Carbon Ion and Photon Radiation Therapy Show Enhanced Antitumoral Therapeutic Efficacy With Neoantigen RNA-LPX Vaccines in Preclinical Colon Carcinoma Models

PURPOSE

Personalized liposome-formulated mRNA vaccines (RNA-LPX) are a powerful new tool in cancer immunotherapy. In preclinical tumor models, RNA-LPX vaccines are known to achieve potent results when combined with conventional X-ray radiation therapy (XRT). Densely ionizing radiation used in carbon ion radiation therapy (CIRT) may induce distinct effects in combination with immunotherapy compared with sparsely ionizing X-rays.

METHODS AND MATERIALS

Within this study, we investigate the potential of CIRT and isoeffective doses of XRT to mediate tumor growth inhibition and survival in murine colon adenocarcinoma models in conjunction with neoantigen (neoAg)-specific RNA-LPX vaccines encoding both major histocompatibility complex (MHC) class I- and class II-restricted tumor-specific neoantigens. We characterize tumor immune infiltrates and antigen-specific T cell responses by flow cytometry and interferon-γ enzyme-linked immunosorbent spot (ELISpot) analyses, respectively.

RESULTS

NeoAg RNA-LPX vaccines significantly potentiate radiation therapy-mediated tumor growth inhibition. CIRT and XRT alone marginally prime neoAg-specific T cell responses detected in the tumors but not in the blood or spleens of mice. Infiltration and cytotoxicity of neoAg-specific T cells is strongly driven by RNA-LPX vaccines and is accompanied by reduced expression of the inhibitory markers PD-1 and Tim-3 on these cells. The neoAg RNA-LPX vaccine shows similar overall therapeutic efficacy in combination with both CIRT and XRT, even if the physical radiation dose is lower for carbon ions than for X-rays.

CONCLUSIONS

We hence conclude that the combination of CIRT and neoAg RNA-LPX vaccines is a promising strategy for the treatment of radioresistant tumors.

High-LET charged particles: radiobiology and application for new approaches in radiotherapy

The number of patients treated with charged-particle radiotherapy as well as the number of treatment centers is increasing worldwide, particularly regarding protons. However, high-linear energy transfer (LET) particles, mainly carbon ions, are of special interest for application in radiotherapy, as their special physical features result in high precision and hence lower toxicity, and at the same time in increased efficiency in cell inactivation in the target region, i.e., the tumor. The radiobiology of high-LET particles differs with respect to DNA damage repair, cytogenetic damage, and cell death type, and their increased LET can tackle cells' resistance to hypoxia. Recent developments and perspectives, e.g., the return of high-LET particle therapy to the US with a center planned at Mayo clinics, the application of carbon ion radiotherapy using cost-reducing cyclotrons and the application of helium is foreseen to increase the interest in this type of radiotherapy. However, further preclinical research is needed to better understand the differential radiobiological mechanisms as opposed to photon radiotherapy, which will help to guide future clinical studies for optimal exploitation of high-LET particle therapy, in particular related to new concepts and innovative approaches. Herein, we summarize the basics and recent progress in high-LET particle radiobiology with a focus on carbon ions and discuss the implications of current knowledge for charged-particle radiotherapy. We emphasize the potential of high-LET particles with respect to immunogenicity and especially their combination with immunotherapy.

Immune checkpoint inhibitors and Carbon iON radiotherapy In solid Cancers with stable disease (ICONIC)

ICONIC is a multicenter, open-label, nonrandomized phase II clinical trial aiming to assess the feasibility and clinical activity of the addition of carbon ion radiotherapy to immune checkpoint inhibitors in cancer patients who have obtained disease stability with pembrolizumab administered as per standard-of-care. The primary end point is objective response rate, and the secondary end points are safety, survival and disease control rate. Translational research is an exploratory aim. The planned sample size is 27 patients. The study combination will be considered worth investigating if at least four objective responses are observed. If the null hypothesis is rejected, ICONIC will be the first proof of concept of the feasibility and clinical activity of the addition of carbon ion radiotherapy to immune checkpoint inhibitors in oncology.

Are charged particles a good match for combination with immunotherapy? Current knowledge and perspectives

Charged particle radiotherapy, mainly using protons and carbon ions, provides physical characteristics allowing for a volume conformal irradiation and a reduction of the integral dose to normal tissue. Carbon ion therapy additionally features an increased biological effectiveness resulting in peculiar molecular effects. Immunotherapy, mostly performed with immune checkpoint inhibitors, is nowadays considered a pillar in cancer therapy. Based on the advantageous features of charged particle radiotherapy, we review pre-clinical evidence revealing a strong potential of its combination with immunotherapy. We argue that the combination therapy deserves further investigation with the aim of translation in clinics, where a few studies have been set up already.

