Recent advances in the biology of heavy-ion cancer therapy

Prediction of Cell Survival Rate Based on Physical Characteristics of Heavy Ion Radiation

The effect of ionizing radiation on cells is a complex process dependent on several parameters. Cancer treatment commonly involves the use of radiotherapy. In addition to the effective killing of cancer cells, another key aspect of radiotherapy is the protection of healthy cells. An interesting position is occupied by heavy ion radiation in the field of radiotherapy due to its high relative biological effectiveness, making it an effective method of treatment. The high biological efficiency of heavy ion radiation can also pose a danger to healthy cells. The extent of cell death induced by heavy ion radiation in cells was investigated using statistical learning methods in this study. The objective was to predict the healthy cell survival rate based on the physical parameters of the available ionizing radiation. This paper is based on secondary research utilizing the PIDE database. Throughout this study, a local regression and a random forest model were generated. Their predictions were compared to the results of a linear-quadratic model commonly utilized in the field of ionizing radiation using various metrics. The relationship between dose and cell survival rate was examined using the linear-quadratic (LQM) model and local regression (LocReg). An R2 value of 88.43% was achieved for LQM and 89.86% for LocReg. Upon incorporating linear energy transfer, the random forest model attained an R2 value of 96.85%. In terms of RMSE, the linear-quadratic model yielded 9.5910-2, the local regression 9.2110-2, and the random forest 1.96 × 10-2 (lower values indicate better performance). All of these methods were also applied to a log-transformed dataset to decrease the right skewedness of the distribution of the datapoints. This significantly reduced the estimates made with LQM and LocReg (28% decrease in the case of R2), while the random forest retained nearly the same level of estimation as the untransformed data. In conclusion, it can be inferred that dose alone provides a somewhat satisfactory explanatory power for cell survival rate, but the inclusion of linear energy transfer can significantly enhance prediction accuracy in terms of variance and explanatory power.

Real-Time Time-Dependent Density Functional Theory for Simulating Nonequilibrium Electron Dynamics

The explicit real-time propagation approach for time-dependent density functional theory (RT-TDDFT) has increasingly become a popular first-principles computational method for modeling various time-dependent electronic properties of complex chemical systems. In this Perspective, we provide a nontechnical discussion of how this first-principles simulation approach has been used to gain novel physical insights into nonequilibrium electron dynamics phenomena in recent years. Following a concise overview of the RT-TDDFT methodology from a practical standpoint, we discuss our recent studies on the electronic stopping of DNA in water and the Floquet topological phase as examples. Our discussion focuses on how RT-TDDFT simulations played a unique role in deriving new scientific understandings. We then discuss existing challenges and some new advances at the frontier of RT-TDDFT method development for studying increasingly complex dynamic phenomena and systems.

Long-Term Outcomes of Ablative Carbon-Ion Radiotherapy for Central Non-Small Cell Lung Cancer: A Single-Center, Retrospective Study

The aim of this study is to assess the efficacy and safety of ablative carbon ion radiotherapy (CIRT) for early stage central non-small cell lung cancer (NSCLC). We retrospectively reviewed 30 patients who had received CIRT at 68.4 Gy in 12 fractions for central NSCLC in 2006-2019. The median age was 75 years, and the median Karnofsky Performance Scale score was 90%. All patients had concomitant chronic obstructive pulmonary disease, and 20 patients (67%) were considered inoperable. In DVH analysis, the median lung V5 and V20 were 15.5% and 10.4%, and the median Dmax, D0.5cc, D2cc of proximal bronchial tree was 65.6 Gy, 52.8 Gy, and 10.0 Gy, respectively. At a median follow-up of 43 months, the 3-year overall survival, disease-specific survival, and local control rates were 72.4, 75.8, and 88.7%, respectively. Two patients experienced grade 3 pneumonitis, but no grade ≥3 adverse events involving the mediastinal organs occurred. Ablative CIRT is feasible and effective for central NSCLC and could be considered as a treatment option, especially for patients who are intolerant of other curative treatments.

Safety and Efficacy of Single-Fraction Carbon-Ion Radiotherapy for Early-Stage Lung Cancer with Interstitial Pneumonia

Patients with lung cancer complicated by interstitial pneumonia (IP) often lose treatment options early owing to acute exacerbation of IP concerns. Carbon-ion radiotherapy (CIRT) can provide superior tumor control and low toxicity at high dose concentrations. We conducted a retrospective analysis of the efficacy and tolerability of a single-fraction CIRT using 50 Gy for IP-complicated lung cancer. The study included 50 consecutive patients treated between April 2013 and September 2022, whose clinical stage of lung cancer (UICC 7th edition) was 1A:1B:2A:2B = 32:13:4:1. Of these, 32 (64%) showed usual interstitial pneumonia patterns. With a median follow-up of 23.5 months, the 3-year overall survival (OS), cause-specific survival, and local control rates were 45.0, 75.4, and 77.8%, respectively. The median lung V5 and V20 were 10.0 and 5.2%, respectively (mean lung dose, 2.6 Gy). The lung dose, especially lung V20, showed a strong association with OS (p = 0.0012). Grade ≥ 2 pneumonia was present in six patients (13%), including two (4%) with suspected grade 5. CIRT can provide a relatively safe and curative treatment for patients with IP-complicated lung cancer. However, IP increases the risk of severe radiation pneumonitis, and further studies are required to assess the appropriate indications.

Spectroscopic investigations of fungal biomarkers after exposure to heavy ion irradiation

The main objective of the ongoing and future space exploration missions is the search for traces of extant or extinct life (biomarkers) on Mars. One of the main limiting factors on the survival of Earth-like life is the presence of harmful space radiation, that could damage or modify also biomolecules, therefore understanding the effects of radiation on terrestrial biomolecules stability and detectability is of utmost importance. Which terrestrial molecules could be preserved in a Martian radiation scenario? Here, we investigated the potential endurance of fungal biomolecules, by exposing de-hydrated colonies of the Antarctic cryptoendolithic black fungus Cryomyces antarcticus mixed with Antarctic sandstone and with two Martian regolith analogues to increasing doses (0, 250 and 1000 Gy) of accelerated ions, namely iron (Fe), argon (Ar) and helium (He) ions. We analyzed the feasibility to detect fungal compounds with Raman and Infrared spectroscopies after exposure to these space-relevant radiations.

Remodeling of Chromatin Accessibility Regulates the Radiological Responses of NSCLC A549 Cells to High-LET Carbon Ions

Carbon-ion radiation therapy (CIRT) may offer remarkable advantages in cancer treatment with its unique physical and biological characteristics. However, the underlying epigenetic regulatory mechanisms of cancer response to CIRT remain to be identified. In this study, we showed consistent but different degrees of biological effects induced in NSCLC A549 cells by carbon ions of different LET. The genome-wide chromatin accessibility and transcriptional profiles of carbon ion-treated A549 cells were performed using transposase-accessible chromatin sequencing (ATAC-seq) and RNA-seq, respectively, and further gene regulatory network analysis was performed by integrating the two sets of genomic data. Alterations in chromatin accessibility by carbon ions of different LET predominantly occurred in intron, distal intergenic and promoter regions of differential chromatin accessibility regions. The transcriptional changes were mainly regulated by proximal chromatin accessibility. Notably, CCCTC-binding factor (CTCF) was identified as a key transcription factor in the cellular response to carbon ions. The target genes regulated by CTCF in response to carbon ions were found to be closely associated with the LET of carbon ions, particularly in the regulation of gene transcription within the DNA replication- and metabolism-related signaling pathways. This study provides a regulatory profile of genes involved in key signaling pathways and highlighted key regulatory elements in NSCLC A549 cells during CIRT, which expands our understanding of the epigenetic mechanisms of carbon ion-induced biological effects and reveals an important role for LET in the regulation of changes in chromatin accessibility, although further research is needed.

