Assessment of horizontal gene transfer-mediated destabilization of Synechococcus elongatus PCC 7942 biocontainment system

Biological containment is a biosafety strategy that prevents the dispersal of genetically modified organisms in natural ecosystems. We previously established a biocontainment system that makes bacterial growth dependent on the availability of phosphite (Pt), an ecologically rare form of phosphorus (P), by introducing Pt metabolic pathway genes and disrupting endogenous phosphate and organic phosphate transporter genes. Although this system proved highly effective, horizontal gene transfer (HGT) mediated recovery of a P transporter gene is considered as a potential pathway to abolish the Pt-dependent growth, resulting in escape from the containment. Here, we assessed the risk of HGT driven escape using the Pt-dependent cyanobacterium Synechococcus elongatus PCC 7942. Transformation experiments revealed that the Pt-dependent strain could regain phosphate transporter genes from the S. elongatus PCC 7942 wild-type genome and from the genome of the closely related strain, S. elongatus UTEX 2973. Transformed S. elongatus PCC 7942 became viable in a phosphate-containing medium. Meanwhile, transformation of the Synechocystis sp. PCC 6803 genome or environmental DNA did not yield escape strains, suggesting that only genetic material derived from phylogenetically-close species confer high risk to generate escape. Eliminating a single gene necessary for natural competence from the Pt-dependent strain reduced the escape occurrence rate. These results demonstrate that natural competence could be a potential risk to destabilize Pt-dependence, and therefore inhibiting exogenous DNA uptake would be effective for enhancing the robustness of the gene disruption-dependent biocontainment.

Accurate axillary staging by superparamagnetic iron oxide-enhanced MRI at 1.5 T with fat-suppression sequence as an alternative to sentinel node biopsy in breast cancer

Superparamagnetic iron oxide (SPIO)-enhanced MRI at 1.5 T with fat-suppression sequence is useful for the detection of metastases in sentinel nodes localized by CT lymphography in patients with breast cancer. SPIO-enhanced MRI may offer an alternative to sentinel node biopsy and avoid axillary surgery itself for patients with breast cancer who have negative sentinel nodes on SPIO-enhanced MRI.

The alarmin interleukin-1α causes preterm birth through the NLRP3 inflammasome

Sterile intra-amniotic inflammation is a clinical condition frequently observed in women with preterm labor and birth, the leading cause of neonatal morbidity and mortality worldwide. Growing evidence suggests that alarmins found in amniotic fluid, such as interleukin (IL)-1α, are central initiators of sterile intra-amniotic inflammation. However, the causal link between elevated intra-amniotic concentrations of IL-1α and preterm birth has yet to be established. Herein, using an animal model of ultrasound-guided intra-amniotic injection of IL-1α, we show that elevated concentrations of IL-1α cause preterm birth and neonatal mortality. Additionally, using immunoblotting techniques and a specific immunoassay, we report that the intra-amniotic administration of IL-1α induces activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in the fetal membranes, but not in the decidua, as evidenced by a concomitant increase in the protein levels of NLRP3, active caspase-1, and IL-1β. Lastly, using Nlrp3-/- mice, we demonstrate that the deficiency of this inflammasome sensor molecule reduces the rates of preterm birth and neonatal mortality caused by the intra-amniotic injection of IL-1α. Collectively, these results demonstrate a causal link between elevated IL-1α concentrations in the amniotic cavity and preterm birth as well as adverse neonatal outcomes, a pathological process that is mediated by the NLRP3 inflammasome. These findings shed light on the mechanisms underlying sterile intra-amniotic inflammation and provide further evidence that this clinical condition can potentially be treated by targeting the NLRP3 inflammasome.

