Particle therapy for cancers: a new weapon in radiation therapy

Treatment strategies and molecular mechanism of radiotherapy combined with immunotherapy in colorectal cancer

Radiotherapy (RT) remodels the tumor immune microenvironment (TIME) and modulates the immune response to indirectly destroy tumor cells, in addition to directly killing tumor cells. RT combined with immunotherapy may significantly enhance the efficacy of RT in colorectal cancer by modulating the microenvironment. However, the molecular mechanisms by which RT acts as an immunomodulator to modulate the immune microenvironment remain unclear. Further, the optimal modalities of RT combined with immunotherapy for the treatment of colorectal cancer, such as the time point of combining RT and immunization, the fractionation pattern and dosage of radiotherapy, and other methods to improve the efficacy, are also being explored parallelly. To address these aspects, in this review, we summarized the mechanisms by which RT modulates TIME and concluded the progress of RT combined with immunization in preclinical and clinical trials. Finally, we discussed heavy ion radiation therapy and the efficacy of prediction markers and other immune combination therapies. Overall, combining RT with immunotherapy to enhance antitumor effects will have a significant clinical implication and will help to facilitate individualized treatment modalities.

Assessing the Impact of Charged Particle Radiation Therapy for Head and Neck Adenoid Cystic Carcinoma: A Systematic Review and Meta-Analysis

Purpose: Head and neck adenoid cystic carcinoma (HNACC) is a radioresistant tumor. Particle therapy, primarily proton beam therapy and carbon-ion radiation, is a potential radiotherapy treatment for radioresistant malignancies. This study aims to conduct a meta-analysis to evaluate the impact of charged particle radiation therapy on HNACC. Methods: A comprehensive search was conducted in Pubmed, Cochrane Library, Web of Science, Embase, and Medline until December 31, 2022. The primary endpoints were overall survival (OS), local control (LC), and progression-free survival (PFS), while secondary outcomes included treatment-related toxicity. Version 17.0 of STATA was used for all analyses. Results: A total of 14 studies, involving 1297 patients, were included in the analysis. The pooled 5-year OS and PFS rates for primary HNACC were 78% (95% confidence interval [CI] = 66-91%) and 62% (95% CI = 47-77%), respectively. For all patients included, the pooled 2-year and 5-year OS, LC, and PFS rates were as follows: 86.1% (95% CI = 95-100%) and 77% (95% CI = 73-82%), 92% (95% CI = 84-100%) and 73% (95% CI = 61-85%), and 76% (95% CI = 68-84%) and 55% (95% CI = 48-62%), respectively. The rates of grade 3 and above acute toxicity were 22% (95% CI = 13-32%), while late toxicity rates were 8% (95% CI = 3-13%). Conclusions: Particle therapy has the potential to improve treatment outcomes and raise the quality of life for HNACC patients. However, further research and optimization are needed due to the limited availability and cost considerations associated with this treatment modality.

Carbon ion radiotherapy combined with immunotherapy: synergistic anti-tumor efficacy and preliminary investigation of ferroptosis

Carbon ion radiotherapy (CIRT) may yield satisfactory clinical outcomes for patients who are resistant to radiotherapy. However, the therapeutic impact of carbon ions is still limited in certain recurring or refractory tumors. Therefore, we aimed to evaluate the synergistic anti-tumor effects of immune checkpoint inhibitors (ICIs) in combination with CIRT. We then explored the involvement of ferroptosis in a preliminary investigation. A tumor-bearing mouse model was established, and mice were inoculated subcutaneously with B16-OVA cells into the flanks of both hind legs. Mice were assigned to four groups to receive CIRT, ICIs, or combined treatment. Thereafter, we conducted transcriptome sequencing (RNA-seq), bioinformatics analysis, and various immune-related experiments on the available tumor tissues to investigate differences in the synergistic anticancer effects and potential mechanisms across the groups. The combination therapies significantly improved the survival of mice and inhibited tumor growth, both at local and distant sites. Based on bioinformatics and RNA-seq data, immune-related pathways and genes, immune cell infiltration, and the production of cytokines and chemokines were the most enhanced in the combined treatment group compared to other groups. Finally, we identified a potential role for ferroptosis in the development of local anti-tumor synergy during CIRT combination treatment. In conclusion, this study showed that CIRT and ICIs can enhance the anti-tumor immune effects. We also proposed that ferroptosis may induce anti-tumor effects in CIRT combination therapy, offering a unique perspective on its ability to enhance immunotherapy responses.

