High sensitivity of host Helios+/Neuropilin-1+ Treg to pretransplant conditioning hampers development of OX40bright/integrin-β7+ regulatory cells in acute gastrointestinal GvHD

This study sought to compare the behavior of Treg subsets displaying different coexpression patterns of Neuropilin-1 (Nrp1) and Helios, under the influence of gut stress unrelated to hematopoietic stem cell transplantation, pretransplantation conditioning, and posttransplant gastrointestinal acute graft versus host disease (GI-aGvHD). Host CD4+/CD25hi/Foxp3+ Treg cells, identified by flow cytometry, were isolated from various tissues of mice affected by these stressors. Expression of CD25, CTLA-4, CD39, OX40, integrin-β7, LAG3, TGFβ/LAP, granzyme-A, -B, and interleukin-10 was compared in four Treg subsets displaying Helios or Nrp1 only, both or none. Fluorescence-activated cell sorter-sorted Treg subsets, displaying markers affected in a conditioning- and GI-aGVHD-restricted manner, were further investigated by transcriptome profiling and T-cell suppression assays. We found that conditioning by irradiation greatly diminished the relative frequency of Helios+/Nrp1+ Treg, shifting the balance toward Helios-/Nrp1- Treg in the host. Upregulation of integrin-β7 and OX40 occurred in GI-aGvHD-dependent manner in Helios+/Nrp1+ cells but not in Helios-/Nrp1- Treg. Sorted Treg subsets, confirmed to overexpress Nrp1, Helios, OX40, or integrin-β7, displayed superior immunosuppressive activity and enrichment in activation-related messenger RNA transcripts. Our data suggest that conditioning-induced shrinkage of the Nrp1+/Helios+ Treg subset may contribute to the development of GI-GvHD by impairing gut homing and decreasing the efficiency of Treg-mediated immunosuppression.

Effect of radiotherapy on the DNA cargo and cellular uptake mechanisms of extracellular vesicles

In the past decades, plenty of evidence has gathered pointing to the role of extracellular vesicles (EVs) secreted by irradiated cells in the development of radiation-induced non-targeted effects. EVs are complex natural structures composed of a phospholipid bilayer which are secreted by virtually all cells and carry bioactive molecules. They can travel certain distances in the body before being taken up by recipient cells. In this review we discuss the role and fate of EVs in tumor cells and highlight the importance of DNA specimens in EVs cargo in the context of radiotherapy. The effect of EVs depends on their cargo, which reflects physiological and pathological conditions of donor cell types, but also depends on the mode of EV uptake and mechanisms involved in the route of EV internalization. While the secretion and cargo of EVs from irradiated cells has been extensively studied in recent years, their uptake is much less understood. In this review, we will focus on recent knowledge regarding the EV uptake of cancer cells and the effect of radiation in this process.

The miRNA Content of Bone Marrow-Derived Extracellular Vesicles Contributes to Protein Pathway Alterations Involved in Ionising Radiation-Induced Bystander Responses

Extracellular vesicles (EVs), through their cargo, are important mediators of bystander responses in the irradiated bone marrow (BM). MiRNAs carried by EVs can potentially alter cellular pathways in EV-recipient cells by regulating their protein content. Using the CBA/Ca mouse model, we characterised the miRNA content of BM-derived EVs from mice irradiated with 0.1 Gy or 3 Gy using an nCounter analysis system. We also analysed proteomic changes in BM cells either directly irradiated or treated with EVs derived from the BM of irradiated mice. Our aim was to identify key cellular processes in the EV-acceptor cells regulated by miRNAs. The irradiation of BM cells with 0.1 Gy led to protein alterations involved in oxidative stress and immune and inflammatory processes. Oxidative stress-related pathways were also present in BM cells treated with EVs isolated from 0.1 Gy-irradiated mice, indicating the propagation of oxidative stress in a bystander manner. The irradiation of BM cells with 3 Gy led to protein pathway alterations involved in the DNA damage response, metabolism, cell death and immune and inflammatory processes. The majority of these pathways were also altered in BM cells treated with EVs from mice irradiated with 3 Gy. Certain pathways (cell cycle, acute and chronic myeloid leukaemia) regulated by miRNAs differentially expressed in EVs isolated from mice irradiated with 3 Gy overlapped with protein pathway alterations in BM cells treated with 3 Gy EVs. Six miRNAs were involved in these common pathways interacting with 11 proteins, suggesting the involvement of miRNAs in the EV-mediated bystander processes. In conclusion, we characterised proteomic changes in directly irradiated and EV-treated BM cells, identified processes transmitted in a bystander manner and suggested miRNA and protein candidates potentially involved in the regulation of these bystander processes.

Prostate Cancer Survivors Present Long-Term, Residual Systemic Immune Alterations

Simple Summary

The development of cancer is very often accompanied by systemic immune alterations which can be further aggravated by major anti-cancer therapies. However, there is very little known about how long these alterations persist in patients successfully cured of cancer. The aim of our work was to investigate how cancer and radiotherapy as major anti-cancer treatment modalities impact the immune system long after the successful treatment of a tumor. We investigated prostate cancer patients treated with a special form of radiotherapy (low-dose rate brachytherapy) often used for the treatment of prostate cancer and followed a wide range of immune parameters at regular intervals up to 3 years after the start of the treatment. Our results showed that some immune alterations did not recover after the treatment of the disease, on the contrary, they persisted, and in some cases got even worse. Further studies are needed to explain the causes and the potential long-term consequences of these alterations.

Abstract

Background: The development of cancer and anti-tumor therapies can lead to systemic immune alterations but little is known about how long immune dysfunction persists in cancer survivors. Methods: We followed changes in the cellular immune parameters of prostate cancer patients with good prognostic criteria treated with low dose rate brachytherapy before and up to 3 years after the initiation of therapy. Results: Patients before therapy had a reduced CD4+ T cell pool and increased regulatory T cell fraction and these alterations persisted or got amplified during the 36-month follow-up. A significant decrease in the total NK cell number and a redistribution of the circulating NK cells in favor of a less functional anergic subpopulation was seen in patients before therapy but tumor regression led to the regeneration of the NK cell pool and functional integrity. The fraction of lymphoid DCs was increased in patients both before therapy and throughout the whole follow-up. Increased PDGF-AA, BB, CCL5 and CXCL5 levels were measured in patients before treatment but protein levels rapidly normalized. Conclusions: while NK cell dysfunction recovered, long-term, residual alterations persisted in the adaptive and partly in the innate immune system.

