MRI Radiomic Features Are Independently Associated With Overall Survival in Soft Tissue Sarcoma

Purpose

Soft tissue sarcomas (STS) represent a heterogeneous group of diseases, and selection of individualized treatments remains a challenge. The goal of this study was to determine whether radiomic features extracted from magnetic resonance (MR) images are independently associated with overall survival (OS) in STS.

Methods and Materials

This study analyzed 2 independent cohorts of adult patients with stage II-III STS treated at center 1 (N = 165) and center 2 (N = 61). Thirty radiomic features were extracted from pretreatment T1-weighted contrast-enhanced MR images. Prognostic models for OS were derived on the center 1 cohort and validated on the center 2 cohort. Clinical-only (C), radiomics-only (R), and clinical and radiomics (C+R) penalized Cox models were constructed. Model performance was assessed using Harrell's concordance index.

Results

In the R model, tumor volume (hazard ratio [HR], 1.5) and 4 texture features (HR, 1.1-1.5) were selected. In the C+R model, both age (HR, 1.4) and grade (HR, 1.7) were selected along with 5 radiomic features. The adjusted c-indices of the 3 models ranged from 0.68 (C) to 0.74 (C+R) in the derivation cohort and 0.68 (R) to 0.78 (C+R) in the validation cohort. The radiomic features were independently associated with OS in the validation cohort after accounting for age and grade (HR, 2.4; P = .009).

Conclusions

This study found that radiomic features extracted from MR images are independently associated with OS when accounting for age and tumor grade. The overall predictive performance of 3-year OS using a model based on clinical and radiomic features was replicated in an independent cohort. Optimal models using clinical and radiomic features could improve personalized selection of therapy in patients with STS.

Abstract P4-11-03: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Kim EY, Park YL, Park CH, Suh BC. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-11-03.

Analysis of Pre-transplant Resuscitation Factors Influencing Immediate Graft Function After Deceased Donor Kidney Transplantation

BACKGROUND

The management of a deceased donor in the intensive care unit before organ transplantation is important for the outcome of the recipient. Herein, we analyze the pre-transplant resuscitation factors managed before procurement that could influence graft function immediately after deceased-donor kidney transplantation (DDKT).

METHODS

A total of 271 DDKTs performed at Seoul St. Mary's Hospital, Korea, from January 2009 to March 2016 were reviewed. We divided the patients into a delayed graft function (DGF) group and a non-DGF group, and compared postoperative outcomes between the 2 groups. We also analyzed the predisposing factors of DGF using multivariate analysis.

RESULTS

A total of 36 cases developed DGF while 235 patients did not, and the demographic characteristics of the recipients in the two groups had no significant difference. Of the pre-transplant resuscitation factors, preoperative polyuria, the maximal levels of serum sodium and BUN, and transfer times were significantly higher in the DGF group (P < .001). In a multivariable analysis, preoperative polyuria (odds ratio 4.835, P = .036), elevated preoperative level of sodium (odds ratio 1.227, P = .001), and extended transfer times (odds ratio 1.001, P < .001) were the independent risk factors of the donor in pre-transplant resuscitation management associated with DGF.

CONCLUSIONS

Polyuria, high levels of sodium before procurement, and prolonged transfer times are independent risk factors for DGF after a DDKT. Active intervention and early implementation of the intensivist can help in managing these factors effectively and thus ultimately improve graft function.

Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma: Current Trends and Controversies

Hepatocellular carcinoma is the fourth leading cause of cancer-related death worldwide. Depending on the extent of disease and competing comorbidities for mortality, multiple liver-directed therapy options exist for the treatment of hepatocellular carcinoma. Advancements in radiation oncology have led to the emergence of stereotactic body radiation therapy as a promising liver-directed therapy, which delivers high doses of radiation with a steep dose gradient to maximize local tumor control and minimize radiation-induced treatment toxicity. In this study, we review the current clinical data as well as the unresolved issues and controversies regarding stereotactic body radiation therapy for hepatocellular carcinoma: (1) Is there a radiation dose–response relationship with hepatocellular carcinoma? (2) What are the optimal dosimetric predictors of radiation-induced liver disease, and do they differ for patients with varying liver function? (3) How do we assess treatment response on imaging? (4) How does stereotactic body radiation therapy compare to other liver-directed therapy modalities, including proton beam therapy? Based on the current literature discussed, this review highlights future possible research and clinical directions.