Degradation of phosphate polymer polyP enhances lactic fermentation in mice

In bacteria, a polymer of inorganic phosphate (Pi) (inorganic polyphosphate; polyP) is enzymatically produced and consumed as an alternative phosphate donor for adenosine triphosphate (ATP) production to protect against nutrient starvation. In vertebrates, polyP has been dismissed as a "molecular fossil" due to the lack of any known physiological function. Here, we have explored its possible role by producing transgenic (TG) mice widely expressing Saccharomyces cerevisiae exopolyphosphatase 1 (ScPPX1), which catalyzes hydrolytic polyP degradation. TG mice were produced and displayed reduced mitochondrial respiration in muscles. In female TG mice, the blood concentration of lactic acid was enhanced, whereas ATP storage in liver and brain tissues was reduced significantly. Thus, we suggested that the elongation of polyP reduces the intracellular Pi concentration, suppresses anaerobic lactic acid production, and sustains mitochondrial respiration. Our results provide an insight into the physiological role of polyP in mammals, particularly in females.

Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs

The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.

Synthetic Phosphorus Metabolic Pathway for Biosafety and Contamination Management of Cyanobacterial Cultivation

Recent progress in genetic engineering and synthetic biology have greatly expanded the production capabilities of cyanobacteria, but concerns regarding biosafety issues and the risk of contamination of cultures in outdoor culture conditions remain to be resolved. With this dual goal in mind, we applied the recently established biological containment strategy based on phosphite (H₃PO₃, Pt) dependency to the model cyanobacterium Synechococcus elongatus PCC 7942 ( Syn 7942). Pt assimilation capability was conferred on Syn 7942 by the introduction of Pt dehydrogenase (PtxD) and hypophosphite transporter (HtxBCDE) genes that allow the uptake of Pt, but not phosphate (H₃PO₄, Pi). We then identified and disrupted the two indigenous Pi transporters, pst (Synpcc7942_2441 to 2445) and pit (Synpcc7942_0184). The resultant strain failed to grow on any media containing various types of P compounds other than Pt. The strain did not yield any escape mutants for at least 28 days with a detection limit of 3.6 × 10^-11 per colony forming unit, and rapidly lost viability in the absence of Pt. Moreover, growth competition of the Pt-dependent strain with wild-type cyanobacteria revealed that the Pt-dependent strain could dominate in cultures containing Pt as the sole P source. Because Pt is rarely available in aquatic environments this strategy can contribute to both biosafety and contamination management of genetically engineered cyanobacteria.

Time zero determination for FEL pump-probe studies based on ultrafast melting of bismuth

A common challenge for pump-probe studies of structural dynamics at X-ray free-electron lasers (XFELs) is the determination of time zero (T₀)-the time an optical pulse (e.g., an optical laser) arrives coincidently with the probe pulse (e.g., a XFEL pulse) at the sample position. In some cases, T₀ might be extracted from the structural dynamics of the sample's observed response itself, but generally, an independent robust method is required or would be superior to the inferred determination of T₀. In this paper, we present how the structural dynamics in ultrafast melting of bismuth can be exploited for a quickly performed, reliable and accurate determination of T₀ with a precision below 20 fs and an overall experimental accuracy of 50 fs to 150 fs (estimated). Our approach is potentially useful and applicable for fixed-target XFEL experiments, such as serial femtosecond crystallography, utilizing an optical pump pulse in the ultraviolet to near infrared spectral range and a pixelated 2D photon detector for recording crystallographic diffraction patterns in transmission geometry. In comparison to many other suitable approaches, our method is fairly independent of the pumping wavelength (UV-IR) as well as of the X-ray energy and offers a favorable signal contrast. The technique is exploitable not only for the determination of temporal characteristics of the experiment at the interaction point but also for investigating important conditions affecting experimental control such as spatial overlap and beam spot sizes.

Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning

Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy, we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. This opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.

Girdin maintains the stemness of glioblastoma stem cells

This corrects the article DOI: 10.1038/onc.2011.466.

Abstract P2-01-27: Sentinel lymph node biopsy by contrast-enhanced ultrasonography with sonazoid in patients with breast cancer - Prospective multicenter study

Background: The aim of this prospective study is to evaluate feasibility of the periareolar injection of contrast agent (Sonazoid (SNZ)) followed by ultrasonography (US) for identification of sentinel lymph node (SLN) in breast cancer patients with clinically negative node.