Automated synthesis of [68Ga]Ga-FAPI-46 without pre-purification of the generator eluate on three common synthesis modules and two generator types

Background

The recent development of quinoline-based radiotracers, which act as fibroblast activation protein inhibitors (FAPIs), has shown promising preclinical and clinical advantages. [⁶⁸Ga]Ga-FAPI-46 is a new radiotracer for in vivo detection of the fibroblast activation protein by positron emission tomography (PET). Recently, the automated synthesis of [⁶⁸Ga]Ga-FAPI-46 was reported based on pre-concentration and purification of the generator eluate by using a cation exchange-cartridge.

Our aim was to simplify the synthesis and shorten the automated synthesis of [⁶⁸Ga]Ga-FAPI-46 to make it accessible and thus even more attractive to a broader clinical and scientific community.

Results

We developed and evaluated the GMP compliant automatic synthesis of [⁶⁸Ga]Ga-FAPI-46 using two different ⁶⁸Ge/⁶⁸Ga generators (an Eckert & Ziegler, GalliaPharm generator, 1.85 GBq/50 mCi and an iThemba generator, 1.85 GBq/50 mCi) Somerset West, South Africa) and three different commercial and customized systems: the EasyOne module from Trasis; the GaSy module from Synthra with a customized synthesis template and a customized single use cassette. Additionally, the automatic synthesis of [⁶⁸Ga]Ga-FAPI-46 was established on a GallElut synthesis module from Scintomics with fixed tubing.

Conclusions

Independent of the synthesis modules or the generators employed we were able to complete the synthesis of [⁶⁸Ga]Ga-FAPI-46 in 12 min including the process of purification and formulation. In all cases, the final products showed more than 99.5% chemical purity and the radiochemical yield reached around 92.5% (decay corrected). All quality control parameters (e.g. sterility, stability and radiochemical purity) were conform to the European Pharmacopoeia.

A simple, reliable and accurate approach for assessing [131I]-capsule activity leading to significant reduction of radiation exposure of medical staff during radioiodine therapy

PURPOSE

According to German law, the [¹³¹I]-capsule activity has to be checked in the context of radioiodine therapy (RIT) immediately before application. The measurement leads to significant radiation exposure of the medical personnel, especially of their hands. We aimed to establish a method for estimating [¹³¹I]-capsule activity by measuring the dose rate (DR) at contact of the delivered lead closed container carrying the [¹³¹I]-capsules and to evaluate radiation exposure in comparison to conventional [¹³¹I]-capsule measurement using a dose calibrator.

METHODS

DR on the surface of the closed lead container was measured at two locations and correlated linearly with the [¹³¹I]-capsule activity measured in a dose calibrator to create calibrating curves. The hand and whole body (effective) doses were determined with official dose meters during validation of our method in clinical practice.

RESULTS

The determination coefficients (R²) of linear calibration curves were greater than 0.9974. The total relative uncertainty for estimating [¹³¹I]-capsule activity with our method was <±7.5% which is lower than the uncertainty of the nominal activity and quite close to the threshold limit for the maximum allowed uncertainty of ± 5% for measuring activity in radioactive drugs. The reduction of the hand dose caused by our method was 97% compared with the conventional measurements of the [¹³¹I]-capsules in a dose calibrator.

CONCLUSION

Measuring DR on the surface of the closed lead containers enables the [¹³¹I]-capsules activity to be estimated simply, reliably and with sufficient accuracy leading to significant reduction of the radiation exposure for the medical staff.

A Combination of Cabozantinib and Radiation Does Not Lead to an Improved Growth Control of Tumors in a Preclinical 4T1 Breast Cancer Model

The tyrosine kinase inhibitor Cabozantinib has been applied in clinical studies in combination with radiotherapy. We investigated the effect of such combination on triple-negative 4T1 cells as a metastatic breast cancer model in vitro and in vivo upon inoculation in BALB/c mice. In vitro assays indicated a potential for improved effects using the combination. Both Cabozantinib (2.5 µM) and 10 Gy of 250 kV x-rays were able to cease the growth of 4T1 cells as revealed by growth curves. In a clonogenic survival assay, the effect of Cabozantinib added on the effects of irradiation and the effectiveness of inhibiting the clonogenic survival was found to be 2 (RBE₁₀). Additionally, cell death measurements of apoptosis plus necrosis revealed a synergistic effect when combining irradiation with Cabozantinib. Surprisingly, however, in vivo tumor growth kinetics showed no additional effect in growth control when irradiation was used together with Cabozantinib. Since both ionizing radiation and Cabozantinib are acknowledged to feature immunogenic effects, we additionally investigated the effect of the treatments on lung metastases. No difference to the control groups was found here, neither for irradiation nor Cabozantinib alone nor in combination. Yet, upon analysis of the mice’ livers, CD11b-positive cells, indicating immune suppressive myeloid derived suppressor cells were found diminished following treatment with Cabozantinib. In conclusion, despite promising in vitro controls of the combination of Cabozantinib and irradiation, tumor growth control was not increased by the combination, which was true also for the occurrence of lung metastases.

