Parallel Pathways Research Articles

In-vivo blood pressure sensing with bi-filler nanocomposite

Conductive elastomers present desirable qualities for sensing pressure in-vivo, such as high piezoresistance in tiny volumes, conformability and, biocompatibility. Many electrically conductive nanocomposites however, are susceptible to electrical drift following repeated stress cycles and chemical aging. Here we propose an innovative approach to stabilize nanocomposite percolation network against incomplete recovery to improve reproducibility and facilitate sensor calibration. We decouple the tunnelling-percolation network of highly-oriented pyrolytic graphite (HOPG) nanoparticles from the incomplete viscoelastic recovery of the polydimethylsiloxane (PDMS) matrix by inserting minute amounts of insulating SiO2 nanospheres. SiO2 nanospheres effectively reduce the number of nearest neighbours at each percolation node switching off the parallel electrical pathways that might become activated under incomplete viscoelastic relaxation. We varied the size of SiO2 nanospheres and their filling fraction to demonstrate nearly complete piezoresistance recovery when SiO2 and HOPG nanoparticles have equal diameters (≈400 nm) and SiO2 and HOPG volume fractions are 1 % and 29.5 % respectively. We demonstrate an in-vivo blood pressure sensor based on this bi-filler composite.

Commonly Existing Hole-Capturer Organics Adsorption-Induced Recombination over Metal/Semiconductor Perimeters: A Possible Important Factor Affecting Photocatalytic Efficiencies.

Photocatalysis is a physiochemical effect arising from the relaxation of photoinduced electrons from the conduction band to the valence band. Controlling the electron relaxation to occur through photocatalytic pathways and prohibiting other relaxations is the main scientific thought for photocatalytic studies. It is needed to know the parallel relaxation pathways that can compete with photocatalytic reactions. By means of in situ photoconductances (PCs) and photoinduced absorptions (PAs), the current research studied the photoinduced electron relaxations of the Au/TiO2 in different atmospheres and at different temperatures. The PC and PA relaxations became different and fast when methanol, ethanol, isopropanol, and acetone were introduced; they also tend to decrease as temperature increases, while that of the undecorated TiO2 in all atmospheres and the Au/TiO2 in pure N2 increased. The results indicated that the organic adsorptions over the Au/TO2 perimeters change the relaxation pathway, and a hole-capturing organics adsorption-induced recombination over the Au/TiO2 perimeter was proposed to explain the relaxations. We found that this relaxation also exists for Ag/TiO2, Pt/TiO2, and Au/ZnO, so it is a commonly existing physical course for the metal/semiconductor (M/S) materials. The effect of the organics and M/S structures on the relaxation was discussed, and the relationship with photocatalytic reactions was also analyzed. Our finding means that blocking this relaxation pathway is an effective way to increase photocatalytic activities, which might open a door for highly active photocatalyst developments.

Modeling of pulse and relaxation of high-rate Li/CFx-SVO batteries in implantable medical devices

We present a Hybrid Multiphase Porous Electrode Theory (Hybrid-MPET) model that accurately predicts the performance of Medtronic’s implantable medical device battery lithium/carbon monofluoride (CFx) - silver vanadium oxide (SVO) under both low-rate background monitoring and high-rate pulsing currents. The distinct properties of multiple active materials are reflected by parameterizing their thermodynamics, kinetics, and mass transport properties separately. Diffusion limitations of Li+ in SVO are used to explain cell voltage transient behavior during pulse and post-pulse relaxation. We also introduce change in cathode electronic conductivity, Li metal anode surface morphology, and film resistance buildup to capture evolution of cell internal resistance throughout multi-year electrical tests. We share our insights on how the Li+ redistribution process between active materials can restore pulse capability of the hybrid electrode, allow CFx to indirectly contribute to capacity release during pulsing, and affect the operation protocols and design principles of batteries with other hybrid electrodes. We also discuss additional complexities in porous electrode model parameterization and electrochemical characterization techniques due to parallel reactions and solid diffusion pathways across active materials. We hope our models can complement future experimental research and accelerate development of multi-active material electrodes with targeted performance.

An emerging role for tissue plasticity in developmental precision.

Reproducible tissue morphology is a fundamental feature of embryonic development. To ensure such robustness during tissue morphogenesis, inherent noise in biological processes must be buffered. While redundant genes, parallel signaling pathways and intricate network topologies are known to reduce noise, over the last few years, mechanical properties of tissues have been shown to play a vital role. Here, taking the example of somite shape changes, I will discuss how tissues are highly plastic in their ability to change shapes leading to increased precision and reproducibility.

