Benefits of digital breast tomosynthesis: A lesion-level analysis.

OBJECTIVE: To compare outcome metrics of digital breast tomosynthesis (DBT) breast cancer screening with full-field digital mammogram (FFDM); specifically, to compare recall rates by the type of recalled finding, and to assess if screening with DBT versus FFDM changes biopsy recommendations and if the likelihood of malignancy varied by lesion type, if detected on DBT or FFDM screening mammogram. METHODS: The outcomes of 22,055 FFDM and DBT screening mammograms were retrospectively reviewed. The exams were performed at an academic institution between August 2015 and September 2016. Performance of screening with FFDM versus DBT was compared in terms of recall rate and percentage of recalled lesions resulting in a cancer diagnosis, with subset analyses performed for specific mammographic findings. RESULTS: The recall rate was 10.6% for FFDM and 8.0% for DBT (p < 0.001). Architectural distortion was more likely to be recalled on DBT screening than FFDM (p = 0.002), and was associated with an increased likelihood of malignancy (p = 0.008). Asymmetries were less likely to be recalled on DBT than FFDM (p < 0.001) screening mammogram, but more likely to be recommended for biopsy when detected on DBT. Calcifications more frequently required short-term follow-up or biopsy on both DBT and FFDM. CONCLUSIONS: DBT screening confers an advantage in detection of architectural distortion representing malignancy. Recall rate of asymmetries are reduced with screening DBT, probably due to reduction of tissue superimposition. Calcifications pose a particularly difficult diagnostic challenge for breast imagers, regardless of screening mammogram type.

Factors Impacting False Positive Recall in Screening Mammography.

RATIONALE AND OBJECTIVES: Our objective was to identify factors impacting false positive recalls in screening mammography. MATERIALS AND METHODS: We retrospectively reviewed our screening mammography database from August 31, 2015 to September 30, 2016, including full field digital mammograms (FFDM) and digital breast tomosynthesis (DBT) mammograms. False positive (FP) exams were defined as Breast Imaging-Reporting and Data System (BI-RADS) 1 or 2 assessments at diagnostic imaging with 1 year cancer-free follow-up, Breast Imaging-Reporting and Data System 3 assessment at diagnostic imaging with 2 years cancer free follow-up, or biopsy with benign pathology. True positives were defined as malignant pathology on biopsy or surgical excision. We evaluated the association of FP recalls with multiple patient-level factors and imaging features. RESULTS: A total of 22,055 screening mammograms were performed, and 1887 patients were recalled (recall rate 8.6%). Recall rate was lower for DBT than full field digital mammograms (8.0% vs 10.6%, p < 0.001). FP results were lower if prior mammograms were available (90.8% vs 95.8%, p = 0.02), and if there was a previous benign breast biopsy (87.6% vs 92.9%, p = 0.01). Mean age for the FP group was lower than the true positive group (56.1 vs 62.9 years, p < 0.001). There were no significant differences in FP recalls based on history of high-risk lesions, family history of breast or ovarian cancer, hormone use, breast density, race, or body mass index. CONCLUSION: FP recalls were significantly less likely with DBT, in older women, in patients with prior mammograms available for comparison, and in patients with histories of benign breast biopsy. This study supports the importance of using DBT in the screening setting and obtaining prior mammograms for comparison.

Glycoconjugate vaccines: some observations on carrier and production methods.

Glycoconjugate vaccines use protein carriers to improve the immune response to polysaccharide antigens. The protein component allows the vaccine to interact with T cells, providing a stronger and longer-lasting immune response than a polysaccharide interacting with B cells alone. Whilst in theory the mere presence of a protein component in a vaccine should be sufficient to improve vaccine efficacy, the extent of improvement varies. In the present review, a comparison of the performances of vaccines developed with and without a protein carrier are presented. The usefulness of analytical tools for macromolecular integrity assays, in particular nuclear magnetic resonance, circular dichroism, analytical ultracentrifugation and SEC coupled to multi-angle light scattering (MALS) is indicated. Although we focus mainly on bacterial capsular polysaccharide-protein vaccines, some consideration is also given to research on experimental cancer vaccines using zwitterionic polysaccharides which, unusually for polysaccharides, are able to invoke T-cell responses and have been used in the development of potential all-polysaccharide-based cancer vaccines.A general trend of improved immunogenicity for glycoconjugate vaccines is described. Since the immunogenicity of a vaccine will also depend on carrier protein type and the way in which it has been linked to polysaccharide, the effects of different carrier proteins and production methods are also reviewed. We suggest that, in general, there is no single best carrier for use in glycoconjugate vaccines. This indicates that the choice of carrier protein is optimally made on a case-by-case basis, based on what generates the best immune response and can be produced safely in each individual case.Abbreviations: AUC: analytical ultracentrifugation; BSA: bovine serum albumin; CD: circular dichroism spectroscopy; CPS: capsular polysaccharide; CRM197: Cross Reactive Material 197; DT: diphtheria toxoid; Hib: Haemophilius influenzae type b; MALS: multi-angle light scattering; Men: Neisseria menigitidis; MHC-II: major histocompatibility complex class II; NMR: nuclear magnetic resonance spectroscopy; OMP: outer membrane protein; PRP: polyribosyl ribitol phosphate; PSA: Polysaccharide A1; Sa: Salmonella; St.: Streptococcus; SEC: size exclusion chromatography; Sta: Staphylococcus; TT: tetanus toxoid; ZPS: zwitterionic polysaccharide(s).

