PNAS Research Articles

Insider trading in discrete time Kyle games

AbstractWe present a new discrete time version of Kyle’s (Econometrica 53(6):1315–1335, 1985) classic model of insider trading, formulated as a generalised extensive form game. The model has three kinds of traders: an insider, random noise traders, and a market maker. The insider aims to exploit her informational advantage and maximise expected profits while the market maker observes the total order flow and sets prices accordingly. First, we show how the multi-period model with finitely many pure strategies can be reduced to a (static) social system in the sense of Debreu (Proc Natl Acad Sci 38(10):886–893, 1952) and prove the existence of a sequential Kyle equilibrium, following Kreps and Wilson (Econometrica 50(4):863–894, 1982). This works for any probability distribution with finite support of the noise trader’s demand and the true value, and for any finite information flow of the insider. In contrast to Kyle (1985) with normal distributions, equilibria exist in general only in mixed strategies and not in pure strategies. In the single-period model we establish bounds for the insider’s strategy in equilibrium. Finally, we prove the existence of an equilibrium for the game with a continuum of actions, by considering an approximating sequence of games with finitely many actions. Because of the lack of compactness of the set of measurable price functions, standard infinite-dimensional fixed point theorems are not applicable.

Formal models and justifications of democracy

Recently, some epistemic democrats have taken a result from Hong and Page (Proc Natl Acad Sci 101(46):16385–16389, 2004) to help justify the virtues of deliberative democracy. In this paper, I present novel computational models and show that the result fails to be robust in ways that undermine it as evidence for justifying the virtues of deliberative democracy. In particular, the same model lauded by epistemic deliberative democrats can also be used to support certain kinds of epistocracy.

8090 A Gut Commensal, Parabacteroides distasonis, and Molecular Mimicry in Type 1 Diabetes

Abstract Disclosure: A. Randall: None. Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by the destruction of pancreatic, insulin-producing beta cells by autoreactive T-cells. The trigger(s) of T1D are unclear and genetics alone cannot explain the recent increase in T1D incidence. The gut microbiome composition in T1D patients is altered and thought to play a key role in T1D pathogenesis. Most longitudinal studies have been descriptive. However, a direct cause-and-effect relationship hasn't been established yet. Insulin is a key autoantigen in T1D autoimmunity, and insulin B-chain amino acids 9-23 (insB:9-23) is an important, commonly recognized T-cell epitope. Molecular mimicry is an autoimmunity mechanism where host-like microbial proteins trigger autoimmune responses. We previously identified a peptide mimic of insB:9-23, amino acids 4-18 of hypoxanthine phosphoribosyl transferase (HPRT:4-18) of Parabacteroides distasonis (Girdhar et al., 2022). HPRT:4-18 stimulated insB:9-23-specific human and non-obese diabetic (NOD) mice T-cells. We hypothesize that P. distasonis HPRT:4-18 is required to accelerate diabetes via molecular mimicry of insB:9-23. By orally gavaging NOD mice (n=40 mice/group), we showed that P. distasonis accelerated diabetes onset. Next, we colonized NOD mice with another common gut commensal, Bacteroides fragilis, as a control, and did not observe any effect on islet infiltration. In addition, P. distasonis colonization increased infiltration of immune cells into the islets of germ-free NOD mice (n=6-8 mice/group), while the diabetes incidence experiment in mice is ongoing. P. distasonis-colonized mice had significantly more splenic CD8 and naïve T-cells, dendritic cells and macrophages but fewer FOXP3 cells (n=3-6 mice/group). To determine whether P. distasonis’s effect is specific to the pancreas, we checked intestinal barrier function and intestinal immune cell composition. Disruption of intestinal barrier function has been associated with diabetes. P. distasonis colonization did not alter gut permeability. Furthermore, P. distasonis did not increase intestinal inflammation. Among the intestinal intraepithelial lymphocytes (IELs), there were fewer naïve, central and effector T-cells and B-cells. The findings indicate that P. distasonis does not stimulate an unspecific immune response and its inflammatory effect is specific to the pancreas, supporting our initial hypothesis. Taken together, our results indicate that exposure to P. distasonis in the first years of life has the potential to stimulate molecular mimicry mechanism and cause T1D onset. Reference: Girdhar, K., Huang, Q., Chow, I. T., Vatanen, T., Brady, C., Raisingani, A., . . . Altindis, E. (2022). A gut microbial peptide and molecular mimicry in the pathogenesis of type 1 diabetes. Proc Natl Acad Sci U S A, 119(31), e2120028119. doi:10.1073/pnas.2120028119 Presentation: 6/2/2024