Periodic heat waves-induced neuronal etiology in the elderly is mediated by gut-liver-brain axis: a transcriptome profiling approach

Heat stress exposure in intermittent heat waves and subsequent exposure during war theaters pose a clinical challenge that can lead to multi-organ dysfunction and long-term complications in the elderly. Using an aged mouse model and high-throughput sequencing, this study investigated the molecular dynamics of the liver-brain connection during heat stress exposure. Distinctive gene expression patterns induced by periodic heat stress emerged in both brain and liver tissues. An altered transcriptome profile showed heat stress-induced altered acute phase response pathways, causing neural, hepatic, and systemic inflammation and impaired synaptic plasticity. Results also demonstrated that proinflammatory molecules such as S100B, IL-17, IL-33, and neurological disease signaling pathways were upregulated, while protective pathways like aryl hydrocarbon receptor signaling were downregulated. In parallel, Rantes, IRF7, NOD1/2, TREM1, and hepatic injury signaling pathways were upregulated. Furthermore, current research identified Orosomucoid 2 (ORM2) in the liver as one of the mediators of the liver-brain axis due to heat exposure. In conclusion, the transcriptome profiling in elderly heat-stressed mice revealed a coordinated network of liver-brain axis pathways with increased hepatic ORM2 secretion, possibly due to gut inflammation and dysbiosis. The above secretion of ORM2 may impact the brain through a leaky blood–brain barrier, thus emphasizing intricate multi-organ crosstalk.

Role of Protein Phosphatase 1 (PP1) Upon KCCs Regulation by WNK3 Kinase During Cell Volume Regulation and Ion Transport

Background: The K-Cl cotransporters (KCCs) are SLC12A cation/chloride cotransporters (CCCs) that mediate epithelial transport, maintain cellular volume, and regulate GABA neurotransmission. These mechanisms are complex, and contain multiple sensors, transducers, and effectors, often operating in parallel pathways. It has been shown that KCCs activity is affected by direct phosphorylation and dephosphorylation. In particular dephosphorylation of important regulatory sites on KCCs is necessary to become fully activated, whereas phosphorylation by SPAK/OSR1 kinases will result in KCCs inhibition. Protein phosphatases (PP) inhibitors reduce KCCs function and so, it is generally accepted the presence of phosphatases on the KCCs signaling pathway. Several studies have proposed protein phosphatase 1 (PP1) as the major PP responsible for KCCs dephosphorylation. On the other hand, WNK3 kinases have been shown to directly regulate KCCs activity bypassing their osmotic regulation. That is wild type (WT) WNK3 phosphorylates KCCs under hypotonic conditions where they are normally active, whereas kinase dead WNK3 (DA) activates KCCs function under isotonic conditions where they are normally inhibited. On the present study we analyze the role of protein phosphatase 1 (PP1) upon KCCs regulation by WNK3 kinase during cell volume regulation and ion transport. Methods: HEK 293 cells and Xenopus laevis oocytes were either transfected or microinjected with KCC3 or KCC4 and one of the following PP1 plasmids: WT, H248K (inactive) or T320A (constitutive active), and/or WT WNK3 /DA WNK3. KCCs dephosphorylation in response to cell swelling, hypotonic conditions, was evaluated by Western blot analysis of KCCs regulatory phosphorylation site (pThr1048 in KCC3a). Phosphatase/kinase interaction and the possible formation of a complex was analyzed by transfecting cells or microinjecting oocytes with WNK3 PP1 putative binding sites mutants (WNK3 PP1a y PP1b). Phosphorylation of SPAK/OSR1 activating regulatory site Ser373 was analyzed in parallel under the same conditions. Results: WT or constitutive active mutant PP1 T320A induced KCCs Thr1048 dephosphorylation in HEK cells and X. laevis oocytes even under isotonic conditions, where KCCs are normally phosphorylated. WT WNK3 prevented KCCs T1048 dephosphorylation under hypotonic conditions, ablating their response to cell swelling. Nevertheless, when co-expressed with PP1 T320A, KCCs became dephosphorylated in both osmotic conditions eliminating WT WNK3 inhibitory effect. PP1 inactivating mutation H248K prevented KCCs Thr1048 dephosphorylation in response to hypotonic conditions. However, when co-expressed with DA WNK3, this KCCs regulatory site, became dephosphorylated under hypotonic conditions. SPAK Ser373 regulation was unaffected in any off the studied conditions. Conclusions: Our results show a direct role for PP1 on KCCs function. PP1WT and PP1T320A regulate KCCs activity by its dephosphorylation. In presence of WT WNK3, PP1 activity predominates over WNK3 surpassing the inhibitory phosphorylation of the regulatory Thr residue. KCCs are not dephosphorylated by PP1H248K under hypotonic conditions. Coexpression of kinase dead WNK3 overcomes this effect, supporting the hypothesis of a phosphatase/kinase complex regulating KCCs cell volume regulatory response. AM CF-2023-I-532, INCar 22-1345 PdlH Papiit IN228123. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Somatotopic organization among parallel sensory pathways that promote a grooming sequence in Drosophila.

