis in patients with cancer. Furthermore, even though several inhibitors have been developed to target tumor resistance, these molecules can induce side effects in nontumor cells due to low specificity and efficiency. However, the role of these mechanisms in CRC has not been extensively studied. This review discusses recent studies regarding the relationship between radioresistance and the alterations in a series of cellular mechanisms and cell signaling pathways that lead to therapeutic failure and tumor recurrence. Our review also presents recent advances in the in vitro/in vivo study models aimed at investigating the radioresistance mechanism in CRC. Furthermore, it provides a relevant biochemical basis in theory, which can be useful to improve radiotherapy sensitivity and prolong patient survival.

Systemic benefit of radiation therapy via abscopal effect

Evidence of a systemic response related to localized radiation therapy (RT) in cancer management is rare. However, enhancing the immune response via immunotherapy followed by localized RT has shown evidence of tumor shrinkage to non-irradiated metastatic disease thereby inducing an "abscopal effect." Combined induction of the cGAS-STING pathway and activation of IFN-gamma signaling cascade related to RT within an activated immune environment promotes neoantigen presentation and expansion of cytotoxic effector cells enabling enhancement of systemic immune response. A proposed mechanism, case examples, and clinical trial evidence of "abscopal effect" benefit are reviewed. Results support strategic therapeutic testing to enhance "abscopal effect."

A Review of the Abscopal Effect in the Era of Immunotherapy

The abscopal effect is a systemic immune response mediated by the effects of radiation on the immune system. This effect has been observed in a number of cancer types in addition to lung cancer, including but not limited to renal cell carcinoma, hepatocellular carcinoma, lymphoma, and melanoma. The combination of radiation therapy and immune checkpoint inhibition (ICI) acts at several stages of the antitumor response, suggesting a mechanism of synergy between the two modalities. This review focuses on recent advances in the understanding of the effect of radiation and immunotherapy in the context of the abscopal effect.

Radiotherapy combined with immunotherapy: the dawn of cancer treatment

Radiotherapy (RT) is delivered for purposes of local control, but can also exert systemic effect on remote and non-irradiated tumor deposits, which is called abscopal effect. The view of RT as a simple local treatment has dramatically changed in recent years, and it is now widely accepted that RT can provoke a systemic immune response which gives a strong rationale for the combination of RT and immunotherapy (iRT). Nevertheless, several points remain to be addressed such as the interaction of RT and immune system, the identification of the best schedules for combination with immunotherapy (IO), the expansion of abscopal effect and the mechanism to amplify iRT. To answer these crucial questions, we roundly summarize underlying rationale showing the whole immune landscape in RT and clinical trials to attempt to identify the best schedules of iRT. In consideration of the rarity of abscopal effect, we propose that the occurrence of abscopal effect induced by radiation can be promoted to 100% in view of molecular and genetic level. Furthermore, the “radscopal effect” which refers to using low-dose radiation to reprogram the tumor microenvironment may amplify the occurrence of abscopal effect and overcome the resistance of iRT. Taken together, RT could be regarded as a trigger of systemic antitumor immune response, and with the help of IO can be used as a radical and systemic treatment and be added into current standard regimen of patients with metastatic cancer.

Reshaping the systemic tumor immune environment (STIE) and tumor immune microenvironment (TIME) to enhance immunotherapy efficacy in solid tumors

The development of combination immunotherapy based on the mediation of regulatory mechanisms of the tumor immune microenvironment (TIME) is promising. However, a deep understanding of tumor immunology must involve the systemic tumor immune environment (STIE) which was merely illustrated previously. Here, we aim to review recent advances in single-cell transcriptomics and spatial transcriptomics for the studies of STIE, TIME, and their interactions, which may reveal heterogeneity in immunotherapy responses as well as the dynamic changes essential for the treatment effect. We review the evidence from preclinical and clinical studies related to TIME, STIE, and their significance on overall survival, through different immunomodulatory pathways, such as metabolic and neuro-immunological pathways. We also evaluate the significance of the STIE, TIME, and their interactions as well as changes after local radiotherapy and systemic immunotherapy or combined immunotherapy. We focus our review on the evidence of lung cancer, hepatocellular carcinoma, and nasopharyngeal carcinoma, aiming to reshape STIE and TIME to enhance immunotherapy efficacy.

The paradox of radiation and T cells in tumors

In this review we consider what appears to be a paradox in immunotherapies based around radiation therapy. The paradox is based on three main points. 1. That T cells are needed for radiation's efficacy; 2. That tumor-specific T cells are enriched in the field of treatment; and 3. That radiation kills T cells in the treatment field. We discuss evidence of the effect of radiation on T cells in the field given their ongoing movement in and out of tissues and the tumor, and how the movement of T cells impacts the treated primary tumor and untreated distant metastases. Given this evidence, we revisit the paradox to understand how the extraordinary efficacy of radiation and immunity in preclinical models is dependent on this radiation sensitive cell.

Abscopal Effects in Metastatic Cancer: Is a Predictive Approach Possible to Improve Individual Outcomes?

Patients with metastatic cancers often require radiotherapy (RT) as a palliative therapy for cancer pain. RT can, however, also induce systemic antitumor effects outside of the irradiated field (abscopal effects) in various cancer entities. The occurrence of the abscopal effect is associated with a specific immunological activation in response to RT-induced cell death, which is mainly seen under concomitant immune checkpoint blockade. Even if the number of reported apscopal effects has increased since the introduction of immune checkpoint inhibition, its occurrence is still considered rare and unpredictable. The cases reported so far may nevertheless allow for identifying first biomarkers and clinical patterns. We here review biomarkers that may be helpful to predict the occurrence of abscopal effects and hence to optimize therapy for patients with metastatic cancers.

Effect of dose and dose rate of gamma irradiation on the formation of micronuclei in bone marrow cells isolated from whole-body-irradiated mice

It is well-known that the cytotoxicity and mutagenic effects of high dose rate (HDR) ionizing radiation (IR) are increased by increasing the dose but less is known about the effects of chronic low dose rate (LDR). In vitro, we have shown that in addition to the immediate interaction of IR with DNA (the direct and indirect effects), low doses and chronic LDR exposure induce endogenous oxidative stress. During elevated oxidative stress, reactive oxygen species (ROS) react with DNA modifying its structure. Here, BL6 mice were exposed to IR at LDR and HDR and were then sacrificed 3 hours and 3 weeks after exposure to examine early and late effects of IR. The levels of micronuclei, MN, were determined in bone marrow cells. Our data indicate that the effects of 200 mGy on MN-induction are transient, but 500 and 1000 mGy (both HDR and LDR) lead to increased levels of MN up to 3 weeks after the exposure.