Abietane-Type Diterpenoids Inhibit Protein Tyrosine Phosphatases by Stabilizing an Inactive Enzyme Conformation

Protein tyrosine phosphatases (PTPs) contribute to a striking variety of human diseases, yet they remain vexingly difficult to inhibit with uncharged, cell-permeable molecules; no inhibitors of PTPs have been approved for clinical use. This study uses a broad set of biophysical analyses to evaluate the use of abietane-type diterpenoids, a biologically active class of phytometabolites with largely nonpolar structures, for the development of pharmaceutically relevant PTP inhibitors. Results of nuclear magnetic resonance analyses, mutational studies, and molecular dynamics simulations indicate that abietic acid can inhibit protein tyrosine phosphatase 1B, a negative regulator of insulin signaling and an elusive drug target, by binding to its active site in a non-substrate-like manner that stabilizes the catalytically essential WPD loop in an inactive conformation; detailed kinetic studies, in turn, show that minor changes in the structures of abietane-type diterpenoids (e.g., the addition of hydrogens) can improve potency (i.e., lower IC₅₀) by 7-fold. These findings elucidate a previously uncharacterized mechanism of diterpenoid-mediated inhibition and suggest, more broadly, that abietane-type diterpenoids are a promising source of structurally diverse-and, intriguingly, microbially synthesizable-molecules on which to base the design of new PTP-inhibiting therapeutics.

Effect of intratumoral (IT) injection of the toll-like receptor 4 (TLR4) agonist G100 on a clinical response and CD4 T-cell response locally and systemically

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Background: Soft tissue sarcomas (STS) are heterogeneous tumors which are morbid and lethal. G100 is under investigation in multiple clinical trials and contains a potent TLR4 agonist (oil-in-water emulsion of glucopyranosyl lipid A) that has been tested as vaccine adjuvant. We hypothesized IT G100 would induce robust local and potentially systemic anti-tumor immune response, leading to improved outcomes. Methods: 15 metastatic STS patients with superficial lesions were treated with weekly IT G100 for 8-12 wks; 12 patients received radiation (RT) for 2 wks to start, while 3 received IT G100 for 6 wks prior to RT. Biopsies and PBMC were collected pre and post treatment, and flow cytometry was performed on biopsies. TIL and PBMC were analyzed with TCR deep sequencing. PBMC were analyzed by single cell multiplex cytokine profiling. Results: No grade ≥ 3 toxicity was observed, and local tumor control was achieved in all evaluable tumors (14/14). Treated tumors tracked post-trial (mean 156 days) had persistent local control with 1 CR (7%), 1 PR (7%), and 11 SD (79%). In 3 patients with long term follow up, treated lesions remained controlled vs index lesions (-53% vs +31% at mean 235 days, p = 0.002). In all tumors after G100 alone, T cell infiltration increased. In P14, CD3 live cells in tumor rose from < 1% to 62%. PBMC clonality increased in 8/14 tested including P06, who had 4× increase in clonality and CR in the injected lesion; PBMC and TIL TCR overlap increased from 13.4% to 21.5%. P13 had a 2.3× rise in TIL clonality; the top clone (a CD4 T cell) expanded from 0.1% to 38% and expressed more TNFα than the rest (p < 0.0001). Single cell cytokine analysis of PBMC showed 7/13 (54%) increased in polyfunctionality (producing > 2 cytokines) in CD4 T cells; no consistent increase was seen in CD8 T cells. TNFα levels in pre-treatment monocytes correlated with PFS (R2= 0.5, p = 0.02). Conclusions: IT G100 is a viable agent for local control of metastatic STS lesions. With or without RT, G100 appears to cause CD4 T cell mediated local and systemic response. Combination of G100 with other immunomodulators could induce clinically significant systemic responses, as seen in follicular NHL treated with G100. Clinical trial information: NCT02180698.

Co-clinical trials demonstrate predictive biomarkers for dovitinib, an FGFR inhibitor, in lung squamous cell carcinoma

Background

We conducted co-clinical trials in patient-derived xenograft (PDX) models to identify predictive biomarkers for the multikinase inhibitor dovitinib in lung squamous cell carcinoma (LSCC).