Erosion of surfaces by trapped vortices

Two two-dimensional free boundary problems describing the erosion of solid surfaces by the flow of inviscid fluid in the presence of trapped vortices are considered. The first problem tackles an initially flat, infinite fluid-solid interface with uniform flow at infinity and a vortex in equilibrium above the surface. The second involves flow around a finite body with a trailing Föppl-type vortex pair. The conformal invariance of the complex potential permits both problems to be formulated as a Polubarinova–Galin (PG) type equation in which the time-dependent eroding surface in the physical z-plane is mapped to the fixed boundary of the ζ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\zeta $$\\end{document}-disk. The Hamiltonian governing the equilibrium position of the vortex (or vortex pair in the second problem) is also found from the same map. In each problem, the PG equation giving the conformal map is found numerically and the time-dependent evolution of the interface and vortex location is determined. Different models governing the erosion of the interface are investigated in which the normal velocity of the boundary depends on some given function of the fluid flow velocity at the boundary. Typically, in the infinite surface case, erosion leads to the formation of a symmetric valley beneath the vortex which, in turn, moves downward toward the interface. A finite body undergoes erosion which is asymmetric in the flow direction leading to a flattening of the lee surface of the body so displaying some similarity to the experiments and associated viscous theory of Ristroph et al, Moore et al (Proc Natl Acad Sci 109(48):19606–19609, 2012, Phys Fluids 25(11):116602, 2013).

Cytochrome c Oxidase Detection in Human Fibroblasts Using Scanning Electrochemical Microscopy

Cytochrome C Oxidase Deficiency (COXD) is a disorder caused by the mutation in genes encoding for the cytochrome c oxidase enzyme (COX),1 a mitochondrial multimeric enzyme which acts as the terminal electron acceptor in the electron transport chain.2 COXD causes serious health issues in affected individuals, including severe muscle weakness, brain damage and disorders in organs such as heart, liver and kidneys.1 Diagnosis is mostly performed by muscle biopsy,3,4 which is invasive and time-consuming. Finding new effective and early diagnostic strategies is therefore crucial to minimize symptoms and long-term disabilities. This research proposes the use of scanning electrochemical microscopy (SECM) as a promising method to quantify COX activity in normal and COXD fibroblasts as cell models. We explore the interaction of the redox probe N,N,N’,N’-tetramethyl-p-phenylene diamine (TMPD) with COX as an indicator of enzymatic activity.5,6 A platinum ultramicroelectrode was used to monitor electrochemical currents at different scan speeds, which were later used to determine an apparent heterogeneous rate constant (k 0) for TMPD regeneration by each cell line using numerical modelling. A significant difference in k 0 values (p < 0.1) was observed when comparing normal and COXD fibroblasts. The further treatment of normal fibroblasts with a COX inhibitor, NaN3,7 induced significant decreases in k 0 (p < 0.01). The COX activity results determined using SECM were in good agreement with a standard spectrophotometric assay. Taken together, our findings confirm SECM as an effective and rapid method to detect COXD in living tissues and provides a foundation for the development of new assays to diagnose COXD in infants. References M. Brischigliaro and M. Zeviani, Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1862, 148335 (2021).A. Timón-Gómez et al., Semin Cell Dev Biol, 76, 163–178 (2018).M. L. Simard, A. Mourier, L. C. Greaves, R. W. Taylor, and J. B. Stewart, Journal of Pathology, 245, 311–323 (2018).S. B. Wortmann, J. A. Mayr, J. M. Nuoffer, H. Prokisch, and W. Sperl, Neuropediatrics, 48, 309–314 (2017).S. Kuss, E. E. L. Tanner, M. Ordovas-Montanes, and R. G. Compton, Chem Sci, 8, 7682–7688 (2017).S. Thind et al., Proc Natl Acad Sci U S A (2023). In press.M. J. Fei et al., Acta Crystallogr D Biol Crystallogr, 56, 529–535 (2000).

Stable Lithium Metal Batteries Enabled by Dilute Cationic Additives

Conventional Li-ion electrolytes consist of carbonate solvents and Li-ion salts that were made for carbonaceous negative electrodes. When the electrolytes are used with metallic lithium anodes, carbonate electrolytes lead to low charge-discharge cycle stability due to adverse reactive species at the anode surface.1-4 This reactive species are called the solid electrolyte interface (SEI).1 SEI instabilities/inhomogeneities result in its continuous thickening and formation of electronically non-active dead lithium.2 SEI composition and structure are affected by both solvent and electrolyte chemistry in bulk solution and, more importantly, at the electrode-electrolyte interface.4 Current research studies suggest that X-rich (where X is a halogen) SEI yields superior performance compared to halogen-free SEI.1,5 Electrolytes that have large volume fractions of halogenated species have statistically higher probability to be reduced at the electrode surface and yield X-rich SEI layers.6 Therefore, the use of halogenated solvent and/or high concentrated (> 1 M) lithium salt with halogenated anions has been actively explored for LiMBs. However, the high cost of Li salts and high viscosity of the electrolyte at high salt concentration make the concentrated electrolytes unrealistic for commercial battery applications. In search of a cost-effective solution for high performance LiMBs, halogenated electrolyte additives could serve as an ideal approach since only a small amount of the additive would be potentially required to induce similar X-rich interface that can be seen in the case of the halogenated ether electrolyte. In this meeting abstract, we present a new concept that leverages favorable electrostatic interactions with the electrolyte additive to drive the formation of robust SEI layers even at low additive content. Specifically, custom-designed additives can be electrostatically attracted to the negatively charged electrode, creating a high population of halogenated species at the anode surface even at a dilute Li salt concentration. Effective SEI formation with a low-concentration additive circumvents the challenges associated with the current state-of-the-art approach of using halogenated species at high concentration (i.e., unfavorably high solution viscosity and high cost). Reference 1 Louli, A. J. et al. Diagnosing and correcting anode-free cell failure via electrolyte and morphological analysis. Nature Energy 5, 693-702, (2020).2 Chen, K.-H. et al. Dead lithium: mass transport effects on voltage, capacity, and failure of lithium metal anodes. Journal of Materials Chemistry A 5, 11671-11681, (2017).3 Lin, D. et al. Three-dimensional stable lithium metal anode with nanoscale lithium islands embedded in ionically conductive solid matrix. Proc Natl Acad Sci U S A 114, 4613-4618, (2017).4 Lin, D., Liu, Y. & Cui, Y. Reviving the lithium metal anode for high-energy batteries. Nat Nanotechnol 12, 194-206, (2017).5 Yu, Z. et al. Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries. Nature Energy 5, 526-533, (2020).6 Yamada, Y., Wang, J., Ko, S., Watanabe, E. & Yamada, A. Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy 4, 269-280, (2019).

