NRG Oncology and Particle Therapy Co-Operative Group Patterns of Practice Survey and Consensus Recommendations on Pencil-Beam Scanning Proton Stereotactic Body Radiation Therapy and Hypofractionated Radiation Therapy for Thoracic Malignancies.

Stereotactic body radiation therapy (SBRT) and hypofractionation using pencil-beam scanning (PBS) proton therapy (PBSPT) is an attractive option for thoracic malignancies. Combining the advantages of target coverage conformity and critical organ sparing from both PBSPT and SBRT, this new delivery technique has great potential to improve the therapeutic ratio, particularly for tumors near critical organs. Safe and effective implementation of PBSPT SBRT/hypofractionation to treat thoracic malignancies is more challenging than the conventionally fractionated PBSPT because of concerns of amplified uncertainties at the larger dose per fraction. The NRG Oncology and Particle Therapy Cooperative Group Thoracic Subcommittee surveyed proton centers in the United States to identify practice patterns of thoracic PBSPT SBRT/hypofractionation. From these patterns, we present recommendations for future technical development of proton SBRT/hypofractionation for thoracic treatment. Among other points, the recommendations highlight the need for volumetric image guidance and multiple computed tomography-based robust optimization and robustness tools to minimize further the effect of uncertainties associated with respiratory motion. Advances in direct motion analysis techniques are urgently needed to supplement current motion management techniques.

Proton Pencil-Beam Scanning Stereotactic Body Radiation Therapy and Hypofractionated Radiation Therapy for Thoracic Malignancies: Patterns of Practice Survey and Recommendations for Future Development from NRG Oncology and PTCOG.

Stereotactic body radiation therapy (SBRT) and hypofractionation using pencil-beam scanning (PBS) proton therapy (PBSPT) is an attractive option for thoracic malignancies. Combining the advantages of target coverage conformity and critical organ sparing from both PBSPT and SBRT, this new delivery technique has great potential to improve the therapeutic ratio, particularly for tumors near critical organs. Safe and effective implementation of PBSPT SBRT/hypofractionation to treat thoracic malignancies is more challenging than the conventionally-fractionated PBSPT due to concerns of amplified uncertainties at the larger dose per fraction. NRG Oncology and Particle Therapy Cooperative Group (PTCOG) Thoracic Subcommittee surveyed US proton centers to identify practice patterns of thoracic PBSPT SBRT/hypofractionation. From these patterns, we present recommendations for future technical development of proton SBRT/hypofractionation for thoracic treatment. Amongst other points, the recommendations highlight the need for volumetric image guidance and multiple CT-based robust optimization and robustness tools to minimize further the impact of uncertainties associated with respiratory motion. Advances in direct motion analysis techniques are urgently needed to supplement current motion management techniques.

A Review of Boron Neutron Capture Therapy: Its History and Current Challenges.

Mechanism of Action: External beam, whether with photons or particles, remains as the most common type of radiation therapy. The main drawback is that radiation deposits dose in healthy tissue before reaching its target. Boron neutron capture therapy (BNCT) is based on the nuclear capture and fission reactions that occur when 10B is irradiated with low-energy (0.0025 eV) thermal neutrons. The resulting 10B(n,α)7Li capture reaction produces high linear energy transfer (LET) α particles, helium nuclei (4He), and recoiling lithium-7 (7Li) atoms. The short range (5-9 µm) of the α particles limits the destructive effects within the boron-containing cells. In theory, BNCT can selectively destroy malignant cells while sparing adjacent normal tissue at the cellular levels by delivering a single fraction of radiation with high LET particles. History: BNCT has been around for many decades. Early studies were promising for patients with malignant brain tumors, recurrent tumors of the head and neck, and cutaneous melanomas; however, there were certain limitations to its widespread adoption and use. Current Limitations and Prospects: Recently, BNCT re-emerged owing to several developments: (1) small footprint accelerator-based neutron sources; (2) high specificity third-generation boron carriers based on monoclonal antibodies, nanoparticles, among others; and (3) treatment planning software and patient positioning devices that optimize treatment delivery and consistency.

American College of Radiology (ACR) and American Society for Radiation Oncology (ASTRO) practice guideline for the performance of total body irradiation (TBI).