Methods

The PDX01-02 were established from LSCC patients enrolled in the phase II trial of dovitinib (NCT01861197) and PDX03-05 were established from LSCC patients receiving surgery. These five PDX tumors were subjected to in vivo test of dovitinib efficacy, whole exome sequencing and gene expression profiling.

Results

The PDX tumors recapitulate histopathological properties and maintain genomic characteristics of originating tumors. Concordant with clinical outcomes of the trial enrolled-LSCC patients, dovitinib produced substantial tumor regression in PDX-01 and PDX-05, whereas it resulted in tumor progression in PDX-02. PDX-03 and -04 also displayed poor antitumor efficacy to dovitinib. Mutational and genome-wide copy number profiles revealed no correlation between genomic alterations of FGFR1-3 and sensitivity to dovitinib. Of note, gene expression profiles revealed differentially expressed genes including FGF3 and FGF19 between PDX-01 and 05 and PDX-02-04. Pathway analysis identified two FGFR signaling-related gene sets, FGFR ligand binding/activation and SHC-mediated cascade pathway were substantially up-regulated in PDX-01 and 05, compared with PDX-02-04. The comparison of gene expression profiles between dovitinib-sensitive versus -resistant lung cancer cell lines in the Cancer Cell Line Encyclopedia database also found that transcriptional activation of 18 key signaling components in FGFR pathways can predict the sensitivity to dovitinib both in cell lines and PDX tumors. These results highlight FGFR pathway activation as a key molecular determinant for sensitivity to dovitinib.

Conclusions

FGFR gene expression signatures are predictors for the response to dovitinib in LSCC.

Dash-and-Recruit Mechanism Drives Membrane Curvature Recognition by the Small Bacterial Protein SpoVM

In Bacillus subtilis, sporulation requires that the 26-amino acid protein SpoVM embeds specifically into the forespore membrane, a structure with convex curvature. How this nanometer-sized protein can detect curves on a micrometer scale is not well understood. Here, we report that SpoVM exploits a "dash-and-recruit" mechanism to preferentially accumulate on the forespore. Using time-resolved imaging and flow cytometry, we observe that SpoVM exhibits a faster adsorption rate onto membranes of higher convex curvature. This preferential adsorption is accurately modeled as a two-step process: first, an initial binding event occurs with a faster on rate, then cooperative recruitment of additional SpoVM molecules follows. We demonstrate that both this biochemical process and effective sporulation in vivo require an unstructured and flexible SpoVM N terminus. We propose that this two-pronged strategy of fast adsorption followed by recruitment of subsequent molecules is a general mechanism that allows small proteins to detect subtle curves with a radius 1,000-fold their size.

Abstract 2947: Intratumoral injection of the toll-like receptor 4 agonist G100 induces a T-cell response in the soft tissue sarcoma microenvironment

Introduction: Soft tissue sarcomas (STS) are heterogeneous mesenchymal tumors which are both morbid and lethal. G100 is a stable oil-in-water emulsion of glucopyranosyl lipid adjuvant, a highly potent toll-like receptor 4 (TLR4) agonist, which has been utilized for intratumoral (IT) injections and as vaccine adjuvants without significant toxicity. We hypothesized that IT G100 would induce a robust local and potentially systemic anti-tumor immune response in the STS microenvironment, leading to improved outcomes.

Methods: 15 metastatic STS patients who had a superficial injectable lesion were treated with weekly IT G100 for 8-12 weeks; 12 patients received concurrent radiation for 2 weeks at the start, while 3 got IT G100 alone for 6 weeks prior to radiation. Biopsies and blood were collected pre and post treatment, and flow cytometry was performed on fresh tumor samples. T-cell receptor (TCR) deep sequencing of tumor-infiltrating lymphocytes (TIL) and peripheral blood mononuclear cells (PBMC) was performed on 7 patients. RECIST v1.1 and the Common Terminology Criteria for Adverse Events were used to monitor clinical outcomes.

