Current Status of Targeted Radioprotection and Radiation Injury Mitigation and Treatment Agents: A Critical Review of the Literature

Tubarial gland sparing with intensity modulated radiation therapy for oropharyngeal cancers: A pilot study of dosimetric feasibility

BACKGROUND

Tubarial glands are a new organ at risk for head and neck cancer radiation therapy (RT). We aimed to study the feasibility of sparing them using intensity-modulated radiation therapy (IMRT).

METHODS

Tubarial glands were delineated for 17 patients with oropharyngeal carcinoma receiving definitive RT, and treatment plans were re-optimized to spare dose to the tubarial glands while maintaining target coverage. A paired t test was performed to compare the mean dose of tubarial glands and target coverage.

RESULTS

The difference in mean doses was 4.9 and 7.0 Gy for the ipsilateral and contralateral tubarial glands, respectively (p < 0.01). The mean dose to tubarial gland was ≤39 Gy in 35% versus 47% (ipsilateral) and 70% versus 100% (contralateral) in clinical and re-optimized plans, respectively. Re-optimized ipsilateral tubarial gland mean ≤39 Gy was achieved more commonly in patients with base of tongue versus tonsil primaries (86% vs. 20%, p = 0.02).

CONCLUSION

This pilot study demonstrates the dosimetric feasibility of tubarial gland sparing with IMRT. Dosimetric constraints need to be determined with larger studies.

Protein-coated cobalt oxide-hydroxide nanospheres deliver photosensitizer IR780 iodide for near-infrared light-triggered photodynamic/photothermal/chemodynamic therapy against colon cancer

Phototherapy has garnered worldwide attention for its minimal invasiveness, controllability, and spatial selectivity in treating cancer. One promising approach involves the use of near-infrared dye IR780, which demonstrates both photodynamic therapy (PDT) and photothermal therapy (PTT) effects under 808 nm laser irradiation. However, this hydrophobic dye's toxicity and limited tumor targeting ability severely hamper its suitability for cancer applications. Herein, a biocompatible nanoplatform CoOOH-IR780@BSA (CoIRB) is developed to efficiently deliver IR780 and provide multi-mode treatments for colon tumors. Due to the nanocarrier coating, CoIRB nanoparticles demonstrated reliable dispersion and stability, and their biotoxicity was substantially reduced for safer blood circulation, which overcame the biological barrier of IR780. The nanoplatform has also shown considerable results in phototherapy in vivo and in vitro experiments, with successful inhibition of MC38 tumor growth through intravenous administration. Additionally, the introduction of cobalt ions could induce Fenton-like reactions to activate the production of toxic hydroxyl radicals (˙OH), exerting an assisted chemodynamic therapy (CDT) effect. Notably, these nanodrugs also exhibited potential as scavengers of reductive glutathione (GSH) and hydrogen sulfide (H2S), leading to amplifying oxidative damage of reactive oxygen species (ROS). Overall, the versatile therapeutic platform, CoIRB, has opened up considerable prospects as a biotherapeutic option for combining PDT/PTT/CDT against colon cancer.

Exploring Natural Products as Radioprotective Agents for Cancer Therapy: Mechanisms, Challenges, and Opportunities

Radiotherapy is an important cancer treatment. However, in addition to killing tumor cells, radiotherapy causes damage to the surrounding cells and is toxic to normal tissues. Therefore, an effective radioprotective agent that prevents the deleterious effects of ionizing radiation is required. Numerous synthetic substances have been shown to have clear radioprotective effects. However, most of these have not been translated for use in clinical applications due to their high toxicity and side effects. Many medicinal plants have been shown to exhibit various biological activities, including antioxidant, anti-inflammatory, and anticancer activities. In recent years, new agents obtained from natural products have been investigated by radioprotection researchers, due to their abundance of sources, high efficiency, and low toxicity. In this review, we summarize the mechanisms underlying the radioprotective effects of natural products, including ROS scavenging, promotion of DNA damage repair, anti-inflammatory effects, and the inhibition of cell death signaling pathways. In addition, we systematically review natural products with radioprotective properties, including polyphenols, polysaccharides, alkaloids, and saponins. Specifically, we discuss the polyphenols apigenin, genistein, epigallocatechin gallate, quercetin, resveratrol, and curcumin; the polysaccharides astragalus, schisandra, and Hohenbuehelia serotina; the saponins ginsenosides and acanthopanax senticosus; and the alkaloids matrine, ligustrazine, and β-carboline. However, further optimization through structural modification, improved extraction and purification methods, and clinical trials are needed before clinical translation. With a deeper understanding of the radioprotective mechanisms involved and the development of high-throughput screening methods, natural products could become promising novel radioprotective agents.