Efficacy and safety of carbon ion radiotherapy for chordomas: a systematic review and meta-analysis

OBJECTIVE

Carbon ion radiotherapy (C-ion RT) for chordomas has been gradually performed in several research centres. This study aimed to systematically review the results of clinical reports from these institutions and to evaluate the safety and efficacy of C-ion RT.

METHODS

In accordance with the PRISMA guidelines and set search strategies, we searched four databases for articles from their inception to February 11, 2023. These articles were screened, and data were extracted independently by two researchers. STATA 14.0 was used for statistical analysis of survival results.

RESULTS

A total of 942 related articles were retrieved, 11 of which were included. Regarding lesion location, 57% (n = 552) originated in the sacral region, 41% (n = 398) in the skull base, and 2% (n = 19) in the spine (upper cervical). The local control (LC) rates at 1, 2, 3, 5, 9, and 10 years in these studies were 96%, 93%, 83%, 76%, 71%, and 54%, respectively. The overall survival (OS) rates at 1, 2, 3, 5, 9, and 10 years in these studies were 99%, 100%, 93%, 85%, 76%, and 69%, respectively. Acute and late toxicities were acceptable, acute toxicities were mainly grade 1 to grade 2 and late toxicities were mainly grade 1 to grade 3.

CONCLUSION

C-ion RT has attractive clinical application prospects and is an important local treatment strategy for chordomas. Encouraging results were observed in terms of LC and OS. Meanwhile, the acute and late toxicities were acceptable. PROSPERO registration number: CRD42023398792.

Noncancer Effects of Ionizing Radiation Exposure on the Eye, the Circulatory System and beyond: Developments made since the 2011 ICRP Statement on Tissue Reactions

For radiation protection purposes, noncancer effects with a threshold-type dose-response relationship have been classified as tissue reactions (formerly called nonstochastic or deterministic effects), and equivalent dose limits aim to prevent occurrence of such tissue reactions. Accumulating evidence demonstrates increased risks for several late occurring noncancer effects at doses and dose rates much lower than previously considered. In 2011, the International Commission on Radiological Protection (ICRP) issued a statement on tissue reactions to recommend a threshold of 0.5 Gy to the lens of the eye for cataracts and to the heart and brain for diseases of the circulatory system (DCS), independent of dose rate. Literature published thereafter continues to provide updated knowledge. Increased risks for cataracts below 0.5 Gy have been reported in several cohorts (e.g., including in those receiving protracted or chronic exposures). A dose threshold for cataracts is less evident with longer follow-up, with limited evidence available for risk of cataract removal surgery. There is emerging evidence for risk of normal-tension glaucoma and diabetic retinopathy, but the long-held tenet that the lens represents among the most radiosensitive tissues in the eye and in the body seems to remain unchanged. For DCS, increased risks have been reported in various cohorts, but the existence or otherwise of a dose threshold is unclear. The level of risk is less uncertain at lower dose and lower dose rate, with the possibility that risk per unit dose is greater at lower doses and dose rates. Target organs and tissues for DCS are also unknown, but may include heart, large blood vessels and kidneys. Identification of potential factors (e.g., sex, age, lifestyle factors, coexposures, comorbidities, genetics and epigenetics) that may modify radiation risk of cataracts and DCS would be important. Other noncancer effects on the radar include neurological effects (e.g., Parkinson's disease, Alzheimer's disease and dementia) of which elevated risk has increasingly been reported. These late occurring noncancer effects tend to deviate from the definition of tissue reactions, necessitating more scientific developments to reconsider the radiation effect classification system and risk management. This paper gives an overview of historical developments made in ICRP prior to the 2011 statement and an update on relevant developments made since the 2011 ICRP statement.

The impact of TP53 status of tumor cells including the type and the concentration of administered 10B delivery agents on compound biological effectiveness in boron neutron capture therapy

Human head and neck squamous cell carcinoma cells transfected with mutant TP53 (SAS/mp53) or neo vector (SAS/neo) were inoculated subcutaneously into left hind legs of nude mice. After the subcutaneous administration of a 10B-carrier, boronophenylalanine-10B (BPA) or sodium mercaptododecaborate-10B (BSH), at two separate concentrations, the 10B concentrations in tumors were measured using γ-ray spectrometry. The tumor-bearing mice received 5-bromo-2'-deoxyuridine (BrdU) continuously to label all intratumor proliferating (P) tumor cells, then were administered with BPA or BSH. Subsequently, the tumors were irradiated with reactor neutron beams during the time of which 10B concentrations were kept at levels similar to each other. Following irradiation, cells from some tumors were isolated and incubated with a cytokinesis blocker. The responses of BrdU-unlabeled quiescent (Q) and total (= P + Q) tumor cells were assessed based on the frequencies of micronucleation using immunofluorescence staining for BrdU. In both SAS/neo and SAS/mp53 tumors, the compound biological effectiveness (CBE) values were higher in Q cells and in the use of BPA than total cells and BSH, respectively. The higher the administered concentrations were, the smaller the CBE values became, with a clearer tendency in SAS/neo tumors and the use of BPA than in SAS/mp53 tumors and BSH, respectively. The values for BPA that delivers into solid tumors more dependently on uptake capacity of tumor cells than BSH became more alterable. Tumor micro-environmental heterogeneity might partially influence on the CBE value. The CBE value can be regarded as one of the indices showing the level of intratumor heterogeneity.

Pragmatic, Prospective Comparative Effectiveness Trial of Carbon Ion Therapy, Surgery, and Proton Therapy for the Management of Pelvic Sarcomas (Soft Tissue/Bone) Involving the Bone: The PROSPER Study Rationale and Design

Surgical treatment of pelvic sarcoma involving the bone is the standard of care but is associated with several sequelae and reduced functional quality of life (QOL). Treatment with photon and proton radiotherapy is associated with relapse. Carbon ion radiotherapy (CIRT) may reduce both relapse rates and treatment sequelae. The PROSPER study is a tricontinental, nonrandomized, prospective, three-arm, pragmatic trial evaluating treatments of pelvic sarcoma involving the bone. Patients aged at least 15 years are eligible for inclusion. Participants must have an Eastern Cooperative Oncology Group Performance Status score of two or less, newly diagnosed disease, and histopathologic confirmation of pelvic chordoma, chondrosarcoma, osteosarcoma, Ewing sarcoma with bone involvement, rhabdomyosarcoma (RMS) with bone involvement, or non-RMS soft tissue sarcoma with bone involvement. Treatment arms include (1) CIRT (n = 30) delivered in Europe and Asia, (2) surgical treatment with or without adjuvant radiotherapy (n = 30), and (3) proton therapy (n = 30). Arms two and three will be conducted at Mayo Clinic campuses in Arizona, Florida, and Minnesota. The primary end point is to compare the 1-year change in functional QOL between CIRT and surgical treatment. Additional comparisons among the three arms will be made between treatment sequelae, local control, and other QOL measures.