Transition between Instability and Seeded Self-Modulation of a Relativistic Particle Bunch in Plasma

We use a relativistic ionization front to provide various initial transverse wakefield amplitudes for the self-modulation of a long proton bunch in plasma. We show experimentally that, with sufficient initial amplitude [≥(4.1±0.4)  MV/m], the phase of the modulation along the bunch is reproducible from event to event, with 3%-7% (of 2π) rms variations all along the bunch. The phase is not reproducible for lower initial amplitudes. We observe the transition between these two regimes. Phase reproducibility is essential for deterministic external injection of particles to be accelerated.

Proton Bunch Self-Modulation in Plasma with Density Gradient

We study experimentally the effect of linear plasma density gradients on the self-modulation of a 400 GeV proton bunch. Results show that a positive or negative gradient increases or decreases the number of microbunches and the relative charge per microbunch observed after 10 m of plasma. The measured modulation frequency also increases or decreases. With the largest positive gradient we observe two frequencies in the modulation power spectrum. Results are consistent with changes in wakefields' phase velocity due to plasma density gradients adding to the slow wakefields' phase velocity during self-modulation growth predicted by linear theory.

Reduction of Lung Metastases in a Mouse Osteosarcoma Model Treated With Carbon Ions and Immune Checkpoint Inhibitors

PURPOSE

The combination of radiation therapy and immunotherapy is recognized as a very promising strategy for metastatic cancer treatment. The purpose of this work is to compare the effectiveness of x-ray and high-energy carbon ion therapy in combination with checkpoint inhibitors in a murine model.

METHODS AND MATERIALS

We used an osteosarcoma mouse model irradiated with either carbon ions or x-rays in combination with 2 immune checkpoint inhibitors (anti-PD-1 and anti-CTLA-4). LM8 osteosarcoma cells were injected in both hind limbs of female C3H/He mice 7 days before exposure to carbon ions or x-rays. In experimental groups receiving irradiation, only the tumor on the left limb was exposed, whereas the tumor on the right limb served as an abscopal mimic. Checkpoint inhibitors were injected intraperitoneally 1 day before exposure as well as concomitant to and after exposure. Tumor growth was measured regularly up to day 21 after exposure, when mice were sacrificed. Both tumors as well as lungs were extracted.

RESULTS

A reduced growth of the abscopal tumor was most pronounced after the combined protocol of carbon ions and the immune checkpoint inhibitors administered sequentially. Radiation or checkpoint inhibitors alone were not sufficient to reduce the growth of the abscopal tumors. Carbon ions alone reduced the number of lung metastases more efficiently than x-rays, and in combination with immunotherapy both radiation types essentially suppressed the metastasis, with carbon ions being again more efficient. Investigation of the infiltration of immune cells in the abscopal tumors of animals treated with combination revealed an increase in CD8+ cells.

CONCLUSIONS

Combination of checkpoint inhibitors with high-energy carbon ion radiation therapy can be an effective strategy for the treatment of advanced tumors.

Medication-related osteonecrosis of the jaws (MRONJ) in cancer patients treated with denosumab VS. zoledronic acid: A systematic review and meta-analysis

Background

The aim of the present study was to analyse the incidence, risk ratio (RR) and prognoses of two types of medication-related osteonecrosis of the jaws (MRONJ): denosumab-related osteonecrosis of the jaws (DRONJ) and Bisphosphonate-Related Osteonecrosis of the Jaws (BRONJ) in cancer patients under treatment with denosumab or zoledronic acid (ZA).

Material and Methods

An electronic and manual search was conducted for randomized controlled trials (RCTs) until May 2019. Assessment of the identified studies, risk of bias and data extraction were performed independently by two reviewers. The incidence of DRONJ and BRONJ and the RR to develop MRONJ were calculated at 1 year, 2 years and 3 years of exposure. It was also calculated the odds ratio (OR) of their respective prognoses. They were calculated normalizing the values of the individual studies to 1 year, 2 years or 3 years when necessary through robust regression models using a statistical program.

Results

From 1.277 references identified, 8 RCTs were included, which comprised a total of 13.857 patients with a variety of neoplasms. The incidence of DRONJ in cancer patients under treatment with denosumab ranged from 0.5 to 2.1% after 1 year, 1.1 to 3.0% after 2 years, and 1.3 to 3.2% after 3 years of exposure. The incidence of BRONJ in cancer patients under treatment with ZA ranged from 0.4 to 1.6% after 1 year of exposure, 0.8 to 2.1% after 2 years, and 1.0 to 2.3% after 3 years of exposure. Statistically significant differences were found between denosumab and ZA in the risk of developing MRONJ after 1, 2 and 3 years of exposure. Nevertheless, there were no significant differences in terms of patient prognosis.

