Large-Scale Recombinant Production of the SARS-CoV-2 Proteome for High-Throughput and Structural Biology Applications

The highly infectious disease COVID-19 caused by the Betacoronavirus SARS-CoV-2 poses a severe threat to humanity and demands the redirection of scientific efforts and criteria to organized research projects. The international COVID19-NMR consortium seeks to provide such new approaches by gathering scientific expertise worldwide. In particular, making available viral proteins and RNAs will pave the way to understanding the SARS-CoV-2 molecular components in detail. The research in COVID19-NMR and the resources provided through the consortium are fully disclosed to accelerate access and exploitation. NMR investigations of the viral molecular components are designated to provide the essential basis for further work, including macromolecular interaction studies and high-throughput drug screening. Here, we present the extensive catalog of a holistic SARS-CoV-2 protein preparation approach based on the consortium's collective efforts. We provide protocols for the large-scale production of more than 80% of all SARS-CoV-2 proteins or essential parts of them. Several of the proteins were produced in more than one laboratory, demonstrating the high interoperability between NMR groups worldwide. For the majority of proteins, we can produce isotope-labeled samples of HSQC-grade. Together with several NMR chemical shift assignments made publicly available on covid19-nmr.com, we here provide highly valuable resources for the production of SARS-CoV-2 proteins in isotope-labeled form.

Phosphotyrosine couples peptide binding and SHP2 activation via a dynamic allosteric network

SHP2 is a ubiquitous protein tyrosine phosphatase, whose activity is regulated by phosphotyrosine (pY)-containing peptides generated in response to extracellular stimuli. Its crystal structure reveals a closed, auto-inhibited conformation in which the N-terminal Src homology 2 (N-SH2) domain occludes the catalytic site of the phosphatase (PTP) domain. High-affinity mono-phosphorylated peptides promote catalytic activity by binding to N-SH2 and disrupting the interaction with the PTP. The mechanism behind this process is not entirely clear, especially because N-SH2 is incapable of accommodating complete peptide binding when SHP2 is in the auto-inhibited state. Here, we show that pY performs an essential role in this process; in addition to its contribution to overall peptide-binding energy, pY-recognition leads to enhanced dynamics of the N-SH2 EF and BG loops via an allosteric communication network, which destabilizes the N-SH2-PTP interaction surface and simultaneously generates a fully accessible binding pocket for the C-terminal half of the phosphopeptide. Subsequently, full binding of the phosphopeptide is associated with the stabilization of activated SHP2. We demonstrate that this allosteric network exists only in N-SH2, which is directly involved in the regulation of SHP2 activity, while the C-terminal SH2 domain (C-SH2) functions primarily to recruit high-affinity bidentate phosphopeptides.

Machine learning enables completely automatic tuning of a quantum device faster than human experts

Variability is a problem for the scalability of semiconductor quantum devices. The parameter space is large, and the operating range is small. Our statistical tuning algorithm searches for specific electron transport features in gate-defined quantum dot devices with a gate voltage space of up to eight dimensions. Starting from the full range of each gate voltage, our machine learning algorithm can tune each device to optimal performance in a median time of under 70 minutes. This performance surpassed our best human benchmark (although both human and machine performance can be improved). The algorithm is approximately 180 times faster than an automated random search of the parameter space, and is suitable for different material systems and device architectures. Our results yield a quantitative measurement of device variability, from one device to another and after thermal cycling. Our machine learning algorithm can be extended to higher dimensions and other technologies.

A distal regulatory region of a class I human histone deacetylase

Histone deacetylases (HDACs) are key enzymes in epigenetics and important drug targets in cancer biology. Whilst it has been established that HDACs regulate many cellular processes, far less is known about the regulation of these enzymes themselves. Here, we show that HDAC8 is allosterically regulated by shifts in populations between exchanging states. An inactive state is identified, which is stabilised by a range of mutations and resembles a sparsely-populated state in equilibrium with active HDAC8. Computational models show that the inactive and active states differ by small changes in a regulatory region that extends up to 28 Å from the active site. The regulatory allosteric region identified here in HDAC8 corresponds to regions in other class I HDACs known to bind regulators, thus suggesting a general mechanism. The presented results pave the way for the development of allosteric HDAC inhibitors and regulators to improve the therapy for several disease states.