Patients and Methods: Patients with T1-2N0M0 breast cancer were recruited in this study. They received the periareolar injection of SNZ followed by US to identify contrast-enhanced SLN. Fine needle aspiration biopsy (FNAB) was done for each CE-SLN. Then, they underwent SLN biopsy with the conventional method, blue dye and/or radiotracer (B/R).

Results: In almost all cases, contrast-enhanced lymphatic vessels were clearly visualized US soon after the periareolar injection of SNZ, and SLN, into which lymphatic flow was draining, was easily identified. The identification rate of SLN was 98% (98/100) by SNZ and 100% (100/100) by B/R. The number of SLNs identified by SNZ (mean per patient, 1.52) was significantly (P < 0.001) lower than that of those by B/R (2.22). Twenty-five patients had at least one metastasis in the SLNs identified by SNZ and/or B/R. In these patients, SLNs (n=39) identified by both SNZ and B/R showed a significantly (P < 0.0001) higher positivity (74.4%) for metastases than those (n=19) identified by B/R alone (21.1%).

Conclusion: Identification of SLN by periareolar injection of SNZ followed by US is a technically easy method and the identification rate of SLN was as high as 98%, being comparable to the conventional B/R. SLNs detected by SNZ seem to represent the true SLNs which first receive lymphatic flow from the tumor among the SLNs detected by B/R.

Citation Format: Shimazu K, Ito T, Uji K, Miyake T, Motomura K, Noguchi S. Sentinel lymph node biopsy by contrast-enhanced ultrasonography with sonazoid in patients with breast cancer - Prospective multicenter study [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 P2-01-27.

Charge transfer to ground-state ions produces free electrons

Inner-shell ionization of an isolated atom typically leads to Auger decay. In an environment, for example, a liquid or a van der Waals bonded system, this process will be modified, and becomes part of a complex cascade of relaxation steps. Understanding these steps is important, as they determine the production of slow electrons and singly charged radicals, the most abundant products in radiation chemistry. In this communication, we present experimental evidence for a so-far unobserved, but potentially very important step in such relaxation cascades: Multiply charged ionic states after Auger decay may partially be neutralized by electron transfer, simultaneously evoking the creation of a low-energy free electron (electron transfer-mediated decay). This process is effective even after Auger decay into the dicationic ground state. In our experiment, we observe the decay of Ne²⁺ produced after Ne 1s photoionization in Ne-Kr mixed clusters.

Time-Resolved Measurement of Interatomic Coulombic Decay Induced by Two-Photon Double Excitation of Ne_{2}

The hitherto unexplored two-photon doubly excited states [Ne^{*}(2p^{-1}3s)]_{2} were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain the rate of ICD, the resulting yield of Ne_{2}^{+} ions was recorded as a function of delay between the extreme ultraviolet pump and UV probe laser pulses. The extracted lifetimes of the long-lived doubly excited states, 390(-130/+450)  fs, and of the short-lived ones, less than 150 fs, are in good agreement with ab initio quantum mechanical calculations.

Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters

Ne clusters (∼5000  atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.

Interatomic Coulombic decay cascades in multiply excited neon clusters

In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning the laser to the lowest resonant transition, the system becomes multiply excited, and more efficient, indirect ionization pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of the species de-excites to its ground state, transferring its energy to ionize another excited species. Here we show that on tuning to a higher resonant transition, a previously unknown type of interatomic Coulombic decay, intra-Rydberg ICD occurs. In it, de-excitation of an atom to a close-lying Rydberg state leads to electron emission from another neighbouring Rydberg atom. Moreover, systems multiply excited to higher Rydberg states will decay by a cascade of such processes, producing even more ions. The intra-Rydberg ICD and cascades are expected to be ubiquitous in weakly-bound systems exposed to high-intensity resonant radiation.

Interatomic Coulombic decay (ICD) is a relaxation of an atom in a weakly bound environment by the transfer of excess energy to ionize the neighbouring atom. Here the authors observe intra-Rydberg ICD in neon clusters, which is a decay that involves the ionization of Rydberg atoms in the cluster.