Results: Patients had a median of 3 (0~5) prior lines of therapy and mean tumor size of 5.6cm (1~20cm). No grade 3 or higher treatment-related toxicity was observed, and local tumor control was achieved in 93% (14/15). 6 (40%) had stable disease after treatment, and 1 (P06) had complete regression of injected tumor. This tumor had a high percentage of infiltrating pre-treatment immune cells (12% CD45+ on flow cytometry versus 2.7% for all other tumors). TCR sequencing showed that the increase in clonality of PBMC after treatment was greater in P06 (389%) compared to 6 other patients (mean 34%). There was also higher overlap in TCR sequence between TIL versus PBMC after treatment (13% versus 22%), suggesting systemic expansion of tumor-specific T-cells. In 7 patients evaluable for tumor-associated macrophages (tumors with &gt;1000 CD45+CD11b+ cells), 71% had a shift from an M2 to M1 phenotype. In all patients who received G100 alone, there was an increase in T-cell infiltration into tumor after treatment. In one patient (P14), the proportion of CD3+ live cells in tumor went from &lt;1% to 62%; of these, 51% were CD4+ and 44% were CD8+. TIL from P14 had a 251% increase in clonality after treatment; at the same time, percentage of live tumor cells that were PD-L1+ increased from 0.02% to 1.3%.

Conclusion: IT G100 provides a potentially viable agent for local control of metastatic STS. With or without radiation, G100 appears to shift the tumor microenvironment into a more inflammatory state with significant infiltration of T cells. The increase in clonality in PBMC and TIL, as well as increased overlap of tumor-associated versus peripheral TCR sequences, suggest induction of a tumor-specific response. Combination of G100 with other immunomodulators may further enhance the adaptive anti-tumor response.

Citation Format: Yongwoo D. Seo, Edward Y. Kim, Ernest U. Conrad, Ryan B. O'Malley, Sara Cooper, Bailey Donahue, Lee D. Cranmer, Hailing Lu, Frank Hsu, Elizabeth T. Loggers, Taylor Hain, Darin J. Davidson, Lynn Bonham, Venu G. Pillarisetty, Gabrielle M. Kane, Stanley R. Riddell, Robin L. Jones, Seth M. Pollack. Intratumoral injection of the toll-like receptor 4 agonist G100 induces a T-cell response in the soft tissue sarcoma microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2947. doi:10.1158/1538-7445.AM2017-2947

Strategies to tackle the challenges of external beam radiotherapy for liver tumors

Primary and metastatic liver cancer is an increasingly common and difficult to control disease entity. Radiation offers a non-invasive treatment alternative for these patients who often have few options and a poor prognosis. However, the anatomy and aggressiveness of liver cancer poses significant challenges such as accurate localization at simulation and treatment, management of motion and appropriate selection of dose regimen. This article aims to review the options available and provide information for the practical implementation and/or improvement of liver cancer radiation programs within the context of stereotactic body radiotherapy and image-guided radiotherapy guidelines. Specific patient inclusion and exclusion criteria are presented given the significant toxicity found in certain sub-populations treated with radiation. Indeed, certain sub-populations, such as those with tumor thrombosis or those with larger lesions treated with transarterial chemoembolization, have been shown to have significant improvements in outcome with the addition of radiation and merit special consideration. Implementing a liver radiation program requires three primary challenges to be addressed: (1) immobilization and motion management; (2) localization; and (3) dose regimen and constraint selection. Strategies to deal with motion include simple internal target volume (ITV) expansions, non-gated ITV reduction strategies, breath hold methods, and surrogate marker methods to enable gating or tracking. Localization of the tumor and organs-at-risk are addressed using contrast infusion techniques to take advantage of different normal liver and cancer vascular anatomy, imaging modalities, and margin management. Finally, a dose response has been demonstrated and dose regimens appear to be converging. A more uniform approach to treatment in terms of technique, dose selection and patient selection will allow us to study liver radiation in larger and, hopefully, multicenter randomized studies.

Prognostic significance of cachexia score assessed by CT in male patients with small cell lung cancer

