Monitoring electron energies during FLASH irradiations

When relativistic electrons are used to irradiate tissues, such as during FLASH pre-clinical irradiations, the electron beam energy is one of the critical parameters that determine the dose distribution. Moreover, during such irradiations, linear accelerators (linacs) usually operate with significant beam loading, where a small change in the accelerator output current can lead to beam energy reduction. Optimisation of the tuning of the accelerator's radio frequency system is often required. We describe here a robust, easy-to-use device for non-interceptive monitoring of potential variations in the electron beam energy during every linac macro-pulse of an irradiation run. Our approach monitors the accelerated electron fringe beam using two unbiased aluminium annular charge collection plates, positioned in the beam path and with apertures (5 cm in diameter) for the central beam. These plates are complemented by two thin annular screening plates to eliminate crosstalk and equalise the capacitances of the charge collection plates. The ratio of the charge picked up on the downstream collection plate to the sum of charges picked up on the both plates is sensitive to the beam energy and to changes in the energy spectrum shape. The energy sensitivity range is optimised to the investigated beam by the choice of thickness of the first plate. We present simulation and measurement data using electrons generated by a nominal 6 MeV energy linac as well as information on the design, the practical implementation and the use of this monitor.

Prospective gating control for highly efficient cardio-respiratory synchronised short and constant TR MRI in the mouse

PURPOSE

Cardiac and respiratory motion derived image artefacts are reduced when data are acquired with cardiac and respiratory synchronisation. Where steady state imaging techniques are required in small animals, synchronisation is most commonly performed using retrospective gating techniques but these invoke an inherent time penalty. This paper reports the development of prospective gating techniques for cardiac and respiratory motion desensitised MRI with significantly reduced minimum scan time compared to retrospective gating.

METHODS

Prospective gating incorporating the automatic reacquisition of data corrupted by motion at the entry to each breath was implemented in short TR 3D spoiled gradient echo imaging. Motion sensitivity was examined over the whole mouse body for scans performed without gating, with respiratory gating, and with cardio-respiratory gating. The gating methods were performed with and without automatic reacquisition of motion corrupted data immediately after completion of the same breath. Prospective cardio-respiratory gating, with acquisition of 64 k-space lines per cardiac R-wave, was used to enable whole body DCE-MRI in the mouse.

RESULTS

Prospective cardio-respiratory gating enabled high fidelity steady state imaging of physiologically mobile organs such as the heart and lung. The automatic reacquisition of data corrupted by motion at the entry to each breath minimised respiratory motion artefact and enabled a highly efficient data capture that was adaptive to changes in the inter-breath interval. Prospective cardio-respiratory gating control enabled DCE-MRI to be performed over the whole mouse body with the acquisition of successive image volumes every 12-15 s at 422 μm isotropic resolution.

CONCLUSIONS

Highly efficient cardio-respiratory motion desensitised steady state MRI can be performed in small animals with prospective synchronisation, centre-out phase-encode ordering, and the automatic reacquisition of data corrupted by motion at the entry to each breath. The method presented is robust against spontaneous changes in the breathing rate. Steady state imaging with prospective cardio-respiratory gating is much more efficient than with retrospective gating, and enables the examination of rapidly changing systems such as those found when using DCE-MRI.

The Development of Technology for Effective Respiratory-Gated Irradiation Using an Image-Guided Small Animal Irradiator