IFPA meeting 2015 workshop report IV: placenta and obesity; stem cells of the feto-maternal interface; placental immunobiology and infection

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialised topics. At the 2015 IFPA annual meeting there were 12 themed workshops, three of which are summarized in this report. These workshops related to various aspects of placental biology and collectively covered areas of obesity and the placenta, stem cells of the feto-maternal interface, and placental immunobiology and infection.

Application of volcanic ash particles for protein affinity purification with a minimized silica-binding tag

We recently reported that the spore coat protein, CotB1 (171 amino acids), from Bacillus cereus mediates silica biomineralization and that the polycationic C-terminal sequence of CotB1 (14 amino acids), designated CotB1p, serves as a silica-binding tag when fused to other proteins. Here, we reduced the length of this silica-binding tag to only seven amino acids (SB7 tag: RQSSRGR) while retaining its affinity for silica. Alanine scanning mutagenesis indicated that the three arginine residues in the SB7 tag play important roles in binding to a silica surface. Monomeric l-arginine, at concentrations of 0.3-0.5 M, was found to serve as a competitive eluent to release bound SB7-tagged proteins from silica surfaces. To develop a low-cost, silica-based affinity purification procedure, we used natural volcanic ash particles with a silica content of ∼70%, rather than pure synthetic silica particles, as an adsorbent for SB7-tagged proteins. Using green fluorescent protein, mCherry, and mKate2 as model proteins, our purification method achieved 75-90% recovery with ∼90% purity. These values are comparable to or even higher than that of the commonly used His-tag affinity purification. In addition to low cost, another advantage of our method is the use of l-arginine as the eluent because its protein-stabilizing effect would help minimize alteration of the intrinsic properties of the purified proteins. Our approach paves the way for the use of naturally occurring materials as adsorbents for simple, low-cost affinity purification.

Femtosecond charge and molecular dynamics of I-containing organic molecules induced by intense X-ray free-electron laser pulses

We studied the electronic and nuclear dynamics of I-containing organic molecules induced by intense hard X-ray pulses at the XFEL facility SACLA in Japan. The interaction with the intense XFEL pulse causes absorption of multiple X-ray photons by the iodine atom, which results in the creation of many electronic vacancies (positive charges) via the sequential electronic relaxation in the iodine, followed by intramolecular charge redistribution. In a previous study we investigated the subsequent fragmentation by Coulomb explosion of the simplest I-substituted hydrocarbon, iodomethane (CH₃I). We carried out three-dimensional momentum correlation measurements of the atomic ions created via Coulomb explosion of the molecule and found that a classical Coulomb explosion model including charge evolution (CCE-CE model), which accounts for the concerted dynamics of nuclear motion and charge creation/charge redistribution, reproduces well the observed momentum correlation maps of fragment ions emitted after XFEL irradiation. Then we extended the study to 5-iodouracil (C₄H₃IN₂O₂, 5-IU), which is a more complex molecule of biological relevance, and confirmed that, in both CH₃I and 5-IU, the charge build-up takes about 10 fs, while the charge is redistributed among atoms within only a few fs. We also adopted a self-consistent charge density-functional based tight-binding (SCC-DFTB) method to treat the fragmentations of highly charged 5-IU ions created by XFEL pulses. Our SCC-DFTB modeling reproduces well the experimental and CCE-CE results. We have also investigated the influence of the nuclear dynamics on the charge redistribution (charge transfer) using nonadiabatic quantum-mechanical molecular dynamics (NAQMD) simulation. The time scale of the charge transfer from the iodine atomic site to the uracil ring induced by nuclear motion turned out to be only ∼5 fs, indicating that, besides the molecular Auger decay in which molecular orbitals delocalized over the iodine site and the uracil ring are involved, the nuclear dynamics also play a role for ultrafast charge redistribution. The present study illustrates that the CCE-CE model as well as the SCC-DFTB method can be used for reconstructing the positions of atoms in motion, in combination with the momentum correlation measurement of the atomic ions created via XFEL-induced Coulomb explosion of molecules.