Mechanosensory neurons located across the body surface respond to tactile stimuli and elicit diverse behavioral responses, from relatively simple stimulus location-aimed movements to complex movement sequences. How mechanosensory neurons and their postsynaptic circuits influence such diverse behaviors remains unclear. We previously discovered that Drosophila perform a body location-prioritized grooming sequence when mechanosensory neurons at different locations on the head and body are simultaneously stimulated by dust (Hampel et al., 2017; Seeds et al., 2014). Here, we identify nearly all mechanosensory neurons on the Drosophila head that individually elicit aimed grooming of specific head locations, while collectively eliciting a whole head grooming sequence. Different tracing methods were used to reconstruct the projections of these neurons from different locations on the head to their distinct arborizations in the brain. This provides the first synaptic resolution somatotopic map of a head, and defines the parallel-projecting mechanosensory pathways that elicit head grooming.

Somatotopic organization among parallel sensory pathways that promote a grooming sequence in Drosophila

Mechanosensory neurons located across the body surface respond to tactile stimuli and elicit diverse behavioral responses, from relatively simple stimulus location-aimed movements to complex movement sequences. How mechanosensory neurons and their postsynaptic circuits influence such diverse behaviors remains unclear. We previously discovered that Drosophila perform a body location-prioritized grooming sequence when mechanosensory neurons at different locations on the head and body are simultaneously stimulated by dust (Hampel et al., 2017; Seeds et al., 2014). Here, we identify nearly all mechanosensory neurons on the Drosophila head that individually elicit aimed grooming of specific head locations, while collectively eliciting a whole head grooming sequence. Different tracing methods were used to reconstruct the projections of these neurons from different locations on the head to their distinct arborizations in the brain. This provides the first synaptic resolution somatotopic map of a head, and defines the parallel-projecting mechanosensory pathways that elicit head grooming.

Abstract P22: C16orf72/HAPSTR1/TAPR1 Interacts with BRCA1 and Senataxin to Regulate R-loops at Stalled Replication Forks and Confer Resistance to PARP Disruption

Abstract Poly (ADP-ribose) polymerase (PARP) proteins play a crucial role in DNA repair, and their inhibition is toxic in cells with defects in homologous recombination (HR). Whilst this interaction is well-established, other synthetic lethal interactions with PARP1/PARP2 disruption are poorly explored. Hence, we performed a genome-wide CRISPR screen to identify genes which are synthetic lethal with PARP1/PARP2 disruption. We discovered that the uncharacterized C16orf72/HAPSTR1/TAPR1 gene is essential for the survival of PARP1/PARP2 double knock-out cells but not the parental wildtype cells. We further show that C16orf72 is a novel modulator of R-loop and is crucial in facilitating replication fork restart and suppressing DNA damage in response to replication stress. We show that C16orf72 functions in a parallel pathway to PARP1/PARP2 to suppress DNA:RNA hybrids that accumulate at stalled replication forks, and it does this by interacting with BRCA1 and the DNA/RNA helicase Senataxin. Citation Format: Abhishek Bharadwaj Sharma, Muhammad Khairul Ramlee, Joel Kosmin, Martin R. Higgs, Amy Wolstenholme, George E. Ronson, Dylan Jones, Daniel Ebner, Noor Shamkhi, David Sims, Paul W. G. Wijnhoven, Josep Forment, Ian Gibbs-Seymour, Nicholas D. Lakin. C16orf72/HAPSTR1/TAPR1 Interacts with BRCA1 and Senataxin to Regulate R-loops at Stalled Replication Forks and Confer Resistance to PARP Disruption [abstract]. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84(8_Suppl):Abstract nr P22.

Four Parallel Pathways in T4 Ligase-Catalyzed Repair of Nicked DNA with Diverse Bending Angles.

