Preclinical evaluation of novel organometallic 99mTc-folate and 99mTc-pteroate radiotracers for folate receptor-positive tumour targeting

Purpose: The folate receptor (FR) is a valuable tumour marker, since it is frequently overexpressed on various cancer types. The purpose of the present study was to pre-clinically evaluate novel site-specifically modified 99mTc(CO)3 folate (γ-derivative 4, α-derivative 5) and pteroate (6) conjugates for FR targeting. Methods: The 99mTc(CO)3 radiotracers 4-6 were prepared by a kit-like procedure. In vitro characterisation (K D and B max) of the radiotracers was performed with FR-positive KB cells. Tissue distribution was studied in tumour-bearing mice. SPECT/CT experiments were performed with a dedicated small animal SPECT/CT scanner. Results: The complexes 4-6 were formed in high yields (>92%). Binding constants of the radiotracers (K D in nM: 4: 2.09; 5: 2.51; 6: 14.52) were similar to those of 3H-folic acid (K D in nM: 7.22). In vivo the folate derivatives showed significantly better tumour uptake (4: 2.3±0.4% ID/g and 5: 1.2±0.2% ID/g, 4h p.i.) than the pteroate derivative (6: 0.4±0.2% ID/g, 4h p.i.). Clearance of all radiotracers from the blood pool and from non-targeted tissues was efficient (tumour to blood ratio approx. 200-350, 24h p.i.). FR-positive tissue and organs were successfully visualised via small animal SPECT/CT. Conclusion: Radiotracers 4-6 are the first 99mTc(CO)3 tracers prepared via a kit formulation which exhibit full biological activity in vitro and in vivo. Folate derivatives 4 and 5 revealed significantly better pharmacokinetic properties than the pteroate derivative 6. Promising pre-clinical SPECT results warrant further assessment of 99mTc(CO)3 radiofolates for detection of FR-positive tumour

Improved Reconstruction of In Silico Gene Regulatory Networks by Integrating Knockout and Perturbation Data

We performed computational reconstruction of the in silico gene regulatory networks in the DREAM3 Challenges. Our task was to learn the networks from two types of data, namely gene expression profiles in deletion strains (the ‘deletion data’) and time series trajectories of gene expression after some initial perturbation (the ‘perturbation data’). In the course of developing the prediction method, we observed that the two types of data contained different and complementary information about the underlying network. In particular, deletion data allow for the detection of direct regulatory activities with strong responses upon the deletion of the regulator while perturbation data provide richer information for the identification of weaker and more complex types of regulation. We applied different techniques to learn the regulation from the two types of data. For deletion data, we learned a noise model to distinguish real signals from random fluctuations using an iterative method. For perturbation data, we used differential equations to model the change of expression levels of a gene along the trajectories due to the regulation of other genes. We tried different models, and combined their predictions. The final predictions were obtained by merging the results from the two types of data. A comparison with the actual regulatory networks suggests that our approach is effective for networks with a range of different sizes. The success of the approach demonstrates the importance of integrating heterogeneous data in network reconstruction