Total body irradiation (TBI) is a specialized radiotherapy technique. It is frequently used as a component of treatment plans involving hematopoietic stem cell transplant for a variety of disorders, most commonly hematologic malignancies. A variety of treatment delivery techniques, doses, and fractionation schemes can be utilized. A collaborative effort of the American College of Radiology and American Society for Radiation Oncology has produced a practice guideline for delivery of TBI. The guideline defines the qualifications and responsibilities of the involved personnel, including the radiation oncologist, physicist, dosimetrist, and radiation therapist. Review of the typical indications for TBI is presented, and the importance of integrating TBI into the multimodality treatment plan is discussed. Procedures and special considerations related to the simulation, treatment planning, treatment delivery, and quality assurance for patients treated with TBI are reviewed. This practice guideline can be part of ensuring quality and safety in a successful TBI program.

Neonatal binge alcohol exposure produces dose dependent deficits in interstimulus interval discrimination eyeblink conditioning in juvenile rats.

Alcohol consumption in neonatal rats produces cerebellar damage and is widely used to model 3rd-trimester human fetal alcohol exposure. Neonatal "binge-like" exposure to high doses of alcohol (5 g/kg/day or more) impairs acquisition of eyeblink classical conditioning (EBC), a cerebellar-dependent Pavlovian motor learning task. We have recently found impairments in interstimulus interval (ISI) discrimination--a complex task variant of EBC--in adult rats following postnatal day (PD) 4-9 alcohol exposure at doses of 3, 4, and 5 g/kg/day. Because robust developmental differences in conditioned response (CR) generation and CR latency measures are present between untreated juveniles and adults in this task, we sought to extend alcohol findings to juvenile rats (PD30). Five neonatal treatment groups were used: (1) undisturbed controls, (2) sham intubation controls, (3) 3 g/kg/day of alcohol (blood alcohol concentration {BAC}=139.9 mg/dl), (4) 4 g/kg/day of alcohol (BAC=237.3 mg/dl), or (5) 5 g/kg/day of alcohol (BAC=301.8 mg/dl). Intubations occurred over PD4-9. ISI discrimination training in juveniles (PD30-33) revealed dose-dependent CR deficits in all three alcohol-exposed groups relative to controls. Contrary to expected outcomes, CR latency measures were not significantly affected as a function of neonatal treatment. Comparison of these findings with our recent study in adults suggests that alcohol-induced impairments in ISI discrimination EBC may be greater in adults relative to juveniles. The present findings provide further evidence that ISI discrimination may provide greater sensitivity to functional deficits resulting from moderate levels of neonatal alcohol exposure relative to single-cue EBC paradigms.

Photo-cross-linkable oligonucleotide probes for in situ hybridization assays.

In situ hybridization techniques have been an important research tool since first introduced 30 years ago, and more recently clinical applications have been expanding greatly. Still, further improvements in the assay sensitivity and protocols that are amenable to routine clinical use are desired. We use a novel photo-cross-linking technology to irreversibly bind short oligonucleotide probes to the target sequence following a hybridization period. The cross-linking agent is incorporated into the backbone of the probe and is activated to react with pyrimidines in the opposite strand by near-UV (300-370 nm) irradiation. By locking the probe to the target, very stringent wash conditions can be used that would otherwise completely remove probes that are hybridized but not cross-linked to the target. Consequently, the probe-specific signal is maximized, while the background signal is minimized to the greatest extent possible with the stringency of the wash. The use of short, photo-cross-linkable probes presents a new strategy for maximizing the sensitivity of probe hybridization or signal amplification-based in situ techniques.

Purification and properties of rat liver nuclear proteins that interact with the hepatitis B virus enhancer 1.

The hepatitis B virus enhancer 1 element plays a fundamental role in the liver-specific regulation of hepatitis B virus gene expression. A central region of enhancer 1, the enhancer core domain, contains at least four cis-acting sequence motifs that are essential for enhancer 1 activity. In this study, we have investigated an essential motif within the core domain previously defined as footprint V (FPV). Transient transfection analyses demonstrate that FPV is capable of independently functioning in a liver-specific manner to activate transcription. Therefore, to further examine the liver-specific properties of FPV-mediated enhancer 1 activity, we have carried out the biochemical purification and characterization of FPV binding activity from rat liver nuclei. This study has conclusively identified hepatocyte nuclear factor 3beta (HNF-3beta), a liver-enriched member of the HNF-3/forkhead gene family, as the predominant purified protein that interacts with the FPV motif. Moreover, a cellular protein(s) that copurified with HNF-3beta specifically interacts with a novel sequence motif that partially overlaps FPV. Since this novel motif contains a palindromic sequence, we have tentatively referred to the protein(s) that binds to this site as palindrome-binding factor (PBF). Additional evidence indicates that HNF-3beta and PBF cooperatively interact with enhancer 1. Therefore, this study supports the hypothesis that FPV-mediated enhancer activity involves a cooperative interplay between HNF-3beta and at least one other enhancer 1-binding protein, PBF.