Extracellular Vesicles Derived from Bone Marrow in an Early Stage of Ionizing Radiation Damage Are Able to Induce Bystander Responses in the Bone Marrow

Ionizing radiation (IR)-induced bystander effects contribute to biological responses to radiation, and extracellular vesicles (EVs) play important roles in mediating these effects. In this study we investigated the role of bone marrow (BM)-derived EVs in the bystander transfer of radiation damage. Mice were irradiated with 0.1Gy, 0.25Gy and 2Gy, EVs were extracted from the BM supernatant 24 h or 3 months after irradiation and injected into bystander mice. Acute effects on directly irradiated or EV-treated mice were investigated after 4 and 24 h, while late effects were investigated 3 months after treatment. The acute effects of EVs on the hematopoietic stem and progenitor cell pools were similar to direct irradiation effects and persisted for up to 3 months, with the hematopoietic stem cells showing the strongest bystander responses. EVs isolated 3 months after irradiation elicited no bystander responses. The level of seven microRNAs (miR-33a-3p, miR-140-3p, miR-152-3p, miR-199a-5p, miR-200c-5p, miR-375-3p and miR-669o-5p) was altered in the EVs isolated 24 hour but not 3 months after irradiation. They regulated pathways highly relevant for the cellular response to IR, indicating their role in EV-mediated bystander responses. In conclusion, we showed that only EVs from an early stage of radiation damage could transmit IR-induced bystander effects.

Influence of sample preparation optimization on the accuracy of dose assessment of an automatic non-fluorescent MN scoring system

PURPOSE

Automatizing the scoring of the cytokinesis-blocked micronucleus assay spares a lot of valuable time. The dose-effect relationship can be applied reliably for dose estimation if the quality of the slides is the same from the perspective of the used image processing algorithm. This aspect brings in additional requirements against the quality of the slides compared to the conventional visual scoring.

MATERIALS AND METHODS

An add-in software was created to the non-fluorescent RS-MN automatic MN scoring system which is capable of measuring quantitatively the degree of typical anomalies. The image processing is less reliable when the presence of these anomalies is more frequent. The behavior of the designed sample quality parameters (SQPs) was tested on in vitro irradiated peripheral blood samples (0, 1, and 2 Gy) obtained from a healthy donor and also on samples from patients undergoing low dose-rate brachytherapy.

RESULTS

We examined 20 different SQPs and identified two that are independent and correlate significantly with the error of the fully automatic MN frequency. One is related to the size of the cells and the other reflects the homogeneity of the environment. An equation was established which presents a connection between the error of the auto MN frequency and the SQPs. By adding a fourth cleaning step to the conventional sample preparation and changing the pre-dripping temperature of the slide, the SQP can be modified, and consequently, the sample quality can be improved. The gain in accuracy is 54 ± 10 MN per 1000 binucleated cells, which corresponds to the effects of 0.5 Gy. Around the lowest limit of detection (<0.5 Gy), it means a 50-100% drop in the error of dose, which is significant. With sample quality harmonization, the positive predictive value was raised to 80-93% depending on the dose.

CONCLUSIONS

With the technique described in this paper, the suitability for automated scoring of a micronucleus slide can be tested quantitatively and objectively. A method is presented with which in some cases the uncertainty of the assessed doses due to variance in sample quality can be decreased or if it is not possible its bias can be predicted. The proposed protocol leads to more reliable estimation of dose. The SQPs are designed in a way that they have the potential to be adapted to similar systems.

Blood-Derived Biomarkers of Diagnosis, Prognosis and Therapy Response in Prostate Cancer Patients

Prostate cancer is among the most frequent cancers in men worldwide. Despite the fact that multiple therapeutic alternatives are available for its treatment, it is often discovered in an advanced stage as a metastatic disease. Prostate cancer screening is based on physical examination of prostate size and prostate-specific antigen (PSA) level in the blood as well as biopsy in suspect cases. However, these markers often fail to correctly identify the presence of cancer, or their positivity might lead to overdiagnosis and consequent overtreatment of an otherwise silent non-progressing disease. Moreover, these markers have very limited if any predictive value regarding therapy response or individual risk for therapy-related toxicities. Therefore, novel, optimally liquid biopsy-based (blood-derived) markers or marker panels are needed, which have better prognostic and predictive value than the ones currently used in the everyday routine. In this review the role of circulating tumour cells, extracellular vesicles and their microRNA content, as well as cellular and soluble immunological and inflammation- related blood markers for prostate cancer diagnosis, prognosis and prediction of therapy response is discussed. A special emphasis is placed on markers predicting response to radiotherapy and radiotherapy-related late side effects.

The effect of ionising radiation on the phenotype of bone marrow-derived extracellular vesicles

OBJECTIVES

Ionising radiation-induced alterations affecting intercellular communication in the bone marrow (BM) contribute to the development of haematological pathologies. Extracellular vesicles (EVs), which are membrane-coated particles released by cells, have important roles in intercellular signalling in the BM. Our objective was to investigate the effects of ionising radiation on the phenotype of BM-derived EVs of total-body irradiated mice.

METHODS

CBA mice were irradiated with 0.1 Gy or 3 Gy X-rays. BM was isolated from the femur and tibia 24 h after irradiation. EVs were isolated from the BM supernatant. The phenotype of BM cells and EVs was analysed by flow cytometry.

RESULTS

The mean size of BM-derived EVs was below 300 nm and was not altered by ionising radiation. Their phenotype was very heterogeneous with EVs carrying either CD29 or CD44 integrins representing the major fraction. High-dose ionising radiation induced a strong rearrangement in the pool of BM-derived EVs which were markedly different from BM cell pool changes. The proportion of CD29 and CD44 integrin-harbouring EVs significantly decreased and the relative proportion of EVs with haematopoietic stem cell or lymphoid progenitor markers increased. Low-dose irradiation had limited effect on EV secretion.

CONCLUSIONS

Ionising radiation induced selective changes in the secretion of EVs by the different BM cell subpopulations.

ADVANCES IN KNOWLEDGE

The novelty of the paper consists of performing a detailed phenotyping of BM-derived EVs after in vivo irradiation of mice.

Mitochondrial DNA damage in the hair bulb: can it be used as a noninvasive biomarker of local exposure to low LET ionizing radiation?

Purpose: Our aim was to evaluate whether mitochondrial DNA (mtDNA) damage in hair bulbs could be a suitable biomarker for the detection of local exposure to ionizing radiation.Materials and methods: Mouse hair was collected 4 and 24 hours, 3 and 10 days after single whole-body exposure to 0, 0.1, and 2 Gy radiation. Pubic hair (treated area) and scalp hair (control area) were collected from 13 prostate cancer patients before and after fractioned radiotherapy with an average total dose of 2.7 Gy to follicles after five fractions. Unspecified lesion frequency of mtDNA was analyzed with long PCR, large mtDNA deletion levels were tested with real-time PCR.Results: Unspecified lesion frequency of mtDNA significantly increased in mouse hair 24 hours after irradiation with 2 Gy, but variance among samples was high. No increase in lesion frequency could be detected after 0.1 Gy irradiation. In prostate cancer patients, there was no significant change in either the unspecified lesion frequency or in the proportion of 4934-bp deleted mtDNA in pubic hair after radiotherapy. The proportions of murine 3860-bp common deletion, human 4977-bp common deletion and 7455-bp deleted mtDNA were too low to be analyzed reliably.Conclusions: Our results suggest that the unspecified lesion frequency and proportion of large deletions of mtDNA in hair bulbs are not suitable biomarkers of exposure to ionizing radiation.