Evaluating Individual Radiosensitivity for the Prediction of Acute Toxicities of Chemoradiotherapy in Esophageal Cancer Patients

In this work, individual radiosensitivity was evaluated using DNA damage response and chromosomal aberrations (CAs) in peripheral blood lymphocytes (PBLs) for the prediction of acute toxicities of chemoradiotherapy (CRT) in esophageal cancer patients. Eighteen patients with esophageal cancer were enrolled in this prospective study. Prescribed doses were 60 Gy in 11 patients and 50 Gy in seven patients. Patients received 2 Gy radiotherapy five days a week. PBLs were obtained during treatment just before and 15 min after 2 Gy radiation therapy on the days when the cumulative dose reached 2, 20, 40 Gy and 50 or 60 Gy. PBLs were also obtained four weeks and six months after radiotherapy in all and 13 patients, respectively. Dicentric and ring chromosomes in PBLs were counted to evaluate the number of CAs. Gamma-H2AX foci per cell were scored to assess DNA double-strand breaks. We analyzed the association between these factors and adverse events. The number of γ-H2AX foci before radiotherapy showed no significant increase during CRT, while their increment was significantly reduced with the accumulation of radiation dose. The mean number of CAs increased during CRT up to 1.04 per metaphase, and gradually decreased to approximately 60% six months after CRT. Five patients showed grade 3 toxicities during or after CRT (overreactors: OR), while 13 had grade 2 or less toxicities (non-overreactors: NOR). The number of CAs was significantly higher in the OR group than in the NOR group at a cumulative dose of 20 Gy (mean value: 0.63 vs. 0.34, P = 0.02), 40 Gy (mean value: 0.90 vs. 0.52, P = 0.04), and the final day of radiotherapy (mean value: 1.49 vs. 0.84, P = 0.005). These findings suggest that number of CAs could be an index for predicting acute toxicities of CRT for esophageal cancer.

Low dose ionizing radiation effects on the immune system

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

The Valproate Mediates Radio-Bidirectional Regulation Through RFWD3-Dependent Ubiquitination on Rad51

Ionizing radiation (IR) can induce DNA double-strand breaks (DSBs) in tumor cells during radiotherapy (RT), but the efficiency of RT is limited because of the toxicity to normal cells. Locating an adjuvant treatment to alleviate damage in normal cells while sensitizing tumor cells to IR has attracted much attention. Here, using the 7,12-dimethylbenz[α]anthracene (DMBA)-induced malignant transformed MCF10A cells, we found that valproate (VPA), a histone deacetylase inhibitor (HDACi), radiosensitized transformed cells while alleviated IR-induced damage in normal cells at a safe dose (0.5 mM). We further demonstrated the decrease of homologous recombination (HR)-associated Rad51 in the transformed cells was related to the increase of its ubiquitination regulated by E3 ligase RFWD3 for the radiosensitization, which was opposite to normal cells, indicating that RFWD3-dependent ubiquitination on Rad51 was involved in the VPA-mediated radio-bidirectional effect. Through DMBA-transformed breast cancer rat model, VPA at 200 mg/kg radiosensitized tumor tissue cells by increasing RFWD3 and inhibited Rad51, while radioprotected normal tissue cells by decreasing RFWD3 and enhanced Rad51. In addition, we found high-level Rad51 was associated with tumorigenesis and poor prognosis in breast cancer patients. Our findings uncovered RFWD3-dependent Rad51 ubiquitination was the novel mechanism of VPA-mediated radio-bidirectional effect, VPA is a potential adjuvant treatment for tumor RT.

The abscopal effect of radiation therapy

Radiation therapy (RT) in some cases results in a systemic anticancer response known as the abscopal effect. Multiple hypotheses support the role of immune activation initiated by RT-induced DNA damage. Optimal radiation dose is necessary to promote the cGAS-STING pathway in response to radiation and initiate an IFN-1 signaling cascade that promotes the maturation and migration of dendritic cells to facilitate antigen presentation and stimulation of cytotoxic T cells. T cells then exert a targeted response throughout the body at areas not subjected to RT. These effects are further augmented through the use of immunotherapeutic drugs resulting in increased T-cell activity. Tumor-infiltrating lymphocyte presence and TREX1, KPNA2 and p53 signal expression are being explored as prognostic biomarkers.

The γH2AX DSB marker may not be a suitable biodosimeter to measure the biological MRT valley dose

PURPOSE

γH2AX biodosimetry has been proposed as an alternative dosimetry method for microbeam radiation therapy (MRT) because conventional dosimeters, such as ionization chambers, lack the spatial resolution required to accurately measure the MRT valley dose. Here we investigated whether γH2AX biodosimetry should be used to measure the biological valley dose of MRT-irradiated mammalian cells.

MATERIALS AND METHODS

We irradiated human skin fibroblasts and mouse skin flaps with synchrotron MRT and broad beam (BB) radiation. BB doses of 1-5 Gy were used to generate a calibration curve in order to estimate the biological MRT valley dose using the γH2AX assay.

RESULTS

Our key finding was that MRT induced a non-linear dose response compared to BB, where doses 2-3 times greater showed the same level of DNA DSB damage in the valley in cell and tissue studies. This indicates that γH2AX may not be an appropriate biodosimeter to estimate the biological valley doses of MRT-irradiated samples. We also established foci yields of 5.9 ± 0.04 and 27.4 ± 2.5  foci/cell/Gy in mouse skin tissue and human fibroblasts respectively, induced by BB. Using Monte Carlo simulations, a linear dose response was seen in cell and tissue studies and produced predicted peak-to-valley dose ratios (PVDRs) of ∼30 and ∼107 for human fibroblasts and mouse skin tissue respectively.

CONCLUSIONS

Our report highlights novel MRT radiobiology, attempts to explain why γH2AX may not be an appropriate biodosimeter and suggests further studies aimed at revealing the biological and cellular communication mechanisms that drive the normal tissue sparing effect, which is characteristic of MRT.