The guide sRNA sequence determines the activity level of box C/D RNPs

2'-O-rRNA methylation, which is essential in eukaryotes and archaea, is catalysed by the Box C/D RNP complex in an RNA-guided manner. Despite the conservation of the methylation sites, the abundance of site-specific modifications shows variability across species and tissues, suggesting that rRNA methylation may provide a means of controlling gene expression. As all Box C/D RNPs are thought to adopt a similar structure, it remains unclear how the methylation efficiency is regulated. Here, we provide the first structural evidence that, in the context of the Box C/D RNP, the affinity of the catalytic module fibrillarin for the substrate-guide helix is dependent on the RNA sequence outside the methylation site, thus providing a mechanism by which both the substrate and guide RNA sequences determine the degree of methylation. To reach this result, we develop an iterative structure-calculation protocol that exploits the power of integrative structural biology to characterize conformational ensembles.

Molecular mechanism of SHP2 activation by PD-1 stimulation

In cancer, the programmed death-1 (PD-1) pathway suppresses T cell stimulation and mediates immune escape. Upon stimulation, PD-1 becomes phosphorylated at its immune receptor tyrosine-based inhibitory motif (ITIM) and immune receptor tyrosine-based switch motif (ITSM), which then bind the Src homology 2 (SH2) domains of SH2-containing phosphatase 2 (SHP2), initiating T cell inactivation. The SHP2-PD-1 complex structure and the exact functions of the two SH2 domains and phosphorylated motifs remain unknown. Here, we explain the structural basis and provide functional evidence for the mechanism of PD-1-mediated SHP2 activation. We demonstrate that full activation is obtained only upon phosphorylation of both ITIM and ITSM: ITSM binds C-SH2 with strong affinity, recruiting SHP2 to PD-1, while ITIM binds N-SH2, displacing it from the catalytic pocket and activating SHP2. This binding event requires the formation of a new inter-domain interface, offering opportunities for the development of novel immunotherapeutic approaches.

HOUT-21. CHARACTERISTICS OF SHORT-TERM SURVIVAL IN PATIENTS WITH GLIOBLASTOMA: A RETROSPECTIVE ANALYSIS

We sought to identify characteristics of glioblastoma (GBM) patients with short survival (< 10 months) in order to identify prognostic factors useful for guiding treatment management. This is an IRB-approved retrospective analysis of adult newly diagnosed GBM patients from 2008–2016 who survived < 10 months from diagnosis. We extracted demographics, tumor characteristics, and treatment details. We calculated survival from surgical diagnosis to date of death. The cohort includes 197 subjects (61% male) with a median age of 68 years (range 19–94). The majority (93%) are non-Hispanic white. The cohort has a median survival of 144 days (95% CI: 130–160). We focused on traditional prognostic indicators, including extent of surgical resection and KPS. A majority had biopsy only (n=92, 46.7%) rather than gross total (n=59, 29.9%) or subtotal (n=46, 23.4%) resection. Moreover, 160 out of 197 patients had a documented KPS with a majority being below 90 (KPS=70–80 (n=96); KPS < 70 (n=31)). Of 179 patients with data on RT course, 18% (n=32) received no RT or opted for hospice after diagnosis, 3% (n=6) received only RT, 54% (n=97) received RT+temozolomide (TMZ), and 24% (n=43) received RT+TMZ+bevacizumab. Of the 147 subjects receiving RT, 79% completed their RT course as prescribed. Most commonly, RT was prescribed as a 6- to 6-1/2-week course (85%), typically 59.4 Gy (45Gy primary, 14.4Gy boost) over 33 fractions or 60 Gy over 30 fractions. In contrast, 15% received a 3-week RT course, typically scheduled as 15 fractions of 2.667 Gy. We concluded that GBM patients with survival < 10 months were more likely to have biopsy only and a KPS < 90, notably associated with poorer prognosis. We continue to explore this dataset for further prognostic factors, particularly inability to complete planned RT course, and are comparing these traits to a larger cohort.