Radio-detoxified LPS alters bone marrow-derived extracellular vesicles and endothelial progenitor cells

Stem cell-based therapies raise hope for cell replacement and provide opportunity for cardiac regenerative medicine and tumor therapy. Extracellular vesicles are a membrane-enclosed intercellular delivery system with the potential to improve the therapeutic efficacy of the treatment of a variety of disorders. As the incidence of breast cancer continues to rise, radiotherapy has emerged as a leading treatment modality. Radiotherapy also increases the risk of coronary heart disease and cardiac mortality. In a chest-irradiated mouse model of cardiac injury, we investigated the effects of local irradiation. We found an increased lethality after 16 Gy irradiation. Importantly, radio-detoxified LPS (RD-LPS) treatment prolonged the survival significantly. By flow cytometry, we demonstrated that upon administration of RD-LPS, the number of bone marrow-derived endothelial progenitor cells increased in the bone marrow and, in particular, in the circulation. Furthermore, mass spectrometry analysis showed that RD-LPS altered the proteomic composition of bone marrow cell-derived small extracellular vesicles (sEVs). RD-LPS treatment increased interferon-induced transmembrane protein-3 (IFITM3) expression markedly both in bone marrow cells and in bone marrow cell-derived small extracellular vesicles. This is the first study to demonstrate that radio-detoxified LPS treatment induces an increase of circulating endothelial progenitor cells (EPCs) in parallel with a reduced radiotherapy-related mortality. While the total number of bone marrow-derived extracellular vesicles was significantly increased 24 h after treatment in the RD-LPS groups, the number of endothelial progenitor cells was reduced in animals injected with GW4896 (a chemical inhibitor of exosome biogenesis) as compared with controls. In contrast to these in vivo results, in vitro experiments did not support the effect of sEVs on EPCs. Our data raise the intriguing possibility that IFITM3 may serve as a marker of the radio-detoxified LPS treatment.

Potential Source Apportionment and Meteorological Conditions Involved in Airborne 131I Detections in January/February 2017 in Europe

Traces of particulate radioactive iodine (¹³¹I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 μBq m^-3 except at one location in western Russia where they reached up to several mBq m^-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of ¹³¹I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to ¹³¹I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network.

Extracellular vesicles mediate low dose ionizing radiation-induced immune and inflammatory responses in the blood

PURPOSE

Radiation-induced bystander effects (RIBE) imply the involvement of complex signaling mechanisms, which can be mediated by extracellular vesicles (EVs). Using an in vivo model, we investigated EV-transmitted RIBE in blood plasma and radiation effects on plasma EV miRNA profiles.

MATERIALS AND METHODS

C57Bl/6 mice were total-body irradiated with 0.1 and 2 Gy, bone marrow-derived EVs were isolated, and injected systemically into naive, 'bystander' animals. Proteome profiler antibody array membranes were used to detect alterations in plasma, both in directly irradiated and bystander mice. MiRNA profile of plasma EVs was determined by PCR array.

RESULTS

M-CSF and pentraxin-3 levels were increased in the blood of directly irradiated and bystander mice both after low and high dose irradiations, CXCL16 and lipocalin-2 increased after 2 Gy in directly irradiated and bystander mice, CCL5 and CCL11 changed in bystander mice only. Substantial overlap was found in the cellular pathways regulated by those miRNAs whose level were altered in EVs isolated from the plasma of mice irradiated with 0.1 and 2 Gy. Several of these pathways have already been associated with bystander responses.

CONCLUSION

Low and high dose effects overlapped both in EV-mediated alterations in signaling pathways leading to RIBE and in their systemic manifestations.

Ionizing Radiation-Induced Immune and Inflammatory Reactions in the Brain

Radiation-induced late brain injury consisting of vascular abnormalities, demyelination, white matter necrosis, and cognitive impairment has been described in patients subjected to cranial radiotherapy for brain tumors. Accumulating evidence suggests that various degrees of cognitive deficit can develop after much lower doses of ionizing radiation, as well. The pathophysiological mechanisms underlying these alterations are not elucidated so far. A permanent deficit in neurogenesis, chronic microvascular alterations, and blood–brain barrier dysfunctionality are considered among the main causative factors. Chronic neuroinflammation and altered immune reactions in the brain, which are inherent complications of brain irradiation, have also been directly implicated in the development of cognitive decline after radiation. This review aims to give a comprehensive overview on radiation-induced immune alterations and inflammatory reactions in the brain and summarizes how these processes can influence cognitive performance. The available data on the risk of low-dose radiation exposure in the development of cognitive impairment and the underlying mechanisms are also discussed.

Extracellular Vesicles Mediate Radiation-Induced Systemic Bystander Signals in the Bone Marrow and Spleen

Radiation-induced bystander effects refer to the induction of biological changes in cells not directly hit by radiation implying that the number of cells affected by radiation is larger than the actual number of irradiated cells. Recent in vitro studies suggest the role of extracellular vesicles (EVs) in mediating radiation-induced bystander signals, but in vivo investigations are still lacking. Here, we report an in vivo study investigating the role of EVs in mediating radiation effects. C57BL/6 mice were total-body irradiated with X-rays (0.1, 0.25, 2 Gy), and 24 h later, EVs were isolated from the bone marrow (BM) and were intravenously injected into unirradiated (so-called bystander) animals. EV-induced systemic effects were compared to radiation effects in the directly irradiated animals. Similar to direct radiation, EVs from irradiated mice induced complex DNA damage in EV-recipient animals, manifested in an increased level of chromosomal aberrations and the activation of the DNA damage response. However, while DNA damage after direct irradiation increased with the dose, EV-induced effects peaked at lower doses. A significantly reduced hematopoietic stem cell pool in the BM as well as CD4⁺ and CD8⁺ lymphocyte pool in the spleen was detected in mice injected with EVs isolated from animals irradiated with 2 Gy. These EV-induced alterations were comparable to changes present in the directly irradiated mice. The pool of TLR4-expressing dendritic cells was different in the directly irradiated mice, where it increased after 2 Gy and in the EV-recipient animals, where it strongly decreased in a dose-independent manner. A panel of eight differentially expressed microRNAs (miRNA) was identified in the EVs originating from both low- and high-dose-irradiated mice, with a predicted involvement in pathways related to DNA damage repair, hematopoietic, and immune system regulation, suggesting a direct involvement of these pathways in mediating radiation-induced systemic effects. In conclusion, we proved the role of EVs in transmitting certain radiation effects, identified miRNAs carried by EVs potentially responsible for these effects, and showed that the pattern of changes was often different in the directly irradiated and EV-recipient bystander mice, suggesting different mechanisms.