The 'stealth-bomber' paradigm for deciphering the tumour response to carbon-ion irradiation

Numerous studies have demonstrated the higher biological efficacy of carbon-ion irradiation (C-ions) and their ballistic precision compared with photons. At the nanometre scale, the reactive oxygen species (ROS) produced by radiation and responsible for the indirect effects are differentially distributed according to the type of radiation. Photon irradiation induces a homogeneous ROS distribution, whereas ROS remain condensed in clusters in the C-ions tracks. Based on this linear energy transfer-dependent differential nanometric ROS distribution, we propose that the higher biological efficacy and specificities of the molecular response to C-ions rely on a 'stealth-bomber' effect. When biological targets are on the trajectories of the particles, the clustered radicals in the tracks are responsible for a 'bomber' effect. Furthermore, the low proportion of ROS outside the tracks is not able to trigger the cellular mechanisms of defence and proliferation. The ability of C-ions to deceive the cellular defence of the cancer cells is then categorised as a 'stealth' effect. This review aims to classify the biological arguments supporting the paradigm of the 'stealth-bomber' as responsible for the biological superiority of C-ions compared with photons. It also explains how and why C-ions will always be more efficient for treating patients with radioresistant cancers than conventional radiotherapy.

Biological Effects of Monoenergetic Carbon Ions and Their Associated Secondary Particles

DNA double-strand breaks (DSBs) are the main factor behind carbon-ion radiation therapy (CIRT)-induced cell death. Nuclear interactions along the beam path between the primary carbon ions and targets result in nuclear fragmentation of carbon ions and recoiled particles. These secondary particles travel further distances past the Bragg peak to the tail region, leading to unwanted biological effects that may result in cytotoxicity in critical organs and secondary induced tumors following CIRT. Here, we confirmed that the density of the DSB distributions increases as the cell survival decreases at the Bragg peak and demonstrated that by visualizing DSBs, the various LET fragmentation ions and recoiled particles produced differences in their biological effects in the post-Bragg peak tail regions. This suggests that the density of the DSBs within the high-LET track structures, rather than only their presence, is important for inducing cell death. These results are essential for CIRT treatment planning to limit the amount of healthy cell damage and reducing both the late effect and the secondary tumor-associated risk.

Comparison of Oncologic Outcomes and Treatment-Related Toxicity of Carbon Ion Radiotherapy and En Bloc Resection for Sacral Chordoma

IMPORTANCE

Maximal resection is the preferred management for sacral chordomas but can be associated with unacceptable morbidity. Outcomes with radiotherapy are poor. Carbon ion radiotherapy (CIRT) is being explored as an alternative when surgery is not preferred.

OBJECTIVE

To compare oncologic outcomes and treatment-related toxicity of CIRT and en bloc resection for sacral chordoma.

DESIGN, SETTING, AND PARTICIPANTS

Univariable logistic regression was performed to evaluate the association between treatment type and oncologic and toxicity outcomes in this retrospective cohort study. Nearest-neighbor propensity score matching was used to match the CIRT cohort with the en bloc resection cohort and 10 National Cancer Database (NCDB) cohorts separately, with the objective of obtaining more homogeneous cohorts when comparing treatments. Patient- and tumor-related characteristics from 2 institutional cohorts were collected for patients diagnosed with sacral chordomas between April 1, 1994, and July 31, 2017. The NCDB was queried for data on patients with sacral chordoma from January 1, 2004, to December 31, 2016, as a comparator in overall survival (OS) analyses. Data analysis was conducted from February 24, 2020, to January 16, 2021.

EXPOSURES

En bloc resection, incomplete resection, photon radiotherapy, proton radiotherapy, and CIRT.

MAIN OUTCOMES AND MEASURES

Overall survival was estimated using the Kaplan-Meier method and compared using the Cox proportional hazards model. Peripheral motor nerve toxic effects were scored using Common Terminology Criteria for Adverse Events, version 4.03.

RESULTS

A total of 911 patients were included in the study (NCDB: n = 669; median age, 64 [IQR, 52-74] years; 410 [61.3%] men; CIRT: n = 188; median age, 66 [IQR, 58-71] years; 128 [68.1%] men; en bloc surgical resection: n = 54; median age, 53.5 [IQR 49-64] years, 36 [66.7%] men). Comparison of the propensity score-matched institutional en bloc resection and CIRT cohorts revealed no statistically significant difference in OS (CIRT: median OS, 68.1 [95% CI, 44.0-102.6] months; en bloc resection: median OS, 58.6 [95% CI, 25.6-123.5] months; P = .57; hazard ratio, 0.71 [95% CI, 0.25-2.06]; P = .53). The CIRT cohort experienced lower rates of peripheral motor neuropathy (odds ratio, 0.13 [95% CI, 0.04-0.40]; P < .001). On comparison of the propensity score-matched NCDB cohorts with the CIRT cohort, significantly higher OS was found for CIRT compared with margin-positive surgery without adjuvant radiotherapy (CIRT: median OS, 64.7 [95% CI, 57.8-69.7] months; margin-positive surgery without adjuvant radiotherapy: median OS, 60.6 [95% CI, 44.2-69.7] months, P = .03) and primary radiotherapy alone (CIRT: median OS, 64.9 [95% CI 57.0-70.5] months; primary radiotherapy alone: 31.8 [95% CI, 27.9-40.6] months; P < .001).

CONCLUSIONS AND RELEVANCE

These findings suggest that CIRT can be used as treatment for older patients with high performance status and sacral chordoma in whom surgery is not preferred. CIRT might provide additional benefit for patients who undergo margin-positive resection or who are candidates for primary photon radiotherapy.

Visualized Analysis of Heavy Ion Radiotherapy: Development, Barriers and Future Directions

Background

Heavy ion radiotherapy (HIRT) has great advantages as tumor radiotherapy.

Methods

Based on 1,558 literatures from core collections of Web of Science from 1980 to 2020, this study visually analyzes the evolution of HIRT research, and sorts out the hotspots and trends of HIRT research using CiteSpace software.

Results

Research on HIRT has received more extensive attention over the last 40 years. The development of HIRT is not only closely related to radiation and oncology, but also closely related to the development of human society. In terms of citation frequency, "International Journal of Radiation Oncology*Biology*Physics" was the top journal. In terms of influence, "Radiotherapy and Oncology" was the top journal. "Radiation therapy" and "carbon ion radiotherapy" were the two most frequently used keywords in this field.

Conclusion

The evolution of the HIRT research has occurred in approximately three stages, including technological exploration, safety and effectiveness research and technological breakthroughs. Finally, some suggestions for future research are put forward.

Effect of spatial distribution of boron and oxygen concentration on DNA damage induced from boron neutron capture therapy using Monte Carlo simulations

PURPOSE

This paper aims to investigate how the spatial distribution of boron in cells and oxygen concentration affect the DNA damage induced by charged particles in boron neutron capture therapy (BNCT) by Monte Carlo simulations, and further to evaluate the relative biological effectiveness (RBE) of DNA double-strand breaks (DSBs) induction.

MATERIALS AND METHODS

The kinetic energy spectra of α, 7Li particles in BNCT arriving at the nucleus surface were obtained from GEANT4 (Geant4 10.05.p01). The DNA damage caused by BNCT was then evaluated using MCDS (MCDS 3.10A).