To determine the prognostic significance of CT-determined cachexia scores (CSs) in 127 consecutive male small cell lung cancer (SCLC) patients, cross-sectional areas of muscle and fat tissues at the third lumbar vertebra (L3) were retrospectively measured on baseline CT images. CSs were determined based on the presence of sarcopenia and/or adipopenia. According to the presence of sarcopenia (L3 muscle index <55 cm² /m² , 86.8%) and adipopenia (L3 fat index <22 cm² /m² , 11.8%), CSs were defined as follows: CS2 (sarcopenia and adipopenia, 11.8%), CS1 (sarcopenia only, 74.8%) and CS0 (13.4%). CS2 was significantly related to lower body mass index (p < .001) and poor performance status (p = .002), and patients with CS2 had shorter OS than patients with CS1 or CS0 (median OS, 5.0 months vs. 8.9 months vs. 18.3 months; p = .007). Multivariable analysis revealed that CS was an independent prognostic factor of poor survival (HR, 1.99 for CS1 and 2.59 for CS2, p = .036 and .023, CS0 as a reference), along with extensive stage (p < .001), supportive care only (p < .001) and an elevated lactate dehydrogenase (p = .005). CT-determined CSs, based on the presence of sarcopenia and/or adipopenia, could be used to predict prognosis in male SCLC.

Theoretical effectiveness of cell survival in fractionated radiotherapy with hypoxia-targeted dose escalation

PURPOSE

The goal of this article is to compute the cell survival during fractionated radiotherapy with non-uniform hypoxia-targeted dose distribution relative to cell survival for a uniform dose distribution with equal integral tumor dose. The analysis is performed for different parameters of radiotherapy with conventional and hypofractionated dose regimens.

METHODS

Our analysis is done using a parsimonious tumor response model that describes the major components of tumor response to radiotherapy such as radiosensitivity, cell proliferation, and hypoxia using as few variables as possible. Two levels of oxygenated and hypoxic cells with the survival curves described by the linear quadratic (LQ) model are implemented in the model. The model allows for analytical solutions for relative cell survival in a single fraction simulation which can be used for additional validation of our numerical simulations. The relative cell survival was computed for conventional and hypofractionated dose regimens in a model problem with radiobiological parameters for the non-small-cell lung cancer. Sensitivity of cell survival to different parameters of radiotherapy such as the relative volume of hypoxic fraction, boost dose ratio, re-oxygenation rate, and delivery errors was investigated.

RESULTS

Our computational and analytical results show that relative cell survival for non-uniform and uniform dose distributions is larger than 1.0 during the first few fractions of radiotherapy with conventional fractionation. This indicates that the uniform dose distribution produces a higher cell killing effect for the equal integral dose. This may stem from domination of linear contribution to the cell killing effect seen in the dose range of 1-2 Gy and a steeper slope of survival curve in the oxygenated tumor region. This effect can only happen if the distribution of clonogens is nearly uniform; therefore, after the first few fractions, the non-uniform dose distributions outperform the uniform dose distribution and relative cell survival becomes less than 1.0. However, re-oxygenation and delivery errors can also reduce the effectiveness of hypoxia-targeted non-uniform dose distributions toward the end of treatment. For hypofractionated radiotherapy with fractional dose >3 Gy, the relative cell survival was always below 1.0, which means the non-uniform dose distributions produced higher cell killing effect than the uniform dose distribution during the entire treatment.

CONCLUSION

The data obtained in this work suggest that non-uniform hypoxia-targeted dose distributions are less effective at cell killing than uniform dose distributions at the beginning of radiotherapy with conventional fractionation. However; non-uniform dose distributions can outperform uniform dose distribution by the end of the treatment if the effects of re-oxygenation and delivery errors are reduced. In hypofractionated radiotherapy, non-uniform hypoxia-targeted dose distributions are more efficient than uniform dose distributions during the entire treatment.

Retrospective review of outcomes in patients (pts) with synchronous metastatic rectal cancer (mRC) receiving initial non-surgical management