The development of image-guided small animal irradiators represents a significant improvement over standard irradiators by enabling preclinical studies to mimic radiotherapy in humans. The ability to deliver tightly collimated targeted beams, in conjunction with gantry or animal couch rotation, has the potential to maximize tumor dose while sparing normal tissues. However, the current commercial platforms do not incorporate respiratory gating, which is required for accurate and precise targeting in organs subject to respiration related motions that may be up to the order of 5 mm in mice. Therefore, a new treatment head assembly for the Xstrahl Small Animal Radiation Research Platform (SARRP) has been designed. This includes a fast X-ray shutter subsystem, a motorized beam hardening filter assembly, an integrated transmission ionization chamber to monitor beam delivery, a kinematically positioned removable beam collimator and a targeting laser exiting the center of the beam collimator. The X-ray shutter not only minimizes timing errors but also allows beam gating during imaging and treatment, with irradiation only taking place during the breathing cycle when tissue movement is minimal. The breathing related movement is monitored by measuring, using a synchronous detector/lock-in amplifier that processes diffuse reflectance light from a modulated light source. After thresholding of the resulting signal, delays are added around the inhalation/exhalation phases, enabling the "no movement" period to be isolated and to open the X-ray shutter. Irradiation can either be performed for a predetermined time of X-ray exposure, or through integration of a current from the transmission monitor ionization chamber (corrected locally for air density variations). The ability to successfully deliver respiratory-gated X-ray irradiations has been demonstrated by comparing movies obtained using planar X-ray imaging with and without respiratory gating, in addition to comparing dose profiles observed from a collimated beam on EBT3 radiochromic film mounted on the animal's chest. Altogether, the development of respiratory-gated irradiation facilitates improved dose delivery during animal movement and constitutes an important new tool for preclinical radiation studies. This approach is particularly well suited for irradiation of orthotopic tumors or other targets within the chest and abdomen where breathing related movement is significant.

Novel antibody-like single-chain TCR antibody Fc fusion protein

We have previously reported the construction of a fusion protein composed of a soluble single-chain T cell receptor genetically linked to the constant domain of the human IgG1 heavy chain (TCR-Ig). The antigen recognition portion of the protein binds to an unmutated peptide derived from human p53 (amino acids 264–272) presented in the context of HLA-A2.1, whereas the IgG1 Fc provides effector functions. The protein is capable of forming dimers, specifically staining tumor cells, and promoting target and effector cell conjugation. The protein also has potent antitumor effects against p53+/HLA-A2.1+ human tumor xenografts in athymic nude mice and can mediate cell killing by antibody-dependent cellular cytotoxicity. Therefore, TCR-Ig behaves like an antibody, but possesses the ability to recognize antigens derived from intracellular targets. To test TCR-Ig in fully immunocompetent models, we have generated murine tumor cells stably expressing the human p53 epitope by constructing a single chain trimer composed of the human p53 peptide genetically linked to murine beta 2 microglobulin genetically linked to HLA-A2.1, with the inclusion of a disulfide trap to enhance stability. Utilizing haNK (NK-92 cells stably expressing high affinity Fc receptor and IL-2) as effector cells in the presence of TCR-Ig we demonstrated specific killing of murine single chain trimer expressing tumor cells. We are currently evaluating the antitumor activities and vaccinal effects of TCR-Ig in an HLA-A2.1 transgenic mouse model. TCR-Ig may represent a novel group of immunotherapeutics that has the potential to expand the range of tumors available for targeted therapies beyond those currently addressed by conventional antibody-based approaches.

An efficient and robust MRI-guided radiotherapy planning approach for targeting abdominal organs and tumours in the mouse

INTRODUCTION

Preclinical CT-guided radiotherapy platforms are increasingly used but the CT images are characterized by poor soft tissue contrast. The aim of this study was to develop a robust and accurate method of MRI-guided radiotherapy (MR-IGRT) delivery to abdominal targets in the mouse.

METHODS

A multimodality cradle was developed for providing subject immobilisation and its performance was evaluated. Whilst CT was still used for dose calculations, target identification was based on MRI. Each step of the radiotherapy planning procedure was validated initially in vitro using BANG gel dosimeters. Subsequently, MR-IGRT of normal adrenal glands with a size-matched collimated beam was performed. Additionally, the SK-N-SH neuroblastoma xenograft model and the transgenic KPC model of pancreatic ductal adenocarcinoma were used to demonstrate the applicability of our methods for the accurate delivery of radiation to CT-invisible abdominal tumours.