RESULTS

When α or 7Li particles were distributed in the cytomembrane or cytoplasm, the difference in DNA damage of the same types was less than 0.5%. Taking the 137Cs photons as the reference radiation, when the oxygen concentration varied from 0% to 50%, the RBE of 0.54MeV protons and recoil protons varied from 5 to 2, whereas it decreased from 10 to 3 for α or 7Li particles.

CONCLUSION

The RBE of DSB induction all charged particles in BNCT decreased with the increase of oxygen concentration. This work indicated that the RBE of different radiation particles of BNCT might be affected by many factors, which should be paid attention to in theoretical research or clinical application.

Radiation-induced lens opacities: Epidemiological, clinical and experimental evidence, methodological issues, research gaps and strategy

In 2011, the International Commission on Radiological Protection (ICRP) recommended reducing the occupational equivalent dose limit for the lens of the eye from 150 mSv/year to 20 mSv/year, averaged over five years, with no single year exceeding 50 mSv. With this recommendation, several important assumptions were made, such as lack of dose rate effect, classification of cataracts as a tissue reaction with a dose threshold at 0.5 Gy, and progression of minor opacities into vision-impairing cataracts. However, although new dose thresholds and occupational dose limits have been set for radiation-induced cataract, ICRP clearly states that the recommendations are chiefly based on epidemiological evidence because there are a very small number of studies that provide explicit biological and mechanistic evidence at doses under 2 Gy. Since the release of the 2011 ICRP statement, the Multidisciplinary European Low Dose Initiative (MELODI) supported in April 2019 a scientific workshop that aimed to review epidemiological, clinical and biological evidence for radiation-induced cataracts. The purpose of this article is to present and discuss recent related epidemiological and clinical studies, ophthalmic examination techniques, biological and mechanistic knowledge, and to identify research gaps, towards the implementation of a research strategy for future studies on radiation-induced lens opacities. The authors recommend particularly to study the effect of ionizing radiation on the lens in the context of the wider, systemic effects, including in the retina, brain and other organs, and as such cataract is recommended to be studied as part of larger scale programs focused on multiple radiation health effects.

Organ-on-a-chip: the next generation platform for risk assessment of radiobiology

Organ-on-a-chip devices have been widely used in biomedical science and technology, for example for experimental regenerative medicine and precision healthcare. The main advantage of organ-on-a-chip technology is the facility to build a specific human model that has functional responses on the level of organs or tissues, thereby avoiding the use of animal models, as well as greatly improving new drug discovery processes for personal healthcare. An emerging application domain for organs-on-chips is the study of internal irradiation for humans, which faces the challenges of the lack of a clear model for risk estimation of internal irradiation. We believe that radiobiology studies will benefit from organ-on-a-chip technology by building specific human organ/tissues in vitro. In this paper, we briefly reviewed the state-of-the-art in organ-on-a-chip research in different domains, and conclude with the challenges of radiobiology studies at internal low-dose irradiation. Organ-on-a-chip technology has the potential to significantly improve the radiobiology study as it can mimic the function of human organs or tissues, and here we summarize its potential benefits and possible breakthrough areas, as well as its limitations in internal low-dose radiation studies.

Organ-on-a-chip technology has great potential for the next generation risk estimation of low dose internal irradiation, due to its success in mimicking human organs/tissues, which possibly can significantly improve on current animal models.

Carbon ion radiotherapy for sacral chordoma: A retrospective nationwide multicentre study in Japan

BACKGROUND AND PURPOSE

Usefulness of carbon ion radiotherapy (CIRT) for sacral chordoma has been reported from single institutions. We conducted a retrospective nationwide multicentre study to evaluate the clinical outcomes of CIRT for sacral chordoma in Japan.

MATERIALS AND METHODS

A total of 219 patients who underwent CIRT for sacral chordoma at institutions across Japan between December 2003 and July 2014 were included in this study.

RESULTS

Median patient age was 67 years (range, 26-87 years). Most patients had no history of surgical resection (96%). The most frequent planning target volume (PTV) range was 100-500 mL (65%). The most frequently used dose-fractionation was 67.2 Gy (relative biological effectiveness) in 16 fractions (65%). The median follow-up was 56 months (range, 7-132 months). The 5-year overall survival (OS), progression-free survival, and local control rates were 84%, 48%, and 72%, respectively. Frequent sites of out-of-field recurrence included bone (9%) and lung (9%) metastases. The Cox proportional hazards model revealed that both younger age (P = 0.004) and smaller PTV (P = 0.001) were associated with significantly better OS. Acute toxicities of ≥Grade 3 occurred in eight patients (4%). Late toxicities of ≥Grade 3 occurred in 13 patients (6%): skin disorders in six patients (3%), pain in three (1%), myositis in three (1%), etc. CONCLUSION: Our retrospective nationwide multicentre study showed that CIRT for sacral chordoma was effective and safe, and replicated the previously reported data from a representative CIRT institution in Japan demonstrating high local control and low toxicity rates.

Serum Proteins as New Biomarkers for Whole-Body Exposure to High- and Low-LET Ionizing Radiation

Exposure to ionizing radiation is a major threat to human health and public security. Since the inherent limitations of current methods for indicating radiation exposure, new minimally invasive biomarkers that can be easily and quickly detected at an early stage are needed for optimal medical treatment. Serum proteins are attractive biomarkers and some radiosensitive proteins have been found, but the proteins in response to low-dose and high-linear energy transfer (LET) radiation have not been reported. In this study, mice were whole body exposed to a variety doses of carbon ions and X-rays. We performed Mouse Antibody Array to detect serum proteins expression profiles at 24 hours postirradiation. After conditional screening, insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-1 (IGFBP-1), and IGFBP-3 were further validated using enzyme-linked immunosorbent assay. After exposure to 0.05 to 1 Gy of carbon ions and 0.5 to 4 Gy of X-rays, only IGFBP-3 showed obvious increase with increased doses, both carbon ions and X-rays. Further, IGFBP-3 was detected for observation of its time-dependent changes. The results showed the expression difference of IGFBP-3 presented from 6 to 24 hours post-irradiation by carbon ions and X-rays. Moreover, the receiver–operating characteristic analysis showed that serum IGFBP-3 is efficient to triage exposed individuals with high sensitivity and specificity. These results suggest that serum IGFBP-3 is extremely sensitive to high- and low-LET ionizing radiation and is able to respond at an early stage, which could serve as a novel minimally invasive indicator for radiation exposure.

Study on the RBE estimation for carbon beam scanning irradiation using a solid-state microdosimeter

PURPOSE

The purpose of this study was to study the field size effect on the estimated Relative Biological Effectiveness (RBE) for carbon scanning beam irradiation.

METHODS

A silicon-on-insulator (SOI) microdosimeter system developed by the Centre for Medical Radiation Physics, University of Wollongong, Australia, was used for lineal-energy measurements (microdosimetric quantity). The RBE values were derived based on the modified microdosimetric kinetic model (MKM) at different depths in a water phantom in the scanning carbon beam for various scanned areas.

RESULTS

Our study shows that the difference in RBE values derived from the SOI microdosimeter measurements with the MKM model and from the Treatment Planning System (TPS). The difference of the RBE values is within 6.5 % at the peak point of the spread-out Bragg Peak (SOBP) region. Compared to the spot-beam, RBE values obtained in the scanned-beam with a larger scanned area of 1.0 × 1.0 cm² have better agreement with which estimated by the TPS.