Abscopal Gene Expression in Response to Synchrotron Radiation Indicates a Role for Immunological and DNA Damage Response Genes

Abscopal effects are an important aspect of targeted radiation therapy due to their implication in normal tissue toxicity from chronic inflammatory responses and mutagenesis. Gene expression can be used to determine abscopal effects at the molecular level. Synchrotron microbeam radiation therapy utilizing high-intensity X rays collimated into planar microbeams is a promising cancer treatment due to its reported ability to ablate tumors with less damage to normal tissues compared to conventional broadbeam radiation therapy techniques. The low scatter of synchrotron radiation enables microbeams to be delivered to tissue effectively, and is also advantageous for out-of-field studies because there is minimal interference from scatter. Mouse legs were irradiated at a dose rate of 49 Gy/s and skin samples in the out-of-field areas were collected. The out-of-field skin showed an increase in Tnf expression and a decrease in Mdm2 expression, genes associated with inflammation and DNA damage. These expression effects from microbeam exposure were similar to those found with broadbeam exposure. In immune-deficient Ccl2 knockout mice, we identified a different gene expression profile which showed an early increase in Mdm2, Tgfb1, Tnf and Ccl22 expression in out-of-field skin that was not observed in the immune-proficient mice. Our results suggest that the innate immune system is involved in out-of-field tissue responses and alterations in the immune response may not eliminate abscopal effects, but could change them.

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

Background

Recent 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.

Methods

We 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.

Results

We 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.

Conclusions

In 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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01883-0.

Macrophage contributes to radiation-induced anti-tumor abscopal effect on transplanted breast cancer by HMGB1/TNF-α signaling factors

Objectives: The roles of innate immunity including macrophages in radiation-induced abscopal effect (RIAE) are ambiguous. In this study, we evaluated the role of macrophage in RIAE and the interaction of cytokines in tumor microenvironment after irradiation.

Materials and Methods: Transplanted tumor of breast cancer cells in BalB/C mice, severe combined immunodeficiency (SCID) mice and non-obese diabetic (NOD)-SCID mice were irradiated with fractionation doses to observe anti-tumor abscopal effect. The underlying mechanism of RIAE was investigated by treating the mice with TNF-α inhibitor or macrophage depletion drug and analyzing the alteration of macrophage distribution in tumors. A co-culture system of breast cancer cells and macrophages was applied to disclose the signaling factors and related pathways involved in the RIAE.

Results: The growth of nonirradiated tumor was effectively suppressed in mice with normal or infused macrophages but not in mice with insufficiency/depletion of macrophage or TNF-α inhibition, where M1-macrophage was mainly involved. Investigation of the bystander signaling factors in vitro demonstrated that HMGB1 released from irradiated breast cancer cells promoted bystander macrophages to secret TNF-α through TLR-4 pathway and further inhibited the proliferation and migration of non-irradiated cancer cells by PI3K-p110γ suppression.

Conclusions: HMGB1 and TNF-α contributes to M1-macrophages facilitated systemic anti-tumor abscopal response triggered by radiotherapy in breast cancer, indicating that the combination of immunotherapy and radiotherapy may has important implication in enhancing the efficiency of tumor treatment.

Safety and Efficacy of Robotic Radiosurgery for Visceral and Lymph Node Metastases of Renal Cell Carcinoma: A Retrospective, Single Center Analysis

Simple Summary

In metastatic renal cell carcinoma (mRCC), systemic treatment with checkpoint inhibitors or tyrosine kinase inhibitors is recommended in guidelines. However, the treatment of patients with oligometastatic disease or mixed responses remains challenging. We aimed to investigate the safety and efficacy of robotic radiosurgery in patients with mRCC. Sixty patients with visceral and lymph node metastases were selected for robotic radiosurgery. The median progression free survival of all patients was 17.4 months, local tumor control was achieved in 96.7% of patients, and only 8.3% of patients experienced adverse events. Robotic radiosurgery might be a powerful tool in addition to systemic treatment for patients with mRCC, but additive effects of both treatments require further investigation.

Abstract

Despite rapid advances of systemic therapy options in renal cell carcinoma (RCC), local tumor or metastases treatment remains important in selected patients. Here, we assess the safety and efficacy of robotic radiosurgery (RRS) as an ablative therapy for visceral and lymph node metastases of RCC. Patients with histologically confirmed RCC and radiologically confirmed progression of visceral or lymph node metastases underwent RRS and were retrospectively analyzed. Overall survival and progression free survival were calculated by the Kaplan–Meier method and log-rank test. Sixty patients underwent RRS and were included in the analysis. Patients presented for RRS treatment with a median age at RRS treatment of 64 years (range 42–83), clear cell histology (88.3%) and favorable international metastatic renal cell carcinoma database (IMDC) risk score (58.3%). Treatment parameters differed for the number of fractions (median visceral metastases: 1, range 1–5; median lymph node metastases: 1, range 0–5; p = 0.003) and prescription dose (median visceral metastases 24 Gy, range 8–26; median lymph node metastases 18 Gy, range 7–26, p < 0.001). The median overall survival was 65.7 months (range: 2.9–108.6), the median progression free survival was 17.4 months (range: 2.7–70.0) and local tumor control was achieved in 96.7% of patients. Adverse events were limited to 8.3% of patients, with one grade 4 toxicity within 6 weeks after RRS therapy. RRS is a safe and effective treatment option in selected patients with metastatic RCC in a multimodal approach. Further research is warranted to confirm our findings prospectively.

Identifying Circulating and Lung Tissue Cytokines Associated with Thoracic Irradiation and AEOL 10150 Treatment in a Nonhuman Primate Model

Inflammatory cytokines have been suggested to play important roles in radiation-induced lung injury (RILI). Identifying significantly changed circulating and tissue cytokines after thoracic irradiation will aid in deciphering the mechanism of RILI and identifying potential biomarkers to predict clinical outcome. Herein, the levels of 24 cytokines were measured in serial plasma samples and lung tissue samples collected from a pilot study where nonhuman primates (NHPs) received 11.5 Gy whole thoracic lung irradiation (WTLI) and were then treated with or without a medical countermeasure, AEOL 10150 [a superoxide dismutase (SOD) mimetic]. Seven plasma cytokines (i.e., IP-10, MCP-1, IL-12, IL-15, IL-16, IL-7 and IL-6) were found to be significantly changed at different time points due to WTLI. Plasma IP-10 and MDC were significantly changed between the vehicle group and the drug group. The levels of IP-10, MCP-1, MIP-1α, TARC, IL-17, TNF-β and IL-6 were significantly elevated in the lung tissue lysates of NHPs that received WTLI versus radiation-naïve NHPs. The terminal plasma concentrations of IP-10, MDC, TARC, IL-12, IL-15 and IL-6 were significantly correlated with their levels in the lung tissue. The levels of four cytokines (MCP-4, IL-17, TNF-β and IL-2) at early time points (≤8 weeks postirradiation) were significantly correlated with their terminal plasma levels, respectively. Statistical analysis indicated that circulating cytokines could be discriminatory predictors of AEOL 10150 treatment. Taken together, our data suggested that the cytokine profiles were significantly changed after WTLI as well as mitigator treatment, and that the plasma cytokine profiles could potentially be used to distinguish vehicle or mitigator treatment after WTLI in a NHP model.