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Background: Management of mRC trends toward initial non-surgical management of the primary tumor based on studies demonstrating low complications rates from un-resected primary colonic tumors. The fixed location of the rectum may increase local complications. This study characterizes complications of pts with synchronous mRC with an intact primary tumor. Methods: A retrospective review of records from 2001 to 2013 identified pts with mRC by ICD-9/10 codes. Pts with treatment-naïve mRC without significant local symptomatology were evaluated. Time to complications and death were calculated. Pathology, stage, baseline CEA, RAS, BRAF and initial treatment were evaluated for prognostic significance. Results: Forty-four pts were identified with mRC; eight were excluded for initial resection for a symptomatic primary. Among the 36 evaluable pts treated with initial chemotherapy, 14 (39%) developed complications related to the primary tumor, of whom 5 (14%) developed two or more complications. Six (17%) required operative intervention due to primary tumor complications (two died prior to planned procedure). Complications were: perforations/abscesses/fistulae (6), bowel obstruction (5), severe bleeding (5), urinary obstruction/infection (3) and, pain requiring palliative treatment (1). Interventions included blood transfusions (5), stents (3), radiotherapy (3), I&D/drains (3) and, nephrostomy (2). Of 22 pts who did not develop any complications, 15 underwent curative resection of all sites of disease. Six remain disease free and nine relapsed, all distantly. None of the 14 who developed complications underwent curative operation. The median time to complication was 2.5 months. Median overall survival was 37 and 52 months for those with and without complications, respectively. Median time from complication to death was 21 months. Pts aged > 50 vs < 50 were more likely to have complications of the primary tumor (57% vs 21%). Conclusions: mRC pts with intact primary tumors may develop complications at a higher rate (39%) than those with colon cancer (11%). These findings will need to be confirmed with larger datasets and examine for specific treatment effects.

Complement C5a Receptor is the Key Initiator of Neutrophil Adhesion Igniting Immune Complex-induced Arthritis

The deposition of immune complexes (IC) in tissues induces a "type III hypersensitivity" that results in tissue damage and underlies the pathogenesis of many autoimmune diseases. The neutrophil is the first immune cell recruited into sites of IC deposition and plays a critical role in shaping the overall tissue response. However, the mechanism by which IC initiate and propagate neutrophil infiltration into tissue is not known. Here, using intravital multiphoton joint imaging of IC-induced arthritis in live mice, we found that the complement C5a receptor (C5aR) was the key initiator of neutrophil adhesion on joint endothelium. C5a presented on joint endothelium induced β2 integrin-dependent neutrophil arrest, facilitating neutrophil spreading and transition to crawling, and subsequent leukotriene B₄ receptor (BLT1)-mediated extravasation of the first neutrophils. The chemokine receptor CCR1 promoted neutrophil crawling on the joint endothelium while CXCR2 amplified late neutrophil recruitment and survival once in the joint. Thus, imaging arthritis has defined a new paradigm for type III hypersensitivity where C5a directly initiates neutrophil adhesion on the joint endothelium igniting inflammation.

Depression, Impulse Control Disorder, and Life Style According to Smartphone Addiction

We examined depression, impulse control disorder, and life style by degree of smartphone addiction. Chi-square tests and ANOVA were used to identify significant variables. CART was used to generate a decision making diagram of variables affecting smartphone addiction. The severe smartphone addiction group had rates of depression and impulse control disorder than the initial smartphone group.

Simultaneous multiview capture and fusion improves spatial resolution in wide-field and light-sheet microscopy

Most fluorescence microscopes are inefficient, collecting only a small fraction of the emitted light at any instant. Besides wasting valuable signal, this inefficiency also reduces spatial resolution and causes imaging volumes to exhibit significant resolution anisotropy. We describe microscopic and computational techniques that address these problems by simultaneously capturing and subsequently fusing and deconvolving multiple specimen views. Unlike previous methods that serially capture multiple views, our approach improves spatial resolution without introducing any additional illumination dose or compromising temporal resolution relative to conventional imaging. When applying our methods to single-view wide-field or dual-view light-sheet microscopy, we achieve a twofold improvement in volumetric resolution (~235 nm × 235 nm × 340 nm) as demonstrated on a variety of samples including microtubules in Toxoplasma gondii, SpoVM in sporulating Bacillus subtilis, and multiple protein distributions and organelles in eukaryotic cells. In every case, spatial resolution is improved with no drawback by harnessing previously unused fluorescence.

Tuning the Catalytic Activity of Subcellular Nanoreactors

Bacterial microcompartments are naturally occurring subcellular organelles of bacteria and serve as a promising scaffold for the organization of heterologous biosynthetic pathways. A critical element in the design of custom biosynthetic organelles is quantitative control over the loading of heterologous enzymes to the interior of the organelles. We demonstrate that the loading of heterologous proteins to the 1,2-propanediol utilization microcompartment of Salmonella enterica can be controlled using two strategies: by modulating the transcriptional activation of the microcompartment container and by coordinating the expression of the microcompartment container and the heterologous cargo. These strategies allow general control over the loading of heterologous proteins localized by two different N-terminal targeting peptides and represent an important step toward tuning the catalytic activity of bacterial microcompartments for increased biosynthetic productivity.