Adhesive Ergothioneine Hyaluronate Gel Protects against Radiation Gastroenteritis by Alleviating Apoptosis, Inflammation, and Gut Microbiota Dysbiosis

Radiation gastroenteritis represents one of the most prevalent and hazardous complications of abdominopelvic radiotherapy, which not only severely reduces patients' life quality but also restricts radiotherapy efficacy. However, there is currently no clinically available oral radioprotector for this threatening disease due to its complex pathogenesis and the harsh gastrointestinal environment. To this end, this study developed a facile but effective oral radioprotector, ergothioneine hyaluronate (EGT@HA) gel, protecting against radiation gastroenteritis by synergistically regulating oxidative stress, inflammation, and gut microbiota. In vitro and cellular experiments verified the chemical stability and free radical scavenging ability of EGT and its favorable cellular radioprotective efficacy by inhibiting intracellular reactive oxidative species (ROS) generation, DNA damage, mitochondrial damage, and apoptosis. At the in vivo level, EGT@HA with prolonged gastrointestinal residence mitigated radiation-induced gastrointestinal tissue injury, apoptosis, neutrophil infiltration, and gut flora dysbiosis. For the first time, this work investigated the protective effects of EGT@HA gel on radiation gastroenteritis, which not only hastens the advancement of the novel gastrointestinal radioprotector but also provides a valuable gastrointestinal radioprotection paradigm by synergistically modulating oxidative stress, inflammation, and gut microbiota disturbance.

Radioprotective countermeasures for radiation injury (Review)

A series of physiological and pathological changes occur after radiotherapy and accidental exposure to ionizing radiation (IR). These changes cause serious damage to human tissues and can lead to death. Radioprotective countermeasures are radioprotective agents that prevent and reduce IR injury or have therapeutic effects. Based on a good understanding of radiobiology, a number of protective agents have achieved positive results in early clinical trials. The present review grouped known radioprotective agents according to biochemical categories and potential clinical use, and reviewed radiation countermeasures, i.e., radioprotectors, radiation mitigators and radiotherapeutic agents, with an emphasis on their current status and research progress. The aim of the present review is to facilitate the selection and application of suitable radioprotectors for clinicians and researchers, to prevent or reduce IR injury.

Discovery of the radio-protecting effect of Ecliptae Herba, its constituents and targeting p53-mediated apoptosis in vitro and in vivo

Radiation protection drugs are often accompanied by toxicity, even amifostine, which has been the dominant radio-protecting drug for nearly 30 years. Furthermore, there is no therapeutic drug for radiation-induced intestinal injury (RIII). This paper intends to find a safe and effective radio-protecting ingredient from natural sources. The radio-protecting effect of Ecliptae Herba (EHE) was discovered preliminarily by antioxidant experiments and the mouse survival rate after ¹³⁷Cs irradiation. EHE components and blood substances in vivo were identified through UPLC‒Q-TOF. The correlation network of "natural components in EHE-constituents migrating to blood-targets-pathways" was established to predict the active components and pathways. The binding force between potential active components and targets was studied by molecular docking, and the mechanism was further analyzed by Western blotting, cellular thermal shift assay (CETSA), and ChIP. Additionally, the expression levels of Lgr5, Axin2, Ki67, lysozyme, caspase-3, caspase-8,8-OHdG, and p53 in the small intestine of mice were detected. It was found for the first time that EHE is active in radiation protection and that luteolin is the material basis of this protection. Luteolin is a promising candidate for RⅢ. Luteolin can inhibit the p53 signaling pathway and regulate the BAX/BCL2 ratio in the process of apoptosis. Luteolin could also regulate the expression of multitarget proteins related to the same cell cycle.