TLR4 Agonist MPLA Ameliorates Heavy-Ion Radiation Damage via Regulating DNA Damage Repair and Apoptosis

Heavy-ion radiation received during radiotherapy as well as the heavy-ion radiation received during space flight are equally considered harmful. Our previous study showed that TLR4 low toxic agonist, monophosphoryl lipid A (MPLA), alleviated radiation injury resulting from exposure to low-LET radiation. However, the role and mechanism of MPLA in heavy-ion-radiation injury are unclear. This study aimed to investigate the role of MPLA on radiation damage. Our data showed that MPLA treatment alleviated the heavy-ion-induced damage to microstructure and the spleen and testis indexes. The number of karyocytes in the bone marrow from the MPLA-treated group was higher than that in the irradiated group. Meanwhile, western blotting analysis of intestine proteins showed that pro-apoptotic proteins (cleaved-caspase3 and Bax) were downregulated while anti-apoptotic proteins (Bcl-2) were upregulated in the MPLA-treated group. Our in vitro study demonstrated that MPLA significantly improved cell proliferation and inhibited cell apoptosis after irradiation. Moreover, immunofluorescence staining and quantification of nucleic γ-H2AX and 53BP1 foci also suggested that MPLA significantly attenuated cellular DNA damage repair. Collectively, the above evidence supports the potential ability of MPLA to protect against heavy-ion-radiation injury by inhibiting apoptosis and alleviating DNA damage in vivo and vitro, which could be a promising medical countermeasure for the prevention of heavy-ion-radiation injury.

Particle radiotherapy in the era of radioimmunotherapy

Radiotherapy (RT) is one of the key modalities for cancer treatment, and more than 70% of tumor patients will receive RT during the course of their disease. Particle radiotherapy, such as proton radiotherapy, carbon-ion radiotherapy (CIRT) and boron neutron capture therapy (BNCT), is currently available for the treatment of patients Immunotherapy combined with photon RT has been successfully used in the clinic. The effect of immunotherapy combined with particle RT is an area of interest. However, the molecular mechanisms underlying the effects of combined immunotherapy and particle RT remain largely unknown. In this review, we summarize the properties of different types of particle RT and the mechanisms underlying their radiobiological effects. Additionally, we compared the main molecular players in photon RT and particle RT and the mechanisms involved the RT-mediated immune response.

Emerging evidence for adapting radiotherapy to immunotherapy

Immunotherapy has revolutionized the clinical management of many malignancies but is infrequently associated with durable objective responses when used as a standalone treatment approach, calling for the development of combinatorial regimens with superior efficacy and acceptable toxicity. Radiotherapy, the most commonly used oncological treatment, has attracted considerable attention as a combination partner for immunotherapy owing to its well-known and predictable safety profile, widespread clinical availability, and potential for immunostimulatory effects. However, numerous randomized clinical trials investigating radiotherapy-immunotherapy combinations have failed to demonstrate a therapeutic benefit compared with either modality alone. Such a lack of interaction might reflect suboptimal study design, choice of end points and/or administration of radiotherapy according to standard schedules and target volumes. Indeed, radiotherapy has empirically evolved towards radiation doses and fields that enable maximal cancer cell killing with manageable toxicity to healthy tissues, without much consideration of potential radiation-induced immunostimulatory effects. Herein, we propose the concept that successful radiotherapy-immunotherapy combinations might require modifications of standard radiotherapy regimens and target volumes to optimally sustain immune fitness and enhance the antitumour immune response in support of meaningful clinical benefits.

Chondrosarcoma Resistance to Radiation Therapy: Origins and Potential Therapeutic Solutions

Chondrosarcoma is a malignant cartilaginous tumor that is particularly chemoresistant and radioresistant to X-rays. The first line of treatment is surgery, though this is almost impossible in some specific locations. Such resistances can be explained by the particular composition of the tumor, which develops within a dense cartilaginous matrix, producing a resistant area where the oxygen tension is very low. This microenvironment forces the cells to adapt and dedifferentiate into cancer stem cells, which are described to be more resistant to conventional treatments. One of the main avenues considered to treat this type of tumor is hadrontherapy, in particular for its ballistic properties but also its greater biological effectiveness against tumor cells. In this review, we describe the different forms of chondrosarcoma resistance and how hadrontherapy, combined with other treatments involving targeted inhibitors, could help to better treat high-grade chondrosarcoma.