RESULTS

The BANG gel phantoms demonstrated a targeting efficiency error of 0.56 ± 0.18 mm. The in vivo stability tests of body motion during MR-IGRT and the associated cradle transfer showed that the residual body movements are within this MR-IGRT targeting error. Accurate MR-IGRT of the normal adrenal glands with a size-matched collimated beam was confirmed by γH2AX staining. Regression in tumour volume was observed almost immediately post MR-IGRT in the neuroblastoma model, further demonstrating accuracy of x-ray delivery. Finally, MR-IGRT in the KPC model facilitated precise contouring and comparison of different treatment plans and radiotherapy dose distributions not only to the intra-abdominal tumour but also to the organs at risk.

CONCLUSION

This is, to our knowledge, the first study to demonstrate preclinical MR-IGRT in intra-abdominal organs. The proposed MR-IGRT method presents a state-of-the-art solution to enabling robust, accurate and efficient targeting of extracranial organs in the mouse and can operate with a sufficiently high throughput to allow fractionated treatments to be given.

The allure and peril of hematopoietic stem cell transplantation: overcoming immune challenges to improve success

Since its inception in the mid-twentieth century, the complication limiting the application and utility of allogeneic hematopoietic stem cell transplantation (allo-HSCT) to treat patients with hematopoietic cancer is the development of graft-versus-host disease (GVHD). Ironically, GVHD is induced by the cells (T lymphocytes) transplanted for the purpose of eliminating the malignancy. Damage ensuing to multiple tissues, e.g., skin, GI, liver, and others including the eye, provides the challenge of regulating systemic and organ-specific GVH responses. Because the immune system is also targeted by GVHD, this both: (a) impairs reconstitution of immunity post-transplant resulting in patient susceptibility to lethal infection and (b) markedly diminishes the individual's capacity to generate anti-cancer immunity--the raison d'etre for undergoing allo-HSCT. We hypothesize that deleting alloreactive T cells ex vivo using a new strategy involving antigen stimulation and alkylation will prevent systemic GVHD thereby providing a platform for the generation of anti-tumor immunity. Relapse also remains the major complication following autologous HSCT (auto-HSCT). While GVHD does not complicate auto-HSCT, its absence removes significant grant anti-tumor responses (GVL) and raises the challenge of generating rapid and effective anti-tumor immunity early post-transplant prior to immune reconstitution. We hypothesize that effective vaccine usage to stimulate tumor-specific T cells followed by their amplification using targeted IL-2 can be effective in both the autologous and allogeneic HSCT setting. Lastly, our findings support the notion that the ocular compartment can be locally targeted to regulate visual complications of GVHD which may involve both alloreactive and self-reactive (i.e., autoimmune) responses.

Comment on "a comparison of buprenorphine + naloxone to buprenorphine and methadone in the treatment of opioid dependence during pregnancy: maternal and neonatal outcomes"

In a recent article, Lund et al sought to compare maternal and neonatal outcomes of various treatment regimens for opioid dependence during pregnancy.1 In their background, discussion the authors state that “In the United States buprenorphine plus naloxone [Suboxone^®] … has been the preferred form of prescribed buprenorphine due to its reduced abuse liability relative to buprenorphine alone [Subutex^®].” This claim is certainly consistent with the view of the firm that has manufactured and sold both products, Reckitt Benckiser. In September of 2011, the company announced that it was “… discontinuing distribution and sale of Subutex^® tablets as we believe that mono product (product containing buprenorphine alone with no naloxone) creates a greater risk of misuse, abuse and diversion …”.2 Supporting evidence for the alleged “reduced abuse liability” appears to be lacking, however, and evidence cannot be located in the two references cited by Dr. Lund and his co-authors, which in fact are silent on the subject of abuse potential.3,4 In contrast, it has been reported that the transition to buprenorphine/naloxone from the mono formulation has been associated with “… no reduction in injection risk behaviors among IDUs.”5