CONCLUSIONS

This study shows the possibility of using the SOI microdosimeter system as a quality assurance (QA) tool for RBE evaluation in carbon-pencil beam scanning radiotherapy.

Comparison of transcriptional profiles in human lymphocyte cells irradiated with 12C ion beams at 0-2.0 Gy

OBJECTIVE

Heavy ions have contributed to tumor site-specific radiotherapy and are a major health risk for astronauts. The purpose of this study was to investigate the changes in gene expression in peripheral lymphocytes of cancer patients and astronauts exposed to 12C ions, and identify suitable molecular biomarkers for health monitoring. We also aimed to observe the effects of treatment and the level of damage, by comparing the transcriptional profiles of human lymphocyte cell lines exposed to 12C ion beams at doses of 0-2.0 Gy.

MATERIALS AND METHODS

A human lymphocyte cell line was irradiated with 12C ion beams at 0, 0.1, 0.5, and 2.0 Gy and transcriptional profiles were evaluated using the Agilent human gene expression microarray at 24 hours after irradiation. Differentially expressed genes were identified using a fold change of ≥2.0. Representative genes were further validated by RT-PCR. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed to determine the roles of differentially expressed mRNAs.

RESULTS

Based on the microarray assays, 1,113 genes were upregulated and 853 genes were downregulated in human lymphocyte cells irradiated with 0.1 Gy 12C ion beams compared with the control group, 1,095 genes were upregulated and 1,220 genes were downregulated in cells irradiated with 0.5 Gy 12C ion beams, and 1,055 genes were upregulated and 1,356 genes were downregulated in cells irradiated with 2.0 Gy. A total of 504 genes were differentially expressed in all irradiated groups, of which 88 genes were upregulated and 416 genes downregulated. Most of these altered genes were related to the cell cycle, apoptosis, signal transduction, DNA transcription, repair, and replication. The expression differences were further confirmed by RT-PCR for a subset of differentially expressed genes.

CONCLUSION

Differentially expressed genes between treatment and control groups at 24 hours post-irradiation increased as the radiation dose increased; upregulated genes gradually decreased and downregulated genes increased. Our data indicated that 12C ion beams could repress a number of genes in a dose-dependent manner, which might lead to the failure of multiple cellular biological functions.

Both irradiated and bystander effects link with DNA repair capacity and the linear energy transfer

AIMS

In comparison with a low linear energy transfer (LET) radiation, a high-LET radiation induces more complex DNA damage. This study wonders whether radiation-induced bystander effect (RIBE) is dependent of LET.

MATERIALS AND METHODS

Chinese hamster ovary CHO-9 cells and its subline EM-C11 cells (SSB repair deficient) and XR-C1 cells (DSB repair deficient) were irradiated by γ-rays, α-particles, or carbon ions with different LETs of 13, 30 and 70 keV/μm. Cell proliferation, cell death, DNA damage, cell cycle distribution and some protein expressions were measured with the cell counting kit-8 (CCK-8), colony formation, micronuclei (MN), flow cytometry and western blot, respectively.

KEY FINDINGS

A series of cell responses were induced by these radiations in a LET-dependent manner, including proliferation inhibition, cell death, MN induction, G₂/M phase arrest and the expression of γH2AX protein. These cell injuries were also depended on DNA repair capacity, and XR-C1 cells were the most sensitive to each radiation. Furthermore, when the cells were treated with the conditioned medium (CM) collected from irradiated CHO-9 cells, the MN induction and cell death response in the bystander cells of EM-C11 or XR-C1 increased along with LET of irradiation, and the bystander damage was easier to be induced in EM-C11 and XR-C1 cells than that in CHO-9 cells.

SIGNIFICANCE

Both cellular DNA repair capacity and the LET value of radiation could deeply influence damage extents of not only the irradiated cells but also the bystander cells.

Inhibitory Effect of Ionizing Radiation on Echinococcus granulosus Hydatid Cyst

BACKGROUND

Heavy ion radiation has more advantages than traditional radiation therapy in the treatment of cancer, mainly because of its superior biological effects. However, there is currently no reliable evidence that heavy ion radiation can induce cell death in hydatid cysts at the cellular and molecular level. In addition, we believe heavy ion therapy could be a potential alternative approach for the treatment of hydatid cysts.

METHODOLOGY/PRINCIPAL FINDING

The hydatid cysts and protoscolices were obtained from an experimentally infected KunMing mice. LD50 was used to evaluate the death of the protoscolex. The cellular and ultrastructure of the parasites were observed under light and electron microscopes, the damage and copy numbers of mitochondrial DNA (mtDNA) were decided by QPCR. The apoptosis was evaluated by the expression and activity of caspase3. Dose-dependent ionizing radiation induced damage to the initial mtDNA. Echinococcosis cyst after ionizing radiation showed sparse cytoplasm, disorganized and clumped organelles, huge vacuoles, and villus deletions. The kinetic of DNA repair activity after X-ray irradiation was faster than those after carbon-ion irradiation. High doses of carbon ion radiation caused irreversible attenuation of mitochondrial DNA. Cysts showed obvious reduction in size after radiation. Carbon ion radiation was more effective than X-ray radiation in inhibiting hydatid cysts.

CONCLUSIONS

These studies provide evidence that heavy-ion radiation can cause the extinction of hydatid cysts in vitro. The carbon-ion radiation is more advantageous than X-ray radiation in suppress hydatid cyst.

Effect of a change in reactor power on response of murine solid tumors in vivo, referring to impact on quiescent tumor cell population

PURPOSE

To examine the effect of a change in reactor power on the response of solid tumors, referring to impact on quiescent (Q) tumor cell population.

MATERIALS AND METHODS

Tumor-bearing mice received 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating (P) tumor cells, and were treated with boronophenylalanine-¹⁰B (BPA) or sodium mercaptododecaborate-¹⁰B (BSH). After reactor neutron beam irradiation at a power of 1 or 5 MW with an identical beam spectrum, cells from tumors were isolated and incubated with a cytokinesis blocker. The responses of BrdU-unlabeled Q and total (P + Q) tumor cells were assessed based on the frequencies of micronucleation using immunofluorescence staining for BrdU.

RESULTS

After neutron irradiation with or without ¹⁰B-carrier, radio-sensitivity was reduced by decreasing reactor power in both cells, especially in Q cells and after irradiation with BPA. The values of relative and compound biological effectiveness were larger at a power of 5 MW and in Q cells than at a power of 1 MW and in total cells, respectively. The sensitivity difference between total and Q cells was widened when combined with ¹⁰B-carrier, especially with BPA, and through decreasing reactor power.