Superparamagnetic iron oxide-enhanced MRI at 3 T for accurate axillary staging in breast cancer

BACKGROUND

The aim of this study was to evaluate whether MRI at 3 T with superparamagnetic iron oxide (SPIO) enhancement is an accurate and useful method for detecting metastases in sentinel nodes identified by CT-lymphography (CT-LG) in patients with breast cancer. The results were compared with those obtained using CT-LG alone and diagnosing metastasis according to size criteria.

METHODS

Patients with clinically node-negative breast cancer were included. Sentinel nodes identified by CT-LG were evaluated prospectively using SPIO-enhanced MRI at 3 T. Sentinel node size was measured on CT-LG, and a node larger than 5 mm in short-axis diameter was considered metastatic. Sentinel nodes localized by CT-LG were removed, and imaging results and histopathological findings were compared.

RESULTS

Sentinel nodes were identified successfully by CT-LG in 69 (99 per cent) of 70 patients. All 19 patients with a finding of metastasis in sentinel nodes at pathology were also shown to have metastases on MRI. Forty-eight of 50 patients with non-metastatic sentinel nodes diagnosed at pathology were classified as having non-metastatic nodes on MRI. On a patient-by-patient basis, the sensitivity, specificity and accuracy of MRI for the diagnosis of sentinel node metastases were 100, 96 and 97 per cent; respective values for CT-LG were 79, 56 and 62 per cent. The specificity and accuracy of MRI were superior to those of CT-LG (P < 0·001 and P = 0·002 respectively).

CONCLUSION

SPIO-enhanced MRI at 3 T is useful for accurate diagnosis of metastatic sentinel nodes, indicating that sentinel node biopsy may be avoided in patients with breast cancer who have non-metastatic sentinel nodes on imaging.

Affinity purification of recombinant proteins using a novel silica-binding peptide as a fusion tag

We recently reported that silica is deposited on the coat of Bacillus cereus spores as a layer of nanometer-sized particles (Hirota et al. 2010 J Bacteriol 192: 111-116). Gene disruption analysis revealed that the spore coat protein CotB1 mediates the accumulation of silica (our unpublished results). Here, we report that B. cereus CotB1 (171 amino acids [aa]) and its C-terminal 14-aa region (corresponding to residues 158-171, designated CotB1p) show strong affinity for silica particles, with dissociation constants at pH 8.0 of 2.09 and 1.24 nM, respectively. Using CotB1 and CotB1p as silica-binding tags, we developed a silica-based affinity purification method in which silica particles are used as an adsorbent for CotB1/CotB1p fusion proteins. Small ubiquitin-like modifier (SUMO) technology was employed to release the target proteins from the adsorbed fusion proteins. SUMO-protease-mediated site-specific cleavage at the C-terminus of the fused SUMO sequence released the tagless target proteins into the liquid phase while leaving the tag region still bound to the solid phase. Using the fluorescent protein mCherry as a model, our purification method achieved 85 % recovery, with a purity of 95 % and yields of 0.60 ± 0.06 and 1.13 ± 0.13 mg per 10-mL bacterial culture for the CotB1-SUMO-mCherry and CotB1p-SUMO-mCherry fusions, respectively. CotB1p, a short 14-aa peptide, which demonstrates high affinity for silica, could be a promising fusion tag for both affinity purification and enzyme immobilization on silica supports.

Application of a phosphite dehydrogenase gene as a novel dominant selection marker for yeasts

The use of antibiotic resistance markers in the commercial application of genetically modified microorganisms is limited due to restrictions on the release of antibiotics and their resistance genes to the environment. To avoid contamination by other microorganisms, the development of a dominant selection marker with low environmental risks is still needed. Here we demonstrated a new selection system for Schizosaccharomyces pombe and Saccharomyces cerevisiae using a bacterial phosphite dehydrogenase gene (ptxD). A Sz. pombe transformant carrying ptxD under a strong promoter or on a multicopy plasmid grew on a minimal medium containing phosphite (Pt) as a sole source of phosphorus. To adapt this system to S. cerevisiae strains, codon optimization of ptxD was necessary. The codon-optimized ptxD system appeared effective in not only laboratorial but also industrial S. cerevisiae strains that are diploid or polyploid. Since Pt is a safe and inexpensive chemical, ptxD could be used as a novel dominant selection marker applicable on an industrial scale.