Immune system in cancer radiotherapy: Resistance mechanisms and therapy perspectives

Radiotherapy is a common modality for more than half of cancer patients. Classically, radiation is known as a strategy to kill cancer cells via direct interaction with DNA or generation of free radicals. Nowadays, we know that modulation of immune system has a key role in the outcome of radiotherapy. Selecting an appropriate dose per fraction is important for stimulation of anti-tumor immunity. Unfortunately, cancer cells and other cells within tumor microenvironment (TME) promote some mechanisms implicated in the attenuation of anti-tumor immunity via exhaustion of CD8 + T lymphocytes and natural killer (NK) cells. Immunotherapy with immune checkpoint inhibitors (ICIs) has shown to be an interesting adjuvant for induction of more effective anti-tumor immunity. Clinical trial studies are ongoing for uncovering more knowledge about the efficacy of ICI combination with radiotherapy. Some newer pre-clinical studies show more effective therapeutic window for targeting PD-1 and some other targets in combination with hypofractionated radiotherapy. In this review, we explain cellular and molecular consequences in the TME following radiotherapy and promising immune targets to enhance anti-tumor immunity.

Monitoring DNA Damage and Repair in Peripheral Blood Mononuclear Cells of Lung Cancer Radiotherapy Patients

Simple Summary

Every patient responds to radiotherapy in individual manner. Some suffer severe side-effects because of normal tissue toxicity. Their radiosensitivity can be caused by inability of DNA repair system to fix radiation-induced damage. The γ-H2AX assay can detect such deficiency in untransformed primary cells (e.g., peripheral blood mononuclear cells, PBMC), over a period of only hours post ex-vivo irradiation. Earlier we have shown that the level and kinetics of decline (repair) of radiation-induced DNA damage detected by the assay is a measure of the cellular radiosensitivity. In this study, we applied the γ-H2AX assay to judge the radiosensitivity of lung cancer radiotherapy patients as normal or abnormal, based on kinetics of DNA damage repair. Considering the potential of the assay as a clinical biodosimeter, we also monitored DNA damage in serial samples of PBMC during the course of radiotherapy. This study opens an opportunity to monitor individual response to radiotherapy treatment.

Abstract

Thoracic radiotherapy (RT) is required for the curative management of inoperable lung cancer, however, treatment delivery is limited by normal tissue toxicity. Prior studies suggest that using radiation-induced DNA damage response (DDR) in peripheral blood mononuclear cells (PBMC) has potential to predict RT-associated toxicities. We collected PBMC from 38 patients enrolled on a prospective clinical trial who received definitive fractionated RT for non-small cell lung cancer. DDR was measured by automated counting of nuclear γ-H2AX foci in immunofluorescence images. Analysis of samples collected before, during and after RT demonstrated the induction of DNA damage in PBMC collected shortly after RT commenced, however, this damage repaired later. Radiation dose to the tumour and lung contributed to the in vivo induction of γ-H2AX foci. Aliquots of PBMC collected before treatment were also irradiated ex vivo, and γ-H2AX kinetics were analyzed. A trend for increasing of fraction of irreparable DNA damage in patients with higher toxicity grades was revealed. Slow DNA repair in three patients was associated with a combined dysphagia/cough toxicity and was confirmed by elevated in vivo RT-generated irreparable DNA damage. These results warrant inclusion of an assessment of DDR in PBMC in a panel of predictive biomarkers that would identify patients at a higher risk of toxicity.

The Prognostic Value of Deficient Mismatch Repair in Stage II-IVa Nasopharyngeal Carcinoma in the Era of IMRT

In the era of intensity-modulated radiotherapy (IMRT), it is important to analyse the prognostic value of deficient mismatch repair (dMMR) in nasopharyngeal carcinoma (NPC). In this study, in pretreatment biopsies of 69 patients with stage II-IVa NPC, the expression levels of MMR proteins, including MLH1, MSH2, MSH6 and PMS2, were assessed by immunohistochemistry (IHC). The median follow-up time was 37.5 months (3.1-87.4 months). 50.7% of cases (35/69) showed preserved expression of all 4 MMR proteins, which was interpreted as proficient mismatch repair (pMMR). Only 1.5% of cases (1/69) lost expression of all 4 MMR proteins, 26.1% of cases (18/69) have PMS2 loss alone and 21.7% of cases (15/69) lost expression of both PMS2 and MLH1. Thus, 49.3% of cases (34/69) lost expression of one or more MMR proteins, which was interpreted as dMMR. There was no significant difference (P > 0.05) in terms of sex, age, clinical stage, T category, N category or therapy regimens between the dMMR and pMMR groups. The multivariate Cox regression analysis revealed that dMMR was an independent significant prognostic factor for distant metastasis-free survival (DMFS) (dMMR vs pMMR: P = 0.01, HR = 0.25, 95% CI: 0.09~0.75). Therefore, NPC patients with dMMR had significantly superior DMFS compared with patients with pMMR. It can be expected that dMMR will become a new independent prognostic factor for NPC.

Systemic modulation of stress and immune parameters in patients treated for prostate adenocarcinoma by intensity-modulated radiation therapy or stereotactic ablative body radiotherapy

Background

In this exploratory study, the impact of local irradiation on systemic changes in stress and immune parameters was investigated in eight patients treated with intensity-modulated radiation therapy (IMRT) or stereotactic ablative body radiotherapy (SABR) for prostate adenocarcinoma to gain deeper insights into how radiotherapy (RT) modulates the immune system.

Patients and methods

RT-qPCR, flow cytometry, metabolomics, and antibody arrays were used to monitor a panel of stress- and immune-related parameters before RT, after the first fraction (SABR) or the first week of treatment (IMRT), after the last fraction, and 3 weeks later in the blood of IMRT (N = 4) or SABR (N = 4) patients. Effect size analysis was used for comparison of results at different timepoints.

Results

Several parameters were found to be differentially modulated in IMRT and SABR patients: the expression of TGFB1, IL1B, and CCL3 genes; the expression of HLA-DR on circulating monocytes; the abundance and ratio of phosphatidylcholine and lysophosphatidylcholine metabolites in plasma. More immune modulators in plasma were modulated during IMRT than SABR, with only two common proteins, namely GDF-15 and Tim‑3.