The structural diversity of biological macromolecules in different environments contributes complexity to enzymological processes vital for cellular functions. Fluorescence resonance energy transfer and electron microscopy are used to investigate the enzymatic reaction of T4 DNA ligase catalyzing the ligation of nicked DNA. The data show that both the ligase-AMP complex and the ligase-AMP-DNA complex can have four conformations. This finding suggests the parallel occurrence of four ligation reaction pathways, each characterized by specific conformations of the ligase-AMP complex that persist in the ligase-AMP-DNA complex. Notably, these complexes have DNA bending angles of ≈0°, 20°, 60°, or 100°. The mechanism of parallel reactions challenges the conventional notion of simple sequential reaction steps occurring among multiple conformations. The results provide insights into the dynamic conformational changes and the versatile attributes of T4 DNA ligase and suggest that the parallel multiple reaction pathways may correspond to diverse T4 DNA ligase functions. This mechanism may potentially have evolved as an adaptive strategy across evolutionary history to navigate complex environments.

A Contour Detection Method Based on the Projective Coding Model of the Visual Cortex Information Flow

Based on the information flow partition projection characteristics of P-type and M-type ganglion cells (referred to as P cells and M cells) and the neural sparse coding mechanism, this paper proposed a new method for image contour detection. First, we considered the difference between M cells and P cells in detail sensitivity and the information transmission of different visual signals. The parallel visual pathway was constructed to simulate the pre-level characteristics of the V1 layer to obtain the primary contour response. Then, we introduced the orientation sensitivity and stimulus response difference of the visual receptive field to construct the visual information difference enhancement model. In consideration of the visual attention mechanism, we proposed an adaptive size sparse coding network model that simulates the pre-level characteristics of the V4 layer to intelligently focus the target contour features. At the same time, de-redundancy was performed to obtain the fine feature image. Finally, the hierarchical information feedback fusion was built, and the fine feature image was used to correct the primary contour response to obtain complete contour detection results. Taking the BSDS500 dataset as experimental objects, the results showed that the proposed method exhibits an effective trade-off between contour extraction and texture suppression.

Critical steps in the assembly process of the bacterial 50S ribosomal subunit.

During assembly, ribosomal particles in bacteria fold according to energy landscapes comprised of multiple parallel pathways. Cryo-electron microscopy studies have identified a critical maturation step that occurs during the late assembly stages of the 50S subunit in Bacillus subtilis. This step acts as a point of convergency for all the parallel assembly pathways of the subunit,where an assembly intermediate accumulates in a 'locked' state, causing maturation to pause. Assembly factors then act on this critical step to 'unlock' the last maturation steps involving the functional sites. Without these factors, the 50S subunit fails to complete its assembly, causing cells to die due to a lack of functional ribosomes to synthesize proteins. In this review, we analyze these findings in B. subtilis and examine other cryo-EM studies that have visualized assembly intermediates in different bacterial species, to determine if convergency points in the ribosome assembly process are a common theme among bacteria. There are still gaps in our knowledge, as these methodologies have not yet been applied to diverse species. However, identifying and characterizing these convergency points can reveal how different bacterial species implement unique mechanisms to regulate critical steps in the ribosome assembly process.

Stage-specific exposure of Caenorhabditis elegans to cadmium identifies unique transcriptomic response cascades and an uncharacterized cadmium responsive transcript.

Age/stage sensitivity is considered a significant factor in toxicity assessments. Previous studies investigated cadmium (Cd) toxicosis in Caenorhabditis elegans, and a plethora of metal-responsive genes/proteins have been identified and characterized in fine detail; however, most of these studies neglected age sensitivity and stage-specific response to toxicants at the molecular level. This present study compared the transcriptome response between C. elegans L3 vs L4 larvae exposed to 20 µM Cd to explore the transcriptional hallmarks of stage sensitivity. The results showed that the transcriptome of the L3 stage, despite being exposed to Cd for a shorter period, was more affected than the L4 stage, as demonstrated by differences in transcriptional changes and magnitude of induction. Additionally, T08G5.1, a hitherto uncharacterized gene located upstream of metallothionein (mtl-2), was transcriptionally hyperresponsive to Cd exposure. Deletion of one or both metallothioneins (mtl-1 and/or mtl-2) increased T08G5.1 expression, suggesting that its expression is linked to the loss of metallothionein. The generation of an extrachromosomal transgene (PT08G5.1:: GFP) revealed that T08G5.1 is constitutively expressed in the head neurons and induced in gut cells upon Cd exposure, not unlike mtl-1 and mtl-2. The low abundance of cysteine residues in T08G5.1 suggests, however, that it may not be involved directly in Cd sequestration to limit its toxicity like metallothionein, but might be associated with a parallel pathway, possibly an oxidative stress response.