Physically-Based Descriptors of the Nitrogen Reduction Reaction on Transition Metal Nitrides

Due to the high energy intensity and consequent carbon footprint of the Haber-Bosch process for ammonia production, researchers have been intensely studying the electrochemical nitrogen reduction reaction (NRR) as a means to directly produce ammonia using clean energy with lower emissions of carbon by-products. One exciting class of materials for NRR catalysis are transition metal nitrides (TMNs), as they have been shown to have good stability, flexible electronic structures, and decent electrochemical activity [1]. Previous studies using density functional theory (DFT) have explored the energetics of known NRR pathways (associative, dissociative, and Mars-van Krevelen) on the mononitrides of all naturally occurring d-block metals in rock salt and zincblende structures [2]. The most favorable NRR mechanism (determined to be the pathway that contains the smallest maximum potential change across all steps of the reaction) on these materials was shown to be the Mars-van Krevelen mechanism. Uncovering electronic, structural, and dynamic descriptors that correlate well with the energetics of this favorable NRR mechanism on TMNs will be useful in mitigating the need to run full DFT calculations when expanding the search space of potential catalyst candidates, such as ternary transition metal nitrides (TTMNs) and perovskite transition metal oxynitrides (TMONs). Previous literature has shown that the proton adsorption energy is a good descriptor for catalytic NRR activity on TMNs [3], oxygen vacancy content [4] and the oxygen p-band center of bulk perovskites [5] are good descriptors for catalytic oxygen evolution reaction performance, and the metal d-band center of pure transition metal catalysts is a good descriptor for reactivity and adsorption energies [6]. Inspired by these results, this work uses DFT on a set of TMNs to calculate a variety of potential physics-based descriptors, including: metal d and nitrogen p-band centers, hybridization between nitrogen p and metal d orbitals, nitrogen vacancy content, surface Bader charges, and phonon band centers. Since the energetics of the NRR can be modulated by the properties of either the atoms in the bulk or in the top surface layers, we calculate all of our descriptors from atoms in the TMN bulk form as well as from surface and subsurface atoms in the TMN slab form.Our results reveal several correlations between the descriptors and material attributes (such as adsorption energies and vacancy formation energies), which in turn govern the energetics of the NRR on the TMNs. We find that the N2 adsorption energy is negatively correlated with the metal d-band center, the N adsorption energy is positively correlated with the nitrogen p-band center, and both the proton adsorption energy and nitrogen vacancy formation energy are negatively correlated with nitrogen p and metal d orbital hybridization. Interestingly, we also find that for some attributes, the subsurface layer atoms dictate the attribute values and not the surface layer atoms. This suggests that heterogeneous catalysis reactivity may be modulated by atomic properties not purely from the bulk or purely from the surface, but rather from multiple subsurface layers as well.Overall, the insights gained from our descriptor analysis can be used to constrain the search and design space of future potential NRR catalysts, such as TTMNs and TMONs. In doing so, the descriptors can be used in future works in either a high-throughput screening or machine learning framework to allow for the inverse material design of optimal NRR catalysts. These optimal catalysts can in turn lead to the emergence of electrochemical ammonia synthesis in industrial production.References Qiao Z, Johnson D and Djire A. Cell Rep Phys Sci 2021; 2.Abghoui Y and Skúlason E. Catal Today 2017; 286: 69-77.Abghoui Y, Garden AL, Hlynsson VF, Björgvinsdóttir S, Ólafsdóttir H and Skúlason E. Physical Chemistry Chemical Physics 2015; 17: 4909-4918.Marelli E, Gazquez J, Poghosyan E, Müller E, Gawryluk DJ, Pomjakushina E, Sheptyakov D, Piamonteze C, Aegerter D, Schmidt TJ, Medarde M and Fabbri E. Angewandte Chemie - International Edition 2021; 60: 14609-14619.Jacobs R, Hwang J, Shao-Horn Y and Morgan D. Chemistry of Materials 2019; 31: 785-797.Nørskov JK, Abild-Pedersen F, Studt F and Bligaard T. Proc Natl Acad Sci U S A 2011; 108: 937-943.