Monte Carlo-Based Radiobiological Investigation of the Most Optimal Ion Beam Forming SOBP for Particle Therapy

Proton (p) and carbon (C) ion beams are in clinical use for cancer treatment, although other particles such as He, Be, and B ions have more recently gained attention. Identification of the most optimal ion beam for radiotherapy is a challenging task involving, among others, radiobiological characterization of a beam, which is depth-, energy-, and cell type- dependent. This study uses the FLUKA and MCDS Monte Carlo codes in order to estimate the relative biological effectiveness (RBE) for several ions of potential clinical interest such as p, ⁴He, ⁷Li, ¹⁰Be, ¹⁰B, and ¹²C forming a spread-out Bragg peak (SOBP). More specifically, an energy spectrum of the projectiles corresponding to a 5-cm SOBP at a depth of 8 cm was used. All secondary particles produced by the projectiles were considered and RBE was determined based on radiation-induced Double Strand Breaks (DSBs), as calculated by MCDS. In an attempt to identify the most optimal ion beam, using the latter data, biological optimization was performed and the obtained depth-dose distributions were inter-compared. The results showed that ¹²C ions are more effective inside the SOBP region, which comes at the expense of higher dose values at the tail (i.e., after the SOBP). In contrast, p beams exhibit a higher DSOPB/DEntrance ratio, if physical doses are considered. By performing a biological optimization in order to obtain a homogeneous biological dose (i.e., dose × RBE) in the SOBP, the corresponding advantages of p and ¹²C ions are moderated. ⁷Li ions conveniently combine a considerably lower dose tail and a DSOPB/DEntrance ratio similar to ¹²C. This work contributes towards identification of the most optimal ion beam for cancer therapy. The overall results of this work suggest that ⁷Li ions are of potential interest, although more studies are needed to demonstrate the relevant advantages. Future work will focus on studying more complex beam configurations.

Boron clusters (ferrabisdicarbollides) shaping the future as radiosensitizers for multimodal (chemo/radio/PBFR) therapy of glioblastoma

Glioblastoma multiforme (GBM) is the most common and fatal primary brain tumor, and is highly resistant to conventional radiotherapy and chemotherapy. Therefore, the development of multidrug resistance and tumor recurrence are frequent. Given the poor survival with the current treatments, new therapeutic strategies are urgently needed. Radiotherapy (RT) is a common cancer treatment modality for GBM. However, there is still a need to improve RT efficiency, while reducing the severe side effects. Radiosensitizers can enhance the killing effect on tumor cells with less side effects on healthy tissues. Herein, we present our pioneering study on the highly stable and amphiphilic metallacarboranes, ferrabis(dicarbollides) ([o-FESAN]^- and [8,8'-I2-o-FESAN]^-), as potential radiosensitizers for GBM radiotherapy. We propose radiation methodologies that utilize secondary radiation emissions from iodine and iron, using ferrabis(dicarbollides) as iodine/iron donors, aiming to achieve a greater therapeutic effect than that of a conventional radiotherapy. As a proof-of-concept, we show that using 2D and 3D models of U87 cells, the cellular viability and survival were reduced using this treatment approach. We also tested for the first time the proton boron fusion reaction (PBFR) with ferrabis(dicarbollides), taking advantage of their high boron (¹¹B) content. The results from the cellular damage response obtained suggest that proton boron fusion radiation therapy, when combined with boron-rich compounds, is a promising modality to fight against resistant tumors. Although these results are encouraging, more developments are needed to further explore ferrabis(dicarbollides) as radiosensitizers towards a positive impact on the therapeutic strategies for GBM.

Modern Radiotherapy Technology: Obstacles and Opportunities to Access in Low- and Middle-Income Countries

Low- and middle-income countries (LMICs) have a large burden of cancer with differential population needs and outcomes compared to high-income countries. Access to radiotherapy, especially modern technology, is a major challenge. Modern radiotherapy has been demonstrated with better utility in overall cancer outcomes. We deliberate various challenges and opportunities unique to LMICs' set up for access to modern radiotherapy technology in the light of discussions and deliberations made during the recently concluded annual meeting of Tata Memorial Centre, India. We take examples available from various LMICs in this direction in our manuscript.

Technological Advancements in External Beam Radiation Therapy (EBRT): An Indispensable Tool for Cancer Treatment

Recent technological advancements have increased the efficacy of radiotherapy, leading to effective management of cancer patients with enhanced patient survival and improved quality of life. Several important developments like multileaf collimator, integration of imaging techniques like positron emission tomography (PET) and computed tomography (CT), involvement of advanced dose calculation algorithms, and delivery techniques have increased tumor dose distribution and decreased normal tissue toxicity. Three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), stereotactic radiotherapy, image-guided radiotherapy (IGT), and particle therapy have facilitated the planning procedures, accurate tumor delineation, and dose estimation for effective personalized treatment. In this review, we present the technological advancements in various types of EBRT methods and discuss their clinical utility and associated limitations. We also reveal novel approaches of using biocompatible yttrium oxide scintillator-photosensitizer complex (YSM) that can generate X-ray induced cytotoxic reactive oxygen species, facilitating X-ray activated photodynamic therapy (XPDT (external beam) and/or iXPDT (internal X-ray source)) and azido-derivatives of 2-deoxy-D-glucose (2-DG) as agents for site-specific radiation-induced DNA damage.