CONCLUSION

5 MW is more advantageous than 1 MW for boron neutron capture therapy.

DNA Repair Deficient Chinese Hamster Ovary Cells Exhibiting Differential Sensitivity to Charged Particle Radiation under Aerobic and Hypoxic Conditions

It has been well established that hypoxia significantly increases both cellular and tumor resistance to ionizing radiation. Hypoxia associated radiation resistance has been known for some time but there has been limited success in sensitizing cells to radiation under hypoxic conditions. These studies show that, when irradiated with low linear energy transfer (LET) gamma-rays, poly (ADP-ribose), polymerase (PARP), Fanconi Anemia (FANC), and mutant Chinese Hamster Ovary (CHO) cells respond similarly to the non-homologous end joining (NHEJ) and the homologous recombination (HR) repair mutant CHO cells. Comparable results were observed in cells exposed to 13 keV/μm carbon ions. However, when irradiated with higher LET spread out Bragg peak (SOBP) carbon ions, we observed a decrease in the oxygen enhancement ratio (OER) in all the DNA of repair mutant cell lines. Interestingly, PARP mutant cells were observed as having the largest decrease in OER. Finally, these studies show a significant increase in the relative biological effectiveness (RBE) of high LET SOBP carbon and iron ions in HR and PARP mutants. There was also an increase in the RBE of NHEJ mutants when irradiated to SOBP carbon and iron ions. However, this increase was lower than in other mutant cell lines. These findings indicate that high LET radiation produces unique types of DNA damage under hypoxic conditions and PARP and HR repair pathways play a role in repairing this damage.

Benchmarking of PHITS for Carbon Ion Therapy

Purpose

Up to now, carbon ions have shown the most favorable physical and radiobiological properties for radiation therapy of, for example, deep-seated radioresistant tumors. However, when carbon ions penetrate matter, they undergo inelastic nuclear reactions that give rise to secondary fragments contributing to the dose in the healthy tissue. This can cause damage to radiosensitive organs at risk when they are located in the vicinity of the tumor. Therefore, predictions of the yields and angular distributions of the secondary fragments are needed to be able to estimate the resulting biological effects in both the tumor region and the healthy tissues. This study presents the accuracy of simulations of therapeutic carbon ion beams with water, with the 3D MC (Monte Carlo) general purpose particle and ion transport code PHITS.

Materials and Methods

Simulations with PHITS of depth-dose distributions, beam attenuation, fragment yields, and fragment angular distributions from interactions of therapeutic carbon ion beams with water are compared to published measurements performed at Gesellschaft für Schwerionen Forschung (GSI).

Results

The results presented in this study demonstrate that PHITS simulations of therapeutic carbon ion beams in water show overall a good agreement with measurements performed at GSI; for example, for light ions like H and He, simulations agree within about 10%. However, there is still a need to further improve the calculations of fragment yields, especially for underproduction of Li of up to 50%, by improving the nucleus-nucleus cross-section models.

Conclusion

The simulated data are clinically acceptable but there is still a need to further improve the models in the transport code PHITS. More reliable experimental data are therefore needed.

Induction of reproductive cell death in Caenorhabditis elegans across entire linear-energy-transfer range of carbon-ion irradiation

Heavy-ion radiation has attracted extensive attention as an effective cancer therapy because of the varying energy deposition along its track and its high cell-killing effect. Reproductive cell death (RCD), also known as clonogenic death, is an important mode of death of the cancer cells after radiotherapy. Although RCD induced by heavy-ion irradiation with various linear energy transfers has been demonstrated using clonogenic assay in vitro, little is known about the distribution of RCD across the range of heavy-ion irradiation at the level of whole organisms. In this study, a vulval tissue model of Caenorhabditis elegans was for the first time used to assess RCD in vivo induced by carbon-ion irradiation. A polymethyl methacrylate wedge was designed to provide a gradually varying thickness of shielding, so worms could be exposed to the entire range of carbon-ion irradiation. The carbon-ion irradiation led to a significant induction of RCD over the entire range in a dose-dependent manner. The biological peak did not correspond to the physical Bragg peak and moved forward, rather than spread forward, as radiation dose increased. The degree and shape of the range-distribution of RCD were also affected by the developmental stages of the worms. The gene mutations in DNA-damage checkpoints did not affect the responses of mutant worms positioned in biological peaks, compared to wild-type worms, but decreased radio-sensitivity in the entrance region. An increased induction of RCD was observed in the worms impaired in homologous recombination (HR), but not in non-homologous end jointing pathway, suggesting a crucial role of HR repair in vulval cells of C. elegans in dealing with the carbon-ion-induced DNA damage. These unique manifestations of RCD in vivo in response to carbon-ion irradiation might provide new clues for further investigating the biological effects of heavy-ion irradiation.

Peripheral lymphocyte subset variation predicts prostate cancer carbon ion radiotherapy outcomes

The immune system plays a complementary role in the cytotoxic activity of radiotherapy. Here, we examined changes in immune cell subsets after heavy ion therapy for prostate cancer. The lymphocyte counts were compared with acute radiotherapy-related toxicity, defined according to the Common Terminology Criteria for Adverse Events, and short-term local efficacy, defined based on prostate-specific antigen concentrations. Confirmed prostate cancer patients who had not received previous radiotherapy were administered carbon ion radiotherapy (CIR) in daily fractions of 2.74 GyE with a total dose of 63-66 GyE. Lymphocyte subset counts were investigated before, during and after radiotherapy, and at a 1 month follow-up. Most notable among our findings, the CD4/CD8 ratio and CD19+ cell counts were consistently higher in patients with a complete response (CR) or partial response (PR) to CIR than in those classified in the stable disease (SD) group (P<0.05 for both). But CD3+ and CD8+ cell counts were lower in the CR and PR groups than in the SD group. These results indicate that variations in peripheral lymphocyte subpopulations are predictive of outcome after CIR for prostate cancer.

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.

Effects of 12C6+ heavy ion beam irradiation on the p53 signaling pathway in HepG2 liver cancer cells

The heavy ion beam is considered to be the ideal source for radiotherapy. The p53 tumor suppressor gene senses DNA damage and transducts intracellular apoptosis signals. Previous reports showed that the heavy ion beam can trigger complex forms of damage to cellular DNA, leading to cell cycle arrest and apoptosis of HepG2 human liver cancer cells; however, the mechanisms remains unclear fully. In order to explore whether the intrinsic or extrinsic pathway participates this process, HepG2 cells were treated with 12C6+ HIB irradiation at doses of 0 (control), 1, 2, 4, and 6 Gy with various methods employed to understand relevant mechanisms, such as detection of apoptosis, cell cycle, and Fas expression by flow cytometry, analysis of apoptotic morphology by electron microscopy and laser scanning confocal microscopy, and screening differentially expressed genes relating to p53 signaling pathway by PCR-array assay following with any genes confirmed by western blot analysis. This study showed that 12C6+ heavy ion beam irradiation at a dose of 6 Gy leads to endogenous DNA double-strand damage, G2/M cell cycle arrest, and apoptosis of human HepG2 cells via synergistic effect of the extrinsic and intrinsic pathways. Differentially expressed genes in the p53 signaling pathway related to DNA damage repair, apoptosis, cycle regulation, metastasis, deterioration and radioresistance were also discovered. Consequently, the expressions of Fas, TP53BP2, TP53AIP1, and CASP9 were confirmed upregulated after 12C6+ HIB irradiation treatment. In conclusion, this study demonstrated the mechanisms of inhibition and apoptosis induced by 12C6+ heavy ion beam irradiation on HepG2 cancer cells is mediated by initiation of the biological function of p53 signaling pathway including extrinsic and intrinsic apoptosis pathway.

Carbon-ion radiotherapy for isolated para-aortic lymph node recurrence from colorectal cancer

BACKGROUND

The safety and effectiveness of carbon-ion radiotherapy (CIRT) for isolated para-aortic lymph node (PALN) metastasis was evaluated retrospectively.