MSphere of Influence: Retreading old ground-the beauty in multi-omic data sets.

Ethan L. Morgan works on human papillomaviruses (HPVs), with a specific interest in identifying how HPV induces tumor formation. In this mSphere of Influence article, he reflects on how three papers influenced him. "Comprehensive genomic characterization of head and neck squamous cell carcinomas" (The Cancer Genome Atlas Network, Nature 517:576-582, 2015, https://doi.org/10.1038/nature14129) and "Integrated genomic and molecular characterization of cervical cancer" (The Cancer Genome Atlas Network, Nature 543: 378-384, 2017, https://doi.org/10.1038/nature21386) showed him the power behind comprehensive multi-omic analyses to understand disease biology, while "Human papillomavirus E7 oncoprotein targets RNF168 to hijack the host DNA damage response" (J. Sitz et al., Proc Natl Acad Sci U S A 116:19552-19562, 2019, https://doi.org/10.1073/pnas.1906102116) reinforced how this can be used to undercover potential new drug targets in HPV-associated disease.

Discovering the Intriguing Properties of Extrasynaptic γ-Aminobutyric Acid Type A Receptors.

Tonic inhibition in mouse hippocampal CA1 pyramidal neurons is mediated by α5 subunit-containing γ-aminobutyric acid type A receptors. By Caraiscos VB, Elliott EM, You-Ten KE, Cheng VY, Belelli D, Newell JG, Jackson MF, Lambert JJ, Rosahl TW, Wafford KA, MacDonald JF, Orser BA. Proc Natl Acad Sci U S A 2004; 101:3662-7. Reprinted with permission. In this Classic Paper Revisited, the author recounts the scientific journey leading to a report published in the Proceedings of the National Academy of Sciences (PNAS) and shares several personal stories from her formative years and "research truths" that she has learned along the way. Briefly, the principal inhibitory neurotransmitter in the brain, γ-aminobutyric acid (GABA), was conventionally thought to regulate cognitive processes by activating synaptic GABA type A (GABAA) receptors and generating transient inhibitory synaptic currents. However, the author's laboratory team discovered a novel nonsynaptic form of tonic inhibition in hippocampal pyramidal neurons, mediated by extrasynaptic GABAA receptors that are pharmacologically distinct from synaptic GABAA receptors. This tonic current is highly sensitive to most general anesthetics, including sevoflurane and propofol, and likely contributes to the memory-blocking properties of these drugs. Before the publication in PNAS, the subunit composition of GABAA receptors that generate the tonic current was unknown. The team's research showed that GABAA receptors containing the α5 subunit (α5GABAARs) generated the tonic inhibitory current in hippocampal neurons. α5GABAARs are highly sensitive to GABA, desensitize slowly, and are thus well suited for detecting low, persistent, ambient concentrations of GABA in the extracellular space. Interest in α5GABAARs has surged since the PNAS report, driven by their pivotal roles in cognitive processes and their potential as therapeutic targets for treating various neurologic disorders.

Abstract 6340: Novel conditionally active tetravalent B7-H3 x CD3 T-cell engagers targeting solid tumors

Abstract B7-H3, also known as CD276, is an immune-checkpoint molecule and a type 1 transmembrane protein that exerts a variety of biological functions. In cancer biology, the overexpression of B7-H3 is correlated with tumor cell invasion and metastasis, decreased T-cell infiltration and function, poor prognosis, and resistance to therapy. As B7-H3 is expressed in multiple solid tumors and plays an important role in modulating anti-tumor immune response as well as promoting cancer cell formation, it became an important target for the development of antibody-based immunotherapy. Many forms of bispecific antibodies targeting B7-H3 have shown antitumor response in preclinical studies. However, bispecific T-cell engagers (TCE) targeting B7H3 and CD3 have been correlated with cytokine release syndrome and hepatic adverse events, a common toxicity observed using TCEs which has limited the development of this immunotherapeutic in clinic. We leveraged BioAtla’s Conditionally Active Biologic (CAB) platform (1) to develop a DualCAB T-cell engager targeting B7-H3 and CD3. This DualCAB-TCE molecule, BA3142, was engineered to bind with high affinity to both recombinant B7-H3 and CD3 receptor/antigens under conditions that mimic the acidic tumor microenvironment, but with low affinity in alkaline physiological conditions. In vitro and in vivo efficacy and toxicity data for the clone BA3142 will be presented. Our data demonstrated that BA3142 promotes cytotoxicity of B7-H3-expressing cancer cells in vitro and induces significant tumor regression in vivo. In Non-Human Primates BA3142 bispecific antibody was tolerated up to 25 mg/kg with minimal cytokine release and no clinical and histopathological signs of toxicities. The CAB technology offers the opportunity to expand the number of targets suitable for drug development in a new class of DualCAB TCEs with superior safety margin and potency in the clinic. (1) Chang HW, Frey G, Liu H, Xing C, Steinman L, Boyle WJ, and Short, J.M. Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches. Proc Natl Acad Sci U S A 2021;118. Citation Format: Ana Paula Cugnetti, PhD, Haizhen Liu, Patricia McNeeley, Kathryn Woodard, Cathy Chang, Gerhard Frey, William J. Boyle, Jay M. Short. Novel conditionally active tetravalent B7-H3 x CD3 T-cell engagers targeting solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6340.