Atorvastatin Attenuates Radiotherapy-Induced Intestinal Damage through Activation of Autophagy and Antioxidant Effects

Abdominal or pelvic radiotherapy (RT) often results in small intestinal injury, such as apoptosis of epithelial cells and shortening of the villi. Atorvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has many biological effects including cholesterol reduction, protection from cell damage, and autophagy activation. To reduce the extent of radiotherapy- (RT-) induced enteritis, we investigated the protective effects of atorvastatin against RT-induced damage of the intestinal tract. In this study, C57BL/6 mice were randomly distributed into the following groups (n = 8 per group): (1) control group: mice were fed water only, (2) atorvastatin group (Ator): mice were administered atorvastatin, (3) irradiation group (IR): mice received abdominal RT, (4) Ator+IR group: mice received abdominal RT following atorvastatin administration, and (5) Ator+IR+3-MA group: abdominal RT following atorvastatin and 3-methyladenine (an autophagy inhibitor) administration. Based on the assessment of modified Chiu's injury score and villus/crypt ratio, we found that atorvastatin administration significantly reduced intestinal mucosal damage induced by RT. Atorvastatin treatment reduced apoptosis (cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase), DNA damage (γH2AX and 53BP1), oxidative stress (OS, 4-hydroxynonenal), inflammatory molecules (phospho-NF-κB p65 and TGF-β), fibrosis (collagen I and collagen III), barrier leakage (claudin-2 and fluorescein isothiocyanate-dextran), disintegrity (fatty acid-binding protein 2), and dysfunction (lipopolysaccharide) caused by RT in small intestinal tissue. In addition, atorvastatin upregulated the expression of autophagy-active molecules (LC3B), antioxidants (heme oxygenase 1 and thioredoxin 1), and tight junction proteins (occludin and zonula occludens 1). However, the biological functions of atorvastatin in decreasing RT-induced enteritis were reversed after the administration of 3-MA; the function of antioxidant molecules and activity of thioredoxin reductase were independent of autophagy activation. Our results indicate that atorvastatin can effectively relieve RT-induced enteritis through autophagy activation and associated biological functions, including maintaining integrity and function and decreasing apoptosis, DNA damage, inflammation, OS, and fibrosis. It also acts via its antioxidative capabilities.

Submandibular gland transfer for the prevention of radiation-induced xerostomia in oropharyngeal cancer: Dosimetric impact in the intensity modulated radiotherapy era

BACKGROUND

Submandibular gland (SMG) transfer decreased radiation-associated xerostomia in the 2/3-dimensional radiotherapy era. We evaluated the dosimetric implications of SMG transfer on modern intensity modulated radiotherapy (IMRT) plans.

METHODS

Eighteen oropharynx cancer patients underwent SMG transfer followed by IMRT; reoptimized plans using the baseline SMG location were generated. Mean salivary gland, oral cavity, and larynx doses were compared between clinical plans and reoptimized plans.

RESULTS

No statistically significant difference in mean SMG dose (27.53 Gy vs. 29.61 Gy) or total salivary gland dose (26.12 Gy vs. 26.41 Gy) was observed with or without SMG transfer (all p > 0.05). Mean oral cavity and larynx doses were not statistically different. Neither tumor site, target volume crossing midline, stage, nor salivary gland volumes were associated with mean doses.

CONCLUSIONS

Salivary gland doses were similar with or without SMG transfer. IMRT likely decreases the benefit of SMG transfer on the risk of radiation-associated xerostomia.

Comparative Study of Radiation-induced Lung Injury Model in Two Strains of Mice

Radiation-induced lung injury (RILI) is a common complication of radiotherapy for thoracic tumor. Its incidence rate is as high as 20%. At present, there is no effective treatment in clinical practice. However, to study the mechanism of radiation-induced lung injury, we should first establish an appropriate animal model. In a series of scientific studies on RILI, mice are the animals most often chosen by researchers. However, there are few reports on which strain of mice is more suitable as a model of RILI. In this study, Kunming (KM) and C57BL/6 strains of mice were used as research objects to find the most suitable mice to replicate the RILI model. C57BL/6 mice and KM mice were exposed to irradiation at a dose of 20 Gy. The lung tissue of C57BL/6 mice exposed to radiation showed dilation and hyperemia of capillaries, infiltration of inflammatory cells, and thickening of alveolar septum, while the lung tissue of KM mice exposed to radiation was not as obvious as that of C57BL/6 mice. After irradiation, the expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in the lung tissue of C57BL/6 mice was significantly increased, while the expression of IL-6 and TNF-α in KM mice was almost unchanged. These studies showed that C57BL/6 mice are more suitable for the model of radiation-induced lung injury because of sensitive inflammatory reaction and the pathological changes of lung tissue.