Abstract A32: Combining early heat shock protein vaccination with directed IL-2 leads to effective and persistent antitumor immunity in recipients of experimental autologous hematopoietic cell transplantation

Tumor relapse remains the major cause of morbidity and mortality in patients with hematologic cancers after aggressive chemo-radiotherapy and autologous hematopoietic cell transplant (HCT) rescue. Therefore, vaccination strategies can be employed early post-HCT during ‘reboot’ of the immune system to mold anti-tumor immunity by taking advantage of both minimal residual disease and lymphopenia. The pre-clinical studies here developed a new strategy uniquely suitable to this environment. We reasoned that by introducing antigen as a heat shock protein (hsp) vaccine, tumor specific CD8 T cells would be rapidly elicited. Subsequently, administration of IL-2 ‘directed’ to CD8 T cells would augment vaccine induced expansion and survival of lymphoma bearing HCT recipients. Recipient B6 mice were therefore conditioned with myeloablative total body irradiation prior to syngeneic HCT. To more precisely model clinical transplants, T cells were obtained from syngeneic donors bearing progressively growing lymphoma (EG7). Transplanted mice were inoculated with a low number of EG7 cells to simulate tumor relapse post-HCT. A multiple vaccination protocol was employed utilizing irradiated EG7 cells transfected to secrete the hsp fusion protein gp96-Ig (EG7-gp96-Ig). To ‘direct’ IL-2 to CD8 T cells, we infused complexes of IL-2 pre-bound to αIL-2 mAb clone S4B6 (IL-2S4B6).

Transplanted animals not vaccinated or vaccinated with parental EG7 cells exhibited an MST of ~1 month with 100% lethality. In contrast, vaccination with EG7-gp96-Ig cells significantly extended MST and increased overall survival to 20% (>100 d post-HCT). Enhanced MST was dependent on transplant of donor T cells since vaccination failed to prolong survival in recipients of T cell depleted marrow grafts. Strikingly, combination therapy with EG7-gp96-Ig and IL-2S4B6 complex resulted in a dramatic increase of overall survival (60%) and MST. Treatment with either: a) unbound ‘free’ IL-2 in combination with vaccine, or b) IL-2S4B6 complex monotherapy (no vaccine), did not induce a survival advantage vs. vaccine therapy alone. Experiments are ongoing to determine which components of the donor graft are required for prolonged survival. Surviving mice (>100 d post-HCT) were re-challenged with a lethal number of EG7 cells. Most HCT recipients (n = 16) vaccinated with EG7-gp96-Ig cells alone or in combination with IL-2S4B6 complex rejected the tumor (87.5%), illustrating the presence of long term anti-tumor memory. To monitor tumor specific T cells, CD8 OT-I were transferred to some donor mice preceding tumor inoculation. This resulted in ~1000 OT-I present in the 2x106 donor T cell inoculum used for HCT. Importantly, no effect on overall survival of HCT recipients was observed regardless of the presence or absence of the transplanted OT-I. Treatment with hsp vaccine and ‘directed’ IL-2 resulted in ~36,000x expansion of OT-I within 2 wk of HCT, compared to ~7000x after vaccination alone. OT-I at the vaccine site produced IFN-γ and TNF-α after ex vivo peptide stimulation. Notably, the combination strategy elicited large increases in both donor CD8 T and NK cells, populations essential for pathogen immunity and vaccine efficacy. Experiments are ongoing to determine if a 2 cycle protocol, administered in part during de novo T cell genesis (>3 wk post-HCT), can elicit additional immunity from these newly derived T cells.

Vaccination approaches employing tumor cells secreting gp96-Ig are presently in clinical trials for lung cancer utilizing an ‘off the shelf’ modified allogeneic lung cancer cell line. Interestingly, others have engineered a human IL-2 “superkine”, resulting in a binding pattern similar to the cytokine/antibody complex used in the present studies. Thus, the combinatorial regimen developed here represents a promising strategy with translational applications for patients with hematologic cancers.