Preliminary Safety and Efficacy of Proton Plus Carbon-Ion Radiotherapy With Concurrent Chemotherapy in Limited-Stage Small Cell Lung Cancer

Objectives

This study aimed to investigate the tolerance and effect of proton plus carbon-ion radiotherapy with concurrent chemotherapy in limited-stage small cell lung cancer using the pencil beam scanning technique.

Materials and Methods

From March 2017 to April 2020, 25 patients with limited-stage small cell lung cancer treated with combined proton and carbon-ion radiotherapy were analyzed. The primary lesions and involved lymph nodes were irradiated using 2-4 portals. Proton and sequential carbon-ion beams were delivered with a median dose of 67.1 (range, 63-74.8) GyE as fraction doses of 2.0-2.2 GyE with proton beams in 20-23 fractions and 3.0-3.8 GyE with carbon ions in 5-8 fractions. Chemotherapy was delivered concurrently with radiotherapy in all patients.

Results

At the last follow-up, the 2-year overall and locoregional progression-free survival rates were 81.7% and 66.7%, respectively. Radiochemotherapy was well tolerated, with grade 1, 2, and 3 acute toxicities occurring in 12.0%, 68.0%, and 20.0% of patients, respectively. All grade 3 acute toxicities were hematologically related changes. One patient experienced grade 3 acute non-hematological toxicity in the esophagus, and one other patient had grade 3 bronchial obstruction accompanied by obstructive atelectasis as a late side effect.

Conclusion

Proton plus carbon-ion radiotherapy using pencil beam scanning yielded promising survival rates and tolerability in patients with limited-stage small cell lung cancer. A prospective clinical study is warranted to validate the therapeutic efficacy of particle radiotherapy in combination with chemotherapy in limited-stage small cell lung cancer.

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.

Technological Advances in Charged-Particle Therapy

Charted-particle therapy (CPT) benefits cancer patients by localizing doses in the tumor volume while minimizing the doses delivered to normal tissue through its unique physical and biological characteristics. The world's first CPT applied on humans was proton beam therapy (PBT), which was performed in the mid-1950s. Among heavy ions, carbon ions showed the most favorable biological characteristics for the treatment of cancer patients. Carbon ions show coincidence between the Bragg peak and maximum value of relative biological effectiveness. In addition, they show low oxygen enhancement ratios. Therefore, carbon-ion radiotherapy (CIRT) has become mainstream in the treatment of cancer patients using heavy ions. CIRT was first performed in 1977 at the Lawrence Berkeley Laboratory. The CPT technology has advanced in the intervening decades, enabling the use of rotating gantry, beam delivery with fast pencil-beam scanning, image-guided particle therapy, and intensity-modulated particle therapy. As a result, as of 2019, a total of 222,425 and 34,138 patients with cancer had been treated globally with PBT and CIRT, respectively. For more effective and efficient CPT, many groups are currently conducting further studies worldwide. This review summarizes recent technological advances that facilitate clinical use of CPT.

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

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

The Impacts of Different Types of Radiation on the CRT and PDL1 Expression in Tumor Cells Under Normoxia and Hypoxia

Introduction

Hypoxia is a hallmark of cancer that may contribute to an immunosuppressive microenvironment and promote radioresistance. High linear energy transfer (LET) radiation is considered to be able to overcome the negative effects of hypoxia. However, the anti-tumorigenic effects induced by low or high LET radiation have not been fully elucidated. This study aimed to compare the effects of different types of radiation on the immune response, particularly the impact on calreticulin (CRT), and programmed cell death ligand 1 (PDL1) expression.

Methods

Four human tumor cell lines were investigated in this study. Cells in normoxic and hypoxic groups were irradiated with 4Gy (physical dose) photon, proton, and carbon-ion radiation, respectively. The expression of CRT and PDL1 was detected 48 h after irradiation, and the median fluorescence intensities (MFIs) were compared by flow cytometry. Meanwhile, the radiosensitivity of tumor cells in each group was also compared by colony formation assays and flow cytometry.

Results

All types of radiation could significantly inhibit the colony formation of tumor cells under normoxia. However, the efficacy of photon and proton radiation was impaired under hypoxia. Carbon-ion radiation could still inhibit colony formation. The percentage of viable cells after irradiation was higher under hypoxia compared with those under normoxia. The CRT expression under normoxia was significantly increased after radiation. Carbon-ion radiation enhanced CRT expression compared to photon and proton radiation. Conversely, under hypoxia, the CRT expression level was significantly upregulated at baseline (0Gy). Radiation could not increase the expression further. PDL1 expression was also significantly increased by radiation under normoxia in all cell lines except the Ln18 cell line. Carbon-ion radiation induced the most significant increase. Under hypoxia, the PDL1 expression level was also upregulated at baseline and radiation could not increase expression further.