Abstract 261: Akt1 and Cyclin D1 govern polarity of self-renewing divisions in breast cancer stem cells

Abstract Background. Stem-like cells contribute to the development and progression of human cancers. Genes that control symmetric cell divisions have an evolutionarily conserved role in the regulation of cell polarity and in tumorigenesis. Two cells generated by asymmetric divisions have reduced proliferative potential compared with symmetric divisions. The cell survival oncoprotein Akt (Protein Kinase B) is encoded by three isoforms that are altered in human cancers. The Akt isoform-specific impact on breast cancer stem cell function and polarity is controversial, with Akt1 either reducing (1) or promoting (2) cell polarity and migration in tissue culture. Deletion of Akt1 reduced mammary tumor progression and metastasis in transgenic mice (2,3). Methods. Analysis of Akt1, cyclin D1 and Notch signaling was conducted from public databases, and human as well as murine breast cancer samples. Cells derived from Akt1 gene deletion MMTV-ErbB2 breast oncomice (MMTV-ErbB2/Akt1+/+ and MMTV-ErbB2/Akt1−/−) and from the human MCF-7 breast cancer cell line with regulated expression of cyclin D1 and p53 were analyzed for the symmetry of cell division, stem cell function, and signaling pathways. Results. In breast tumors derived from MMTV-ErbB2 transgenics, associated with reduced metastasis, Akt1 genetic deletion reduced the frequency of symmetric cell divisions and the production of mammospheres. Akt1 deletion increased p53 and reduced cyclin D1. Pharmacological reactivation of p53 with Nutlin correlated with the reinduction of asymmetric cellular divisions and reduction in mammospheres in murine and human BCa cells. Akt1 deletion abrogated Nutlin-mediated induction of asymmetric cell divisions. Cyclin D1 induced symmetrical cell divisions, mammosphere formation and reduced p53 and Numb. Conclusions. Akt1 promoted symmetrical cell division at least in part via cyclin D1 suppression of Numb, and induction of γ secretase activity and thereby Notch signaling. Reference. (1) Irie HY, Pearline RV, Grueneberg D, Hsia M, Ravichandran P, Kothari N, et al. Distinct roles of Akt1 and Akt2 in regulating cell migration and epithelial-mesenchymal transition. J Cell Biol 2005;171:1023-34. (2) Ju X, Katiyar S, Wang C, Liu M, Jiao X, Li S, et al. Akt1 governs breast cancer progression in vivo. Proc Natl Acad Sci U S A 2007;104:7438-43. (3) Chen X, Ariss MM, Ramakrishnan G, Nogueira V, Blaha C, Putzbach W, et al. Cell-Autonomous versus Systemic Akt Isoform Deletions Uncovered New Roles for Akt1 and Akt2 in Breast Cancer. Mol Cell 2020;80:87-101 e5 Citation Format: Xuanmao Jiao, Xin Sun, Zhiping Li, Xiaoming Ju, Danni Li, Ritika Harish, Gordon Robertson, Anthony W. Ashton, Richard G. Pestell. Akt1 and Cyclin D1 govern polarity of self-renewing divisions in breast cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 261.

Abstract 744: Novel conditionally active biologic (CAB) tetravalent T-cell engagers targeting solid tumors

Abstract The use of T-cell engagers (TCEs) has great therapeutic potential in oncology. This potential, however, is diminished due to severe toxicity (cytokine release effects, as well as on-target off-tumor toxicities). We leveraged BioAtla’s Conditionally Active Biologic (CAB) technology (1) to develop bispecific antibodies which have no or very little binding to CD3 and to the tumor target antigen (TAA) in healthy tissue (normal physiological conditions), yet have strong binding in diseased tissues (i.e. tumor microenvironment, TME) derived from glycolytic tumor metabolism, which supports tumor growth (Warburg effect). The conditional activity in the TME is achieved by optimizing the sequences of the binding domains and does not require masking and subsequent activation of the binding domain as used in pro-drugs. We have developed dual-CAB T-cell engagers targeting serval well-established tumor associated antigens. Data demonstrating superior potency with reduced off-target binding through in vitro and in vivo characterization of three new DualCAB TCEs, targeting PSMA, Trop2, and Tissue Factor (TF) will be presented.(1) Chang HW, Frey G, Liu H, Xing C, Steinman L, Boyle WJ and Short, JM Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches. Proc Natl Acad Sci U S A 2021;118. Citation Format: Ana Paula Cugnetti, Haizhen Liu, Patricia McNeeley, Charles Xing, Kathryn Woodard, Hwai Chang, Gerhard Frey, William J. Boyle, Jay M. Short. Novel conditionally active biologic (CAB) tetravalent T-cell engagers targeting solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 744.