Research progress on radioprotective effects of bee products

Radiation exposure is an on going and serious threat in military and public health concern. There is an unmet need for effective preventative or mitigative treatments against radiation-induced injuries. The handful of Food and Drug Administration in the US approved radiation protection agents cannot be widely used due to their side effects. Some natural nontoxic compounds such as bee products have been reported to prevent and treat radiation-induced injuries (e.g. scavenging free radicals, inhibiting cell apoptosis and reducing DNA damage), indicating that they may be a potential option as a safe radioprotective agent. Bee products are nontoxic and have no known side effects on the human body, and are effective in the field of radiation protection. They are expected to be interesting drug candidates for preventing and treating radiation-induced injuries. This article reviews the prevention and treatment of bee products on radiation-induced injuries.

The protective effect of oleuropein against radiation-induced cytotoxicity, apoptosis, and genetic damage in cultured human lymphocytes

PURPOSE

The aim of this study was to evaluate the effects of oleuropein radiation protection and to find an effective radioprotector.

MATERIALS AND METHOD

Human mononuclear cells were treated with oleuropein at the concentration of 100 μM (optimum concentration), incubated for 24 h, and then exposed to 2 Gy gamma-rays. The anti-radiation effect of oleuropein was assessed by MTT assay, flow cytometry, comet assay, and micronucleus (MN) assay.

RESULTS

It was found that pretreatment with oleuropein (25, 50, 75, 100, 200, 400, and 800 nM, and 1, 5, 10, 15, 20, 25, 30, 40, 50, 75, 100, 125, 150, 175, and 200 µM) significantly increased the percentage of cell viability compared to the irradiated group (p < .001). Moreover, oleuropein treatment with the above concentrations defined without gamma-ray did not show any cytotoxicity effect in human mononuclear cells. The LD_50/24h dose was calculated as 2.9 Gy, whereas by 200, 150, 50, and 100 µM oleuropein prior to radiation (1, 2,and 4 Gy), radiation LD_50/24h increased to 3.36, 3.54, 3.81, and >4 Gy, in that order. A very noticeable dose-modifying factor (DMF) of 1.16, 1.23, 1.31, and 1.72 was observed for 200, 150, 50, and 100 µM, in order. Therefore, 100 µM of oleuropein was selected as the desirable dose for radio-protection trial, and 2 Gy gamma-rays were used for further research. Human mononuclear cells treatment with oleuropein (100 µM) prior to 2 Gy gamma-rays significantly decreased apoptosis, genomic damage, and MN occurrence in human mononuclear caused by gamma-radiation (p < .001). Furthermore, treatment with oleuropein (100 µM) without radiation did not lead to apoptosis, genotoxicity, or clastogenic effects caused by oleuropein in human mononuclear cells.

CONCLUSION

The results revealed that oleuropein is able to significantly reduce cytotoxicity, apoptosis, genotoxic, and clastogenic effects of gamma-rays.

Radioprotection and Radiomitigation: From the Bench to Clinical Practice

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

Rosmarinic Acid Prevents Radiation-Induced Pulmonary Fibrosis Through Attenuation of ROS/MYPT1/TGFβ1 Signaling Via miR-19b-3p

The mechanism of pulmonary fibrosis caused by irradiation remains obscure. Since rosmarinic acid (RA) have anti-oxidant and anti-inflammatory properties, we aimed to evaluate the effect of RA on the X-ray-induced lung injury. Male rats received RA (30, 60, or 120 mg/kg) 7 days before 15 Gy of X-ray irradiation. Here, we showed that RA reduced X-ray-induced the expression of inflammatory related factors, and the level of reactive oxygen species. RA down-regulated the phosphorylation of nuclear factor kappa-B (NF-κB). We found that thoracic tumor patients whose lung regions received radiation showed lower level of microRNA-19b-3p (miR-19b-3p). Furthermore, we provided evidence that miR-19b-3p targets myosin phosphatase target subunit 1 (MYPT1), and RA attenuated RhoA/Rock signaling through upregulating miR-19b-3p, leading to the inhibition of fibrosis. In conclusion, RA may be an effective agent to relieve the pulmonary fibrosis caused by radiotherapy of thoracic tumor.