TRLS-10. MITIGATING NEUROCOGNITIVE DEFICITS FROM WHOLE-BRAIN RADIOTHERAPY IN PATIENTS WITH NUMEROUS BRAIN METASTASES VIA A NOVEL SUPEROXIDE DISMUTASE MIMETIC: RATIONALE & DESIGN OF A CLINICAL TRIAL

BACKGROUND: Patients with a large number of brain metastases (BM) and/or micrometastatic disease in the brain present a clinical challenge. While technical innovations in stereotactic radiosurgery (SRS) have extended the number of BM that can be effectively treated, SRS does not treat occult disease and distant brain failure (DBF) post-SRS remains high. Immuno- and targeted therapies show promise in treating metastatic disease to the brain, though response rates are variable. In contrast, whole-brain radiotherapy (WBRT) provides high rates of local control and, compared to SRS, reduces the risk of distant brain failure. Unfortunately, WBRT is also associated with substantial neurocognitive deficits and neither altered fractionation nor the use of available neuroprotectants has adequately addressed this issue. An agent that safely minimizes the adverse effects of WBRT while preserving or enhancing tumor control would provide meaningful clinical benefit. TRIAL DESIGN: BMX-001, a novel Mn-porphyrin superoxide dismutase mimetic, has been shown to protect normal tissues from ionizing radiation in preclinical trials, reducing neurocognitive adverse effects as well as enhancing tumor response. Based on the first-in-human trial of this agent in patients with high-grade gliomas, we have instituted a clinical trial of WBRT +/- BMX-001 in adult patients with more than 10 BM from melanoma, non-small-cell lung, breast and renal cancer. Following a safety lead-in of 5 patients, all of whom will receive WBRT and BMX-001, 69 patients will be randomized to WBRT (3Gy/fraction x 10 fractions) with or without BMX-001 administered subcutaneously before, twice weekly during and once after WBRT (6 injections total.) The primary endpoint is cognition, as measured by the Hopkins Verbal Learning, Trailmaking A/B and Controlled Oral Word Association tests. Secondary endpoints include health-related quality-of-life, overall and progression-free survival, rates of radiation necrosis, DBF and neurologic death. Enrollment began January 2019. (ClinicalTrials.gov Identifier: NCT03608020.)

RADI-06. SINGLE- VERSUS MULTI-FRACTION STEREOTACTIC RADIOSURGERY FOR BRAINSTEM METASTASES

BACKGROUND: For intracranial metastases with planning target volume (PTV) overlap of the brainstem (BSmet), the radiosurgical dose-fractionation that optimizes the therapeutic window is unknown. MATERIALS/METHODS: A retrospective review of brain metastases (BM) with/without BSmets treated with single-fraction stereotactic radiosurgery (SRS) or hypofractionated (2–5 fractions) radiosurgery (HF-SRS) between 2012–2016 was performed. Brainstem biologically effective doses (BED) and single-fraction equivalents of brainstem V10/V12 were calculated using α/β=3. Characteristics were compared between patients with/without BSmet and between SRS/HF-SRS cohorts using Wilcoxon rank sum, chi-square, or Fisher’s exact tests. Radiographic progression (RP) was assessed in patients with post-treatment contrasted MRI and defined as BSmet enlargement regardless of etiology (progression, radionecrosis, indeterminate). Kaplan-Meier estimates were compared between cohorts using log-rank test. RESULTS: 634 SRS/HF-SRS courses were identified, of which 59 (9.3%) treated ≥1 BSmet in 55 patients. BSmets occurred more commonly in patients with &gt;4 BM (31% vs 10%, p&lt; 0.001) and intracranial recurrence (39% vs 20%, p=0.003). BSmets were treated in 1 (22/59; 37%), 2 (1/59; 2%), or 5 (36/59; 61%) fractions. Age, KPS, and primary tumor site were balanced between SRS/HF-SRS cohorts. The HF-SRS cohort had significantly larger BSmet PTV (median 1.39cc vs 0.39cc, p=0.021), marginal dose (median 25Gy vs 15Gy, p&lt; 0.001), brainstem V10 (median 1.60cc vs 0.47cc, p&lt; 0.001), brainstem V12 (median 0.78cc vs 0.06cc, p&lt; 0.001), and mean brainstem BED (median 9.27Gy3 vs 6.55Gy3, p=0.019). The SRS cohort was more likely to have prior whole brain radiotherapy (50% vs 14%, p=0.005) and restart steroids post-treatment (78% vs 41%, p=0.019). RP occurred in 6/17 vs 2/25 patients in the SRS vs HF-SRS cohorts, respectively (p=0.045). HF-SRS trended to higher freedom from RP (93% vs 74% @12mo; p=0.072). There was no overall survival difference (p=0.36). CONCLUSIONS: HF-SRS was associated with decreased RP and decreased likelihood of restarting steroids despite treating larger BSmets.