[The effect of radiotherapy on the antitumor immune response. Possibilities to combine radiotherapy with immunotherapy]

The past three decades of immunology research led to a drastic increase in the knowledge of antitumor immune response mechanisms and in parallel to a rapid development in various antitumor immune therapy strategies. This will most probably result in the implementation of immunotherapeutic protocols within the standard anticancer regimens in a very near future. Though, it is obvious that combination of immunotherapy with traditional anticancer treatment modalities will only be legitimate if the combination has at least an additive, or perhaps a synergistic effect. The similarly dynamic progress in the radiobiological knowledge proved that ionizing radiation does not have a general immune suppressing effect, as it has been thought for decades, but might possess certain immune stimulatory effects, as well. It is also known by now that local irradiation due to its out-of-field effects has systemic immune modulatory capacity, too. In the light of all these novel findings the optimal combination between antitumor immunotherapy and radiotherapy has become an increasing option. The first part of the present review summarizes the main antitumor mechanisms that can be influenced by ionizing radiation, and the second part attempts to provide a comprehensive overview of those antitumor immunotherapeutic modalities that are currently being used in combination with radiotherapy in preclinical and/or clinical trials for the treatment of various tumors.

TP53inp1 Gene Is Implicated in Early Radiation Response in Human Fibroblast Cells

Tumor protein 53-induced nuclear protein-1 (TP53inp1) is expressed by activation via p53 and p73. The purpose of our study was to investigate the role of TP53inp1 in response of fibroblasts to ionizing radiation. γ-Ray radiation dose-dependently induces the expression of TP53inp1 in human immortalized fibroblast (F11hT) cells. Stable silencing of TP53inp1 was done via lentiviral transfection of shRNA in F11hT cells. After irradiation the clonogenic survival of TP53inp1 knockdown (F11hT-shTP) cells was compared to cells transfected with non-targeting (NT) shRNA. Radiation-induced senescence was measured by SA-β-Gal staining and autophagy was detected by Acridine Orange dye and microtubule-associated protein-1 light chain 3 (LC3B) immunostaining. The expression of TP53inp1, GDF-15, and CDKN1A and alterations in radiation induced mitochondrial DNA deletions were evaluated by qPCR. TP53inp1 was required for radiation (IR) induced maximal elevation of CDKN1A and GDF-15 expressions. Mitochondrial DNA deletions were increased and autophagy was deregulated following irradiation in the absence of TP53inp1. Finally, we showed that silencing of TP53inp1 enhances the radiation sensitivity of fibroblast cells. These data suggest functional roles for TP53inp1 in radiation-induced autophagy and survival. Taken together, we suppose that silencing of TP53inp1 leads radiation induced autophagy impairment and induces accumulation of damaged mitochondria in primary human fibroblasts.

Growth Differentiation Factor-15 (GDF-15) is a potential marker of radiation response and radiation sensitivity

We have investigated the importance of GDF-15 (secreted cytokine belonging to the TGF-β superfamily) in low and high dose radiation-induced cellular responses. A telomerase immortalized human fibroblast cell line (F11hT) was used in the experiments. A lentiviral system encoding small hairpin RNAs (shRNA) was used to establish GDF-15 silenced cells. Secreted GDF-15 levels were measured in culture medium by ELISA. Cell cycle analysis was performed by flow cytometry. The experiments demonstrated that in irradiated human fibroblasts GDF-15 expression increased with dose starting from 100mGy. Elevated GDF-15 expression was not detected in bystander cells. The potential role of GDF-15 in radiation response was investigated by silencing GDF-15 in immortalized human fibroblasts with five different shRNA encoded in lentiviral vectors. Cell lines with considerably reduced GDF-15 levels presented increased radiation sensitivity, while a cell line with elevated GDF-15 was more radiation resistant than wild type cells. We have investigated how the reduced GDF-15 levels alter the response of several known radiation inducible genes. In F11hT-shGDF-15 cells the basal expression level of CDKN1A was unaltered relative to F11hT cells, while GADD45A and TGF-β1 mRNA levels were slightly higher, and TP53INP1 was considerably reduced. The radiation-induced expression of TP53INP1 was lower in the silenced than in wild type fibroblast cells. Cell cycle analysis indicated that radiation-induced early G2/M arrest was abrogated in GDF-15 silenced cells. Moreover, radiation-induced bystander effect was less pronounced in GDF-15 silenced fibroblasts. In conclusion, the results suggest that GDF-15 works as a radiation inducible radiation resistance increasing factor in normal human fibroblast cells, acts by regulating the radiation-induced transcription of several genes and might serve as a radiation-induced early biomarker in exposed cells.

The effect of ionizing radiation on regulatory T cells in health and disease

Treg cells are key elements of the immune system which are responsible for the immune suppressive phenotype of cancer patients. Interaction of Treg cells with conventional anticancer therapies might fundamentally influence cancer therapy response rates. Radiotherapy, apart from its direct tumor cell killing potential, has a contradictory effect on the antitumor immune response: it augments certain immune parameters, while it depresses others. Treg cells are intrinsically radioresistant due to reduced apoptosis and increased proliferation, which leads to their systemic and/or intratumoral enrichment. While physiologically Treg suppression is not enhanced by irradiation, this is not the case in a tumorous environment, where Tregs acquire a highly suppressive phenotype, which is further increased by radiotherapy. This is the reason why the interest for combined radiotherapy and immunotherapy approaches focusing on the abrogation of Treg suppression has increased in cancer therapy in the last few years. Here we summarize the basic mechanisms of Treg radiation response both in healthy and cancerous environments and discuss Treg-targeted pre-clinical and clinical immunotherapy approaches used in combination with radiotherapy. Finally, the discrepant findings regarding the predictive value of Tregs in therapy response are also reviewed.

Low dose cranial irradiation-induced cerebrovascular damage is reversible in mice

Background

High-dose radiation-induced blood-brain barrier breakdown contributes to acute radiation toxicity syndrome and delayed brain injury, but there are few data on the effects of low dose cranial irradiation. Our goal was to measure blood-brain barrier changes after low (0.1 Gy), moderate (2 Gy) and high (10 Gy) dose irradiation under in vivo and in vitro conditions.