METHODS

CIRT for isolated PALN metastasis from CRC was performed in 34 cases from June 2006 to August 2015 in our institute. A median dose of 52.8 Gy(RBE) (range, 48-52.8 Gy(RBE)) was delivered with a median daily dose of 4.4 Gy(RBE) (range, 4.0-4.4 Gy(RBE)).

RESULTS

The median follow-up duration for all patients was 24.4 months (range, 7-82.8 months). There were 13 cases (38.2%) who achieved complete response after treatment. The local control rates at 2 and 3 years were 70.1% and 70.1%, respectively. The overall survival rates at 2 and 3 years were 83.3% and 63.0%, respectively. The 3-year survival rates for Stage I-III were 68.7%, while those for Stage IV was 0%. The overall survival of cases with rectal cancer or with high CA19-9 values pre-CIRT tended to be worse. The median survival period was 41.7 months. Twelve of the 34 patients survived for more than 3 years. There were no adverse effects of Grade 3 or higher.

CONCLUSIONS

CIRT for isolated PALN recurrence after curative resection for CRC appears effective and safe, and it is considered a promising therapy.

Low-dose photon irradiation induces invasiveness through the SDF-1α/CXCR4 pathway in malignant mesothelioma cells

Background

Low-dose photon irradiation has repeatedly been suspected to increase a risk of promoting local recurrence of disease or even systemic dissemination. The purpose of this study was to investigate the motility of malignant pleural mesothelioma (MPM) cell lines after low-doses of photon irradiation and to elucidate the mechanism of the detected phenotype.

Methods

H28 and H226 MPM cells were examined in clonogenic survival experiments and migration assays with and without various doses of photon and carbon ion irradiation. C-X-C chemokine receptor type 4 (CXCR4), SDF-1α, β₁ integrin, α₃ integrin, and α₅ integrin expressions were analyzed by quantitative FACS analysis, ELISA and western blots. Apoptosis was assessed via Annexin-V-staining.

Results

The migration of MPM cells was stimulated by both fetal bovine serum and by stromal cell-derived factor 1α (SDF-1α). Low doses of photon irradiation (1 Gy and 2 Gy) suppressed clonogenicity, but promoted migration of both H28 and H226 cells through the SDF-1α/CXCR4 pathway. Hypermigration was inhibited by the administration of CXCR4 antagonist, AMD3100. In contrast, corresponding doses of carbon ion irradiation (0.3 Gy and 1 Gy) suppressed clonogenicity, but did not promote MPM cell migration.

Conclusion

Our findings suggest that the co-administration of photon irradiation and the CXCR4-antagonist AMD3100 or the use of carbon ions instead of photons may be possible solutions to reduce the risk of locoregional tumor recurrence after radiotherapy for MPM.

Carbon Ion Radiotherapy: A Review of Clinical Experiences and Preclinical Research, with an Emphasis on DNA Damage/Repair

Compared to conventional photon-based external beam radiation (PhXRT), carbon ion radiotherapy (CIRT) has superior dose distribution, higher linear energy transfer (LET), and a higher relative biological effectiveness (RBE). This enhanced RBE is driven by a unique DNA damage signature characterized by clustered lesions that overwhelm the DNA repair capacity of malignant cells. These physical and radiobiological characteristics imbue heavy ions with potent tumoricidal capacity, while having the potential for simultaneously maximally sparing normal tissues. Thus, CIRT could potentially be used to treat some of the most difficult to treat tumors, including those that are hypoxic, radio-resistant, or deep-seated. Clinical data, mostly from Japan and Germany, are promising, with favorable oncologic outcomes and acceptable toxicity. In this manuscript, we review the physical and biological rationales for CIRT, with an emphasis on DNA damage and repair, as well as providing a comprehensive overview of the translational and clinical data using CIRT.

Inhibiting autophagy with chloroquine enhances the anti-tumor effect of high-LET carbon ions via ER stress-related apoptosis

Energetic carbon ions (CI) offer great advantages over conventional radiations such as X- or γ-rays in cancer radiotherapy. High linear energy transfer (LET) CI can induce both endoplasmic reticulum (ER) stress and autophagy in tumor cells under certain circumstances. The molecular connection between ER stress and autophagy in tumor exposed to high-LET radiation and how these two pathways influence the therapeutic effect against tumor remain poorly understood. In this work, we studied the impact of autophagy and apoptosis induced by ER stress following high-LET CI radiation on the radiosensitivity of S180 cells both in vitro and in vivo. In the in vitro experiment, X-rays were also used as a reference radiation. Our results documented that the combination of CI radiation with chloroquine (CQ), a special autophagy inhibitor, produced more pronounced proliferation suppression in S180 cells and xenograft tumors. Co-treatment with CI radiation and CQ could block autophagy through the IRE1/JNK/Beclin-1 axis and enhance apoptotic cell death via the activation of C/EBP homologous protein (CHOP) by the IRE1 pathway rather than PERK in vitro and in vivo. Thus, our study indicates that inhibiting autophagy might be a promising therapeutic strategy in CI radiotherapy via aggravating the ER stress-related apoptosis.

Comparative analysis of the serum proteome for biomarker discovery to reveal hepatotoxicity induced by iron ion radiation in mice

AIMS

Proteomic analysis of serum biomarkers to determine liver toxicity after exposure to cosmic radiation has not been performed previously. This study was to identify serum biomarkers associated with hepatotoxicity following exposure to iron ion radiation.

MAIN METHODS

Male mice were whole-body irradiated with a 2grayunit (Gy) iron ion beam, and after 3months, serum and liver samples were collected. Two-dimensional electrophoresis (2-DE) was used to separate the identified serum proteins, and matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-TOF-TOF) was performed to identify differentially expressed proteins. Enzyme-linked immunosorbent assays and immunoblotting were applied to evaluate protein expression, and immunohistochemistry and immunofluorescence were used to investigate protein localization. Real-time polymerase chain reaction (PCR) was performed to confirm altered gene expression.

KEY FINDINGS

A total of 11 spots that showed differential expression were screened and identified as seven proteins. Of these, six proteins were in the same bioinformatics network and included complement component 3, serum amyloid P-component, apolipoprotein E, alpha-2-macroglobulin, fibrinogen alpha chain, and fibrinogen gamma chain. All of these proteins are synthesized by the liver, and may play an important role in liver toxicity. We also confirmed the mRNA transcription, and found that mRNA expression of the six identified proteins increased in the liver in irradiated mice.

SIGNIFICANCE

These results suggest that these proteins may be potential biomarkers of hepatotoxicity in astronauts enduring long space missions.

Relative biological effectiveness in canine osteosarcoma cells irradiated with accelerated charged particles

Heavy ions, characterized by high linear energy transfer (LET) radiation, have advantages compared with low LET protons and photons in their biological effects. The application of heavy ions within veterinary clinics requires additional background information to determine heavy ion efficacy. In the present study, comparison of the cell-killing effects of photons, protons and heavy ions was investigated in canine osteosarcoma (OSA) cells in vitro. A total of four canine OSA cell lines with various radiosensitivities were irradiated with 137Cs gamma-rays, monoenergetic proton beams, 50 keV/µm carbon ion spread out Bragg peak beams and 200 keV/µm iron ion monoenergetic beams. Clonogenic survival was examined using colony-forming as says, and relative biological effectiveness (RBE) values were calculated relative to gamma-rays using the D₁₀ value, which is determined as the dose (Gy) resulting in 10% survival. For proton irradiation, the RBE values for all four cell lines were 1.0-1.1. For all four cell lines, exposure to carbon ions yielded a decreased cell survival compared with gamma-rays, with the RBE values ranging from 1.56-2.10. Iron ions yielded the lowest cell survival among tested radiation types, with RBE values ranging from 3.51-3.69 observed in the three radioresistant cell lines. The radiosensitive cell line investigated demonstrated similar cell survival for carbon and iron ion irradiation. The results of the present study suggest that heavy ions are more effective for killing radioresistant canine OSA cells when compared with gamma-rays and protons. This markedly increased efficiency of cell killing is an attractive reason for utilizing heavy ions for radioresistant canine OSA.