Conclusions

Denosumab is associated with a significantly higher risk of developing MRONJ compared to ZA. Nevertheless, no differences were found in its prognoses.

Key words:Denosumab, zoledronic acid, bisphosphonate-associated osteonecrosis of the Jaws, medication-related osteonecrosis of the jaws, neoplasms.

Proton-driven plasma wakefield acceleration in AWAKE

In this article, we briefly summarize the experiments performed during the first run of the Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal of AWAKE Run 1 (2013-2018) was to demonstrate that 10-20 MeV electrons can be accelerated to GeV energies in a plasma wakefield driven by a highly relativistic self-modulated proton bunch. We describe the experiment, outline the measurement concept and present first results. Last, we outline our plans for the future. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities

We give direct experimental evidence for the observation of the full transverse self-modulation of a long, relativistic proton bunch propagating through a dense plasma. The bunch exits the plasma with a periodic density modulation resulting from radial wakefield effects. We show that the modulation is seeded by a relativistic ionization front created using an intense laser pulse copropagating with the proton bunch. The modulation extends over the length of the proton bunch following the seed point. By varying the plasma density over one order of magnitude, we show that the modulation frequency scales with the expected dependence on the plasma density, i.e., it is equal to the plasma frequency, as expected from theory.

Experimental Observation of Plasma Wakefield Growth Driven by the Seeded Self-Modulation of a Proton Bunch

We measure the effects of transverse wakefields driven by a relativistic proton bunch in plasma with densities of 2.1×10^{14} and 7.7×10^{14}  electrons/cm^{3}. We show that these wakefields periodically defocus the proton bunch itself, consistently with the development of the seeded self-modulation process. We show that the defocusing increases both along the bunch and along the plasma by using time resolved and time-integrated measurements of the proton bunch transverse distribution. We evaluate the transverse wakefield amplitudes and show that they exceed their seed value (<15  MV/m) and reach over 300  MV/m. All these results confirm the development of the seeded self-modulation process, a necessary condition for external injection of low energy and acceleration of electrons to multi-GeV energy levels.

Combining Heavy-Ion Therapy with Immunotherapy: An Update on Recent Developments

Clinical trials and case reports of cancer therapies combining radiation therapy with immunotherapy have at times demonstrated total reduction or elimination of metastatic disease. While virtually all trials focus on the use of immunotherapy combined with conventional photon irradiation, the dose-distributive benefits of particles, in particular the distinct biological effects of heavy ions, have unknown potential vis-a-vis systemic disease response. Here, we review recent developments and evidence with a focus on the potential for heavy-ion combination therapy.

Acceleration of electrons in the plasma wakefield of a proton bunch

High-energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. To increase the energy of the particles or to reduce the size of the accelerator, new acceleration schemes need to be developed. Plasma wakefield acceleration^1–5, in which the electrons in a plasma are excited, leading to strong electric fields (so called ‘wakefields’), is one such promising acceleration technique. Experiments have shown that an intense laser pulse^6–9 or electron bunch^10,11 traversing a plasma can drive electric fields of tens of gigavolts per metre and above—well beyond those achieved in conventional radio-frequency accelerators (about 0.1 gigavolt per metre). However, the low stored energy of laser pulses and electron bunches means that multiple acceleration stages are needed to reach very high particle energies^5,12. The use of proton bunches is compelling because they have the potential to drive wakefields and to accelerate electrons to high energy in a single acceleration stage¹³. Long, thin proton bunches can be used because they undergo a process called self-modulation^14–16, a particle–plasma interaction that splits the bunch longitudinally into a series of high-density microbunches, which then act resonantly to create large wakefields. The Advanced Wakefield (AWAKE) experiment at CERN^17–19 uses high-intensity proton bunches—in which each proton has an energy of 400 gigaelectronvolts, resulting in a total bunch energy of 19 kilojoules—to drive a wakefield in a ten-metre-long plasma. Electron bunches are then injected into this wakefield. Here we present measurements of electrons accelerated up to two gigaelectronvolts at the AWAKE experiment, in a demonstration of proton-driven plasma wakefield acceleration. Measurements were conducted under various plasma conditions and the acceleration was found to be consistent and reliable. The potential for this scheme to produce very high-energy electron bunches in a single accelerating stage²⁰ means that our results are an important step towards the development of future high-energy particle accelerators^21,22.

Electron acceleration to very high energies is achieved in a single step by injecting electrons into a ‘wake’ of charge created in a 10-metre-long plasma by speeding long proton bunches.