Conclusion

Tumor cells were resistant to photon and proton but sensitive to carbon-ion radiation under hypoxia. Carbon-ion radiation could induce the highest CRT and PDL1 expression under normoxia. However, under hypoxia, radiation could not further enhance the high baseline expression of CRT and PDL1.

Comparison of the effects of photon, proton and carbon-ion radiation on the ecto-calreticulin exposure in various tumor cell lines

Background

Accumulating evidence suggested that radiotherapy can activate anti-tumor immune responses by triggering immunogenic cell death (ICD) of tumor cells. Calreticulin is regarded as one of the most important markers of ICD. The cell surface translocation of calreticulin (ecto-CRT) serves as an "eat me" signal for phagocytosis of dying cells, which plays a pivotal role in activating anti-tumor immunity. However, there is limited knowledge describing the effects of proton and carbon-ion radiation on ecto-CRT exposure. Hence, we investigated ecto-CRT exposure in multiple human carcinoma cell lines irradiated by proton and carbon-ion in comparison to photon.

Methods

This study examined four human cancer cell lines including A549 (lung adenocarcinoma), U251MG (glioma), Tca8113 (tongue squamous carcinoma), and CNE-2 (nasopharyngeal carcinoma). Cell lines were irradiated with photon, proton or carbon-ion at 0, 2, 4, 10 Gy (physical dose). The ecto-CRT exposure level was analyzed by flow cytometry at 12, 24, and 48 h post-irradiation. The median fluorescence intensity was calculated by FlowJo.

Results

All three types of radial beam increased ecto-CRT exposure of the 4 tumor cell lines in a time-dependent manner. Ecto-CRT exposure significantly elevated 1.5-2.4 times over 48 h post-irradiation compared with controls (P<0.05). Proton and photon increased ecto-CRT exposure with dose escalation. Photon and proton at 10 Gy increased the most ecto-CRT exposure (P<0.05), while carbon-ion increased most ecto-CRT exposure at 4 Gy rather than 10 or 2 Gy. When compared with iso-physical dose at 48 h post-irradiation, proton showed a similar effectiveness with photon. While carbon-ion has significantly stronger effects on increasing ecto-CRT than proton and photon at 2 and 4 Gy, but changed oppositely at 10 Gy (P<0.05).

Conclusions

All the three types of radiation can increase the ecto-CRT exposure in a time-dependent manner. Proton and photon radiation were equally effective in inducing ecto-CRT exposure, while carbon-ion revealed a different effectiveness in comparison to photon and proton.

Overcoming radioresistance in WiDr cells with heavy ion irradiation and radiosensitization by 2-deoxyglucose with photon irradiation

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2-DG acts as a radiosensitizer to photons depending on the time of its application.

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There is no sensitization to ¹²C irradiation by 2-DG.

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¹²C combination therapy still has the higher dose effectiveness.

Background and purpose

Radiosensitizers and heavy ion irradiation could improve therapy for female patients with malignant tumors located in the pelvic region through dose reduction. Aim of the study was to investigate the radiosensitizing potential of 2-deoxy-d-glucose (2-DG) in combination with carbon ion-irradiation (¹²C) in representative cell lines of cancer in the female pelvic region.

Materials and methods

The human cervix carcinoma cell line CaSki and the colorectal carcinoma cell line WiDr were used. 2-DG was employed in two different settings, pretreatment and treatment simultaneous to irradiation. Clonogenic survival, α and β values for application of the linear quadratic model and relative biological effectiveness (RBE) were determined. ANOVA tests were used for statistical group comparison. Isobolograms were generated for curve comparisons.

Results

The comparison of monotherapy with ¹²C versus photons yielded RBE values of 2.4 for CaSki and 3.5 for WiDr along with a significant increase of α values in the ¹²C setting. 2-DG monotherapy reduced the colony formation of both cell lines. Radiosensitization was found in WiDr for the combination of photon irradiation with synchronous application of 2-DG. The same setup for ¹²C showed no radiosensitization, but rather an additive effect. In all settings with CaSki, the combination of irradiation and 2-DG exhibited additive properties.

Conclusion

The combination of 2-DG and photon therapy, as well as irradiation with carbon ions can overcome radioresistance of tumor cells such as WiDr.