Abstract 1634: Cyclin D1 induces Akt1 activity in RB deficient prostate cancer

Abstract Background: Prostate cancer (PCa), the second leading cause of death in American men, is a genetically heterogeneous disease. The aberrant activation of AKT is one of the most frequent alterations in human cancers, and an elevated level of phosphorylated AKT at Ser473 site (pSer473) is associated with metastatic cancers (1). In prostate cancer (PCa), PI3K/AKT activation induces tumorigenesis (2), androgen receptor (AR)-mediated signaling, enzalutamide resistance and stemness, synergizing with other pathways including the notch intracellular domain (NICD). The cyclin D1 gene (CCND1), which is overexpressed in PCa, conveys canonical function by encoding the regulatory subunit of a holoenzyme that phosphorylates the retinoblastoma gene (RB) product, and non-canonical functions through phosphorylating other substrates and transcriptional activities. Cyclin D1 expression augments growth of some castrate-resistant PCa (CRPC) and clinical trials are targeting the cyclin D1 related CDK kinase activity in pRB+ PCa. Several Rb-independent mechanisms of action have been described (3). In recent studies the effect of CDK inhibitors was similar in patients with Rb+ vs. Rb− PCa (4). Whether Rb expression is required for the antiproliferative effects of CKD4/6 inhibition in PCa remains to be established. Methods: The kinetics of Akt1 induction by mitogens was assessed using the phosphorylation of the dichromic fluorescent (DCF) dye substrate LS456. We used cyclin D1 shRNA to show endogenous cyclin D1 augmented AKT1 signaling in response to mitogens. Results: Cyclin D1 reintroduction into cyclin D1−/− cells augmented Akt1 phosphorylation, requiring the cyclin D1 K112 residue. CDK inhibitors reduced Akt activity in RB+ and RB− human prostate cancer cell lines. Prostate-specific epithelial cell deletion of cyclin D1 (probasin-CRE-cyclin D1fl/fl) reduced prostate epithelial cell Akt1 activity assessed by immunohistochemical (IHC) staining. pAktSer473 was reduced in cell nuclei and the cytoplasm of both epithelial cells and stromal fibroblasts without a significant change in the abundance of Akt1. The downstream targets of Akt signaling (pTSC2Ser939, and pFKHRSer319) and ARSer213P were reduced in both epithelial cells and stromal fibroblasts. Genetic deletion of both epithelial cell and stromal cyclin D1 further reduced Akt1 activity, prostate epithelial cell proliferation, and markers of cancer stem cells. Proteomic analysis of cyclin D1-expressing stroma identified heterotypic chemokine signals that augment PCa AKT activity. Conclusions: Cyclin D1 induces Akt1 activity in both RB+ and RB− PCa cells which may contribute to tumor progression and therapy resistance. Reference: (1) Chen YL, Law PY, Loh HH. Curr Med Chem Anticancer Agents 2005;5:575-892. (2) Stoyanova T, et al. Proc Natl Acad Sci U S A 2013;110:20111-63. (3) Chen K, et al. Cell Rep 2020;32:1081514. (4) de Kouchkovsky I, et al. Clin Cancer Res 2022;28:1531-9 Citation Format: Xuanmao Jiao, Anthony W. Ashton, Zhiping Li, Ritika Harish, Danni Li, Gordon Robertson, Duanwen Shen, Xiaoming Ju, Ke Chen, Wei Zhang, Samuel Archilefu, Kenneth A. Iczkowski, Hallgeir Rui, Beatrice Knudsen, Paul Timpson, Max Nobis, Richard G. Pestell. Cyclin D1 induces Akt1 activity in RB deficient prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1634.

Abstract 743: Using a novel NextGen linker system to generate a conditionally active biologic (CAB) anti-nectin4-ADC demonstrates improved efficacy in pancreatic PDX cancer models and improved tolerability and toxicity profile in non-human primates

Abstract Antibody-drug conjugates (ADCs) are a promising treatment for various forms of cancer. The treatment efficacy is often limited by on-target/off-tumor toxicity caused by the antigen expression in healthy tissue and by unwanted payload release outside the tumor caused by cleavage of the linker via circulating proteases. Our conditionally active biologics (CAB) technology addresses the on-target/off-tumor toxicity and assists in reducing the off-target/off-tumor toxicity by reducing binding to the target under normal physiological conditions (1). To eliminate the remaining off-target/off-tumor toxicity, we developed a novel linker with superior serum stability, solubility, and tumor-specific payload release. Conjugation can be accomplished using regular IgG backbones without the need for sequence modification. Here we report the in vitro and in vivo characterization of a NextGen linker system to generate a CAB anti-Nectin4-ADC that combines the advantages of CAB antibody pH selectivity with the new linker technology. In vivo efficacy data demonstrated complete tumor regression in several cell line derived xenograft models as well as superior efficacy to an enfortumab vedotin analogue in a patient derived pancreatic cancer model. PK and tox data from a toxicology study in non-human primates will be presented. In addition, data demonstrating the influence of linker technology on specific cancer models will also be presented. In conclusion, the NextGen Nectin4 CAB ADC represents a potentially more effective treatment with increased safety in the clinic. (1) Chang HW, Frey G, Liu H, Xing C, Steinman L, Boyle WJ,and Short JM Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches. Proc Natl Acad Sci U S A 2021;118 Citation Format: Jing Wang, Jian Chen, Gerhard Frey, Haizhen Liu, Charles Xing, Kathryn Woodard, Hwai Chang, William J. Boyle, Jay M. Short. Using a novel NextGen linker system to generate a conditionally active biologic (CAB) anti-nectin4-ADC demonstrates improved efficacy in pancreatic PDX cancer models and improved tolerability and toxicity profile in non-human primates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 743.