Advances in Radiation Biology of Particle Irradiation

The increasing number of centers providing proton or carbon beam therapy underlines the growing importance of charged particle therapy within the spectrum of cancer radiotherapy. Whereas protons are more widely used around the world, carbon ions, which are known to bear a higher efficacy as compared to protons, are still neglected to some extent, especially due to a lack of clinical data on adverse side effects. Yet, an increasing amount of clinical data indicates the distinguished efficacy of carbon ion therapy. Notwithstanding, the radiobiological mechanisms of particle radiation are not completely understood and lag behind advances in technology, which potentially enable new therapy regimens. However, an increased knowledge is required for their application with maximal benefit and sufficient risk estimation. Differential gene expression, distinct molecular mechanisms and signal pathways in the radiation response, and systemic effects, such as increased immunogenicity, and the possibilities of combined treatments arising from them, are important fields of particle radiobiology in which new discoveries and advances have occurred. These aspects are contemplated with respect to an individualization of radiotherapy; radiation type and treatment regimen might be chosen on the basis of the radiosensitivity of the individual and the cancer type. Here, we provide an update on a few recent findings and advances in particle radiobiology. A comprehensive essay on the basics of particle radiobiology is beyond the scope of this article. The focus is directed on a few subjects currently undergoing intense study and which are of current interest with respect to advances in therapy.

New horizons in anticoagulation: Direct oral anticoagulants and their implications in oral surgery

Background

Thrombotic disorders remain a leading cause of death in the Western World. For decades, vitamin K antagonists used in the prevention of this pathology, such as warfarin or sintrom, were the only oral agents available for long-term anticoagulation, in spite of their disadvantages.

Material and Methods

An electronic database search was carried out on MedLine and The Cochrane Library Plus, without restrictions on the type of study nor dates, in English and Spanish. Abstracts were reviewed, and complete articles if necessary, considering all articles that included recommendations on DOACs and oral surgery.

Results

In recent years, the so-called “new oral anticoagulants” have been introduced in clinical practice to treat those patients whose medical conditions require long-term anticoagulant treatment, replacing traditional oral anticoagulants.

Conclusions

The new oral anticoagulants represent new therapeutic options, with a number of advantages such as poor interaction with food, minor drug interactions, and do not require periodic dose adjustments or routine controls. The purpose of this review is to establish an update on the new oral anticoagulants: Dabigatran, Rivarozaban, Apixaban and Edoxaban.

Key words:Novel oral anticoagulants, Dabigatran, Rivaroxaban, Apixaban, Edoxaban, bleeding management, oral surgery, Anti-IIa, Anti Xa.

The Immunoregulatory Potential of Particle Radiation in Cancer Therapy

Cancer treatment, today, consists of surgery, chemotherapy, radiation, and most recently immunotherapy. Combination immunotherapy-radiotherapy (CIR) has experienced a surge in public attention due to numerous clinical publications outlining the reduction or elimination of metastatic disease, following treatment with specifically ipilimumab and radiotherapy. The mechanism behind CIR, however, remains unclear, though it is hypothesized that radiation transforms the tumor into an in situ vaccine which immunotherapy modulates into a larger immune response. To date, the majority of attention has focused on rotating out immunotherapeutics with conventional radiation; however, the unique biological and physical benefits of particle irradiation may prove superior in generation of systemic effect. Here, we review recent advances in CIR, with a particular focus on the usage of charged particles to induce or enhance response to cancerous disease.

Surgical complications in zygomatic implants: A systematic review

BACKGROUND

The use of zygomatic implants in the prosthetic rehabilitation of the patient with severe maxillary bone atrophy is another therapeutic alternative, not exempt from complications. The main objective of this review is to analyze and describe the most frequent surgical complications associated with the use of zygomatic implants.

MATERIAL AND METHODS

An electronic database search on PubMed, along with a manual search, without taking into account date nor language, was undertaken by two observers, selecting studies that comprised a study period from 6 to 12 months, any type of clinical trial, and series that included a follow-up and/or review period during the aforementioned margin, that mentioned at least two types of complications.

RESULTS

Out of the initial search that yielded 455 studies, 67 were considered potentially relevant for the present study, out of which 14 were finally selected. Out of the most frequent surgical complications, sinusitis (3,9%) and failure in osseointegration (2,44%) are highlighted.

CONCLUSIONS

The analysis of the results shows that the most frequent complications are sinusitis and failure in osseointegration of the zygomatic implant. However, a standardised data collection system for the data on complications is needed.

Hibernation for space travel: Impact on radioprotection

Hibernation is a state of reduced metabolic activity used by some animals to survive in harsh environmental conditions. The idea of exploiting hibernation for space exploration has been proposed many years ago, but in recent years it is becoming more realistic, thanks to the introduction of specific methods to induce hibernation-like conditions (synthetic torpor) in non-hibernating animals. In addition to the expected advantages in long-term exploratory-class missions in terms of resource consumptions, aging, and psychology, hibernation may provide protection from cosmic radiation damage to the crew. Data from over half century ago in animal models suggest indeed that radiation effects are reduced during hibernation. We will review the mechanisms of increased radioprotection in hibernation, and discuss possible impact on human space exploration.