Conclusion

Locally delivered RT induces systemic modulation of the immune system in prostate adenocarcinoma patients. IMRT and SABR appear to specifically affect distinct immune components.

Electronic supplementary material

The online version of this article (10.1007/s00066-020-01637-5) contains supplementary material, which is available to authorized users.

89Zr-PET imaging of DNA double-strand breaks for the early monitoring of response following α- and β-particle radioimmunotherapy in a mouse model of pancreatic ductal adenocarcinoma

Rationale: The evaluation of early treatment response is critical for patient prognosis and treatment planning. When the current methods rely on invasive protocols that evaluate the expression of DNA damage markers on patient biopsy samples, we aim to evaluate a non-invasive PET imaging approach to monitor the early expression of the phosphorylated histone γH2AX in the context of pancreatic cancer targeted radionuclide therapy. Pancreatic ductal adenocarcinoma has a poor patient prognosis due to the absence of curative treatment for patients with advanced disease. There is therefore a critical need for the fast clinical translation of new therapeutic options. In line with these observations, our group has been focusing on the development of radiotheranostic agents based on a fully human monoclonal antibody (5B1) with exceptional affinity for CA19.9, an antigen overexpressed in PDAC. Two on-going clinical trials resulted from these efforts, one with 89Zr (diagnosis) and one with 177Lu (β-particle therapy). More recently, we successfully developed and evaluated in PDAC mouse models a targeted α-therapy strategy with high clinical translation potential. We aim to expedite the clinical translation of the developed radioimmunotherapy approaches by investigating the early therapeutic response and effect of radiation therapy in a PDAC mouse model via PET imaging. Methods: Mice bearing BxPC3 tumor xenografts were treated with α- and β-particle pretargeted radioimmunotherapy (PRIT), external beam radiotherapy (EBRT), or sham-treated (vehicle). The phosphorylated histone γH2AX produced as a response to DNA double strand breaks was quantified with the PET radiotracer, [89Zr]Zr-DFO-anti-γH2AX-TAT. Results: PET imaging studies in BxPC3 PDAC mouse models demonstrated increased uptake of [89Zr]Zr-DFO-anti-γH2AX-TAT (6.29 ± 0.15 %IA/g) following β-PRIT in BxPC3 PDAC xenografts as compared to the saline control group (4.58 ± 0.76 %IA/g) and EBRT control group (5.93 ± 0.76 %IA/g). Similarly, significantly higher uptake of [89Zr]Zr-DFO-anti-γH2AX-TAT was observed in tumors of the 225Ac-PRIT and EBRT (10 Gy) cohorts (7.37 ± 1.23 and 6.80 ± 1.24 %IA/g, respectively) compared to the negative control cohort (5.08 ± 0.95 %IA/g). Ex vivo γH2AX immunohistochemistry and immunofluorescence analysis correlated with in vivo89Zr-anti-γH2AX PET/CT imaging with increased γH2AX positive cell and γH2AX foci per cell in the treated cohorts. When α-PRIT resulted in prolonged overall survival of treated animals (107.5 days) as compared to β-PRIT (73.0 days), no evidence of difference in [89Zr]Zr-DFO-anti-γH2AX-TAT uptake at the tumor site was observed, highlighting that DNA damage is not the sole radiobiology paradigm and that off-targeted (bystander) effects should be considered. Conclusions: PET imaging studies with [89Zr]Zr-DFO-anti-γH2AX-TAT following α- and β-particle PRIT in a BxPC3 PDAC subcutaneous xenograft mouse model allowed the monitoring of tumor radiobiological response to treatment.

Selenium as an adjuvant for modification of radiation response

Ionizing radiation plays a central role in several medical and industrial purposes. In spite of the beneficial effects of ionizing radiation, there are some concerns related to accidental exposure that could pose a threat to the lives of exposed people. This issue is also very critical for triage of injured people in a possible terror event or nuclear disaster. The most common side effects of ionizing radiation are experienced in cancer patients who had undergone radiotherapy. For complete eradication of tumors, there is a need for high doses of ionizing radiation. However, these high doses lead to severe toxicities in adjacent organs. Management of normal tissue toxicity may be achieved via modulation of radiation responses in both normal and malignant cells. It has been suggested that treatment of patients with some adjuvant agents may be useful for amelioration of radiation toxicity or sensitization of tumor cells. However, there are always some concerns for possible severe toxicities and protection of tumor cells, which in turn affect radiotherapy outcomes. Selenium is a trace element in the body that has shown potent antioxidant and radioprotective effects for many years. Selenium can potently stimulate antioxidant defense of cells, especially via upregulation of glutathione (GSH) level and glutathione peroxidase activity. Some studies in recent years have shown that selenium is able to mitigate radiation toxicity when administered after exposure. These studies suggest that selenium may be a useful radiomitigator for an accidental radiation event. Molecular and cellular studies have revealed that selenium protects different normal cells against radiation, while it may sensitize tumor cells. These differential effects of selenium have also been revealed in some clinical studies. In the present study, we aimed to review the radiomitigative and radioprotective effects of selenium on normal cells/tissues, as well as its radiosensitive effect on cancer cells.

Long-Term Endocrine and Metabolic Consequences of Cancer Treatment: A Systematic Review

The number of patients surviving ≥5 years after initial cancer diagnosis has significantly increased during the last decades due to considerable improvements in the treatment of many cancer entities. A negative consequence of this is that the emergence of long-term sequelae and endocrine disorders account for a high proportion of these. These late effects can occur decades after cancer treatment and affect up to 50% of childhood cancer survivors. Multiple predisposing factors for endocrine late effects have been identified, including radiation, sex, and age at the time of diagnosis. A systematic literature search has been conducted using the PubMed database to offer a detailed overview of the spectrum of late endocrine disorders following oncological treatment. Most data are based on late effects of treatment in former childhood cancer patients for whom specific guidelines and recommendations already exist, whereas current knowledge concerning late effects in adult-onset cancer survivors is much less clear. Endocrine sequelae of cancer therapy include functional alterations in hypothalamic-pituitary, thyroid, parathyroid, adrenal, and gonadal regulation as well as bone and metabolic complications. Surgery, radiotherapy, chemotherapy, and immunotherapy all contribute to these sequelae. Following irradiation, endocrine organs such as the thyroid are also at risk for subsequent malignancies. Although diagnosis and management of functional and neoplastic long-term consequences of cancer therapy are comparable to other causes of endocrine disorders, cancer survivors need individually structured follow-up care in specialized surveillance centers to improve care for this rapidly growing group of patients.