Interactions of the intact FsrC membrane histidine kinase with the tricyclic peptide inhibitor siamycin I revealed through synchrotron radiation circular dichroism.

The suitability of synchrotron radiation circular dichroism spectroscopy (SRCD) for studying interactions between the tricyclic peptide inhibitor siamycin I and the intact FsrC membrane sensor kinase in detergent micelles has been established. In the present study, tertiary structural changes demonstrate that inhibitor binding occurs at a different, non-overlapping site to the native ligand, GBAP.

Interactions of the intact FsrC membrane histidine kinase with its pheromone ligand GBAP revealed through synchrotron radiation circular dichroism.

FsrC is the membrane-bound histidine kinase component of the Fsr two-component signal transduction system involved in quorum sensing in the hospital-acquired infection agent Enterococcus faecalis. Synchrotron radiation circular dichroism spectroscopy was used here to study the intact purified protein solubilised in detergent micelles. Conditions required for FsrC stability in detergent were firstly determined and tested by prolonged exposure of stabilised protein to far-ultraviolet radiation. Using stabilised purified protein, far-ultraviolet synchrotron radiation circular dichroism revealed that FsrC is 61% alpha-helical and that it is relatively thermostable, retaining at least 57% secondary structural integrity at 90 degrees C in the presence or absence of gelatinase biosynthesis-activating pheromone (GBAP). Whilst binding of the quorum pheromone ligand GBAP did not significantly affect FsrC secondary structure, near-ultraviolet spectra revealed that the tertiary structure in the regions of the Tyr and Trp residues was significantly affected. Titration experiments revealed a calculated kd value of 2 microM indicative of relatively loose binding ofgelatinase biosynthesis-activating pheromone to FsrC. Although use of synchrotron radiation circular dichroism has been applied to membrane proteins previously, to our knowledge this is the first report of its use to determine a kd value for an intact membrane protein. Based on our findings, we suggest that synchrotron radiation circular dichroism will be a valuable technique for characterising ligand binding by other membrane sensor kinases and indeed other membrane proteins in general. It further provides a valuable screening tool for membrane protein stability under a range of detergent conditions prior to downstream structural methods such as crystallisation and NMR experiments particularly when lower detergent concentrations are used.

Anti-HIV siamycin I directly inhibits autophosphorylation activity of the bacterial FsrC quorum sensor and other ATP-dependent enzyme activities.

Siamycin I disrupts growth and quorum sensing in Enterococcus faecalis. Using purified intact protein, we demonstrate here that quorum membrane sensor kinase FsrC is a direct target of siamycin I, reducing pheromone-stimulated autophosphorylation activity by up to 91%. Inhibition was non-competitive with ATP as substrate. Other ATP-binding enzymes were also inhibited, including nine other membrane sensor kinases of E. faecalis, Rhodobacter sphaeroides PrrB, porcine Na(+)-dependent ATPase and the catalytic subunit of bovine protein kinase A, but not bacterial ß-galactosidase, confirming targeted inhibition of a wide range of ATP dependent reactions, and elucidating a likely mechanism underlying the lethality of the inhibitor.

Redox-responsive in vitro modulation of the signalling state of the isolated PrrB sensor kinase of Rhodobacter sphaeroides NCIB 8253.

Prr is a global regulatory system that controls a large and diverse range of genes in Rhodobacter sphaeroides in response to changing conditions of environmental redox potential. PrrB is the membrane-bound sensor kinase and previously we showed that the purified, detergent-solubilised intact membrane protein is functional in autophosphorylation, phosphotransfer and phosphatase activities. Here we confirm that it also senses and responds directly to its environmental signal, redox potential; strong autophosphorylation of PrrB occurred in response to dithiothreitol (DTT)-induced reducing conditions (and levels increased in response to a wide 0.1-100 mM DTT range), whilst under oxidising conditions, PrrB exhibited low, just detectable levels of autophosphorylation. The clear response of PrrB to changes in reducing conditions confirmed its suitability for in vitro studies to identify modulators of its phosphorylation signalling state, and was used here to investigate whether PrrB might sense more than one redox-related signal, such as signals of cell energy status. NADH, ATP and AMP were found to exert no detectable effect on maintenance of the PrrB-P signalling state. By contrast, adenosine diphosphate produced a very strong increase in PrrB-P dephosphorylation rate, presumably through the back-conversion of PrrB-P to PrrB.