Radioprotective effect of newly synthesized toll-like receptor 5 agonist, KMRC011, in mice exposed to total-body irradiation

Exposure to ionizing radiation leads to severe damages in radiosensitive organs and induces acute radiation syndrome, including effects on the hematopoietic system and gastrointestinal system. In this study, the radioprotective ability of KMRC011, a novel toll-like receptor 5 (TLR5) agonist, was investigated in C57BL6/N mice exposed to lethal total-body gamma-irradiation. In a 30-day survival study, KMRC011-treated mice had a significantly improved survival rate compared with control after 11 Gy total-body irradiation (TBI), and it was found that the radioprotective activity of KMRC011 depended on its dosage and repeated treatment. In a 5-day short-term study, we demonstrated that KMRC011 treatment stimulated cell proliferation and had an anti-apoptotic effect. Furthermore, KMRC011 increased the expressions of genes related to DNA repair, such as Rad21, Gadd45b, Sod2 and Irg1, in the small intestine of lethally irradiated mice. Interestingly, downregulation of NF-κB p65 in the mouse intestine by KMRC011 treatment was observed. This data indicated that KMRC011 exerted a radioprotective activity partially by regulating NF-κB signaling. Finally, peak expression levels of G-CSF, IL-6, IFN-γ, TNF-α and IP-10 induced by KMRC011 treatment were different depending on the route of administration and type of cytokine. These cytokines could be used as candidate biomarkers for the evaluation of KMRC011 clinical efficacy. Our data indicated that KMRC011 has radioprotective activity in lethally irradiated mice and may be developed as a therapeutic agent for radioprotection.

Bystander effectors of chondrosarcoma cells irradiated at different LET impair proliferation of chondrocytes

While the dose-response relationship of radiation-induced bystander effect (RIBE) is controversial at low and high linear energy transfer (LET), mechanisms and effectors of cell-to-cell communication stay unclear and highly dependent of cell type. In the present study, we investigated the capacity of chondrocytes in responding to bystander factors released by chondrosarcoma cells irradiated at different doses (0.05 to 8 Gy) with X-rays and C-ions. Following a medium transfer protocol, cell survival, proliferation and DNA damages were quantified in bystander chondrocytes. The bystander factors secreted by chondrosarcoma cells were characterized. A significant and major RIBE response was observed in chondrocyte cells (T/C-28a2) receiving conditioned medium from chondrosarcoma cells (SW1353) irradiated with 0.1 Gy of X-rays and 0.05 Gy of C-ions, resulting in cell survivals of 36% and 62%, respectively. Micronuclei induction in bystander cells was observed from the same low doses. The cell survival results obtained by clonogenic assays were confirmed using impedancemetry. The bystander activity was vanished after a heat treatment or a dilution of the conditioned media. The cytokines which are well known as bystander factors, TNF-α and IL-6, were increased as a function of doses and LET according to an ELISA multiplex analysis. Together, the results demonstrate that irradiated chondrosarcoma cells can communicate stress factors to non-irradiated chondrocytes, inducing a wide and specific bystander response related to both doses and LET.

Whole-Body 12C Irradiation Transiently Decreases Mouse Hippocampal Dentate Gyrus Proliferation and Immature Neuron Number, but Does Not Change New Neuron Survival Rate

High-charge and -energy (HZE) particles comprise space radiation and they pose a challenge to astronauts on deep space missions. While exposure to most HZE particles decreases neurogenesis in the hippocampus—a brain structure important in memory—prior work suggests that ¹²C does not. However, much about ¹²C’s influence on neurogenesis remains unknown, including the time course of its impact on neurogenesis. To address this knowledge gap, male mice (9–11 weeks of age) were exposed to whole-body ¹²C irradiation 100 cGy (IRR; 1000 MeV/n; 8 kEV/µm) or Sham treatment. To birthdate dividing cells, mice received BrdU i.p. 22 h post-irradiation and brains were harvested 2 h (Short-Term) or three months (Long-Term) later for stereological analysis indices of dentate gyrus neurogenesis. For the Short-Term time point, IRR mice had fewer Ki67, BrdU, and doublecortin (DCX) immunoreactive (+) cells versus Sham mice, indicating decreased proliferation (Ki67, BrdU) and immature neurons (DCX). For the Long-Term time point, IRR and Sham mice had similar Ki67+ and DCX+ cell numbers, suggesting restoration of proliferation and immature neurons 3 months post-¹²C irradiation. IRR mice had fewer surviving BrdU+ cells versus Sham mice, suggesting decreased cell survival, but there was no difference in BrdU+ cell survival rate when compared within treatment and across time point. These data underscore the ability of neurogenesis in the mouse brain to recover from the detrimental effect of ¹²C exposure.