Drosophila Fog/Cta and T48 pathways have overlapping and distinct contributions to mesoderm invagination.

The regulation of the cytoskeleton by multiple signaling pathways, sometimes in parallel, is a common principle of morphogenesis. A classic example of regulation by parallel pathways is Drosophila gastrulation, where the inputs from the Folded gastrulation (Fog)/Concertina (Cta) and the T48 pathways induce apical constriction and mesoderm invagination. Whether there are distinct roles for these separate pathways in regulating the complex spatial and temporal patterns of cytoskeletal activity that accompany early embryo development is still poorly understood. We investigated the roles of the Fog/Cta and T48 pathways and found that, by themselves, the Cta and T48 pathways both promote timely mesoderm invagination and apical myosin II accumulation, with Cta being required for timely cell shape change ahead of mitotic cell division. We also identified distinct functions of T48 and Cta in regulating cellularization and the uniformity of the apical myosin II network, respectively. Our results demonstrate that both redundant and distinct functions for the Fog/Cta and T48 pathways exist.

Abstract 3278: Analysis of the mechanism of resistance to selpercatinib in thyroid cancer cells with RET/PTC1 fusion gene

Abstract Purpose: Precision oncology, in which molecularly targeted drugs are selected based on genetic mutations, has begun in thyroid cancer, and drugs targeting BRAF, RET, and NTRK are already in clinical use. However, as with previous therapeutic agents for malignant tumors, there have been cases of resistance to these drugs either initially or during treatment, and the mechanisms of drug resistance need to be elucidated. So far, little is known about the mechanisms of resistance to molecularly targeted drugs in thyroid cancer. To overcome resistance to the RET inhibitor, selpercatinib (SEL), and to consider next therapeutic strategies, we aimed to elucidate the mechanisms of resistance to SEL. Method: We used papillary carcinoma cell lines TPC-1 and CUTC48, which harbor the RET/PTC1 fusion gene. We established an SEL-resistant subline (TPC-1/SELR) in TPC-1 by long-term exposure to SEL. The growth inhibitory effect of drugs was analyzed using the WST assay. The alteration of intracellular signal transduction was analyzed by western blotting. Result: The 50% inhibitory concentration (IC50) for SEL in the parental TPC-1 was 3 nM, while growth inhibition in TPC-1/SELR did not reach 50% even at more than 100 nM of SEL. On the other hand, growth inhibition by SEL in CUTC48 did not reach 50% even at more than 100 nM of SEL. The sensitivity to SEL in CUTC48 was comparable to that in TPC-1/SELR, and CUTC48 showed an intrinsic resistance to SEL. TPC-1/SELR showed increased phosphorylation of EGFR, Erk, Akt, and mTOR compared to TPC-1. In CUTC48, phosphorylation of EGFR and Erk was not increased compared to that of TPC-1, while phosphorylation of Akt and mTOR was increased. We investigated the growth inhibitory effect of an mTOR inhibitor everolimus and found that TPC-1 (IC50: 1.3 nM), TPC-1/SELR (5 nM), and CUTC48 (9.4 nM) were all highly sensitive to everolimus. Discussion: Our results showed that Akt and mTOR phosphorylation were elevated in the SEL-resistant TPC-1/SELR and the SEL-intrinsic resistant CUTC48 in common, suggesting the involvement of activation of the Akt-mTOR pathway in SEL resistance in thyroid cancer. The inhibition of the Akt-mTOR pathway in parallel with RET may have therapeutic potential to overcome SEL resistance in thyroid cancer. Citation Format: Masatsugu Amitani, Ken-ichi Ito. Analysis of the mechanism of resistance to selpercatinib in thyroid cancer cells with RET/PTC1 fusion gene [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 3278.