Effects of Charged Particles on Human Tumor Cells

The use of charged particle therapy in cancer treatment is growing rapidly, in large part because the exquisite dose localization of charged particles allows for higher radiation doses to be given to tumor tissue while normal tissues are exposed to lower doses and decreased volumes of normal tissues are irradiated. In addition, charged particles heavier than protons have substantial potential clinical advantages because of their additional biological effects, including greater cell killing effectiveness, decreased radiation resistance of hypoxic cells in tumors, and reduced cell cycle dependence of radiation response. These biological advantages depend on many factors, such as endpoint, cell or tissue type, dose, dose rate or fractionation, charged particle type and energy, and oxygen concentration. This review summarizes the unique biological advantages of charged particle therapy and highlights recent research and areas of particular research needs, such as quantification of relative biological effectiveness (RBE) for various tumor types and radiation qualities, role of genetic background of tumor cells in determining response to charged particles, sensitivity of cancer stem-like cells to charged particles, role of charged particles in tumors with hypoxic fractions, and importance of fractionation, including use of hypofractionation, with charged particles.

Monitoring bone and soft-tissue tumors after carbon-ion radiotherapy using ¹⁸F-FDG positron emission tomography: a retrospective cohort study

Background

The results of treatment for malignant bone and soft-tissue tumors arising from the deep trunk and pelvis are still not acceptable due to the relatively high recurrence and low overall survival rates. Recently, carbon ion radiotherapy (CIRT) was applied for several malignancies, including bone and soft-tissue sarcomas, and provided favorable results. However, it has been unclear what modalities should be used for evaluating the response and for the follow-up of these patients. Here, we analyzed the methods used to predict local recurrence and to find local failures or metastases.

Methods

We analyzed 37 patients with bone and soft-tissue tumors who received CIRT at our institute. The patients were examined with FDG positron emission tomography (PET) and enhanced MRI before and three months after CIRT. The pre-treatment maximum standardized uptake value (SUVmax), and that three months after treatment, the difference between the pre- and post-CIRT SUVmax, the ratio of the post- to pre-SUVmax in FDG-PET and the size of the tumors were evaluated as predictors for local recurrence. FDG-PET and enhanced MRI were used to detect local recurrence.

Results

Local recurrence appeared in 10 cases after CIRT. Nine of the 10 lesions (90.0 %) were detected with FDG-PET, while enhanced MRI detected just 50.0 % of the recurrences. One case of local recurrence, in which the lesion was negative on FDG-PET, was detected using enhanced MRI. A receiver operating characteristic curve analysis showed that neither the SUVmax on FDG-PET nor the tumor size before or three months after CIRT could be used to predict local recurrence.

Conclusions

The combination of FDG-PET and enhanced MRI is recommended to detect local recurrence for patients with sarcomas who have received CIRT; however, no parameters obtained during the examinations performed before and three months after CIRT accurately predicted the development of local recurrence.

Ionizing Particle Radiation as a Modulator of Endogenous Bone Marrow Cell Reprogramming: Implications for Hematological Cancers

Exposure of individuals to ionizing radiation (IR), as in the case of astronauts exploring space or radiotherapy cancer patients, increases their risk of developing secondary cancers and other health-related problems. Bone marrow (BM), the site in the body where hematopoietic stem cell (HSC) self-renewal and differentiation to mature blood cells occurs, is extremely sensitive to low-dose IR, including irradiation by high-charge and high-energy particles. Low-dose IR induces DNA damage and persistent oxidative stress in the BM hematopoietic cells. Inefficient DNA repair processes in HSC and early hematopoietic progenitors can lead to an accumulation of mutations whereas long-lasting oxidative stress can impair hematopoiesis itself, thereby causing long-term damage to hematopoietic cells in the BM niche. We report here that low-dose ¹H- and ⁵⁶Fe-IR significantly decreased the hematopoietic early and late multipotent progenitor (E- and L-MPP, respectively) cell numbers in mouse BM over a period of up to 10 months after exposure. Both ¹H- and ⁵⁶Fe-IR increased the expression of pluripotent stem cell markers Sox2, Nanog, and Oct4 in L-MPPs and 10 months post-IR exposure. We postulate that low doses of ¹H- and ⁵⁶Fe-IR may induce endogenous cellular reprogramming of BM hematopoietic progenitor cells to assume a more primitive pluripotent phenotype and that IR-induced oxidative DNA damage may lead to mutations in these BM progenitors. This could then be propagated to successive cell lineages. Persistent impairment of BM progenitor cell populations can disrupt hematopoietic homeostasis and lead to hematologic disorders, and these findings warrant further mechanistic studies into the effects of low-dose IR on the functional capacity of BM-derived hematopoietic cells including their self-renewal and pluripotency.

Inhibition of DNA-PKcs enhances radiosensitivity and increases the levels of ATM and ATR in NSCLC cells exposed to carbon ion irradiation

Non-small cell lung cancer (NSCLC) exhibits radioresistance to conventional rays, due to its DNA damage repair systems. NSCLC may potentially be sensitized to radiation treatment by reducing those factors that continuously enhance the repair of damaged DNA. In the present study, normal lung fibroblast MRC-5 and lung cancer A549 cells were treated with NU7026 and CGK733, which are inhibitors of the DNA-dependent protein kinase catalytic subunit (PKcs) and ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR), respectively, followed by exposure to X-rays and carbon ion irradiation. The cytotoxic activity, cell survival rate, DNA damage repair ability, cell cycle arrest and apoptosis rate of the treated cells were analyzed with MTT assay, colony formation assay, immunofluorescence and flow cytometry, respectively. The transcription and translation levels of the ATM, ATR and DNA-PKcs genes were detected by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The results indicated that the radiosensitivity and DNA repair ability of A549 cells were reduced, and the percentages of apoptotic cells and those arrested at the G₂/M phase of the cell cycle were significantly increased, following ionizing radiation with inhibitor-pretreatment. The expression levels of ATM, ATR, DNA-PKcs and phosphorylated histone H2AX, a biomarker for DNA double-strand breaks, were all upregulated at the transcriptional or translational level in A549 cells treated with carbon ion irradiation, compared with the control and X-rays-treated cells. In addition, the treatment with 5–50 µM NU7026 or CGK733 did not produce any obvious cytotoxicity in MRC-5 cells, and the effect of the DNA-PKcs-inhibitor on enhancing the radiosensitivity of A549 cells was stronger than that observed for the ATM and ATR-inhibitor. These findings demonstrated a minor role for ATM and ATR in radiation-induced cell death, since the upregulation of ATM and ATR did not rescue the A549 cells subjected to ionizing irradiation. Therefore, future studies on DNA-PKcs, ATM and ATR may lead to novel specific therapies that supplement general radiotherapy for the treatment of lung cancer.