Abstract P2-18-03: Feasibility of sentinel node biopsy following neoadjuvant chemotherapy in cytology-proven node positive breast cancer before chemotherapy

BACKGROUND: Sentinel node biopsy (SNB) for the node negative breast cancer is standard treatment as an accurate assessment of axillary lymph node status; however, axillary node dissection is a standard procedure for the node positive breast cancer. Neoadjuvant chemotherapy (NAC) has become the standard of care for patients with locally advanced breast cancer. It is reported that 40% of node positive disease convert to node negative after NAC. It remains controversial whether SLB could be applied to patients who present with node-positive disease before neoadjuvant chemotherapy. In this study, we evaluated the accuracy of SNB following NAC in breast cancer patients presenting with cytology-proven axillary node metastasis before chemotherapy.

METHODS: A multicenter prospective study was performed from September 2011 to April 2013 in 101 breast cancer patients with positive axillary nodes, proven by ultrasound-guided fine-needle aspiration at initial diagnosis (T1-3, N1, M0). After the confirmation of patients as clinically node-negative by preoperative imaging following NAC, all patients underwent breast surgery, with SNB and complete axillary lymph node dissection. The sentinel nodes were examined by hematoxylin-eosin staining, immunohistochemical analysis or one-step nucleic acid amplification assay (OSNA).The false negative rate and detection rate were analyzed.

RESULTS: Among the 101 patients analyzed, all cases presented with invasive ductal carcinoma. with a mean tumor size of 3.4cm. Thirty-six cases were hormone receptor (HR) positive and HER2 negative (Lum), 14 cases were HR positive and HER2 positive (Triple-Positive), 27 cases were positive for HER2 (HER2-enriched), and 24 cases were Triple-Negative. After neoadjuvant chemotherapy, a complete clinical response in the primary tumor was seen in 24.8%(25/101), a partial response in 66.3%(67/101), and no response in 7.9%(8/101). Pathological complete response of primary tumor was 39.6%. The pathological complete nodal response rate was 42.2%. The sentinel lymph node could be identified in 91 of 101 cases (90.1%); 88.9% (32/36) of patients with Lum, 100%(14/14)of those with Triple-Positive, 85.2% (23/27) of those with HER2-enriched, and 91.7% (22/24)% of those with Triple-Negative breast cancer subtype. The false negative rate was 12.7%; 35.7 (5/14) for Lum, 0% (0/8) for Triple-Positive, 5.0% (1/20) for HER2-enriched, and 7.7% (1/13) for Triple-Negative subtype (P = 0.03).

CONCLUSION: SNB following NAC in patients with node-positive breast cancer was found to be technically feasible, but is not recommended for the Lum subtype. However, it might be safely considered in selected patients, those with Triple-Positive, HER2-enrich and Triple-Negative subtype breast cancers.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-18-03.

Dynamics of hollow atom formation in intense x-ray pulses probed by partial covariance mapping

When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called "partial covariance mapping" to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

Deep inner-shell multiphoton ionization by intense x-ray free-electron laser pulses

We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that Xe(n+) with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n≥24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers.

Stable polyphosphate accumulation by a pseudo-revertant of an Escherichia coli phoU mutant

phoU mutants of bacteria are potentially useful for the removal of inorganic phosphate (Pi) from sewage because they can accumulate a large amounts of polyphosphate (polyP). However, the growth of phoU mutants is severely defective and is easily outgrown by revertant(s) that have lost the ability to accumulate polyP during growth in a nutrient-rich medium. We found that a pseudo-revertant, designated LAP[+], that appeared in a culture of an Escherichia coli phoU mutant that could accumulate polyP even after ten serial passages. Reduction in the expression of the Pi-specific transporter Pst in LAP[+] may contribute to relieving stresses such as excess Pi incorporation that could stimulate reversions. The discovery of a LAP[+] provides a clue to generate phoU mutants that accumulate polyP in a stable manner.