The Grammar of Persuasion: A Meta-Analytic Review Disconfirming the Role of Nouns as Linguistic Cues of Subsequent Behavior

Recent discoveries suggest that nouns, as a word class, exhibit a greater capacity to model real-life behavior. In some previous studies participants prompted with a noun label rather than a semantically corresponding verb ( be a voter vs. vote) were more likely to vote. However, many attempts to replicate the original results have shown unsuccessful. To shed light on the effectiveness of subtle linguistic manipulations, we conducted a meta-analysis of 28 effect sizes ( N = 13,376), being an exact or conceptual replications of original studies. Although the average effect was significant ( g = 0.12), the concurrent diagnostics indicated a low trust in the replicability or stability of the effect. Based on that, we cannot conclude that the greater effectiveness of nouns as cues has been reliably demonstrated. We discuss theoretical prospects involving the verb-action link as well as the self-verification motives.

Generalized Partitioned Local Depth

In this paper, we provide a generalization of the concept of cohesion as introduced recently by Berenhaut et al. (Proc Natl Acad Sci 119:2003634119, 2022). The formulation presented builds on the technique of partitioned local depth by distilling two key probabilistic concepts: local relevance and support division. Earlier results are extended within the new context, and examples of applications to revealing communities in data with uncertainty are included. The work sheds light on the foundations of partitioned local depth, and extends the original ideas to enable probabilistic consideration of uncertain, variable and potentially conflicting information.

A Countable-Type Branching Process Model for the Tug-of-War Cancer Cell Dynamics.

We consider a time-continuous Markov branching process of proliferating cells with a countable collection of types. Among-type transitions are inspired by the Tug-of-War process introduced by McFarland et al. (Proc Natl Acad Sci 111(42):15138-15143, 2014) as a mathematical model for competition of advantageous driver mutations and deleterious passenger mutations in cancer cells. We introduce a version of the model in which a driver mutation pushes the type of the cell L-units up, while a passenger mutation pulls it 1-unit down. The distribution of time to divisions depends on the type (fitness) of cell, which is an integer. The extinction probability given any initial cell type is strictly less than 1, which allows us to investigate the transition between types (type transition) in an infinitely long cell lineage of cells. The analysis leads to the result that under driver dominance, the type transition process escapes to infinity, while under passenger dominance, it leads to a limit distribution. Implications in cancer cell dynamics and population genetics are discussed.

Embedding-Based Comparison of Reaction Networks of Wnt Signaling

This work introduces a new method for comparing two reaction networks of the same or closely related systems through their embedded networks in terms of the shared set of species. Hence, we call this method the Common Species Embedded Networks (CSEN) analysis. Using this approach, we conduct a comparison of existing reaction networks associated with Wnt signaling models (Lee, Schmitz, MacLean, and Feinberg) that we have identified. The analysis yields three important results for these Wnt models. First, the CSEN analysis of the Lee (mono-stationary) and Feinberg (multi-stationary) shows a strong similarity, justifying the study of the Feinberg model, which was a modified Lee model constructed to study an important network property called ``concordance''. It also challenge the absoluteness of discrimination of the models into mono-stationarity versus multi-stationarity, which is a main result of Maclean et al. (PNAS USA 2015). Second, the CSEN analysis provides evidence supporting a strong similarity between the Schmitz and MacLean models, as indicated by the ``proximate equivalence'' that we have identified. Third, the analysis underscores the absence of a comparable relationship between the Feinberg and MacLean models, highlighting distinctive differences between the two. Thus, our approach could be a useful tool to compare mathematical models of the same or closely related systems.

Equilibria Decomposition-Based Comparison of Reaction Networks of Wnt Signaling

The Wnt signaling pathway plays a critical role in various biochemical processes, including embryonic development, tissue homeostasis, and cancer progression. In this paper, we conduct a comparative analysis of $\beta$-catenin-dependent Wnt signaling reaction networks, which we refer to as Feinberg, Schmitz, and MacLean models, based on the previous study by MacLean et al. (PNAS USA 2015). Using the methods of finest independent decomposition (FID) and Equilibria Parametrizations (EP), along with our newly developed Common Reactions Equilibria (CORE) and Concordance Profile (CP) analyses, we uncover three interesting results. Firstly, employing FID and EP reveals that both the Schmitz and MacLean models lack absolute concentration robustness (ACR) property, whereas the Feinberg model demonstrates ACR in a single species. Second, utilizing FID and CORE unveils significant relationships within the equilibria sets of augmented Schmitz and MacLean models, while also highlighting the lack of substantial associations between Feinberg and MacLean models. Finally, based on concordance levels, CP analysis indicates greater similarity between MacLean and Schmitz models compared to MacLean and Feinberg models. Therefore, the methods could detect differences between models that are not evident in the standard reaction network analysis.