Computational and experimental studies of diffusion in monoclinic HfO2

Research on hafnia and zirconia has received a boost in the last two decades, mainly because of their electrical properties. As materials with high dielectric permittivity and a wide band-gap, they can replace SiO2 in Si-based semiconductor devices as the gate dielectric, and they can be employed as the insulator in metal—insulator—metal structures, showing memristive behavior.[1,2] Anion, and possibly cation, transport is of fundamental importance for the annealing of such devices and the proposed mechanism of resistive switching (filament switching in the case of HfO2).[2,3] In this study, we investigated both cation and anion diffusion in HfO2 using diffusion experiments, with subsequent determination of the diffusion profiles by Secondary Ion Mass Spectrometry (SIMS). For the diffusion of oxygen in dense ceramics of monoclinic HfO2,, (18O/16O) isotope exchange anneals were performed in the temperature range 573 ≤ T / K ≤ 973 at an oxygen partial pressure of pO2 = 200 mbar.[4] All measured isotope profiles exhibited two features: the first feature, closer to the surface, was attributed to slow oxygen diffusion in an impurity silicate phase; the second feature, deeper in the sample, was attributed to oxygen diffusion in a homogeneous bulk phase. The activation enthalpy of oxygen tracer diffusion in bulk HfO2 was found to be ΔHD* ≈ 0.5 eV. In contrast to oxygen diffusion, diffusion of cations in HfO2 and other oxide-ion conductors is experimentally much more challenging. It is slow, requiring, therefore, high temperatures and long diffusion times. In the case of HfO2, there is also the problem of Si impurities (see above), which are hard to get rid of in ceramic samples. To alleviate these problems somewhat, we directly investigated the diffusion of Zr in thin films of nanocrystalline, monoclinic HfO2, prepared by Atomic Layer Deposition (ALD) and coupled with a sputtered top layer of ZrO2 as a diffusion source. Diffusion experiments were performed in the temperature range 1173 ≤ T / K ≤ 1323 in air. All measured diffusion profiles exhibited bulk diffusion and fast grain-boundary diffusion. Using numerical simulations, we were able to describe the profiles and extract diffusion coefficients for Zr diffusion in bulk HfO2 and along its grain boundaries. The activation enthalpies of diffusion in both cases were, surprisingly, the same at ΔHDb/Dgb ≈ 2.1 eV. They are also much lower than activation energies predicted by static atomistic simulations.[5] In order to aid the interpretation of the experimental data, we conducted atomistic simulations of cation diffusion in HfO2. Specifically we performed Molecular Dynamics (MD) simulations using the empirical pair potentials derived by Catlow and Lewis.[6,7] These potentials are suitable for describing defect behaviour in HfO2.[8,9] The activation enthalpy of Hf diffusion in bulk HfO2 we obtained from the MD simulations agrees exceedingly well with the experimental results: ΔHD* ≈ 2 eV. The reasons for this behaviour are discussed. [1]: V. A. Gritsenko et al., Phys. Rep 613, 1 (2016). [2]: R. Waser et al., Adv. Mater. 21, 2632 (2009). [3]: S. Uhlenbruck et al., Solid State Ionics 180, 418 (2009). [4]: M. P. Mueller, R. A. De Souza, Appl. Phys. Lett. 112, 051908 (2018). [5]: S. Beschnitt et al., J. Phys. Chem. C 119, 27307 (2015). [6]: C. R. A. Catlow, Proc. R. Soc. Lond. A. 353(1675), 533 (1977). [7]: G. Lewis, C. R. A. Catlow, J. Phys. C: Solid State Phys. 18(6), 1149 (1985). [8]: M. Schie et al., J. Chem. Phys. 146, 094508 (2017). [9]: M. Schie et al., Phys. Rev. Mat. 2, 035002 (2018

Integrating Neural Networks with a Quantum Simulator for State Reconstruction

We demonstrate quantum many-body state reconstruction from experimental data generated by a programmable quantum simulator, by means of a neural network model incorporating known experimental errors. Specifically, we extract restricted Boltzmann machine (RBM) wavefunctions from data produced by a Rydberg quantum simulator with eight and nine atoms in a single measurement basis, and apply a novel regularization technique to mitigate the effects of measurement errors in the training data. Reconstructions of modest complexity are able to capture one- and two-body observables not accessible to experimentalists, as well as more sophisticated observables such as the R\'enyi mutual information. Our results open the door to integration of machine learning architectures with intermediate-scale quantum hardware.Comment: 15 pages, 13 figure

Different roles for prepared and spontaneous thoughts: A practice-based study of musical performance from memory