Retinoid X receptor alpha transactivates the hepatitis B virus enhancer 1 element by forming a heterodimeric complex with the peroxisome proliferator-activated receptor.

The hepatitis B virus enhancer 1 contains a retinoic acid responsive element (RARE). We have previously demonstrated that retinoid X receptor alpha (RXR alpha) transactivates enhancer 1 by binding to the RARE. The present study has revealed that a heterodimeric complex composed of RXR alpha and peroxisome proliferator-activated receptor (PPAR) interacts with the hepatitis B virus RARE. Transient transfection studies, in conjunction with in vitro DNA binding data, support the hypothesis that the RXR alpha-PPAR heterodimer transactivates enhancer 1.

Regulation of hepatitis B virus gene expression.

Human hepatitis B virus (HBV) mainly infects hepatocytes. HB viral gene expression has been demonstrated to be liver-specific using DNA transfection methods. This liver-specific gene expression is regulated by promoter/enhancer elements. HBV contains two enhancer elements. Enhancer element I has been studied in detail at the DNA-protein level. This is further substantiated by DNA transfections of liver and non-liver cell lines with expression plasmids containing enhancer elements controlling the transcription of reporter genes. Genetic analysis of the enhancer elements defined the minimal sequences which play a key role in the regulation of enhancer function. One of the factors binding in this region is RXR alpha. Using only the DNA binding domain of the liver-specific RXR alpha expressed in E. coli, we demonstrated binding of RXR alpha to the putative retinoic acid receptor response element (RARE) in the HBV enhancer. Our studies implicate a potentially important role of retinoic acid and its receptor in the liver-specific regulation of HBV gene expression and the disease pathogenesis associated with infection.

Retinoid X receptor RXR alpha binds to and trans-activates the hepatitis B virus enhancer.

A retinoid X receptor (RXR) response element was located within the functionally defined hepatitis B virus (HBV) enhancer element. A short segment of the enhancer that contains this region has been shown with genetic analysis to play a key role in the regulation of enhancer function and to represent a major determinant of liver-specific activity. Both the full-length protein and the DNA-binding domain of the liver-specific receptor RXR alpha bound to the putative retinoic acid response element in the HBV enhancer. In vivo, an HBV enhancer-reporter gene construct responds to induction with retinoic acid when cotransfected with an RXR alpha expression vector. A single-base transition (G----A) in the HBV retinoic acid response element leads to a dramatic reduction both in the in vitro binding activity of RXR alpha and the in vivo activity of the HBV enhancer. Thus, retinoic acid and the RXR alpha are implicated as being significant determinants in the liver-specific regulation of HBV gene expression and the resultant disease pathogenesis.

In vivo mapping of a sequence required for interference with the yeast killer virus.

The Saccharomyces cerevisiae viruses are noninfectious double-stranded RNA viruses whose segments are separately encapsidated. A large viral double-stranded RNA (L1; 4580 base pairs) encodes all required viral functions. M1, a double-stranded RNA of 1.9 kilobases, encodes an extracellular toxin (killer toxin) and cellular immunity to that toxin. Some strains contain smaller, S, double-stranded RNAs, derived from M1 by internal deletion. Particles containing these defective interfering RNAs can displace M1 particles by faster replication and thus convert the host strain to a nonkiller phenotype. In this work, we report the development of an assay in which the expression of S plus-strand from an inducible plasmid causes the loss of M1 particles. This assay provides a convenient method for identifying in vivo cis-acting sequences important in viral replication and packaging. We have mapped the sequence involved in interference to a region of 132 base pairs that includes two sequences similar to the viral binding site sequence previously identified in L1 by in vitro experiments.