Histone chaperone exploits intrinsic disorder to switch acetylation specificity

Histones, the principal protein components of chromatin, contain long disordered sequences, which are extensively post-translationally modified. Although histone chaperones are known to control both the activity and specificity of histone-modifying enzymes, the mechanisms promoting modification of highly disordered substrates, such as lysine-acetylation within the N-terminal tail of histone H3, are not understood. Here, to understand how histone chaperones Asf1 and Vps75 together promote H3 K9-acetylation, we establish the solution structural model of the acetyltransferase Rtt109 in complex with Asf1 and Vps75 and the histone dimer H3:H4. We show that Vps75 promotes K9-acetylation by engaging the H3 N-terminal tail in fuzzy electrostatic interactions with its disordered C-terminal domain, thereby confining the H3 tail to a wide central cavity faced by the Rtt109 active site. These fuzzy interactions between disordered domains achieve localization of lysine residues in the H3 tail to the catalytic site with minimal loss of entropy, and may represent a common mechanism of enzymatic reactions involving highly disordered substrates.

Structural characterization of the Asf1-Rtt109 interaction and its role in histone acetylation

Acetylation of histone H3 at lysine-56 by the histone acetyltransferase Rtt109 in lower eukaryotes is important for maintaining genomic integrity and is required for C. albicans pathogenicity. Rtt109 is activated by association with two different histone chaperones, Vps75 and Asf1, through an unknown mechanism. Here, we reveal that the Rtt109 C-terminus interacts directly with Asf1 and elucidate the structural basis of this interaction. In addition, we find that the H3 N-terminus can interact via the same interface on Asf1, leading to a competition between the two interaction partners. This, together with the recruitment and position of the substrate, provides an explanation of the role of the Rtt109 C-terminus in Asf1-dependent Rtt109 activation.

Perspectives on Inflammatory Breast Cancer (IBC) Research, Clinical Management and Community Engagement from the Duke IBC Consortium

Inflammatory breast cancer (IBC) is an understudied and aggressive form of breast cancer with a poor prognosis, accounting for 2-6% of new breast cancer diagnoses but 10% of all breast cancer-related deaths in the United States. Currently there are no therapeutic regimens developed specifically for IBC, and it is critical to recognize that all aspects of treating IBC - including staging, diagnosis, and therapy - are vastly different than other breast cancers. In December 2014, under the umbrella of an interdisciplinary initiative supported by the Duke School of Medicine, researchers, clinicians, research administrators, and patient advocates formed the Duke Consortium for IBC to address the needs of patients in North Carolina (an ethnically and economically diverse state with 100 counties) and across the Southeastern United States. The primary goal of this group is to translate research into action and improve both awareness and patient care through collaborations with local, national and international IBC programs. The consortium held its inaugural meeting on Feb 28, 2018, which also marked Rare Disease Day and convened national research experts, clinicians, patients, advocates, government representatives, foundation leaders, staff, and trainees. The meeting focused on new developments and challenges in the clinical management of IBC, research challenges and opportunities, and an interactive session to garner input from patients, advocates, and community partners that would inform a strategic plan toward continuing improvements in IBC patient care, research, and education.