Background in music performance. During musical performance, experienced soloists have a mental map of the music in mind. Landmarks in this map remind them of where they are and what to do next. Background in music psychology. These performance cues (PCs) are prepared during practice so that they come to mind automatically, ensuring that the performance unfolds as planned. Aims. Do musicians use the same PCs in each performance? What other thoughts do they have during performance? Main contribution. To answer these questions, a singer (the first author) reported the thoughts she had as she practised Arnold Schoenberg’s two Songs, Op. 14 (1907-1908), and then again as she performed the songs in a public concert. Seventeen months later, she reconstructed the songs from memory, then performed them and reported her thoughts again. Comparison of the three sets of reports showed that slightly more than half of her thoughts in each of the two performances were PCs, i.e., had occurred during practice, and slightly less than half were spontaneous, new thoughts about the music or performance. The PCs were more stable over time: 17 (25%) occurred in both performances compared to only three (4%) of the spontaneous thoughts. Both PCs and spontaneous thoughts reflected the singer’s current concerns, but in different ways. When the singer performed the songs again after the reconstruction, her thoughts were shaped by the memory problems that she had experienced during the reconstruction that preceded the performance. She thought about the PCs that she had needed to stop at and about the new locations that she had just used as starting places. Implications. PCs are prepared during practice to provide the mental landmarks needed for a secure performance while spontaneous thoughts reflect more transitory experiences and insights

Exhaled nitric oxide decreases after positive food-allergen challenge

Background: Exhaled nitric oxide (FeNO) is a well described marker of airway inflammation in asthma and is also known to increase after chronic exposure to inhaled allergens. It is not known whether monitoring FeNO could be useful during food challenges to detect early or subclinical reactions. Methods: Forty children aged 3 to 16 years undergoing an allergen-food challenge at two centres were prospectively recruited for this study. FeNO was assessed before and repeatedly after the food-challenge. Results: Data were obtained from a total of 53 challenges (16 positive, 37 negative) and were compared between the two groups. Half of the patients with a positive food challenge exhibited clinical upper respiratory symptoms. The FeNO significantly decreased in 7 of 16 patients with a positive challenge test within 60 to 90 minutes after the first symptoms of an allergic reaction. Conclusion: Our results show a significant decrease in FeNO after a positive food challenge suggesting involvement of the lower airways despite absence of clinical and functional changes of lower airways. Prospective blinded studies are needed to confirm these results

A preexisting rare PIK3CA e545k subpopulation confers clinical resistance to MEK plus CDK4/6 inhibition in NRAS melanoma and is dependent on S6K1 signaling

Combined MEK and CDK4/6 inhibition (MEKi + CDK4i) has shown promising clinical outcomes in patients with NRAS- mutant melanoma. Here, we interrogated longitudinal biopsies from a patient who initially responded to MEKi + CDK4i therapy but subsequently developed resistance. Whole-exome sequencing and functional validation identified an acquired PIK3CA E545K mutation as conferring drug resistance. We demonstrate that PIK3CA E545K preexisted in a rare subpopulation that was missed by both clinical and research testing, but was revealed upon multiregion sampling due to PIK3CA E545K being nonuniformly distributed. This resistant population rapidly expanded after the initiation of MEKi + CDK4i therapy and persisted in all successive samples even after immune checkpoint therapy and distant metastasis. Functional studies identified activated S6K1 as both a key marker and specific therapeutic vulnerability downstream of PIK3CA E545K -induced resistance. These results demonstrate that difficult-to-detect preexisting resistance mutations may exist more often than previously appreciated and also posit S6K1 as a common downstream therapeutic nexus for the MAPK, CDK4/6, and PI3K pathways. SIGNIFICANCE: We report the first characterization of clinical acquired resistance to MEKi + CDK4i, identifying a rare preexisting PIK3CA E545K subpopulation that expands upon therapy and exhibits drug resistance. We suggest that single-region pretreatment biopsy is insufficient to detect rare, spatially segregated drug-resistant subclones. Inhibition of S6K1 is able to resensitize PIK3CA E545K -expressing NRAS-mutant melanoma cells to MEKi + CDK4i. © 2018 AAC