Homogeneity study of proton and carbon ion scanning beams using combinations of different spot sizes and grid sizes

PURPOSE

Different scanning ion beam delivery systems have different delivery accuracies, and the resulting delivery errors will affect field homogeneity. This study was performed to determine an appropriate combination of spot size (FWHM) and spot grid size (GS), which can provide homogenous dose distributions for both proton and carbon ion scanning beam radiotherapy. The combination of the two parameters is represented by a combination factor named n, which is the quotient of FWHM divided by GS.

METHODS

Delivery uncertainties of our beam delivery system were analyzed using log files from the treatment of 28 patients. Square fields for different n values were simulated with and without considering the delivery uncertainties, and the homogeneity of these square fields was analyzed. All spots were located on a rectilinear grid with equal spacing in the x and y directions. In addition to the simulations, we performed experimental measurements using both protons and carbon ions. We selected six energy levels for both proton and carbon ions. For each energy level, we created six square field plans with different n values (1, 1.5, 2, 2.5, 3, 3.5). These plans were delivered and the field homogeneity was determined using a film measurement.

RESULTS

The simulations demonstrated that under ideal condition (i.e., the delivery system has no delivery errors), the homogeneity is within 3% when n ≥ 1.1. When delivery uncertainties were included in the simulation, the homogeneity is within 3% when n ≥ 2.3. For film measurements, homogeneity under 3% was achieved when n ≥ 2.5.

CONCLUSION

A practical method to determine the appropriate combination of spot size and grid size is here presented. Considering the uncertainties of the beam delivery system, an n value of 2.5 is good enough to meet the lateral homogeneity requests in our center. The methods used here can be easily repeated in other particle therapy centers.

Functional image-guided dose escalation in gliomas using of state-of-the-art photon vs. proton therapy

BACKGROUND

Recurrences of glioma are usually local, suggesting the need for higher tumor dose. We investigated the boundaries for dose escalation of an ¹⁸F-fluoro-ethyl-tyrosine positron emission tomography defined target by intensity-modulated photon therapy (IMRT), volumetric modulated arc therapy (VMAT) and intensity-modulated proton therapy (IMPT).

MATERIALS AND METHODS

Standard dose (60 Gy) and dose-escalated plans were calculated for seven patients using IMRT, VMAT and IMPT. The achieved boost dose, the dose to the organs at risk (OAR), the dose homogeneity (defined as overdose volume, ODV) and the ratio of the 30 Gy isodose curve and the boost volume (R30) were compared. The risk of radionecrosis was estimated using the ratio of the dose volume histograms of the brain (range 30-60 Gy).

RESULTS

The mean boost dose was 77.1 Gy for IMRT, 79.2 Gy for VMAT and 85.1 GyE for IMPT. Compared with the standard plan, the ODV was unchanged and the R30 increased (17%) for IMRT. For VMAT, the ODV decreased (7%) and the R30 was unchanged whereas IMPT substantially decreased ODV (61%), R30 (22%), OAR doses as well as the risk of radionecrosis.

CONCLUSIONS

Dose escalation can be achieved with IMRT, VMAT and IMPT while respecting normal tissue constraints, yet with IMPT being most favorable.

Microirradiation techniques in radiobiological research

The aim of this work is to review the uses of laser microirradiation and ion microbeam techniques within the scope of radiobiological research. Laser microirradiation techniques can be used for many different purposes. In a specific condition, through the use of pulsed lasers, cell lysis can be produced for subsequent separation of different analytes. Microsurgery allows for the identification and isolation of tissue sections, single cells and subcellular components, using different types of lasers. The generation of different types of DNA damage, via this type of microirradiation, allows for the investigation of DNA dynamics. Ion microbeams are important tools in radiobiological research. There are only a limited number of facilities worldwide where radiobiological experiments can be performed. In the beginning, research was mostly focused on the bystander effect. Nowadays, with more sophisticated molecular and cellular biological techniques, ion microirradiation is used to unravel molecular processes in the field of radiobiology. These include DNA repair protein kinetics or chromatin modifications at the site of DNA damage. With the increasing relevance of charged particles in tumour therapy and new concepts on how to generate them, ion microbeam facilities are able to address unresolved questions concerning particle tumour therapy.

Role for radiation therapy in melanoma

Although melanoma is generally considered a relative radioresistant tumor, radiation therapy (RT) remains a valid and effective treatment option in definitive, adjuvant, and palliative settings. Definitive RT is generally only used in inoperable patients. Despite a high-quality clinical trial showing adjuvant RT following lymphadenectomy in node-positive melanoma patients prevents local and regional recurrence, the role of adjuvant RT in the treatment of melanoma remains controversial and is underused. RT is highly effective in providing symptom palliation for metastatic melanoma. RT combined with new systemic options, such as immunotherapy, holds promise and is being actively evaluated.