P3-07-46: Accuracy of SPIO-Enhanced MR Imaging Alone for the Diagnosis of Sentinel Node Metastases in Patients with Breast Cancer

Background

Superparamagnetic iron oxide (SPIO)-enhanced MR imaging has been reported to be promising for the detection of metastases in sentinel nodes localized by CT lymphography in patients with breast cancer (Motomura, Ann Surg Oncol 2011). The current SPIO technique involves imaging before and after contrast administration. This study evaluated the accuracy of SPIO-enhanced MR imaging alone without unenhanced imaging.

Methods: This study included 120 patients with breast cancer demonstrating clinically negative nodes. Sentinel nodes were identified by CT lymphography, and MR imaging of the axilla before and 18–24 hr after interstitial administration of SPIO was performed. A node was considered non-metastatic if it showed a homogenous low signal intensity and metastatic if there was an absence of low signal intensity either in the entire node or in a focal area on SPIO-enhanced MR imaging. The diagnostic accuracy of the SPIO-enhanced imaging alone was compared with that of combined unenhanced and SPIO-enhanced imaging.

Results: The mean number of sentinel nodes identified by CT lymphography was 1.2 (range 1–3). Pathologic evaluation demonstrated that 28 (23.3%) of 120 patients showed metastasis to at least one node. One false negative result was added when the evaluation was based solely on SPIO-enhanced MR imaging. Consequently, the sensitivity decreased from 84.0% to 80.0% and the accuracy decreased from 89.2% to 88.3%, respectively, in the SPIO-enhanced MR imaging alone. However, the differences in sensitivity and accuracy between SPIO-enhanced MR imaging alone and the combined unenhanced and SPIO-enhanced imaging were not significant (McNemar's test; p=1.0). The specificity of enhanced imaging alone and that of combined unenhanced and SPIO-enhanced imaging were both 90.5%.

Conclusions: A single MR imaging examination performed after SPIO administration can be used for accurate diagnosis of sentinel node metastases, and thus reduce the time and cost of imaging.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-46.

Second-order autocorrelation of XUV FEL pulses via time resolved two-photon single ionization of He

Second-order autocorrelation spectra of XUV free-electron laser pulses from the Spring-8 Compact SASE Source (SCSS) have been recorded by time and momentum resolved detection of two-photon single ionization of He at 20.45 eV using a split-mirror delay-stage in combination with high-resolution recoil-ion momentum spectroscopy (COLTRIMS). From the autocorrelation trace we extract a coherence time of 8 ± 2 fs and a mean pulse duration of 28 ± 5 fs, much shorter than estimations based on electron bunch-length measurements. Simulations within the partial coherence model [Opt. Lett. 35, 3441 (2010)] are in agreement with experiment if a pulse-front tilt across the FEL beam diameter is taken into account that leads to a temporal shift of about 6 fs between both pulse replicas.

Girdin maintains the stemness of glioblastoma stem cells

Glioblastomas (GBMs) are the most common and aggressive type of brain tumor. GBMs usually show hyperactivation of the PI3K-Akt pathway, a pro-tumorigenic signaling cascade that contributes to pathogenesis. Girdin, an actin-binding protein identified as a novel substrate of Akt, regulates the sprouting of axons and the migration of neural progenitor cells during early postnatal-stage neurogenesis in the hippocampus. Here, we show that Girdin is highly expressed in human glioblastoma (GBM). Stable Girdin knockdown in isolated GBM stem cells resulted in decreased expression of stem cell markers, including CD133, induced multilineage neural differentiation, and inhibited in vitro cell motility, ex vivo invasion, sphere-forming capacity and in vivo tumor formation. Furthermore, exogenous expression of the Akt-binding domain of Girdin, which competitively inhibits its Akt-mediated phosphorylation, diminished the expression of stem cell markers, SOX2 and nestin, and migration on the brain slice and induced the expression of neural differentiation markers glial fibrillary acidic protein/βIII Tubulin. Our results reveal that Girdin is required for GBM-initiating stem cells to sustain the stemness and invasive properties.