Citation Format: Robert G. Newman, Eckhard R. Podack, Robert B. Levy. Combining early heat shock protein vaccination with directed IL-2 leads to effective and persistent antitumor immunity in recipients of experimental autologous hematopoietic cell transplantation. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A32.

What's so special about methadone maintenance?

Despite the proven effectiveness of methadone maintenance treatment in the management of opiate dependence, methadone maintenance programmes have met with almost universal opposition and controversy in countries all over the world. The unique aspects of methadone treatment are examined, including the stringent restrictions imposed on methadone programmes and the convention of sub-optimal dosing adhered to in many programmes. Finally, some reasons for the under-utilization of this treatment mode are proposed, and the implications of current attitudes towards methadone maintenance programmes are examined.

The cloning and expression of matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase 2 in normal canine lymph nodes and in canine lymphoma

Matrix metalloproteinase-2 (MMP-2) and its inhibitor, tissue inhibitor of matrix metalloproteinase 2 (TIMP2), are known to be important in cancer. The purposes of this study were to determine the cDNA sequence of canine MMP-2 and to investigate the expression patterns of MMP-2 and TIMP2 in normal canine lymph nodes and spontaneously arising canine lymphomas. We cloned and sequenced a PCR product containing most (1901 base pairs) of the coding sequence of canine MMP-2 that translates into a 623 amino acid protein. The cDNA and deduced amino acid sequences are highly homologous to those of other mammalian species. Canine MMP-2 and TIMP2 mRNAs were detectable in the majority of normal lymph node and lymphomatous samples evaluated. No statistical difference was identified when comparing the expression of either gene with regard to normal versus neoplastic nodes, nodal versus extranodal lymphoma, lymphoma grade, or B versus T cell immunophenotype.

Expansion of opiate agonist treatment: an historical perspective

Untreated opiate addiction remains a major health care crisis in New York and in most other urban centers in America. Optimism for closing the gap between need and demand for treatment and its availability has greeted the recent approval of a new opiate medication for addiction, buprenorphine – which unlike methadone may be prescribed by independent, office-based practitioners. The likelihood of buprenorphine fulfilling its potential is assessed in the light of the massive expansion of methadone treatment more than 30 years earlier. It is concluded that the key, indispensable ingredient of success will be true commitment on the part of Government to provide care to all those who need it.

Methadone maintenance in prison: evaluation of a pilot program in Puerto Rico

OBJECTIVES

To describe and evaluate a pilot methadone maintenance program for heroin-dependent inmates of Las Malvinas men's prison in San Juan, Puerto Rico.

METHODS

Data from self-report of inmates' drug use before and during incarceration, attitudes about drug treatment in general and methadone maintenance in particular, and expectations about behaviors upon release from prison and from testing inmates' urine were analyzed comparing program patients (n=20) and inmates selected at random from the prison population (n=40). Qualitative data obtained by interviewing program staff, the correctional officers and superintendent, and commonwealth officials responsible for establishing and operating the program were analyzed to identify attitudes about methadone and program effectiveness.

RESULTS

Heroin use among prisoners not in treatment was common; 58% reported any use while incarcerated and 38% reported use in past 30 days. All patients in the treatment program had used heroin in prison in the 30 days prior to enrolling in treatment. While in treatment, the percentage of patients not using heroin was reduced, according to both self-report and urine testing, to one in 18 (94% reduction) and one in 20 (95% reduction), respectively. Participation in treatment was associated with an increased acceptance of methadone maintenance. Prison personnel and commonwealth officials were supportive of the program.

CONCLUSIONS

The program appears to be a success, and prison officials have begun an expansion from the current ceiling of 24 inmates to treat 300 or more inmates.

Comment on Soar, et al.'s Case Study of Problems and Use of Ecstasy

This case report provides no basis for drawing any conclusions regarding possible adverse effects of use of Ecstasy.

Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release

3-(4-Methylcoumarin-7-yloxy)methylindole-4,7-diones were synthesised as model prodrugs in order to investigate the correlation between rates of reductive elimination from the (indolyl-3-yl)methyl position with reductive metabolism by hypoxic tumor cells and NADPH: cytochrome P450. Rates of elimination of the chromophore/fluorophore (7-hydroxy-4-methylcoumarin) following one-electron reduction of indolequinones to their semiquinone radicals (Q*-) was measured by pulse radiolysis utilising spectrophotometric and fluorometric detection. Incorporation of a thienyl or methyl substituent at the (indol-3-yl)CHR-position (where R=thienyl or methyl adjacent to the phenolic ether linking bond) significantly shortened the half-life of reductive elimination from 87 to 6 and 2 ms, respectively. Elimination from the methyl substituted analogue can thus compete effectively with the reaction of the semiquinone radical with oxygen at levels typically present in tumours (half-life approximately 1.8 ms at 0.5% O2). Chemical kinetic predictions were confirmed by metabolism in breast tumour MCF-7 cells between 0-2.1% O2. Rates of reductive release of the fluorophore from the non-fluorescent parent indolequinones (R=H, Me, thienyl) were similar under anoxia ( approximately 1.7 nmol coumarinmin(-1)mg protein(-1)) reflecting the similarity in one-electron reduction potential. Whereas coumarin release from the indolequinone (R=H) was completely inhibited above 0.5% O2, the enhanced rate of reductive elimination when R=thienyl or Me increased the metabolic rate of release to approximately 0.35 and 0.7 nmol coumarinmin(-1)mg protein(-1), respectively at 0.5% O2; complete inhibition occurring by 2.1% O2. Similar 'oxygen profiles' of release were observed with NADPH: cytochrome P450 reductase. In conclusion, it is possible to modify rates of reductive elimination from indolequinones to control the release of drugs over a range of tumour hypoxia.

Frequency and perception of cough severity

OBJECTIVE

The frequency of the common symptom of cough in children is unknown. The aim of this study was to compare cough frequency and perception of cough severity in children with and without recurrent cough.

METHODOLOGY

Eighty-four children with (C) and without (NC) recurrent cough were recruited in the same season. Cough frequency (measured with cough-meter) and subjective cough severity (measured on parent-completed and child-completed diary cards on two subjective systems), were compared between the two groups.

RESULTS

Cough frequency in C (median 65/day) was significantly higher than in NC (10/day). The correlation between daytime and night-time cough was higher in NC (rs = 0.51, P < 0.00001) than in C (rs = 0.3, P = 0.05). The C group had significantly higher coughs per score than NC, for both subjective methods.

CONCLUSIONS

Children with recurrent cough have a higher frequency and different pattern of cough than controls enrolled in the same season. Subjective perception of cough severity is dependent on the population studied.

A novel approach to monitoring adherence to preventive therapy for tuberculosis in adolescence

OBJECTIVES

To evaluate the usefulness of a microelectronic tablet-dispenser for monitoring adherence to preventive therapy for tuberculosis infection in adolescents.

METHODOLOGY

Twenty-one patients with positive Mantoux tests were treated with isoniazid (INH), dispensed in a microelectronic tablet-dispenser that recorded the date, time and duration that the container was opened. Other measures of adherence included attendance at clinic, patient self-report, tablet count, and measurement of urinary INH metabolites.

RESULTS

The mean adherence rates were: 83% using attendance at clinic, 91% using tablet counts, 79% using urine assays, and 66% using the electronic tablet-dispenser. Self-reporting appeared to over-estimate adherence.

CONCLUSIONS

Adherence to 6 months of INH calculated using different measures is higher in this study than in previous reports. Microelectronic tablet-dispensers are an effective method to objectively measure adherence on a daily basis. Other measures are less helpful.