Abstract 3296: IK-595, a best-in-class MEK-RAF molecular glue, drives broad and potent anti-tumor activity across RAS-MAPK pathway-altered cancers as a monotherapy and in combination

Abstract Alterations in the RAS/RAF/MEK/ERK pathway are the most common drivers of oncogenesis. Although MEK is a clinically validated cancer target and several MEK inhibitors have been approved by the FDA, their clinical utility has been limited to BRAF V600 mutant cancers and NF1 mutant neurofibromas. We developed the molecular glue, IK-595, a potent inhibitor of the MEK-RAF complex, to overcome the limitations of available MEK inhibitors. IK-595 traps MEK in an inactive complex with all RAF isoforms, as well as mutant forms of BRAF (Class I, II, and III), and blocks RAF-dependent MEK phosphorylation, thereby alleviating CRAF-mediated MEK reactivation that limits the efficacy of approved MEK inhibitors in RAS/RAF-driven tumors. We demonstrate that IK-595 leads to potent and prolonged inhibition of MEK and ERK1/2 phosphorylation in RAS-mutant cancer models. Importantly, IK-595 has a much slower off-rate binding to MEK and retains CRAF longer in an inactive complex with MEK than other MEK/RAF inhibitors, allowing for prolonged target engagement and durable pathway inhibition in RAS/RAF mutant cancer cells. IK-595 exhibits potent single agent activity across a wide range of cancer model indications harboring various RAS/MAPK pathway alterations, including KRAS, NRAS, BRAF and NF1 mutations, and BRAF and CRAF fusions. The benefits of combining IK-595 with inhibitors targeting key resistance mechanisms both within the RAS/MAPK pathway and across parallel survival pathways has also been observed in multiple models. Additionally, IK-595 improved the response of KRAS-driven tumor models to standard of care chemotherapeutic agents, expanding the potential clinical opportunity for IK-595. Key to the design of IK-595 is its PK profile that enables transient high plasma drug exposure and flexible dosing schedules. Intermittent dosing of IK-595 every other day (QOD) or every three days (Q3D) in KRAS-mutant mouse tumor models shows similar efficacy and improved tolerability compared to daily dosing (QD), affording a larger therapeutic window. Preclinical pharmacology studies provide clear guidance to the clinical development plan of IK-595, where flexible dosing schedules, multiple expansion cohorts in RAS/RAF altered patient populations, and combination therapies with mediators of resistance will be explored. IK-595 is a novel MEK-RAF molecular glue that prolongs pathway inhibition, minimizing the potential for resistance, while providing an optimal therapeutic window for patients with RAS/RAF-driven cancer. Citation Format: Eric Haines, Rachel Catterall, Victor De Jesus, Daniel Hidalgo, Jill Cavanaugh, Marta Sanchez-Martin, Joseph D. Manna, Michael Burke, Bin Li, Sarah R. Wessel, Ao Yang, Sergio Santillana, Jeffrey Ecsedy, X. Michelle Zhang, Sabine K. Ruppel. IK-595, a best-in-class MEK-RAF molecular glue, drives broad and potent anti-tumor activity across RAS-MAPK pathway-altered cancers as a monotherapy and in combination [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 3296.

Abstract 1925: Wild-type RAS signaling is an essential therapeutic target in RAS-mutated cancers

Abstract Single-agent targeting of RAS-mutated cancers using RAF/MEK/ERK or PI3K/AKT pathway inhibitors is ineffective; blocking one pathway relieves negative feedback control of RTK signaling and hyperactivates parallel effector pathways. While combined MEK and PI3K inhibition is effective in preclinical models, toxicity of this combination prevents its clinical use. Alternative strategies for treating RAS-mutated cancers are essential. Therapeutics directly targeting mutated RAS proteins have the potential to spare normal cellular function thereby lessening overall toxicity. Unfortunately, direct RAS inhibition as a monotherapy does not fully block RAS effector signaling. RAS proteins show differential activation of RAF and PI3K pathways: KRAS potently activates RAF but poorly activates PI3K, whereas HRAS effectively activates PI3K but poorly activates RAF. Further, mutant RAS inhibition relieves negative feedback controls leading to rapid hyperactivation of RTK−WT RAS signaling. A more comprehensive understanding of the interplay between mutant RAS and RTK−WT RAS signaling is essential to developing rational therapeutic approaches to treat RAS-mutated cancers. We found that WT RAS enhanced mutant RAS-driven transformation by activating RAS effectors poorly engaged by mutated RAS. Further, inhibition of RAS effectors activated poorly by mutant RAS synergized with and limited resistance to mutant HRAS and KRAS inhibitors. The mutant HRAS inhibitor tipifarnib blocked PI3K signaling and synergized with MEK inhibitors in HRAS-mutated cancer cell lines; covalent KRASG12C inhibitors blocked MEK signaling and synergized with PI3K inhibitors in KRASG12C- mutated cell lines. Synergy between inhibitors of mutant RAS and RAS effectors was dependent on intact RTK/WT RAS signaling and was lost in both RASless or SOSless MEFs. Dual knock-out of WT RAS isoforms in KRAS- and HRAS-mutated cancer cell lines reduced PI3K signaling in KRAS-mutant cell lines and MAPK signaling in HRAS-mutant cell lines and reduced proliferation, confirming our findings in MEF cells. Overall, our data highlight the critical role of WT RAS isoforms in supporting mutant RAS signaling and should be considered when designing combination therapies in RAS-mutated cancers. Citation Format: Nancy E. Sealover, Bridget Finniff, Jacob Hughes, Hyun Lee, Robert L. Kortum. Wild-type RAS signaling is an essential therapeutic target in RAS-mutated cancers [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 1925.