Sentinel lymph node biopsy following neoadjuvant chemotherapy in clinically node-negative breast cancer patients

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Background: Sentinel lymph node biopsy (SLNB) is a widely accepted staging method for patients with early breast cancer. But SLNB following neoadjuvant chemotherapy (NAC) is also controversial because of insufficient evidence to recommend as a standard procedure. The aim of our study was to demonstrate the feasibility of SNLB following NAC.

Methods: The clinical study of SLNB for clinically node-negative breast cancer patient was conducted as a large cohort study to confirm the identification rate and safety of this procedure. It was investigated by The Japanese Breast Cancer Society and was accomplished between the years March 2008 and October 2009. In this study 11,228 cases are registered before SLNB from 64 institutions. Of the 11,228 eligible cases, analysis was conducted among 489 cases that were introduced neoadjuvant chemotherapy.

Results: SLNB was performed in 110 cases before NAC, 379 cases after NAC. The sentinel node identification rate before NAC was 106/110 cases (96.4%), after NAC was 373/379 cases (98.4%). Intraoperative frozen section analysis was performed in 280 cases, 71 cases were positive. The remaining 219 patients displayed no metastasis in the intraoperative examination, and 6 of these 219 (2.7%) were positive in the final pathological analysis.

Conclusions: The identification rate of SLNB following NAC is not inferior to the result of major clinical studies previously reported in the world. There is insufficient evidence to recommend this as a standard procedure. Further research with subgroup analysis is necessary to identify whether SLNB following NAC is feasible or not (planned study). The primary end point for Group A is local relapse rate, Group B is not only the accuracy and false negative rate also the utility of One-step Nucleic Acid Amplification (OSNA).

A nomogram to predict nonsentinel lymph node involvement in breast cancer patients with sentinel lymph node metastases

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Background: Several nomograms have been described as predictors of non-sentinel axially lymph node (non-SN) metastases in breast cancer with positive sentinel nodes (SN). However, all these predicting models were based on data from western countries. The purpose of this study was to examine predictive factors of non-SN status among SN metastatic patients, in order to develop a nomogram based on Japanese large data set.

Methods: This research was analyzed by using a clinical database of 11,228 Japanese breast cancer patients who registerd to cohort study as SN biopsy between March 2008 and Octover 2009 in Japan. We reviewed data retrospectively to extract patients with SN metastases who underwent complementary axillary lymph node dissection. In this cohort, we examined predictive factors of non-SN metastases. All clinical and pathologic features were analyzed to predict the non-SN status, by using univariate and multivariate logistic regression model. A receiver operating characteristic curve was constructed and the area under the curve (AUC) was calculated.

Results: Among the database, SN metastases were found in 1,029 patients, and 345 (33.5%) were non-SN positive. Univariate analysis showed a significant association between non-SN involvement and primary tumor size (p<0.001), histologic grade (p=0.011), lymphatic invasion (p<0.001), venous invasion (p=0.005) and the number of involved SNs among all identified SNs (p<0.001). Tumor size (p<0.001), lymphatic invasion (p<0.001), and the size of SN metastasis (p<0.001) were associated with non-SN metastasis in multivariate analysis. Based on the multivariate analysis, we developed a scoring system to predict the likelihood of non-SN metastases in breast cancer patients with SN involvement. The discriminatory ability of our nomogram, as measured by the AUC, was 0.752.

Conclusions: In patients with invasive breast cancer and a positive SN, primary tumor size, lymphatic invasion, and the size of SN metastases among all identified SNs were independently predictive of non-SN involvement, and used for a nomogram. Validation study will be performed in the future investigation.