Assessment of concurrent stereotactic radiosurgery and bevacizumab treatment of recurrent malignant gliomas using multi-modality MRI imaging and radiomics analysis

PURPOSE

To assess the response and predict the overall survival (OS) of recurrent malignant gliomas (MG) patients treated with concurrent BVZ/SRS using multi-modality MRI imaging and radiomics analysis.Methods and materials: SRS was delivered in a single fraction (18/24Gy) or 25Gy in 5 fractions. BVZ was administered immediately before SRS and 2 weeks after. MRI scans were performed before SRS, 1 week and 2 months after SRS. The MR protocol included 2 anatomical (T1w and T2w) and 2 functional (dynamic contrast-enhanced DCE-MRI and diffusion weighted DW-MRI) modalities. Functional biomarkers including apparent diffusion coefficient (ADC), micro-vascular transfer constant Ktrans, brain blood flow F_B, and blood volume V_B were analyzed. Radiomics analysis was performed to extract imaging features from anatomical MRI images and functional biomarker maps. Wicoxon signed rank tests were performed to evaluate treatment-induced changes, and Mann-Whitney U tests were performed to compare the differences of treatment-induced changes between different patient groups. Selected biomarkers and radiomics features were used to predict the OS after treatment using Support Vector Regression (SVR) with leave-one-out cross validation (LOOCV).

RESULTS

Twelve patients with recurrent MG were studied. The median OS was 13.8 months post SRS. DCE results showed that Ktrans (p=0.035) and V_B (p=0.035) showed significant decrease 2 months after SRS, and F_B showed significant decrease as early as 1 week (p=0.017) after SRS. No functional parameters reflected statistically significant treatment response 1 week after SRS. A total of 888 radiomics features were extracted. 31/126 features demonstrated significant changes 1 week/2 months after SRS, respectively. 9 features' changes were significantly different between WHO Grade III vs IV patient groups, and 6 features' changes were found to be linearly correlated with OS. Using 5 selected features, 9 patients' survival time could be accurately predicted (Mean absolute error = 1.47 months, RMSE = 2.10 months).

CONCLUSION

The results of this work demonstrate the potential of combined radiomics analysis and functional MR imaging in quantitatively identifying early treatment response of concurrent SRS/BVZ.

Characterization of Water-Clear Polymeric Gels for Use as Radiotherapy Bolus

Our purpose was to investigate polymeric gels for use as a highly transparent radiotherapy bolus and determine the relevant physical and dosimetric properties. We first quantified tensile properties (maximum stress, strain, and Young modulus) for various polymeric gels, along with a commercial bolus product in order to illustrate the wide variety of potential materials. For a select polymeric gel with tensile properties similar to currently used radiotherapy bolus, we also evaluated mass and electron density, effective atomic number, optical transparency, and percent depth dose in clinical megavoltage photon and electron beams. For this polymeric gel, mass density was 872 ± 12 and 896 ± 13 g/cm³ when measured via weight/volume and computed tomography Hounsfield units, respectively. Electron density was 2.95 ± 0.04 ×10²³ electrons/cm³. Adding fused silica (9% by weight) increases density to that of water. The ratio of the effective atomic number to that of water without and with added silica was 0.780 and 0.835 at 1 MeV, 0.767 and 0.826 at 6 MeV, and 0.746 and 0.809 at 20 MeV. Percent depth dose for 6 MV photons was within 2% of water within the first 2.5 cm and after scaling by the density coincided within 1% out to >7 cm. For 6 and 20 MeV electrons, after scaling for density D_80% was within 1.3 and 1.5 mm of water, respectively. The high transparency and mechanical flexibility of polymeric gels indicate potential for use as a radiotherapy bolus; differences in density from water may be managed via either using “water equivalent thickness” or by incorporating fused silica into the material.