Abstract 6484: Overcoming resistance to EGFR-TKI in NSCLC by simultaneously inhibition of anti-apoptotic proteins

Abstract Lung cancer is the second most common cancer worldwide with 1.8 million deaths in 2020 being the leading cause of cancer related death. With 86% of cases, non-small cell lung cancer (NSCLC) is the most prominent subtype. The survival rate improved over the past 20 years by application of targeted therapies. Driver mutations in protein kinases such as the epidermal growth factor receptor (EGFR) are frequent and have evolved as therapeutic targets in anti-cancer therapy. Inhibitors of receptor tyrosine kinase (RTKIs), prominently EGFR-TKIs, are effective in anti-cancer therapy but tumor evolution inevitably generates resistance. Thus, strategies for the treatment of patients with acquired resistance to RTKIs remains an urgent need. Resistance in solid tumors is overcome by a combination of bortezomib with the BH3-mimetic ABT-199 (Muenchow et al. 2020). Also, overcoming ALK-TKI resistance in NSCLC was described by Tanimoto et al. (2021) by proteasome inhibiton that mediates induction of NOXA. Furthermore, the novel described BCL-2 independent activity of ABT-199 to transactivate NOXA expression (Weller et al. 2022) represents a generally active principle by combining drugs with independent mechanism of action. We hypothesize, that combined treatment of EGFR-TKI Osimertinib (OSI) with BH3-mimetics enhances sensitivity to apoptosis induction. To explore this hypothesis, we investigated cell death induction by combined administration of OSI and BH3-mimetics or PIs in NSCLC differing in their mutational status. In addition, we analyzed the expression of BCL-2 family proteins and their relevance and regulation during RTKI-induced cell death by RNA sequencing and Western Blot. These analyses will be performed in cellular model systems of NSCLC with specific resistance mediating mutations of EGFR or activated parallel survival pathways. We found that BCL-2 inhibitors enhance efficacy of OSI in NSCLC, resulting in synergistic cell death induction. Additionally, the sensitivity to BCL-2 inhibitors tends to increase in OSI-resistant NSCLC. Western Blot analysis and RNA sequencing data of OSI-resistant NSCLC identified BCL-2 overexpression and an EMT signature as resistance-mediating mechanisms, which can be overcome by combination of OSI with BCL-2 inhibitors. Indeed, our data suggest that combination of OSI with BCL-2 inhibitors disrupts resistance to OSI in NSCLC. We propose that BCL-2 inhibitors sensitize OSI-resistant NSCLC to effectively induce cell death. Thus, studying the molecular mechanism of synergistic efficacy of RTKI/BCL-2 inhibitor combination therapies, should prompt future efforts in the clinical evaluation of combinatorial regimens. We hypothesize that a general therapeutic concept which relies on simultaneous blocking of driver mutations and survival-promoting BCL-2 proteins represents a generally active principle of a tumor-agnostic mechanism of action. Citation Format: Sandra Weller, Tobias Beigl, Frank Essmann, Annika Harsch, Hans-Georg Kopp, Tom Ekstrom. Overcoming resistance to EGFR-TKI in NSCLC by simultaneously inhibition of anti-apoptotic proteins [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 6484.