Methodology

Cranial irradiation was performed on 10-day-old and 10-week-old mice. Blood-brain barrier permeability for Evans blue, body weight and number of peripheral mononuclear and circulating endothelial progenitor cells were evaluated 1, 4 and 26 weeks postirradiation. Barrier properties of primary mouse brain endothelial cells co-cultured with glial cells were determined by measurement of resistance and permeability for marker molecules and staining for interendothelial junctions. Endothelial senescence was determined by senescence associated β-galactosidase staining.

Principle Findings

Extravasation of Evans blue increased in cerebrum and cerebellum in adult mice 1 week and in infant mice 4 weeks postirradiation at all treatment doses. Head irradiation with 10 Gy decreased body weight. The number of circulating endothelial progenitor cells in blood was decreased 1 day after irradiation with 0.1 and 2 Gy. Increase in the permeability of cultured brain endothelial monolayers for fluorescein and albumin was time- and radiation dose dependent and accompanied by changes in junctional immunostaining for claudin-5, ZO-1 and β-catenin. The number of cultured brain endothelial and glial cells decreased from third day of postirradiation and senescence in endothelial cells increased at 2 and 10 Gy.

Conclusion

Not only high but low and moderate doses of cranial irradiation increase permeability of cerebral vessels in mice, but this effect is reversible by 6 months. In-vitro experiments suggest that irradiation changes junctional morphology, decreases cell number and causes senescence in brain endothelial cells.

Structural analysis of oval-cell-mediated liver regeneration in rats

We have analyzed the architectural aspects of progenitor-cell-driven regenerative growth in rat liver by applying the 2-acetaminofluorene/partial hepatectomy experimental model. The regeneration is initiated by the proliferation of so-called oval cells. The oval cells at the proximal tips of the ductules have a more differentiated phenotype and higher proliferative rate. This preferential growth results in the formation of a seemingly random collection of small hepatocytes, called foci. These foci have no clonal origin, but possess a highly organized structure, which shows similarities to normal hepatic parenchyma. Therefore, they can easily remodel into the lobular structure. Eventually, the regenerated liver is constructed by enlarged hepatic lobules; no new lobules are formed during this process. The foci of the Solt-Farber experimental hepatocarcinogenesis model have identical morphological features; accordingly, they also represent only regenerative, not neoplastic, growth.

CONCLUSION

Progenitor-cell-driven liver regeneration is a well-designed, highly organized tissue reaction, and better comprehension of the architectural events may help us to recognize this process and understand its role in physiological and pathological reactions.

Analysis of the common deletions in the mitochondrial DNA is a sensitive biomarker detecting direct and non-targeted cellular effects of low dose ionizing radiation

One of the key issues of current radiation research is the biological effect of low doses. Unfortunately, low dose science is hampered by the unavailability of easily performable, reliable and sensitive quantitative biomarkers suitable detecting low frequency alterations in irradiated cells. We applied a quantitative real time polymerase chain reaction (qRT-PCR) based protocol detecting common deletions (CD) in the mitochondrial genome to assess direct and non-targeted effects of radiation in human fibroblasts. In directly irradiated (IR) cells CD increased with dose and was higher in radiosensitive cells. Investigating conditioned medium-mediated bystander effects we demonstrated that low and high (0.1 and 2Gy) doses induced similar levels of bystander responses and found individual differences in human fibroblasts. The bystander response was not related to the radiosensitivity of the cells. The importance of signal sending donor and signal receiving target cells was investigated by placing conditioned medium from a bystander response positive cell line (F11-hTERT) to bystander negative cells (S1-hTERT) and vice versa. The data indicated that signal sending cells are more important in the medium-mediated bystander effect than recipients. Finally, we followed long term effects in immortalized radiation sensitive (S1-hTERT) and normal (F11-hTERT) fibroblasts up to 63 days after IR. In F11-hTERT cells CD level was increased until 35 days after IR then reduced back to control level by day 49. In S1-hTERT cells the increased CD level was also normalized by day 42, however a second wave of increased CD incidence appeared by day 49 which was maintained up to day 63 after IR. This second CD wave might be the indication of radiation-induced instability in the mitochondrial genome of S1-hTERT cells. The data demonstrated that measuring CD in mtDNA by qRT-PCR is a reliable and sensitive biomarker to estimate radiation-induced direct and non-targeted effects.

Triiodothyronine accelerates differentiation of rat liver progenitor cells into hepatocytes

The 2-acetaminofluorene/partial hepatectomy (AAF/Phx) model is widely used to induce oval/progenitor cell proliferation in the rat liver. We have used this model to study the impact of a primary hepatocyte mitogen, triiodothyronine (T3) on the liver regenerating by the recruitment of oval/progenitor cells. Administration of T3 transiently accelerates the proliferation of the oval cells, which is followed by rapid differentiation into small hepatocytes. The oval cell origin of the small hepatocytes has been proven by tracing retrovirally transduced and BrdU marked oval cells. The differentiating oval cells become positive for hepatocyte nuclear factor-4 and start to express hepatocyte specific connexin 32, alpha1 integrin, Prox1, cytochrom P450s, and form CD 26 positive bile canaliculi. At the same time oval cell specific OV-6 and alpha-fetoprotein expression is lost. The upregulation of hepatocyte specific mRNAs: albumin, tyrosine aminotransferase and tryptophan 2,3-dioxygenase detected by real-time PCR also proves hepatocytic maturation. The hepatocytic conversion of oval cells occurs on the seventh day after the Phx in this model while the first small hepatocytes appear 5 days later without T3 treatment. The administration of the primary hepatocyte mitogen T3 accelerates the differentiation of hepatic progenitor cells into hepatocytes in vivo, and that may have therapeutic potential.

Microarray analysis of radiation response genes in primary human fibroblasts

PURPOSE

To identify radiation-induced early transcriptional responses in primary human fibroblasts and understand cellular pathways leading to damage correction.

METHODS AND MATERIALS

Primary human fibroblast cell lines were irradiated with 2 Gy gamma-radiation and RNA isolated 2 h later. Radiation-induced transcriptional alterations were investigated with microarrays covering the entire human genome. Time- and dose dependent radiation responses were studied by quantitative real-time polymerase chain reaction (RT-PCR).