The Influence of C-Ions and X-rays on Human Umbilical Vein Endothelial Cells

Damage to the endothelium of blood vessels, which may occur during radiotherapy, is discussed as a potential precursor to the development of cardiovascular disease. We thus chose human umbilical vein endothelial cells as a model system to examine the effect of low- and high-linear energy transfer (LET) radiation. Cells were exposed to 250 kV X-rays or carbon ions (C-ions) with the energies of either 9.8 MeV/u (LET = 170 keV/μm) or 91 MeV/u (LET = 28 keV/μm). Subculture of cells was performed regularly up to 46 days (~22 population doublings) post-irradiation. Immediately after exposure, cells were seeded for the colony forming assay. Additionally, at regular intervals, mitochondrial membrane potential (MMP) (JC-1 staining) and cellular senescence (senescence-associated β-galactosidase staining) were assessed. Cytogenetic damage was investigated by the micronucleus assay and the high-resolution multiplex fluorescence in situ hybridization (mFISH) technique. Analysis of radiation-induced damage shortly after exposure showed that C-ions are more effective than X-rays with respect to cell inactivation or the induction of cytogenetic damage (micronucleus assay) as observed in other cell systems. For 9.8 and 91 MeV/u C-ions, relative biological effectiveness values of 2.4 and 1.5 were obtained for cell inactivation. At the subsequent time points, the number of micronucleated cells decreased to the control level. Analysis of chromosomal damage by mFISH technique revealed aberrations frequently involving chromosome 13 irrespective of dose or radiation quality. Disruption of the MMP was seen only a few days after exposure to X-rays or C-ions. Cellular senescence was not altered by radiation at any time point investigated. Altogether, our data indicate that shortly after exposure C-ions were more effective in damaging endothelial cells than X-rays. However, late damage to endothelial cells was not found for the applied conditions and endpoints.

Ionizing Radiation Impacts on Cardiac Differentiation of Mouse Embryonic Stem Cells

Little is known about the effects of ionizing radiation on the earliest stages of embryonic development although it is well recognized that ionizing radiation is a natural part of our environment and further exposure may occur due to medical applications. The current study addresses this issue using D3 mouse embryonic stem cells as a model system. Cells were irradiated with either X-rays or carbon ions representing sparsely and densely ionizing radiation and their effect on the differentiation of D3 cells into spontaneously contracting cardiomyocytes through embryoid body (EB) formation was measured. This study is the first to demonstrate that ionizing radiation impairs the formation of beating cardiomyocytes with carbon ions being more detrimental than X-rays. However, after prolonged culture time, the number of beating EBs derived from carbon ion irradiated cells almost reached control levels indicating that the surviving cells are still capable of developing along the cardiac lineage although with considerable delay. Reduced EB size, failure to downregulate pluripotency markers, and impaired expression of cardiac markers were identified as the cause of compromised cardiomyocyte formation. Dysregulation of cardiac differentiation was accompanied by alterations in the expression of endodermal and ectodermal markers that were more severe after carbon ion irradiation than after exposure to X-rays. In conclusion, our data show that carbon ion irradiation profoundly affects differentiation and thus may pose a higher risk to the early embryo than X-rays.

Fate of D3 mouse embryonic stem cells exposed to X-rays or carbon ions

The risk of radiation exposure during embryonic development is still a major problem in radiotoxicology. In this study we investigated the response of the murine embryonic stem cell (mESC) line D3 to two radiation qualities: sparsely ionizing X-rays and densely ionizing carbon ions. We analyzed clonogenic cell survival, proliferation, induction of chromosome aberrations as well as the capability of cells to differentiate to beating cardiomyocytes up to 3 days after exposure. Our results show that, for all endpoints investigated, carbon ions are more effective than X-rays at the same radiation dose. Additionally, in long term studies (≥8 days post-irradiation) chromosomal damage and the pluripotency state were investigated. These studies reveal that pluripotency markers are present in the progeny of cells surviving the exposure to both radiation types. However, only in the progeny of X-ray exposed cells the aberration frequency was comparable to that of the control population, while the progeny of carbon ion irradiated cells harbored significantly more aberrations than the control, generally translocations. We conclude that cells surviving the radiation exposure maintain pluripotency but may carry stable chromosomal rearrangements after densely ionizing radiation.

Differentiation status of human squamous cell carcinoma xenografts does not appear to correlate with the repopulation capacity of clonogenic tumour cells during fractionated irradiation

PURPOSE

To investigate the magnitude and kinetics of repopulation in a moderately well differentiated UT-SCC-14 human squamous cell carcinoma [hSCC] in nude mice. This question is of interest because clinical data indicate a higher repopulation capacity in those SCC that have preserved characteristics of differentiation, which appears to be in contrast to results on FaDu and GL hSCC previously reported from this laboratory.