Spherical nanoparticle supported lipid bilayers for the structural study of membrane geometry-sensitive molecules

Many essential cellular processes including endocytosis and vesicle trafficking require alteration of membrane geometry. These changes are usually mediated by proteins that can sense and/or induce membrane curvature. Using spherical nanoparticle supported lipid bilayers (SSLBs), we characterize how SpoVM, a bacterial development factor, interacts with differently curved membranes by magic angle spinning solid-state NMR. Our results demonstrate that SSLBs are an effective system for structural and topological studies of membrane geometry-sensitive molecules.

Nigrosome 1 Detection at 3T MRI for the Diagnosis of Early-Stage Idiopathic Parkinson Disease: Assessment of Diagnostic Accuracy and Agreement on Imaging Asymmetry and Clinical Laterality

BACKGROUND AND PURPOSE

In the early stages of idiopathic Parkinson disease, motor symptoms are usually asymmetric. We aimed to assess the feasibility of nigrosome 1 detection at 3T MR imaging to analyze the agreement of its asymmetry and clinical laterality.

MATERIALS AND METHODS

High-resolution 3D multiecho imaging was performed at 3T MR imaging in 13 healthy subjects and 24 patients with idiopathic Parkinson disease confirmed by N-3-fluoropropyl-2-β-carbomethoxy-3-β-(4-iodophenyl) nortropane ((18)F-FP-CIT) PET. The nigrosome 1 detection findings by using the MR imaging data were rated as "normal," "possibly abnormal," and "abnormal" by 2 independent reviewers. The degree of (18)F-FP-CIT binding was visually assessed in the caudate nucleus and putamen on PET images. Clinical laterality was evaluated by scores of the Unified Parkinson Disease Rating Scale, Part III. Asymmetry of the affected nigrosome 1 and the degree of (18)F-FP-CIT binding were analyzed for agreement with clinical laterality.

RESULTS

The diagnostic sensitivity, specificity, and accuracy of the nigrosome 1 detection at 3T MR imaging was 100%, 84.6%, and 94.6%, respectively. Interrater agreements for the abnormality and asymmetry of nigrosome 1 were excellent (κ = 0.863 and 0.835, respectively). In patients with idiopathic Parkinson disease, the agreement of asymmetry between clinical laterality and nigrosome 1 detection was good (κ = 0.724). The degree of the (18)F-FP-CIT PET binding showed fair agreement (κ = 0.235) with clinical laterality.

CONCLUSIONS

The abnormality involving nigrosome 1 can be detected at 3T MR imaging with an accuracy of 94.6%. The clinical laterality is in high concordance with the laterality of the nigrosome 1 detection at 3T (κ = 0.724).

Localization of proteins to the 1,2-propanediol utilization microcompartment by non-native signal sequences is mediated by a common hydrophobic motif

Various bacteria localize metabolic pathways to proteinaceous organelles known as bacterial microcompartments (MCPs), enabling the metabolism of carbon sources to enhance survival and pathogenicity in the gut. There is considerable interest in exploiting bacterial MCPs for metabolic engineering applications, but little is known about the interactions between MCP signal sequences and the protein shells of different MCP systems. We found that the N-terminal sequences from the ethanolamine utilization (Eut) and glycyl radical-generating protein MCPs are able to target reporter proteins to the 1,2-propanediol utilization (Pdu) MCP, and that this localization is mediated by a conserved hydrophobic residue motif. Recapitulation of this motif by the addition of a single amino acid conferred targeting function on an N-terminal sequence from the ethanol utilization MCP system that previously did not act as a Pdu signal sequence. Moreover, the Pdu-localized signal sequences competed with native Pdu targeting sequences for encapsulation in the Pdu MCP. Salmonella enterica natively possesses both the Pdu and Eut operons, and our results suggest that Eut proteins might be localized to the Pdu MCP in vivo. We further demonstrate that S. enterica LT2 retained the ability to grow on 1,2-propanediol as the sole carbon source when a Pdu enzyme was replaced with its Eut homolog. Although the relevance of this finding to the native system remains to be explored, we show that the Pdu-localized signal sequences described herein allow control over the ratio of heterologous proteins encapsulated within Pdu MCPs.