Small Nucleolar RNA, C/D Box 16 (SNORD16) Acts as a Potential Prognostic Biomarker in Colon Cancer

Colon cancer (CC) is considered one of the most common and lethal malignancies occurring both in male and female. Its widespread prevalence demonstrates the need for novel diagnostic and prognostic biomarkers for CC. Emerging evidence has shown that small nucleolar RNAs play critical roles in tumor development. In this study, we investigated the expression profile and functions of SNORD16 in CC. Our data showed that SNORD16, rather than its host gene (RPL4), was upregulated in CC cell lines. Compared to matched adjacent normal tissues, CC tissues showed higher SNORD16 expression levels, and no correlation was found between SNORD16 and RPL4. Patients with high SNORD16 expression levels had a worse prognosis, and multivariate analysis showed the high SNORD16 expression was an independent prognostic factor for CC. In vitro gain- and loss-of-function studies revealed that SNORD16 can promote cell growth, proliferation, migration, and invasion of CC cells by inhibiting apoptosis. These results suggested that SNORD16 has an oncogenic role in CC and might be a novel diagnostic and prognostic biomarker for CC.

A novel class of small molecule inhibitors with radioprotective properties

The goal of this study was to develop novel radioprotective agents targeting the intrinsic apoptotic pathway and thus decreasing the radiation-induced damage. For that purpose, we designed, synthesized and analyzed ten new compounds based on the 1-(4-(2-hydroxyethyl)piperazin-1-yl)-3-phenoxypropan-2-ol leading structure. The cytotoxicity of the newly synthesized substances was tested in vitro on cell lines derived from different progenitor cells by WST-1 proliferation assay. MTT test was utilized to assess half-maximal inhibitory concentrations and maximum tolerated concentrations of novel compounds in A-549 cells. Screening for radioprotective properties was performed using flow-cytometry in MOLT-4 cells exposed to ⁶⁰Co ionizing gamma radiation. Selected candidates underwent in vivo testing in C57Bl/6 J mice having a positive impact on their immunological status. In summary, we report here promising compounds with radioprotective effect in vivo.

Serum amyloid A1 as a biomarker for radiation dose estimation and lethality prediction in irradiated mouse

Background

Fast and reliable biomarkers are needed to distinguish whether individuals were exposed or not to radiation and assess radiation dose, and to predict the severity of radiation damage in a large-scale radiation accident. Serum amyloid A1 (SAA1) is a protein induced by multiple factors including inflammatory. Therefore, this study aimed at exploring the role of SAA1 in the radiation dose estimation and lethality prediction after radiation.

Methods

C57BL/6J female mice were exposed to total body irradiation (TBI) at different doses and time points and amifostine, a drug used to reduce the side effects of radiotherapy, was injected before irradiation. Patients with nasopharyngeal carcinoma subjected to radiotherapy were used as the irradiation model in humans.

Results

A moderate SAA1 increase was observed at 6 hours in serum samples from irradiated mice at all doses used, with a peak at 12 hours, then decreased to day 3 after exposure. A second SAA1 increase was observed from day 5 to 7, which was associated to subsequent lethality. Treatment with amifostine before irradiation could prevent mice death and inhibit the second SAA1 increase. SAA1 increase after radiation was confirmed in human serum of nasopharyngeal carcinoma patients after radiotherapy.

Conclusions

Serum SAA1 levels could represent a biomarker for radiation dose estimation and its second increase might be a useful lethality indicator after radiation in a mouse model.

Dual benefit of supplementary oral 5-aminolevulinic acid to pelvic radiotherapy in a syngenic prostate cancer model

BACKGROUND

Normal tissue damage caused by radiotherapy remains the largest dose-limiting factor in radiotherapy for cancer. Therefore, the aim of this study was to investigate the supplementary oral 5-aminolevulinic acid (ALA) to standard radiation therapy as a novel radioprotective approach that would not compromise the antitumor effect of radiation in normal rectal and bladder mucosa in a syngenic prostate cancer (PCa) model.

METHODS

To evaluate the radiosensitizing effect of ALA in vitro, clonogenic survival assays were performed in DU145, PC3, and MyC-CaP cell lines. To evaluate the effect of ALA in vivo a single dose (25 Gy) of radiation with or without ALA was given to healthy mice. Next, a syngenic PCa model of MyC-CaP cells in FVB mice was created, and multiple doses (12 Gy total) of radiation were administered to the mouse pelvic area with or without ALA administration. Resected tumors, recta, and urinary bladders were immunostained with antibodies against Ki-67, γ-H2AX, CD204, and uroplakin-III. Total RNA levels in recta and urinary bladders were analyzed via RT2 Profiler polymerase chain reaction (PCR) arrays related to "Stress & Toxicity PathwayFinder," "Mitochondria," and "Inflammasomes."