Re-examining TG-142 recommendations in light of modern techniques for linear accelerator based radiosurgery

PURPOSE

The recent development of multifocal stereotactic radiosurgery (SRS) using a single isocenter volumetric modulated arc theory (VMAT) technique warrants a re-examination of the quality assurance (QA) tolerances for routine mechanical QA recommended by the American Association of Physicists in Medicine Task Group Report Number 142. Multifocal SRS can result in targets with small volumes being at a large off-axis distance from the treatment isocenter. Consequently, angular errors in the collimator, patient support assembly (PSA), or gantry could have an increased impact on target coverage.

METHODS

The authors performed a retrospective analysis of dose deviations caused by systematic errors in PSA, collimator, and gantry angle at the tolerance level for routine linear accelerator QA as recommended by TG-142. Dosimetric deviations from multifocal SRS plans (N = 10) were compared to traditional single target SRS using dynamic conformal arcs (N = 10). The chief dosimetric quantities used in determining clinical impact were V_100% and D_99% of the individual planning target volumes and V_12Gy of the healthy brain.

RESULTS

Induced errors at tolerance levels showed the greatest change in multifocal SRS target coverage for collimator rotations (±1.0°) with the average changes to V_100% and D_99% being 5% and 6%, respectively, with maximum changes of 33% and 20%. A reduction in the induced error to half the TG-142 tolerance (±0.5°) demonstrated similar changes in coverage loss to traditional single target SRS assessed at the recommended tolerance level. The observed change in coverage for multifocal SRS was reduced for gantry errors (±1.0°) at 2% and 4.5% for V_100% and D_99%, respectively, with maximum changes of 18% and 12%. Minimal change in coverage was noted for errors in PSA rotation.

CONCLUSIONS

This study indicates that institutions utilizing a single isocenter VMAT technique for multifocal disease should pay careful attention to the angular mechanical tolerances in designing a robust and complete QA program.

Abstract P5-08-12: HER2 status remains the primary predictor of improved survival in patients with BCBM over the past 2 decades (1996-2015)

BACKGROUND: Brain metastasis is a complication in advanced breast cancer (ABC) and is associated with poor prognosis. Incidence of breast cancer brain metastasis (BCBM) is increasing with advances in therapy, allowing patients to survive long enough to develop CNS metastasis. Improved outcomes have been documented in ABC over the past decades, largely related to the use of trastuzumab in HER2+ ABC. However, it remains unclear whether survival has improved in HER2- ABC in patients with BCBM. This study asks: has the improvement in systemic and radiotherapies for HER2- breast cancer impacted survival in patients with breast cancer brain metastasis.

OBJECTIVES: 1) To estimate whether date of BCBM diagnosis is associated with overall survival (OS) in patients diagnosed between 1996-2015. 2) To estimate whether OS of this patient population depends upon other demographic and clinical factors.

METHODS: This is a retrospective chart review of patients with diagnosis of BCBM between 1996-2015. Data collection includes: age at BCBM diagnosis, ethnicity, ER/PR/HER2 status, date of BCBM diagnosis, date of primary breast cancer diagnosis, date of death/last clinical follow-up, and treatment. Kaplan-Meier analysis and the log-rank test compared OS (time from diagnosis of BCBM until death or last clinical FU) between groups diagnosed in 5-year cohorts (1996-2000, 2001-2005, 2006-2010, 2011-2015). A univariate proportional hazards model was used to regress OS on date of diagnosis. A multivariate proportional hazards model was used which included the subset of patients diagnosed with BCBM in 2001 and later. This model adjusted for additional factors: race, time to development of BCBM diagnosis, age at the time of BCBM diagnosis, year of diagnosis as a continuous factor, ER, PR, while testing the significance of HER2 status. A p-value &lt; 0.05 was significant.