RESULTS

About 200 genes responded to ionizing radiation on the transcriptional level in primary human fibroblasts. The expression profile depended on individual genetic backgrounds. Thirty genes (28 up- and 2 down-regulated) responded to radiation in identical manner in all investigated cells. Twenty of these consensus radiation response genes were functionally categorized: most of them belong to the DNA damage response (GADD45A, BTG2, PCNA, IER5), regulation of cell cycle and cell proliferation (CDKN1A, PPM1D, SERTAD1, PLK2, PLK3, CYR61), programmed cell death (BBC3, TP53INP1) and signaling (SH2D2A, SLIC1, GDF15, THSD1) pathways. Four genes (SEL10, FDXR, CYP26B1, OR11A1) were annotated to other functional groups. Many of the consensus radiation response genes are regulated by, or regulate p53. Time- and dose-dependent expression profiles of selected consensus genes (CDKN1A, GADD45A, IER5, PLK3, CYR61) were investigated by quantitative RT-PCR. Transcriptional alterations depended on the applied dose, and on the time after irradiation.

CONCLUSIONS

The data presented here could help in the better understanding of early radiation responses and the development of biomarkers to identify radiation susceptible individuals.

Cancer gene therapy: Combination with radiation therapy and the role of bystander cell killing in the anti-tumor effect

Current anti-cancer modalities such as surgery, chemo- and radiation therapies have only limited success in cancer treatment. Gene therapy is a promising new tool to improve outcomes. In this review, first we summarize the various strategies to kill tumor cells, and then focus on the bystander effect of gene therapy. A variety of strategies, such as gene-directed enzyme pro-drug therapy, activation of an anti-tumor immune attack, application of replication-competent and oncolytic viral vectors, tumor-specific as well as radiation- and hypoxiainduced gene expression, might be applied to target tumor cells. We put special emphasis on the combination of these approaches with local tumor irradiation. Using the available vector systems, only a small portion of cancer cells contains the therapeutic genes under clinical situations. However, cells directly targeted by gene therapy will transfer death signals to neighboring cancer cells. This bystander cell killing improves the efficiency of cancer gene therapy. Death signals are delivered by cell-to-cell communication through gap junction intercellular contacts, release of toxic metabolites into the neighborhood or to larger distances, phagocytosis of apoptotic bodies, and the activation of the immune system. Bystander cell killing can be enhanced by the introduction of gap junction proteins into cells, by further activating the immune system with immune-stimulatory molecules, or by introducing genes that help the transfer of cytotoxic genes and/or metabolites into bystander cells. In conclusion, although bystander cell killing can improve therapeutic effects, there should be additional developments in cancer gene therapy for a more efficient clinical application.

Detailed characterization of the mouse glioma 261 tumor model for experimental glioblastoma therapy

Mouse glioma 261 (Gl261) cells are used frequently in experimental glioblastoma therapy; however, no detailed description of the Gl261 tumor model is available. Here we present that Gl261 cells carry point mutations in the K-ras and p53 genes. Basal major histocompatibility complex (MHC)I, but not MHCII, expression was detected in Gl261 cells. The introduction of interferon-gamma-encoding genes increased expression of both MHCI and MHCII. A low amount of B7-1 and B7-2 RNA was detected in wild-type cells, but cytokine production did not change expression levels. Gl261 cells were transduced efficiently by adenoviral vectors; the infectivity of retroviral vectors was limited. Low numbers of transplanted Gl261 cells formed both subcutaneous and intracranial tumors in C57BL/6 mice. The cells were moderately immunogenic: prevaccination of mice with irradiated tumor cells 7 days before intracranial tumor challenge prevented tumor formation in approximately 90% of mice. When vaccination was carried out on the day or 3 days after tumor challenge, no surviving animals could be found. In vitro-growing cells were radiosensitive: less than 2 Gy was required to achieve 50% cell mortality. Local tumor irradiation with 4 Gy X-rays in brain tumor-bearing mice slowed down tumor progression, but none of the mice were cured off the tumor. In conclusion, the Gl261 brain tumor model might be efficiently used to study the antitumor effects of various therapeutic modalities, but the moderate immunogenicity of the cells should be considered.

Phenotypic profiling of engineered mouse melanomas with manipulated histamine production identifies histamine H2 receptor and rho-C as histamine-regulated melanoma progression markers

In the present study, the impact of acquired neoplastic L-histidine decarboxylase (HDC) expression, and its direct consequence, the release of histamine in the tumor environment, was assessed on melanoma tumor progression. B16-F10 mouse melanoma cells were manipulated via stable transfection, and nine novel transgenic variants were generated in triplicates, constitutively expressing the full-length sense mouse HDC mRNA, a mock control, and an antisense HDC RNA segment, respectively. Establishing both primary skin tumors and lung metastases in C57BL/6 mice, the nine variants with different histamine-releasing capacities were subjected to a comprehensive comparative progression profiling in vivo. Our analyses showed trends of markedly accelerated tumor growth (P < 0.001), and moderately increased metastatic colony-forming potential (P = 0.010) along with rising levels of local histamine production. Using RNase protection assay for screening of the melanoma progression profile, and Western blotting for subsequent result validation, we looked for molecular progression markers affected by melanoma histamine secretion. Investigation of 21 functionally clustered markers associated with tumor proliferation, angiogenesis, invasivity, metastasis formation, local or systemic immunomodulation, and histamine signaling revealed positive correlations between histamine production, tumor histamine H2 receptor and rho-C expression (P < 0.001, P = 0.002, respectively). These observations confirm the involvement of histamine in the molecular machinery of melanoma progression.

Partial breast irradiation with interstitial 60CO brachytherapy results in frequent grade 3 or 4 toxicity. evidence based on a 12-year follow-up of 70 patients

PURPOSE

To investigate the radiation-induced toxicity and cosmesis of brachytherapy (BT) alone in early stage breast cancer.

METHODS AND MATERIALS

A total of 70 women diagnosed with Stage I or II breast carcinoma participated in a BT study at the Municipal Oncoradiological Center, Uzsoki Hospital, Budapest, Hungary, between November 1987 and June 1992. They had undergone breast-conserving surgery with an unknown surgical margin. The postoperative tumor bed irradiation was performed with interstitial (60)Co sources with an active length of 4 cm, with 10-mm center-to-center spacing arranged in a single plane. The median number of inserted sources was 5 (range, 2-8), with a linear activity of 133-137 MBq/cm at the beginning of the study. The 50 Gy delivered dose at 5 mm from the surface of the (60)Co sources was administered during 10-22 h to the virtual postoperative lumpectomy cavity (i.e., plane). For radiobiologic considerations, the clinical target volume (CTV) was calculated retrospectively with a 10-mm safety margin, resulting in a 72-cm(3) median CTV (range, 36-108 cm(3)) irradiated with a reference dose of 28 Gy. In the assessment of the skin and subcutaneous toxicity, the RTOG late radiation morbidity scoring system was applied. The radiosensitivity of the cultured fibroblasts was determined by clonogenic assay to check whether individual radiosensitivity played a role in the development and course of radiation-induced side-effects.