RESULTS

The addition of in vitro single or in vivo repeated administration of exogenous ALA acted as a radiosensitizer for PCa cells. Rectal toxicity was characterized by histological changes including loss of surface epithelium, fibrosis, severe DNA damage, and the aggregation of M2 macrophages. Urinary bladder toxicity was characterized by bladder wall thickening and urothelium denuding. The higher dose (300 mg/kg/day) of ALA exerted a better radioprotective profile than the lower dose (30 mg/kg/day) in normal recta and urinary bladders. Out of the 252 genes tested, 35 (13.4%) were detected as relevant genes which may be involved in the radioprotective role of ALA administration. These included interleukin-1a (IL-1a), IL-1b, IL-12, chemokine (C-X-C motif) ligand 1 (CXCL1), CXCL3, and NLRP3.

CONCLUSIONS

Our study provides novel and comprehensive insights into the dual benefits including radiosensitizing PCa tumor tissues and radioprotection of normal pelvic organs from radiation therapy. Knowledge of the underlying mechanism will facilitate the search for optimal treatment parameters for supplemental oral ALA during radiotherapy for PCa.

Molecular and epigenetic regulatory mechanisms of normal stem cell radiosensitivity

Ionizing radiation (IR) therapy is a major cancer treatment modality and an indispensable auxiliary treatment for primary and metastatic cancers, but invariably results in debilitating organ dysfunctions. IR-induced depletion of neural stem/progenitor cells in the subgranular zone of the dentate gyrus in the hippocampus where neurogenesis occurs is considered largely responsible for deficiencies such as learning, memory, and spatial information processing in patients subjected to cranial irradiation. Similarly, IR therapy-induced intestinal injuries such as diarrhea and malabsorption are common side effects in patients with gastrointestinal tumors and are believed to be caused by intestinal stem cell drop out. Hematopoietic stem cell transplantation is currently used to reinstate blood production in leukemia patients and pre-clinical treatments show promising results in other organs such as the skin and kidney, but ethical issues and logistic problems make this route difficult to follow. An alternative way to restore the injured tissue is to preserve the stem cell pool located in that specific tissue/organ niche, but stem cell response to ionizing radiation is inadequately understood at the molecular mechanistic level. Although embryonic and fetal hypersensity to IR has been very well known for many decades, research on embryonic stem cell models in culture concerning molecular mechanisms have been largely inconclusive and often in contradiction of the in vivo observations. This review will summarize the latest discoveries on stem cell radiosensitivity, highlighting the possible molecular and epigenetic mechanism(s) involved in DNA damage response and programmed cell death after ionizing radiation therapy specific to normal stem cells. Finally, we will analyze the possible contribution of stem cell-specific chromatin's epigenetic constitution in promoting normal stem cell radiosensitivity.

Hepatocyte Transplantation: Quo Vadis?

Orthotopic liver transplantation (OLT) has been effective in managing end-stage liver disease since the advent of cyclosporine immunosuppression therapy in 1980. The major limitations of OLT are organ supply, monetary cost, and the burden of lifelong immunosuppression. Hepatocyte transplantation, as a substitute for OLT, has been an exciting topic of investigation for several decades. HT is potentially minimally invasive and can serve as a vehicle for delivery of personalized medicine through autologous cell transplant after modification ex vivo. However, 3 major hurdles have prevented large-scale clinical application: (1) availability of transplantable cells; (2) safe and efficient ex vivo gene therapy methods; and (3) engraftment and repopulation efficiency. This review will discuss new sources for transplantable liver cells obtained by lineage reprogramming, clinically acceptable methods of genetic manipulation, and the development of hepatic irradiation-based preparative regimens for enhancing engraftment and repopulation of transplanted hepatocytes. We will also review the results of the first 3 patients with genetic liver disorders who underwent preparative hepatic irradiation before hepatocyte transplantation.

Randomized, double-blind, placebo-controlled phase II trial of nanocurcumin in prostate cancer patients undergoing radiotherapy

Clinical potential of curcumin in radiotherapy (RT) setting is outstanding and of high interest. The main purpose of this randomized controlled trial (RCT) was to assess the beneficial role of nanocurcumin to prevent and/or mitigate radiation-induced proctitis in prostate cancer patients undergoing RT. In this parallel-group study, 64 eligible patients with prostate cancer were randomized to receive either oral nanocurcumin (120 mg/day) or placebo 3 days before and during the RT course. Acute toxicities including proctitis and cystitis were assessed weekly during the treatment and once thereafter using CTCAE v.4.03 grading criteria. Baseline-adjusted hematologic nadirs were also analyzed and compared between the two groups. The patients undergoing definitive RT were followed to evaluate the tumor response. Nanocurcumin was well tolerated. Radiation-induced proctitis was noted in 18/31 (58.1%) of the placebo-treated patients versus 15/33 (45.5%) of nanocurcumin-treated patients (p = 0.313). No significant difference was also found between the two groups with regard to radiation-induced cystitis, duration of radiation toxicities, hematologic nadirs, and tumor response. In conclusion, this RCT was underpowered to indicate the efficacy of nanocurcumin in this clinical setting but could provide a considerable new translational insight to bridge the gap between the laboratory and clinical practice.