RESULTS: A total of 165 patients with BCBM were included in this analysis, with a median age of 53.8 (SD 13.0) at time of BCBM diagnosis. Most patients were Caucasian (66%; 109/165) or African-American (29%; 48/165). Although statistical significance was not attained, greater median overall survival was seen for patients diagnosed with BCBM in more recent 5-year cohorts (2011-2016, 9.5 months; 2006-2010, 8 months) than patients in older cohorts (2001-2006, 3.6 months; 1996-2000, 5.3 months), p=0.3. Date of diagnosis of BCBM as a continuous variable is predictive of overall survival (HR 0.83 [95% CI: 0.71-0.97] comparing 5-year intervals, p=0.016). After adjusting for the covariates listed above, HER2 positive status is predictive of overall survival (HR 0.34 [95% CI: 0.34-0.56]; p&lt;0.0001).

CONCLUSIONS: While survival has improved by 5.9 months over the past two decades, it remains highly dependent on HER2 status. Novel therapies for BCBM are greatly needed for ER+ and triple negative subtypes. Final results will include an expanded analysis to incorporate additional cases and three other categorical covariates measured during follow-up: whether the patient received radiotherapy, surgery, and/or medical therapy after diagnosis of brain metastases.

GRANT FUNDING: TL-1 CTSA Pre-Doctoral Training Grant (5TL1TR001116-03).

Citation Format: Narloch JL, Harnden K, Broadwater G, Peterson B, Hyslop T, Kirkpatrick J, Fecci P, Kim G, Blackwell KL. HER2 status remains the primary predictor of improved survival in patients with BCBM over the past 2 decades (1996-2015) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-12.

The horseshoe kidney: Surgical anatomy and embryology

Horseshoe kidneys are a common, yet enigmatic, renal malformation. This review critically appraised the literature surrounding the embryology, etiology and clinical anatomy of horseshoe kidneys. The systematic literature search produced 104 articles, and 56 primary and further secondary references. There were several etiological theories regarding horseshoe kidneys. The established view was that during ascent, the kidneys come into close apposition as they pass through an arterial fork. Another possible mechanism related to lateral flexion of the trunk or rotation of the caudal embryo; the association of asymmetrical horseshoe kidneys with a number of vertebral conditions supported this hypothesis. More recent animal models implicated the notochord and sonic hedgehog signaling. Furthermore, it has been suggested that the isthmus may be the result of ectopic mesenchymal tissue. Surgical anatomy of the horseshoe kidney is complex, due to variability in location, orientation and blood supply. Both arterial and venous anatomy is highly variable. This raised the question of whether anomalous blood supply is the cause or result of abnormal renal position. In the majority of cases, the isthmus contained functional renal parenchyma. In over 90% of cases, fusion between the kidneys occurred at the lower pole. Despite commonly being quoted as 'held back by the inferior mesenteric artery' at L3, in reality the isthmus was only found immediately inferior to this in 40% of cases.

Outcomes and toxicity of stereotactic radiosurgery for melanoma brain metastases in patients receiving ipilimumab

Purpose

Patients with melanoma treated with ipilimumab and radiosurgery (stereotactic radiosurgery [SRS]) were reviewed for efficacy/safety.

Methods

Patients who received ipilimumab and SRS for brain metastases were analyzed for control of SRS-treated metastasis and overall survival.

Results

We identified 27 patients, 26 were assessable for outcomes. Median time-to-treated metastasis progression was 6.3 months (95% CI: 3.1-12.2). Overall survival was 23.4 months (95% CI: 5.7-not estimable) for SRS prior to/during ipilimumab (n = 14), and 10.4 months (95% CI: 1.9-not estimable) for SRS after ipilimumab (n = 12). Overall, no unexpected toxicities were seen: 11% of patients experienced grade 3 CNS toxicity and 7% developed radionecrosis.

Conclusion

SRS for melanoma brain metastases with ipilimumab was well-tolerated. There may be improved survival for patients receiving SRS prior to/during ipilimumab.