METHODS AND MATERIALS

UT-SCC-14 tumours were transplanted subcutaneously into the right hind leg of NMRI nu/nu mice. Fractionated radiation treatments were delivered, either under clamped hypoxia at 5.4 Gy/fraction or under ambient conditions (consistent with an OER of 2.7). Tumours were irradiated every day, every 2nd day, or every 3rd day with 6, 12 or 18 fractions. 1, 2 or 3 days after the last fraction, graded top-up-doses under clamped conditions were given for the purpose of estimating the 50% tumour control dose (TCD50). A total of 22 TCD50 assays were performed and analysed using maximum likelihood techniques.

RESULTS

The data demonstrate a slow but significant repopulation of clonogenic cells during fractionated irradiation of UT-SCC-14 hSCC. The results under hypoxic conditions are consistent with a constant repopulation rate, with a clonogenic doubling time (Tclon) of 15.6 days (95% CI: 9.7, 21.4). This contrasts with ambient conditions where Tclon was 68.5 days (95% CI: 124, 161). Both Tclon values are longer than the 6-day volume doubling time of untreated tumours.

CONCLUSIONS

Less pronounced repopulation for irradiation under ambient compared to clamped hypoxic conditions might be explained by preferential survival of hypoxic and therefore non-proliferating clonogenic cells. Taken together with previous studies on poorly differentiated FaDu and moderately well differentiated GL hSCC, the results are consistent with considerable variability in the magnitude and kinetics of repopulation in different experimental squamous cell carcinomas, and with a relationship between reoxygenation and repopulation during fractionated irradiation. The differentiation status of hSCC growing in nude mice does not to appear to correlate with the proliferative capacity of clonogenic tumour cells during treatment. The results do not support the hypothesis gained from clinical data of higher repopulation in well-differentiated tumours.

Identification of sequence determinants that direct different intracellular folding pathways for aquaporin-1 and aquaporin-4

Homologous aquaporin water channels utilize different folding pathways to acquire their transmembrane (TM) topology in the endoplasmic reticulum (ER). AQP4 acquires each of its six TM segments via cotranslational translocation events, whereas AQP1 is initially synthesized with four TM segments and subsequently converted into a six membrane-spanning topology. To identify sequence determinants responsible for these pathways, peptide segments from AQP1 and AQP4 were systematically exchanged. Chimeric proteins were then truncated, fused to a C-terminal translocation reporter, and topology was analyzed by protease accessibility. In each chimeric context, TM1 initiated ER targeting and translocation. However, AQP4-TM2 cotranslationally terminated translocation, while AQP1-TM2 failed to terminate translocation and passed into the ER lumen. This difference in stop transfer activity was due to two residues that altered both the length and hydrophobicity of TM2 (Asn(49) and Lys(51) in AQP1 versus Met(48) and Leu(50) in AQP4). A second peptide region was identified within the TM3-4 peptide loop that enabled AQP4-TM3 but not AQP1-TM3 to reinitiate translocation and cotranslationally span the membrane. Based on these findings, it was possible to convert AQP1 into a cotranslational biogenesis mode similar to that of AQP4 by substituting just two peptide regions at the N terminus of TM2 and the C terminus of TM3. Interestingly, each of these substitutions disrupted water channel activity. These data thus establish the structural basis for different AQP folding pathways and provide evidence that variations in cotranslational folding enable polytopic proteins to acquire and/or maintain primary sequence determinants necessary for function.

Transmembrane biogenesis of Kv1.3

Using a combination of protease protection, glycosylation, and carbonate extraction assays, we have characterized the topogenic determinants encoded by Kv1.3 segments that mediate translocation events during endoplasmic reticulum (ER) biogenesis. Transmembrane segments S1, S2, S3, S5, and S6 initiate translocation, only S1 and S2 strongly (>60%) anchor themselves in the membrane, S5 exhibits signal anchor activity and contains a cryptic cleavage site, and S3 and S6 fail to integrate into the membrane. Elongation of each single-transmembrane construct to include multiple transmembrane segments alters integration and translocation efficiencies, indicating that multiple topogenic determinants cooperate during Kv1. 3 topogenesis and assembly. Several surprising findings emerged from these studies. First, in the presence of T1, the N-terminal recognition domain, S1 was unable to initiate either translocation or membrane integration. As a result, S2 likely functions as the initial signal sequence to establish Kv1.3 N-terminus topology. Second, S4 independently integrates into the membrane. Third, S6 plus the C-terminus of Kv1.3 is a secretory protein but can be converted to a membrane-integrated protein with a correctly oriented, cytosolic C-terminus by linking S6 to S5 and the pore loop. These results have implications for the role of the N-terminus in Kv biogenesis and on the mechanisms of dominant negative suppression of Kv1.3 by truncated Kv1.3 fragments [Tu et al. (1996) J. Biol. Chem. 271, 18904-18911].