Radiation biology and oncology in the genomic era

Radiobiology research is building the foundation for applying genomics in precision radiation oncology. Advances in high-throughput approaches will underpin increased understanding of radiosensitivity and the development of future predictive assays for clinical application. There is an established contribution of genetics as a risk factor for radiotherapy side effects. An individual's radiosensitivity is an inherited polygenic trait with an architecture that includes rare mutations in a few genes that confer large effects and common variants in many genes with small effects. Current thinking is that some will be tissue specific, and future tests will be tailored to the normal tissues at risk. The relationship between normal and tumor cell radiosensitivity is poorly understood. Data are emerging suggesting interplay between germline genetic variation and epigenetic modification with growing evidence that changes in DNA methylation regulate the radiosensitivity of cancer cells and histone acetyltransferase inhibitors have radiosensitizing effects. Changes in histone methylation can also impair DNA damage response signaling and alter radiosensitivity. An important effort to advance radiobiology in the genomic era was establishment of the Radiogenomics Consortium to enable the creation of the large radiotherapy cohorts required to exploit advances in genomics. To address challenges in harmonizing data from multiple cohorts, the consortium established the REQUITE project to collect standardized data and genotyping for ~5,000 patients. The collection of detailed dosimetric data is important to produce validated multivariable models. Continued efforts will identify new genes that impact on radiosensitivity to generate new knowledge on toxicity pathogenesis and tests to incorporate into the clinical decision-making process.

Interobserver reliability in describing radiographic lung changes after stereotactic body radiation therapy

PURPOSE

Radiographic lung changes after stereotactic body radiation therapy (SBRT) vary widely between patients. Standardized descriptions of acute (≤6 months after treatment) and late (>6 months after treatment) benign lung changes have been proposed but the reliable application of these classification systems has not been demonstrated. Herein, we examine the interobserver reliability of classifying acute and late lung changes after SBRT.

METHODS AND MATERIALS

A total of 280 follow-up computed tomography scans at 3, 6, and 12 months post-treatment were analyzed in 100 patients undergoing thoracic SBRT. Standardized descriptions of acute lung changes (3- and 6-month scans) include diffuse consolidation, patchy consolidation and ground glass opacity (GGO), diffuse GGO, patchy GGO, and no change. Late lung change classifications (12-month scans) include modified conventional pattern, mass-like pattern, scar-like pattern, and no change. Five physicians scored the images independently in a blinded fashion. Fleiss' kappa scores quantified the interobserver agreement.

RESULTS

The Kappa scores were 0.30 at 3 months, 0.20 at 6 months, and 0.25 at 12 months. The proportion of patients in each category at 3 and 6 months was as follows: Diffuse consolidation 11% and 21%; patchy consolidation and GGO 15% and 28%; diffuse GGO 10% and 11%; patchy GGO 15% and 15%; and no change 49% and 25%, respectively. The percentage of patients in each category at 12 months was as follows: Modified conventional 46%; mass-like 16%; scar-like 26%; and no change 12%. Uniform scoring between the observers occurred in 26, 8, and 14 cases at 3, 6, and 12 months, respectively.

CONCLUSIONS

Interobserver reliability scores indicate a fair agreement to classify radiographic lung changes after SBRT. Qualitative descriptions are insufficient to categorize these findings because most patient scans do not fit clearly into a single classification. Categorization at 6 months may be the most difficult because late and acute lung changes can arise at that time.

Diabetes mellitus and radiation induced lung injury after thoracic stereotactic body radiotherapy

BACKGROUND

Radiographic radiation induced lung injury (RILI) is frequently observed after stereotactic body radiotherapy (SBRT). Models of radiographic change can identify patient risk factors that predict clinical toxicity. We examined the association between radiographic lung changes and lung tissue dose-density response over time with clinical risk factors for RILI, such as diabetes.