Abstract 682: Development of novel eIF4E inhibitors to potently and selectively suppress tumor growth across multiple indications

Abstract Despite considerable progress in treating cancer, drug resistance remains the primary hurdle to achieving cures in patients. Tumors often develop resistance through reactivation of the drug-targeted pathway, or activation of alternative parallel pathways, thereby maintaining the original downstream signaling effects. One of the furthest downstream effectors and critical nodes for many oncogenic signaling pathways is eukaryotic translation initiation factor 4E (eIF4E); the main regulator and rate limiting factor for protein synthesis. eIF4E is reactivated by many resistance mechanisms to promote translation of multiple pro-oncogenic factors including Cyclin D1/3, making it an attractive target to potentiate the anti-cancer activity of targeted therapies and to overcome drug resistance. Here, we present the development of novel, potent, and selective eIF4E inhibitors for use in both treatment-naïve and resistance settings across multiple tumor indications. To capitalize on the potential of targeting eIF4E, we developed a series of compounds with unique properties that maintain anti-tumor efficacy while minimizing toxicity. Our novel, selective, and potent oral eIF4E inhibitors (RBX-eIF4Ei) elicit a reversible, dose-dependent cell cycle arrest. Unlike targeting eIF4A, eIF4E inhibition selectively regulates translation of cancer-dependent pathway proteins instead of global protein synthesis, thus reducing on-target toxicity and increasing tolerability. Cellular profiling demonstrates RBX-eIF4Ei are highly selective, nanomolar inhibitors across many tumor types including, NSCLC, CRC, breast, and melanoma. Additionally, RBX-eIF4Ei demonstrate consistent efficacy across both sensitive and resistant cell lines, including intrinsic and acquired resistance models. Combining RBX-eIF4Ei with standard of care targeted therapies produces additive responses in both settings, suggesting its potential anti-neoplastic benefits post progression. In vivo, daily oral monotherapy treatment with RBX-EIF4Ei causes significant tumor growth inhibition across a variety of indications including BRAFmut CRC, BRAFmut melanoma and ER+ breast cancer, with minimal signs of toxicity. Intratumoral concentration of RBX-eIF4Ei correlate with significant tumor cell growth inhibition, as well as reductions in eIF4E target proteins, ODC1 and Cyclin D1. Combination studies with standard of care in both the treatment naïve and resistant settings are ongoing. Collectively, these data support the addition of RBX-eIF4Ei to standard of care in both the naïve and treatment resistance settings across a variety of indications including NSCLC, breast, CRC, and melanoma. IND enabling studies are planned, marking a significant step toward advancing these promising eIF4E inhibitors into clinical development. Citation Format: Matthew B. Friedersdorf, Devon R. Blake, Sarah E. Thompson, Roheeth Pavana, Ramamurty V. Changalvala, Andrew S. Truong, Krista Marran, Abha Bias, Jessica A. Sorrentino. Development of novel eIF4E inhibitors to potently and selectively suppress tumor growth across multiple indications [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 682.

ESI-MS analysis of Cu(I) binding to apo and Zn7 human metallothionein 1A, 2, and 3 identifies the formation of a similar series of metallated species with no individual isoform optimization for Cu(I).

Metallothioneins (MTs) are cysteine-rich proteins involved in metal homeostasis, heavy metal detoxification, and protection against oxidative stress. Whether the four mammalian MT isoforms exhibit different metal binding properties is not clear. In this paper, the Cu(I) binding properties of the apo MT1A, apo MT2, and apo MT3 are compared and the relative Cu(I) binding affinities are reported. In all three isoforms, Cu4, Cu6, and Cu10 species form cooperatively, and MT1A and MT2 also form a Cu13 species. The Cu(I) binding properties of Zn7-MT1A, Zn7-MT2, and Zn7-MT3 are compared systematically using isotopically pure 63Cu(I) and 68Zn(II). The species formed in each MT isoform were detected through electrospray ionization-mass spectrometry and further characterized using room temperature phosphorescence spectroscopy. The mixed metal Cu, Zn species forming in MT1A, MT2, and MT3 have similar stoichiometries and their emission spectral properties indicate that analogous clusters form in the three isoforms. Three parallel metallation pathways have been proposed through analysis of the detailed Cu, Zn speciation in MT1A, MT2, and MT3. Pathway ① results in Cu5Zn5-MT and Cu9Zn3-MT. Pathway ② involves Cu6Zn4-MT and Cu10Zn2-MT. Pathway ③ includes Cu8Zn4-MT. Speciation analysis indicates that Pathway ② is the preferred pathway for MT2. This is also evident in the phosphorescence spectra with the 750nm emission from Cu6Zn4-MT being most prominent in MT2. We see no evidence for different MT isoforms being optimized or exhibiting preferences for certain metals. We discuss the probable stoichiometry for MTs in vivo based on the in vitro determined binding constants.