Liability, UAPs and you

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Coupled translocation events generate topological heterogeneity at the endoplasmic reticulum membrane

Topogenic determinants that direct protein topology at the endoplasmic reticulum membrane usually function with high fidelity to establish a uniform topological orientation for any given polypeptide. Here we show, however, that through the coupling of sequential translocation events, native topogenic determinants are capable of generating two alternate transmembrane structures at the endoplasmic reticulum membrane. Using defined chimeric and epitope-tagged full-length proteins, we found that topogenic activities of two C-trans (type II) signal anchor sequences, encoded within the seventh and eighth transmembrane (TM) segments of human P-glycoprotein were directly coupled by an inefficient stop transfer (ST) sequence (TM7b) contained within the C-terminus half of TM7. Remarkably, these activities enabled TM7 to achieve both a single- and a double-spanning TM topology with nearly equal efficiency. In addition, ST and C-trans signal anchor activities encoded by TM8 were tightly linked to the weak ST activity, and hence topological fate, of TM7b. This interaction enabled TM8 to span the membrane in either a type I or a type II orientation. Pleiotropic structural features contributing to this unusual topogenic behavior included 1) a short, flexible peptide loop connecting TM7a and TM7b, 2) hydrophobic residues within TM7b, and 3) hydrophilic residues between TM7b and TM8.

Co- and posttranslational translocation mechanisms direct cystic fibrosis transmembrane conductance regulator N terminus transmembrane assembly

Transmembrane topology of most eukaryotic polytopic proteins is established cotranslationally at the endoplasmic reticulum membrane through the action of alternating signal and stop transfer sequences. Here we demonstrate that the cystic fibrosis transmembrane conductance regulator (CFTR) achieves its N terminus topology through a variation of this mechanism that involves both co- and posttranslational translocation events. Using a series of defined chimeric and truncated proteins expressed in a reticulocyte lysate system, we have identified two topogenic determinants encoded within the first (TM1) and second (TM2) membrane-spanning segments of CFTR. Each sequence independently (i) directed endoplasmic reticulum targeting, (ii) translocated appropriate flanking residues, and (iii) achieved its proper membrane-spanning orientation. Signal sequence activity of TM1, however, was inefficient due to the presence of two charged residues, Glu92 and Lys95, located within its hydrophobic core. As a result, TM1 was able to direct correct topology for less than half of nascent CFTR chains. In contrast to TM1, TM2 signal sequence activity was both efficient and specific. Even in the absence of a functional TM1 signal sequence, TM2 was able to direct CFTR N terminus topology through a ribosome-dependent posttranslational mechanism. Mutating charged residues Glu92 and Lys95 to alanine improved TM1 signal sequence activity as well as the ability of TM1 to independently direct CFTR N terminus topology. Thus, a single functional signal sequence in either the first or second TM segment was sufficient for directing proper CFTR topology. These results identify two distinct and redundant translocation pathways for CFTR N terminus transmembrane assembly and support a model in which TM2 functions to ensure correct topology of CFTR chains that fail to translocate via TM1. This novel arrangement of topogenic information provides an alternative to conventional cotranslational pathways of polytopic protein biogenesis.

Dietitians in breastfeeding management: an untapped resource in the hospital

Maternity care nurses were surveyed to gather data on the state of breastfeeding in Utah hospitals. A questionnaire was distributed to labor and delivery, well-baby nursery, and postpartum nurses at 18 hospitals representing 86% of births in the state. The results indicated that of dietitians, physicians, and nurses, dietitians were the health care professionals least likely to provide breastfeeding information and assistance.

Respiratory rehabilitation, exercise capacity and quality of life in chronic airways disease in old age

Respiratory rehabilitation improves exercise capacity and quality of life in younger patients but is untried in the aged. We aimed to: (a) assess repeatability of the 6-minute walk test, factors affecting it and its relation to quality of life in elderly patients with chronic obstructive airways disease (COAD); (b) assess compliance of such patients with an intensive respiratory rehabilitation protocol; (c) pilot the assessment of the effect of respiratory rehabilitation on the 6-minute walk test in these patients. Seventeen subjects with stable, symptomatic COAD were recruited, 15 (six men), 70-89 (mean 76) years, completed the study. Mean (standard deviation) 1-second forced expiratory volume (FEV1) = 49 (5)% predicted. Six-minute walk tests were repeated single-blind, 2-10 days apart. Quality of life was measured using Guyatt respiratory questionnaire. Patients underwent 12 weeks incremental respiratory rehabilitation (x4/day step-ups, unweighed arm raises, inflating balloons). Baseline 6-minute walk was repeatable and was correlated with the log Guyatt dyspnoea score (r = 0.65, p = 0.006). In multiple regression neither age nor FEV1 predicted walk distance: body mass index, maximal expiratory mouth pressure; calorie intake. Mean (SEM) 6-minute walk distance after-rehabilitation was greater than baseline (p = 0.003). Elderly patients with COAD tolerate intensive respiratory rehabilitation and a controlled, blinded study is needed.