METHODS

424 baseline and follow up CT scans at 3, 6, and 12 months post-treatment were analyzed in 116 patients (27 with diabetes) undergoing thoracic SBRT. Volumes of dense/hazy regions and lung parenchyma dose-density response curves were evaluated with respect to follow up time, diabetes, and other factors.

RESULTS

Dense and hazy tissue regions were larger in the diabetic population, with the effect most pronounced at 3 months. Similarly, dose-density response curves showed greater density change versus dose in the diabetic group (all p < 0.05). Diabetes, time, the interaction of diabetes and time, smoking status, African American race, baseline lung density, and tumor location were significantly associated with radiographic changes on mixed effect analyses. PTV size, pulmonary function, and medication exposure did not significantly impact RILI. Clinical grade 1-2 pneumonitis was more prevalent in diabetic patients (p = 0.02). However, radiographic change did not correlate with clinical pneumonitis.

CONCLUSIONS

The presence of diabetes and other clinical factors is associated with increased volume and density of radiographic RILI after lung SBRT, most prominently early after treatment. This is the first report demonstrating the increased severity of RILI after SBRT in diabetic patients. Increased caution treating diabetic patients may be warranted.

A Potential Biomarker for Predicting the Risk of Radiation-Induced Fibrosis in the Lung

Biomarkers could play an essential role during triage in the aftermath of a radiological event, where exposure to radiation will be heterogeneous and complicated by concurrent trauma. Used alongside biodosimetry, biomarkers can identify victims in need of treatment for acute radiation effects, and might also provide valuable information on later developing consequences that need to be addressed as part of a treatment strategy. Indeed, because the lung is particularly sensitive to radiation and resultant late effects not only affect quality of life, but can also lead to morbidity, the risk of developing downstream pulmonary complications in exposed individuals requires assessment. In this study, analyses of changes in pulmonary and circulating content of club cell secretory protein (CCSP) and surfactant protein D (SP-D), expressed by epithelial club cells and type II pneumocytes in the lung, respectively, were used to evaluate pulmonary epithelial damage in several lung injury models. Using a combined radiation exposure model, fibrosis-susceptible C57BL/6J (C57) and alveolitis-prone C3H/HeJ (C3H) mice received 5 Gy total-body irradiation plus 2.5-10 Gy whole-lung irradiation, and lung and plasma samples were collected throughout the course of the radiation response, at time points ranging from 24 h to 26 weeks postirradiation. Radiation significantly reduced bronchiole CCSP coverage in C57 mice at 26 weeks, a response that varied in extent among animals, but correlated with the severity of fibrosis in each animal. Interestingly, plasma CCSP content was elevated in C57 mice at multiple time points preceding and during the fibrotic period; this response that was not observed in C3H mice. Circulating CCSP/SP-D ratios, calculated as an index of lung integrity, were similarly increased throughout the time course in C57, but not C3H, mice. Furthermore, when the thoracic doses were reduced to subthreshold levels for fibrosis induction (2.5 or 7.5 Gy), although the CCSP/SP-D ratio in lung homogenates demonstrated dose-responsive changes, this was not reflected in the plasma ratios at acute and late time points. Importantly, plasma CCSP/SP-D ratios also were not significantly altered in C57 mice exposed to LPS, and only transiently decreased in influenza-exposed mice, demonstrating a level of specificity for radiation-induced lung injury. These results indicate that the CCSP/SP-D ratio, measured in plasma, is sensitive to individual variation in radiation sensitivity, correlates with fibrosis development, can be detected early after exposure and is specific to radiation-induced injury. This suggests that the CCSP/SP-D ratio may be useful as a biomarker of radiation-induced pulmonary fibrosis.

Use of recombinant Lactobacillus sakei for the prevention and treatment of radiation-induced enteritis

Radiation-induced enteritis is one of the most common complications in patients under radiotherapy at abdominal or pelvic cavity. Up to 50% of patients treated with pelvic radiotherapy has been reported radiation-induced acute enteritis, and half of them developed chronic enteritis. Overproduction of free radicals, activation of inflammatory pathways and vascular endothelial dysfunction were considered as the primary mechanisms of radiation-induced enteritis. Because probiotics have been demonstrated as a promising potential candidate for treating intestinal diseases, it may be a safer and more effective radioprotector for the enteritis compared to conventional chemical agents with inherent toxicities. Here, we propose that a recombinant Lactobacillus sakei would decrease the complications or symptoms significantly through against different pathogenic mechanisms simultaneously. Therefore, application of higher radiation dose for tumor control would be feasible when co-treating with recombinant Lactobacillus sakei.