An RNA-seq-Based Expression Profiling of Radiation-Induced Esophageal Injury in a Rat Model

Radiation-induced acute injury is the main reason for the suspension of radiotherapy and unsuccessful treatment of cancer. It is of great importance to understand the molecular mechanism of radiation-induced esophageal injury. We used RNA-seq data from normal esophageal tissue and irradiated esophageal tissues and applied computational approaches to identify and characterize differentially expressed genes and detected 40 059 messenger RNAs (mRNAs) previously annotated and 717 novel long noncoding RNAs (lncRNAs). There were 14 upregulated and 32 downregulated lncRNAs among the differentially expressed lncRNA group. Their target genes were involved in the mRNA surveillance pathway, pathological immune responses, and cellular homeostasis. Additionally, we found 853 differentially expressed mRNAs, and there were 384 upregulated and 469 downregulated mRNAs. Notably, we found that the differentially expressed mRNAs were enriched for steroid biosynthesis, the tumor necrosis factor signaling pathway, focal adhesion, pathways in cancer, extracellular matrix-receptor interaction, and so on. The response of normal esophageal tissues to ionizing radiation is multifarious. The radiation-induced cell damage response by multiple pathways followed by pathological immune responses activated. Studies on the dynamic network of molecules involved in radiation-induced esophageal injury are under way to clarify the regulatory mechanisms and identify the candidate targets.

The Abscopal Effect of Stereotactic Radiotherapy and Immunotherapy: Fool's Gold or El Dorado?

An 'abscopal' effect if often used to refer to distant tumour regression after localised irradiation. Since the first report of the abscopal effect in the 1950s, well-documented cases with radiotherapy alone are very rare. It is widely accepted that the immune response plays an important role in the abscopal effect, although the mechanism is still unclear. With the recent success of cancer immunotherapy, there is growing interest in combining immunotherapy with radiotherapy to boost abscopal response rates. Compared with conventional radiotherapy, stereotactic ablative radiotherapy (SABR) not only delivers ablative dose to the tumour, but may also induce robust immune responses. In this review we examine studies that combine SABR and immunotherapy. We review the preclinical rationale for SABR and immunotherapy combinations, the case for and against abscopal effects, and the current landscape of clinical trials.

Radiation-induced DNA damage response and resistance in colorectal cancer stem-like cells

Purpose: Radiation therapy is an integral part of current treatment modality for colorectal cancer. Recent studies have revealed the presence of cancer stem-like cells (CSCs) population, in different tumors are responsible for therapeutic resistance and disease relapse, including colorectal cancer with poorer survival rate. Hence, characterization of the effect of Ionizing Radiation (IR) in colorectal cancer may serve to explain possible mechanisms. Material and methods: Parental HCT116 and HCT-15 cells and derived colonospheres were irradiated and dose was optimized based on cell survival assay and cell cycle analysis. DNA damage response (DDR) was elucidated by γH2AX foci formation, COMET assay, and ATM, p-ATM, ERCC1 expression post-treatment. The expression level of developmental marker (β-catenin), CSC markers (CD44, KLF4) and telomeric components (TRF2, RAP1, hTERT) were evaluated. Results: We observed cell survival was more in colonospheres post-irradiation and also exhibited decreased γH2AX foci, olive tail moment, increased ERCC1, and p-ATM expression than its parental counterpart which corresponds to efficient DDR. Differential expression of developmental marker, CSC markers, and telomeric components were observed after irradiation. Conclusion: This study highlighted the presence of CSC phenotype in colonospheres having increased DNA repair capacity. Differential expression of developmental marker, CSC markers and telomeric components between parental and colonospheres may contribute in radio-resistance property of CSCs.

Tumor-Targeted and Biocompatible MoSe2 Nanodots@Albumin Nanospheres as a Dual-Modality Therapy Agent for Synergistic Photothermal Radiotherapy

Integrating multiple tumor therapy functions into one nanoplatform has been a new tumor therapy strategy in recent years. Herein, a dual-modality therapy agent consisting of molybdenum selenide nanodots (MoSe2 NDs) and bovine serum albumin (BSA) assembled nanospheres (MoSe2@BSA NSs) was successfully synthesized. After conjugation of folic acid (FA) molecules via polyethylene glycol (PEG) "bridges," the FA-MoSe2@BSA NSs were equipped with tumor-targeting function. The BSA and PEG modifications provided the unstable MoSe2 NDs with excellent physiological stability. Since the end-product FA-MoSe2@BSA NSs had strong near-infrared (NIR) and X-ray absorbance properties, they exhibited good photothermal properties with excellent photothermal stability and radio-sensitization ability, hence, were explored as photothermal radiotherapy agents. In vitro and in vivo experiments indicated that the FA-MoSe2@BSA NSs possessed highly efficient tumor-targeting effect, great biocompability, and synergistic photothermal radiotherapy effect. This work suggests that such biocompatible FA-MoSe2@BSA NSs may be a promising multifunctional dual-modality tumor therapy agent for use in combination tumor therapy.

A Functional Immune System Is Required for the Systemic Genotoxic Effects of Localized Irradiation

PURPOSE

Nontargeted effects of ionizing radiation, by which unirradiated cells and tissues are also damaged, are a relatively new paradigm in radiobiology. We recently reported radiation-induced abscopal effects (RIAEs) in normal tissues; namely, DNA damage, apoptosis, and activation of the local and systemic immune responses in C57BL6/J mice after irradiation of a small region of the body. High-dose-rate, synchrotron-generated broad beam or multiplanar x-ray microbeam radiation therapy was used with various field sizes and doses. This study explores components of the immune system involved in the generation of these abscopal effects.

METHODS AND MATERIALS

The following mice with various immune deficiencies were irradiated with the microbeam radiation therapy beam: (1) SCID/IL2γR^-/- (NOD SCID gamma, NSG) mice, (2) wild-type C57BL6/J mice treated with an antibody-blocking macrophage colony-stimulating factor 1 receptor, which depletes and alters the function of macrophages, and (3) chemokine ligand 2/monocyte chemotactic protein 1 null mice. Complex DNA damage (ie, DNA double-strand breaks), oxidatively induced clustered DNA lesions, and apoptotic cells in tissues distant from the irradiation site were measured as RIAE endpoints and compared with those in wild-type C57BL6/J mice.