RESULTS

The median follow-up was 12 years (range, 10-15 years). The population of the final study (34 cases) comprised all survivors with tumor-free breasts (27 cases) and patients with breasts erroneously ablated/excised for misinterpreted radiation-induced sequelae (7 patients). A total of 97% of the cohort (33/34) had grade > or =2, and 59% (20/34) had grade > or =3 radiation-induced toxicity. By the end of the follow-up, 85% of the patients experienced Grade > or =2 telangiectasis and 41% had Grade 3 telangiectasis. Eighty-eight percent had fibrosis of some form, and 35% had grade > or =3 fibrosis. Forty-one percent of the cohort displayed fat necrosis, which was always accompanied by Grade > or =3 fibrosis or telangiectasis. The cosmetic results were poor in 50% (17/34) of the patients. The radiosensitivity of the fibroblasts was increased in only 2/24 patients (8% of the investigated cases, in agreement with data published for the general population). Comparisons of our fibrosis prevalence data with those of others allowed an estimate of 0.47 h(-1) for the rate of recovery of DNA damage in the fibroblasts.

CONCLUSIONS

Interstitial (60)Co BT of the breast tumor bed alone with a limited CTV (median, 72 cm(3)) and a total dose of 28 Gy is associated with a high rate (59%) of grade > or =3 radiation-induced toxicity and a high rate (50%) of poor cosmetic outcome at the end of a median follow-up of 12 years. A relatively high BT dose rate (1.3-2.8 Gy/h) applied during a short overall treatment time (10-22 h) and a possible geographic miss (close to skin implantation) might have contributed to the development of these sequelae.

Characteristics of radiogenic lower motor neurone disease, a possible link with a preceding viral infection

OBJECTIVE

To investigate the pathogenesis of the rare radiogenic lower motor neurone disease (LMND) on the basis of a meta-analysis of the published case histories.

MATERIALS AND METHODS

The authors reviewed 47 well-documented radiogenic LMND cases from the English literature.

RESULTS

The disease typically occurs following the irradiation of radiosensitive cancers situated near the spinal cord. It arises predominantly (46 cases) in the lower extremities; only one case involved the upper extremities. There is a male predominance (male:female ratio 7.8:1), and the patients are characteristically young (13-40 years, with four exceptions). An overdose does not seem to be a particular risk factor for the development of the disease, as total dose, fraction size and biologically effective dose are typically below 50 Gy, 2 Gy and 128 Gy2, respectively, which are regarded as safe doses. Other risk factors (chemotherapy, operations, etc) have been identified only rarely. Radiogenic LMND is manifested in an apparently random manner, 4-312 (mean 48.7) months after the completion of radiotherapy.

DISCUSSION

The complete lack of a dose-effect relationship argues strongly against a pure radiogenic nature of the pathological process. The latency period is typically several years and it varies extremely, which excludes a direct and complete causal relationship between radiotherapy and LMND. As the interaction of ionizing radiation with living tissues is highly unspecific, thus a selective motor injury due to irradiation alone, without comparable effects on the sensory and vegetative fibers, seems improbable.

CONCLUSIONS

On analogy with the viral motor neurone diseases, we suppose that radiogenic LMND may be preceded by viral (enterovirus/poliovirus) infection. Based on the meta-analysis, it is suggested that irradiation may be only a single component of the set of factors jointly resulting in the clinical state regarded as radiogenic LMND.

PET identifies transitional metabolic change in the spinal cord following a subthreshold dose of irradiation

Positron emission tomographic (PET) investigations were performed to obtain in vivo information on symptomless radiation-induced pathological changes in the human spinal cord. PET investigations were carried out prior to radiotherapy and during the regular follow-up in an early hypopharyngeal cancer patient (the spinal cord was irradiated with a biologically effective dose of 80 Gy2), with [18F]fluorodeoxyglucose (FDG), [11C]methionine and [15O]butanol as tracers; radiosensitivity and electroneuronographic (ENG) studies were also performed. A very low background FDG accumulation (mean standardized uptake values, i.e. SUV: 0.84) was observed in the spinal cord before the initiation of radiotherapy. An increased FDG uptake was measured 2 months after the completion of radiotherapy (mean SUV: 1.69), followed by a fall-off, as measured 7 months later (mean SUV: 1.21). By 44 months after completion of irradiation, the FDG accumulation in the irradiated segments of the spinal cord had decreased to a level very close to the initial value (mean SUV: 1.11). The simultaneous [15O]butanol uptake results demonstrated a set of perfusion changes similar to those observed in connection with the FDG accumulation. The patient exhibited an extremely low [11C]methionine uptake within the irradiated and the nonirradiated spinal cord during the clinical course. She has not had any neurological symptoms, and the results of central ENG measurements before radiotherapy and 2 months following its completion proved normal. Radiobiological investigations did not reveal unequivocal signs of an increased radiosensitivity. A transitory increased spinal cord FDG uptake following radiotherapy may be related to the posttherapeutic mild inflammatory and regenerative processes. The normal [11C]methionine accumulation observed is strong evidence against intensive cell proliferation. The high degree of normalization of the temporarily increased FDG uptake of the irradiated spinal cord segments by 44 months is in good agreement with the results of monkey studies, which demonstrated a nearly complete recovery from radiation-induced spinal cord injury.

Increased Metabolic Activity in the Spinal Cord of Patients with Long-Standing Lhermitte’s Sign

PURPOSE

To investigate the pathophysiology of the radiation-induced, chronic Lhermitte's sign (LS) on the basis of long-standing case histories with partial functional recovery.

PATIENTS AND METHODS

As radiotherapy in two nasopharyngeal cancer patients, a biologically effective dose (BED) of 103.8 Gy(2) (case 1) and 94.8 Gy(2) (case 2) was delivered to the cervical spinal cord. Neurologic signs relating to the irradiated spinal cord segments developed after 2 months (case 1) and 5 years (case 2), with radiation-induced damage equivalent to grade 3 (case 1) and grade 2 (case 2) toxicity (Common Toxicity Criteria, Version 2.0). The clinical status improved to grade 2 (case 1) and grade 1 (case 2). Positron emission tomography (PET) and fibroblast clonogen assay were applied 25 and 7 years postirradiation, respectively, to characterize this rare clinical picture.

RESULTS

PET demonstrated increased [(18)F]fluorodeoxyglucose (FDG) accumulation and [(15)O]butanol perfusion, but negligible [(11)C]methionine uptake in the irradiated spinal cord segments in both patients. In clonogenic assays, fibroblasts from case 1 displayed much higher radiation sensitivity than in healthy controls, while in case 2 the fibroblasts sensitivity was normal.

CONCLUSIONS

These data suggests a close direct relationship between regional perfusion and metabolism of the spinal cord, similarly as in the brain. The postirradiation recovery may be related to energy-demanding conduction, explaining the increased metabolism and perfusion. The increased radiosensitivity and higher spinal cord BED may have contributed to the more severe sequelae in case 1.