Integrin-based meningioma cell migration is promoted by photon but not by carbon-ion irradiation

PURPOSE

Sublethal doses of photon irradiation (IR) are suspected to increase tumor cell migration and support locoregional recurrence of disease, which has already been shown in other cell lines. This manuscript describes the effect of photon and carbon-ion IR on WHO class I meningioma cell migration and provides an approach to the underlying cellular mechanisms.

MATERIALS AND METHODS

Meningioma cells were gained operatively at the university hospital in Homburg/Saar, Germany. For migration, membranes (8-µm pore sizes) were coated with collagen I, with collagen IV, and with fibronectin. Cells were analyzed in migration experiments with or without serum stimulation, with or without photon and carbon IR 24 h prior to experiments, and with or without integrin antibodies. Fluorescence-activated cell sorting (FACS) analyses of the integrins ανβ1, ανβ3, and ανβ5 were performed without IR and 6, 12 and 24 h after IR. Enzyme-linked immunosorbent assay (ELISA) analyses of matrix metalloproteinases (MMP)-2 and MMP-9 were realized with and without IR after cells were cultured on collagen I, collagen IV, or fibronectin for 24 h. Cells and supernatants for FACS and ELISA were stored at - 18 °C. The significance level was set at 5 % using both Student's t test and two-way ANOVA.

RESULTS

Migration of meningioma cells was serum-inducible (p < 0.001). It could be increased by photon IR (p < 0.02). The integrins ανβ1 and ανβ5 showed a 21 and 11 % higher expression after serum stimulation (not significant), respectively, and ανβ1 expression was raised by 14 % (p = 0.0057) after photon IR. Antibody blockage of the integrins ανβ1 and ανβ5 inhibited serum- and photon-induced migration. Expression of MMP-2 and MMP-9 remained unchanged after both IR and fetal bovine serum (FBS). Carbon-ion IR left both integrin expression and meningioma cell migration unaffected.

CONCLUSION

Photon but not carbon-ion IR promotes serum-based meningioma cell migration. Fibronectin receptor integrin ανβ1 signaling can be identified as an important mechanism for serum- and photon-induced migration of WHO class I meningioma cells.

Radiation oncology: physics advances that minimize morbidity

ABSTRACT 

Radiation therapy has become an ever more successful treatment for many cancer patients. This is due in large part from advances in physics including the expanded use of imaging protocols combined with ever more precise therapy devices such as linear and particle beam accelerators, all contributing to treatments with far fewer side effects. This paper will review current state-of-the-art physics maneuvers that minimize morbidity, such as intensity-modulated radiation therapy, volummetric arc therapy, image-guided radiation, radiosurgery and particle beam treatment. We will also highlight future physics enhancements on the horizon such as MRI during treatment and intensity-modulated hadron therapy, all with the continued goal of improved clinical outcomes.

Carbon ion radiotherapy of human lung cancer attenuates HIF-1 signaling and acts with considerably enhanced therapeutic efficiency

Carbon ion irradiation is an emerging therapeutic option for various tumor entities. Radiation resistance of solid tumors toward photon irradiation is caused by attenuation of DNA damage in less oxygenated tumor areas and by increased hypoxia-inducible factor (HIF)-1 signaling. Carbon ion irradiation acts independently of oxygen; however, the role of HIF-1 is unclear. We analyzed the effect of HIF-1 signaling after carbon ions in comparison to photons by using biological equivalent radiation doses in a human non-small-cell cancer model. The studies were performed in cultured A549 and H1299 cell lines and in A549 xenografts. Knockdown of HIF-1α in vivo combined with photon irradiation delayed tumor growth (23 vs. 13 d; P<0.05). Photon irradiation induced HIF-1α and target genes, predominantly in oxygenated cells (1.6-fold; P<0.05), with subsequent enhanced tumor angiogenesis (1.7-fold; P<0.05). These effects were not observed after carbon ion irradiation. Micro-DNA array analysis indicated that photons, but not carbon ions, significantly induced components of the mTOR (mammalian target of rapamycin) pathway (gene set enrichment analysis; P<0.01) as relevant for HIF-1α induction. After carbon ion irradiation in vivo, we observed substantially decreased HIF-1α levels (8.9-fold; P<0.01) and drastically delayed tumor growth (P<0.01), an important finding that indicates a higher relative biological effectiveness (RBE) than anticipated from the cell survival data. Taken together, the evidence showed that carbon ions mediate an improved therapeutic effectiveness without tumor-promoting HIF-1 signaling.

Advantages of proton therapy in non-small cell lung cancers

The advantage of proton therapy over conventional radiotherapy is enormous, with many clinical advantages. In this review, we summarized the important literature in the advantages of Proton Therapy in Non-small Cell Lung Cancers.