RESULTS

Wild-type mice accumulated double-strand breaks, oxidatively induced clustered DNA lesions, and apoptosis, enforcing our RIAE model. However, these effects were completely or partially abrogated in mice with immune disruption, highlighting the pivotal role of the immune system in propagation of systemic genotoxic effects after localized irradiation.

CONCLUSIONS

These results underline the importance of not only delineating the best strategies for tumor control but also mitigating systemic radiation toxicity.

Targeted and Off-Target (Bystander and Abscopal) Effects of Radiation Therapy: Redox Mechanisms and Risk/Benefit Analysis

SIGNIFICANCE

Radiation therapy (from external beams to unsealed and sealed radionuclide sources) takes advantage of the detrimental effects of the clustered production of radicals and reactive oxygen species (ROS). Research has mainly focused on the interaction of radiation with water, which is the major constituent of living beings, and with nuclear DNA, which contains the genetic information. This led to the so-called target theory according to which cells have to be hit by ionizing particles to elicit an important biological response, including cell death. In cancer therapy, the Poisson law and linear quadratic mathematical models have been used to describe the probability of hits per cell as a function of the radiation dose. Recent Advances: However, in the last 20 years, many studies have shown that radiation generates "danger" signals that propagate from irradiated to nonirradiated cells, leading to bystander and other off-target effects.

CRITICAL ISSUES

Like for targeted effects, redox mechanisms play a key role also in off-target effects through transmission of ROS and reactive nitrogen species (RNS), and also of cytokines, ATP, and extracellular DNA. Particularly, nuclear factor kappa B is essential for triggering self-sustained production of ROS and RNS, thus making the bystander response similar to inflammation. In some therapeutic cases, this phenomenon is associated with recruitment of immune cells that are involved in distant irradiation effects (called "away-from-target" i.e., abscopal effects).

FUTURE DIRECTIONS

Determining the contribution of targeted and off-target effects in the clinic is still challenging. This has important consequences not only in radiotherapy but also possibly in diagnostic procedures and in radiation protection.

Prevention of radiation-induced bystander effects by agents that inactivate cell-free chromatin released from irradiated dying cells

Radiation-induced bystander effect (RIBE) is a poorly understood phenomenon wherein non-targeted cells exhibit effects of radiation. We have reported that cell-free chromatin (cfCh) particles that are released from dying cells can integrate into genomes of surrounding healthy cells to induce DNA damage and inflammation. This raised the possibility that RIBE might be induced by cfCh released from irradiated dying cells. When conditioned media from BrdU-labeled irradiated cells were passed through filters of pore size 0.22 µm and incubated with unexposed cells, BrdU-labeled cfCh particles could be seen to readily enter their nuclei to activate H2AX, active Caspase-3, NFκB, and IL-6. A direct relationship was observed with respect to activation of RIBE biomarkers and radiation dose in the range of 0.1-0 Gy. We confirmed by FISH and cytogenetic analysis that cfCh had stably integrated into chromosomes of bystander cells and had led to extensive chromosomal instability. The above RIBE effects could be abrogated when conditioned media were pre-treated with agents that inactivate cfCh, namely, anti-histone antibody complexed nanoparticles (CNPs), DNase I and a novel DNA degrading agent Resveratrol-copper (R-Cu). Lower hemi-body irradiation with γ-rays (0.1-50 Gy) led to activation of H2AX, active Caspase-3, NFκB, and IL-6 in brain cells in a dose-dependent manner. Activation of these RIBE biomarkers could be abrogated by concurrent treatment with CNPs, DNase I and R-Cu indicating that activation of RIBE was not due to radiation scatter to the brain. RIBE activation was seen even when mini-beam radiation was delivered to the umbilical region of mice wherein radiation scatter to brain was negligible and could be abrogated by cfCh inactivating agents. These results indicate that cfCh released from radiation-induced dying cells are activators of RIBE and that it can be prevented by treatment with appropriate cfCh inactivating agents.

Addition of radiotherapy to the primary tumour in oligometastatic NSCLC: A systematic review and meta-analysis

Oligometastatic non-small cell lung cancer (NSCLC) has a discrete number of distant lesions (<5) that can be amenable to radical treatment. The treatment of the primary lung tumour in such stage IV cases is still debated. We conducted a systematic review and meta-analysis to evaluate the outcome of these patients and the added benefit in terms of overall survival (OS) and progression-free survival (PFS) when radical treatment of the primary tumour with radiotherapy (RT) was delivered. PubMed, EMBASE and Cochrane Library were systematically searched to identify relevant studies published up to July 2018. Prospective trials and retrospective series comparing RT vs no RT to the primary NSCLC in the presence of oligometastases were included. Hazard ratios (HRs) for OS and PFS were aggregated according to a fixed or random effect model. Twenty-one studies for a total of 924 synchronous oligometastatic NSCLC were analysed. Median OS and PFS were 20.4 and 12 months. Pooled 1-2-3 and 5-year OS were 70.3%, 43.5%, 29.3% and 20.2% respectively. Overall survival was improved with the addition of thoracic RT (HR = 0.44, 95%CI 0.32-0.6; P < 0.001). Similarly, RT added to the primary tumour increased PFS (HR = 0.42, 95%CI 0.33-0.55; P < 0.001). The only variable associated with the median OS was the year of publication with most recent series associated with a better outcome. In patients with oligometastatic NSCLC and disease controlled with ablative therapy of distant metastases, a consolidation with radical RT to the primary tumour is associated with better survival and could be considered as a treatment modality in selected cases.

Cytokines and radiation-induced pulmonary injuries

Radiation therapy is one of the most common treatment strategies for thorax malignancies. One of the considerable limitations of this therapy is its toxicity to normal tissue. The lung is the major dose-limiting organ for radiotherapy. That is because ionizing radiation produces reactive oxygen species that induce lesions, and not only is tumor tissue damaged, but overwhelming inflammatory lung damage can occur in the alveolar epithelium and capillary endothelium. This damage may result in radiation-induced pneumonitis and/or fibrosis. While describing the lung response to irradiation generally, the main focus of this review is on cytokines and their roles and functions within the individual stages. We discuss the relationship between radiation and cytokines and their direct and indirect effects on the formation and development of radiation injuries. Although this topic has been intensively studied and discussed for years, we still do not completely understand the roles of cytokines. Experimental data on cytokine involvement are fragmented across a large number of experimental studies; hence, the need for this review of the current knowledge. Cytokines are considered not only as molecular factors involved in the signaling network in pathological processes, but also for their diagnostic potential. A concentrated effort has been made to identify the significant immune system proteins showing positive correlation between serum levels and tissue damages. Elucidating the correlations between the extent and nature of radiation-induced pulmonary injuries and the levels of one or more key cytokines that initiate and control those damages may improve the efficacy of radiotherapy in cancer treatment and ultimately the well-being of patients.