A review on radiogenic Lhermitte's sign

Radiation myelopathy is a rare, but extremely serious side-effect of radiotherapy. Recovery from radiation-induced motor sequelae is rare, whereas, the regeneration of sensory losses is relatively frequent. Among the sensory radiogenic injuries of the spinal cord, Lhermitte's sign (LS) is most frequent. This review describes the clinical picture and diagnostic imaging signs of radiogenic LS. There have been only a few studies on large patient groups with radiogenic LS, demonstrating a rate of occurrence of 3.6-13%, relating mainly to mantle irradiation or the radiotherapy of head and neck tumors. These cases typically manifest themselves 3 months following radiotherapy and gradually disappear within 6 months. Only 3 LS cases have been described in the English literature with extraordinarily severe symptoms lasting for more than 1 year. MRI, a sensitive tool in the detection of demyelination, failed to reveal any pathological sign accompanying radiogenic LS. However, positron emission tomography demonstrated increased [18F]fluorodeoxyglucose accumulation and [15O]butanol perfusion, but a negligible [11C]methionine uptake in the irradiated spinal cord segments in patients with long-standing LS. These imaging data are suggestive of a close direct relationship between the regional perfusion and metabolism of the spinal cord, very much like the situation in the brain. We postulate that an altered, energy-demanding conduction along the demyelinated axons of patients with chronic radiogenic LS may explain the increased metabolism and perfusion.

A PET study on the characterization of partially reversible radiogenic lower motor neurone disease

OBJECTIVE

To investigate the pathomechanism of the rare radiogenic lower motor neurone disease (LMND) on the basis of a case history involving a partial functional recovery.

PATIENT

A 31-year-old seminoma patient received postoperative para-aortic and para-iliac telecobalt irradiation with a biologically effective dose of 88 Gy(2) (44 Gy in 2 Gy fractions/day, with an estimated alpha/beta of 2 Gy) delivered to the spinal cord following a single cycle of chemotherapy. LMND developed 4 months after the completion of radiotherapy. The patient exhibited flaccid paraparesis of the lower extremities (without sensory or vegetative signs), followed by a worsening after further chemotherapy, due to pulmonary metastatization. A gradual spontaneous functional improvement commenced and led several years later to a stabilized state involving moderately severe symptoms.

METHODS

In the 15th year of the clinical course, magnetic resonance imaging (MRI) and positron emission tomography (PET) with [(18)F]fluorodeoxyglucose (FDG) and [(11)C] methionine were conducted. Four lines of experiments (clonogenic assay using fibroblasts isolated from a skin biopsy sample of the patient, comet assay, micronucleus assay, and the testing of chromosome aberrations after in vitro irradiation of peripheral blood samples) were performed in a search for an increased individual radiosensitivity.

RESULTS

MRI investigations failed to reveal any pathological change. PET demonstrated an increased FDG accumulation, but a negligible [(11)C] methionine uptake in the irradiated spinal cord segments. The radiobiological investigations did not indicate any sign of an increased individual radiosensitivity.

CONCLUSIONS

We suggest that the observed partial functional recovery and stabilization of the symptoms of radiogenic LMND may be explained by the higher than normal density of sodium channels expressed along the demyelinated axons of the restored conduction. The increased energy demands of this type of conduction are proved by a higher metabolic rate (increased FDG uptake) of the irradiated spinal cord segments without a substantial regenerative process (lack of detectable protein synthesis).

Apoptotic and mitotic activity in squamous cell carcinoma cells after combined modality treatment with gamma-irradiation and dibromodulcitol

A-431 squamous cell carcinoma cells were treated in vitro with either 4 Gy radiation of 15 (or 45) microg/ml dibromodulcitol (DBD), as well as with combined 4 Gy irradiation and DBD, with the latter as either a pretreatment or post-treatment. DBD alone or in combination with radiation had a greater effect on cell proliferation than the effect of radiation alone. The difference is due to a higher level of apoptosis induced by DBD, especially in conjunction with radiation. Such a combination may therefore be useful in the treatment of squamous cell carcinoma, which in general responds poorly to radiation therapy.

Carcinogenic alterations in murine liver, lung, and uterine tumors induced by in utero exposure to ionizing radiation

The atomic bombing of Hiroshima and Nagasaki and the nuclear accident at Chernobyl raised the question of prenatal sensitivity to ionizing radiation-induced cancer. In this study, mice were exposed to single doses of gamma-radiation (0.2-2.0 Gy) at different embryonic stages. The tumor incidence increased with dose from 15% in control mice to 35% in mice irradiated with 2.0 Gy on 18 d of prenatal life. Various oncogenic events were investigated in lymphoid, liver, lung, and uterine tumors. We observed threefold to fivefold increases in myc expression in 25% of the lymphomas, and the expression of Ha-ras and p53 genes decreased in 40% and 60% of the lung tumors by twofold to fivefold. Point mutations were tissue specific: Ha-ras codon 61 mutations were found in about 40% of the liver adenocarcinomas, Ki-ras codon 12 mutations in about 17% of lung tumors, and p53 mutations in about 15% of the lymphomas. Amplification and rearrangement of the p53, myc, and Ha-, Ki- and N-ras genes were not detected. Loss of heterozygosity on chromosome 4 at the multiple tumor suppressor 1 and 2 genes was observed in all types of malignancies. Allelic losses on chromosome 11 at the p53 locus were found in lymphoid, liver, and lung tumors, but they were absent from uterine tumors. Multiple oncogenic changes were often detected. The frequency of carcinogenic alterations was similar in spontaneous and radiation-induced lymphoid, liver, and uterine tumors. In radiation-induced lung adenocarcinomas, however, the incidences of many oncogenic changes were different from those found in their spontaneous counterparts. This suggests that different oncogenic pathways are activated during spontaneous and in utero gamma-radiation-induced murine lung carcinogenesis.

Oncogenic changes in murine lymphoid tumors induced by in utero exposure to ionizing radiation

We have investigated the oncogenic alterations in murine lymphomas induced by in utero exposure to gamma-radiation. The expression of the myc oncogene increased in 23% of the tumors. Alterations in the expression of the ras oncogenes and in the p53 tumor suppressor gene were not characteristic. The p53 gene was mutated in a low percentage of the tumors (12%). Ras mutations were not detected. Loss of heterozygosity (LOH) at the p53 locus was found in 30% of the tumors, and LOH at the mts tumor suppressor gene was detected in 23% of lymphomas. Multiple oncogenic changes were infrequent in the investigated tumors. There were no essential differences in the frequency of carcinogenic alterations in spontaneous and gamma-radiation-induced lymphomas.