Impact of Reinforced Polymer Electrolyte Membrane Scratch on Fuel Cell Durability Using 4D X-Ray Computed Tomography Technique

PEMFCs, or Polymer Electrolyte Membrane Fuel Cells, can be used in both stationary power and transportation applications and are promising for use in heavy duty electric vehicles due to their high energy density, ability to be refueled quickly, and extended range, which are key challenges for battery-powered vehicles [1]. Despite these advantages, there are still obstacles preventing the widespread commercialization of PEMFCs, one of which is production cost [2]. To reduce manufacturing costs, it is imperative to ensure that quality control rejects and scraps are minimized. Moreover, enhancing component integration defect detection would ensure the durability of the fuel cell and enhance its operational lifetime. However, robust quality control requires a thorough understanding of potential non-uniformities and their effects on fuel cell performance and operational degradation.Non-uniformities of the membrane electrolyte assembly (MEA) can result in durability issues by damaging the membrane and making it more vulnerable to mechanical and chemical stress during the operation [3]. Several studies have been done on cation contamination and membrane pinholes and their effect on fuel cell performance and durability [4,5] but little attention has been paid to other types of non-uniformities such as membrane scratches and foreign particles, which may also conceivably affect durability [6]. By implementing 4D in-situ X-ray computed tomography (XCT) [7,8], the current work aims to track the evolution of scratches that appear on a reinforced membrane surface during fabrication and its specific objective is to determine the impacts of membrane scratches on membrane durability in fuel cells.The study was conducted by using small-scale fuel cells with GORE-SELECT® membranes that were intentionally scratched with a razor blade, subjecting them to combined chemomechanical membrane accelerated stress test (AST), and monitoring the membrane degradation and evolution of the scratches using 4D-XCT throughout the AST. During the fabrication step, the depth of scratches was regulated by a weak bond between the reinforcement layer and the perfluorosulfonic acid (PFSA) layer, i.e., the scratches did not tear through the reinforcement. Furthermore, the scratches did not adversely impact the initial cell performance. However, during AST operation the evolution of the scratched region was affected by several factors, including the friction between the layers of the membrane electrode assembly, the width of the scratch (Figure 1), the presence of membrane debris, and the extent of membrane strain. Additionally, it was observed that changes in the quality of catalyst layer transfer onto the scratched region can alter the degradation pattern and potentially create a self-mitigating mechanism. These findings may be used to develop more optimized quality control measures for membrane scratches in fuel cell production. Acknowledgements This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, Ballard Power Systems, and W.L. Gore & Associates. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program. Keywords: fuel cell; membrane durability; X-ray computed tomography; membrane scratch; manufacturing References [1] Cullen DA, Neyerlin KC, Ahluwalia RK, Mukundan R, More KL, Borup RL, et al. New roads and challenges for fuel cells in heavy-duty transportation. Nat Energy 2021;6:462–74. https://doi.org/10.1038/s41560-021-00775-z.[2] Whiston MM, Azevedo IL, Litster S, Whitefoot KS, Samaras C, Whitacre JF. Expert assessments of the cost and expected future performance of proton exchange membrane fuel cells for vehicles. Proc Natl Acad Sci U S A 2019;116:4899–904.[3] De Bruijn FA, Dam VAT, Janssen GJM. Review: Durability and degradation issues of PEM fuel cell components. Fuel Cells 2008;8:3–22.[4] Tavassoli A, Lim C, Kolodziej J, Lauritzen M, Knights S, Wang GG, et al. Effect of catalyst layer defects on local membrane degradation in polymer electrolyte fuel cells. J Power Sources 2016;322:17–25.[5] Lü W, Liu Z, Wang C, Mao Z, Zhang M. The effects of pinholes on proton exchange membrane fuel cell performance. Int J Energy Res 2011;35:24–30.[6] Kundu S, Fowler MW, Simon LC, Grot S. Morphological features (defects) in fuel cell membrane electrode assemblies. J Power Sources 2006;157:650–6.[7] Ramani D, Singh Y, White RT, Wegener M, Orfino FP, Dutta M, et al. 4D in situ visualization of mechanical degradation evolution in reinforced fuel cell membranes. Int J Hydrogen Energy 2020;45:10089–103.[8] White RT, Eberhardt SH, Singh Y, Haddow T, Dutta M, Orfino FP, et al. Four-dimensional joint visualization of electrode degradation and liquid water distribution inside operating polymer electrolyte fuel cells. Sci Rep 2019;9:1–12. Figure 1