Serum cytokine profiles and metabolic tumor burden in patients with non-small cell lung cancer undergoing palliative thoracic radiation therapy

Purpose

Radiation therapy effectively kills cancer cells and elicits local effects in the irradiated tissue. The aim of this study was to investigate the kinetics of cytokines in the serum of patients with lung cancer undergoing radiation therapy and to identify associations with metabolic tumor burden as determined by 2-deoxy-2-fluoro-D-glucose (¹⁸F-FDG) positron emission tomography (PET).

Methods and materials

Forty-five patients with advanced non-small cell lung cancer were included in a phase 2 clinical trial and randomized between fractionated thoracic radiation therapy alone or concurrent with an epidermal growth factor receptor inhibitor. Blood was sampled at 4 different time points: prior to treatment, midtherapy, at the end of therapy, and 6 to 8 weeks after the start of treatment. The serum concentrations of 48 cytokines and 9 matrix metalloproteinases were measured with multiplex immunoassays. A subset of patients was examined by ¹⁸F-FDG PET/computed tomography before, during, and after radiation therapy. The maximum standardized uptake values (SUV_max) of the primary lung tumor, whole-body metabolic tumor volume, and total lesion glycolysis were calculated, and correlations between the PET parameters and cytokines were investigated.

Results

The SUV_max decreased from baseline through midtherapy to posttherapy ¹⁸F-FDG PET/computed tomography (P = .018). The serum levels of C-C motif chemokine ligand (CCL) 23, CCL24, C-X3-C motif chemokine ligand 1, and interleukin-8 (C-X-C motif ligand [CXCL]8) were significantly correlated to SUV_max, metabolic tumor volume, and total lesion glycolysis before, during, and after radiation therapy. CXCL2 (P = .030) and CXCL6 (P = .010) decreased after the start of therapy and changed significantly across the sample time points. Serum concentrations of CCL15 (P = .031), CXCL2 (P = .028), and interleukin-6 (P = .007) were positively correlated to the irradiated volume during the second week of treatment.

Conclusions

Cytokine serum levels vary and correlate with metabolic tumor burden in patients with advanced non-small cell lung cancer undergoing palliative thoracic radiation therapy.

Tumor molecular profiling of responders and non-responders following pembrolizumab monotherapy in chemotherapy resistant advanced cervical cancer

Optimal treatment for advanced cervical cancer after first line chemotherapy remains undefined. Immune checkpoint inhibition with pembrolizumab, a programmed cell death protein 1(PD-1) inhibitor, is under investigation. We analyzed the micro-environmental and molecular genetic profile of tumors from 4 patients with metastatic cervical cancer treated with off-label second-line pembrolizumab in an effort to identify predictive biomarkers. All patients received 2 mg/kg of pembrolizumab, 3-weekly until disease progression. Immunohistochemistry(IHC) for PD-1, PD-L1, CD3 and CD8, as well as next generation sequencing (NGS) for 50 cancer-related genes were performed on tumor samples. All patients tolerated treatment well with no discontinuation of treatment due to toxicity. One patient experienced dramatic and prolonged partial response, and remains stable on pembrolizumab with a progression free survival (PFS) of 21 months at the time of reporting of this series. Three patients experienced disease progression as best response. In the exceptional responder, there was no tumoral expression of PD-L1, however, combined positive score (CPS) for PD-L1 was 1 and we identified somatic mutations in ERBB4(R612W), PIK3CA(E542K) and RB1(E365K). In 2 patients, despite progressive disease defined by RECIST v1.1, symptom stabilization on pembrolizumab was observed. The tumors of both patients had PD-1 expression in ≥1% of stromal lymphocytes. All patients with response or clinical benefit had CPS for PD-L1 ≥ 1. NGS revealed PIK3CA mutations in 3 tumors. Pembrolizumab is a promising therapeutic option in advanced cervical cancer. Further evaluation of biomarkers may guide optimal patient selection.

Radiation therapy-induced metastasis: radiobiology and clinical implications

Radiation therapy is an effective means of achieving local control in a wide range of primary tumours, with the reduction in the size of the tumour(s) thought to mediate the observed reductions in metastatic spread in clinical trials. However, there is evidence to suggest that the complex changes induced by radiation in the tumour environment can also present metastatic risks that may counteract the long-term efficacy of the treatment. More than 25 years ago, several largely theoretical mechanisms by which radiation exposure might increase metastatic risk were postulated. These include the direct release of tumour cells into the circulation, systemic effects of tumour and normal tissue irradiation and radiation-induced changes in tumour cell phenotype. Here, we review the data that has since emerged to either support or refute these putative mechanisms focusing on how the unique radiobiology underlying modern radiotherapy modalities might alter these risks.

Localized Synchrotron Irradiation of Mouse Skin Induces Persistent Systemic Genotoxic and Immune Responses

The importance of nontargeted (systemic) effects of ionizing radiation is attracting increasing attention. Exploiting synchrotron radiation generated by the Imaging and Medical Beamline at the Australian Synchrotron, we studied radiation-induced nontargeted effects in C57BL/6 mice. Mice were locally irradiated with a synchrotron X-ray broad beam and a multiplanar microbeam radiotherapy beam. To assess the influence of the beam configurations and variations in peak dose and irradiated area in the response of normal tissues outside the irradiated field at 1 and 4 days after irradiation, we monitored oxidatively induced clustered DNA lesions (OCDL), DNA double-strand breaks (DSB), apoptosis, and the local and systemic immune responses. All radiation settings induced pronounced persistent systemic effects in mice, which resulted from even short exposures of a small irradiated area. OCDLs were elevated in a wide variety of unirradiated normal tissues. In out-of-field duodenum, there was a trend for elevated apoptotic cell death under most irradiation conditions; however, DSBs were elevated only after exposure to lower doses. These genotoxic events were accompanied by changes in plasma concentrations of macrophage-derived cytokine, eotaxin, IL10, TIMP1, VEGF, TGFβ1, and TGFβ2, along with changes in tissues in frequencies of macrophages, neutrophils, and T lymphocytes. Overall, our findings have implications for the planning of therapeutic and diagnostic radiation treatments to reduce the risk of radiation-related adverse systemic effects. Cancer Res; 77(22); 6389-99. ©2017 AACR.