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Approved inhibitors of KRASG12C prevent oncogenic activation by sequestering the inactive, GDP-bound (OFF) form rather than directly binding and inhibiting the active, GTP-bound (ON) form. This approach provides no direct target coverage of the active protein. Expectedly, adaptive resistance to KRASG12C (OFF)-only inhibitors is observed in association with increased expression and activity of KRASG12C(ON). To provide optimal KRASG12C target coverage, we have developed BBO-8520, a first-in-class, direct dual inhibitor of KRASG12C(ON) and (OFF) forms. BBO-8520 binds in the Switch-II/Helix3 pocket, covalently modifies the target cysteine and disables effector binding to KRASG12C(ON). BBO-8520 exhibits potent signaling inhibition in growth factor activated states where current (OFF)-only inhibitors demonstrate little measurable activity. In vivo, BBO-8520 demonstrates rapid target engagement and inhibition of signaling, resulting in durable tumor regression in multiple models, including those resistant to KRASG12C(OFF)-only inhibitors. BBO-8520 is in Phase 1 clinical trials in patients with KRASG12C non-small cell lung cancer (NSCLC).

The RAS family GTPases are the most frequently mutated oncogene family in human cancers. Activating mutations in either of the three RAS isoforms (HRAS, KRAS, or NRAS) are found in nearly 20% of all human tumors with NRAS mutated in ~25% of melanomas. Despite remarkable advancements in therapies targeted against mutant KRAS, NRAS-specific pharmacologics are lacking. Thus, development of inhibitors of NRAS would address a critical unmet need to treating primary tumors harboring NRAS mutations as well as BRAF-mutant melanomas, which frequently develop resistance to clinically approved BRAF inhibitors through NRAS mutation. Building upon our previous studies with the monobody NS1 that recognizes HRAS and KRAS but not NRAS, here we report the development of a monobody that specifically binds to both GDP and GTP-bound states of NRAS and inhibits NRAS-mediated signaling in a mutation-agnostic manner. Further, this monobody can be formatted into a genetically encoded NRAS-specific degrader. Our study highlights the feasibility of developing NRAS selective inhibitors for therapeutic efforts., Competing Interests: Competing interests: JPO, AK and SK are listed as inventors on a patent application on Monobodies targeting the nucleotide-free state of RAS files by the Medical University of South Carolina and New York University (No. 62/862,924). KWT, AK, and SK are listed as inventors on a patent application on mutant RAS targeting Monobodies filed by New York University (Application No. 63/121,903). AK and SK are listed as inventors on issued and pending patents on Monobody technology filed by The University of Chicago (US Patent 9512199 B2 and related pending applications), and on a pending patent on NRAS-selective monobodies (WO2023192915A1). SK is a co-founder and holds equity in Aethon Therapeutics; is a co-founder and holds equity in Revalia Bio; was an SAB member and received consulting fees from Black Diamond Therapeutics; has received research funding from Aethon Therapeutics, Argenx BVBA, Black Diamond Therapeutics, and Puretech Health. The other authors declare no competing interests. The other authors declare no competing interests. Ethics approval and consent to participate: This study did not use any human subjects, vertebrate animals or identifiable images from human research patients., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

In cancer research, RAS biology has been focused on only a handful of tumor types. While RAS genes have long been suspected as common contributors to a wide spectrum of cancer types, robust evidence is required to firmly establish their critical oncogenic significance. We present a data mining study using DepMap genome-wide CRISPR screening data, which provide substantial evidence to support the prominent pervasive oncogenic role and tissue-specific permissiveness of RAS gene mutations. Differential analysis of CRISPR effect scores identifies K- or N-RAS genes as the most differential gene in contrasts of (K-, N-, combined) RAS mutant versus wild-type cell lines across multiple tissue types. The distinguished tissue-specific pattern of KRAS vs. NRAS as top differential genes in subsets of tissue types and evidence from genome data supported the idea of KRAS- and NRAS-engaged tissue types. To our knowledge, this is the first report of prominent pervasive oncogenic role of RAS mutations revealed by gene dependency data that is beyond the current understanding of the oncogenic role of RAS genes and their well-known involved tissue types. Our findings strongly support RAS mutations as primary oncogenic drivers beyond traditionally recognized cancer types and offer insights into their tissue-specific permissiveness., (© 2024. The Author(s).)

To dissect variant-function relationships in the KRAS oncoprotein, we performed deep mutational scanning (DMS) screens for both wild-type and KRAS G12D mutant alleles. We defined the spectrum of oncogenic potential for nearly all possible KRAS variants, identifying several novel transforming alleles and elucidating a model to describe the frequency of KRAS mutations in human cancer as a function of transforming potential, mutational probability, and tissue-specific mutational signatures. Biochemical and structural analyses of variants identified in a KRAS G12D second-site suppressor DMS screen revealed that attenuation of oncogenic KRAS can be mediated by protein instability and conformational rigidity, resulting in reduced binding affinity to effector proteins, such as RAF and PI3-kinases, or reduced SOS-mediated nucleotide exchange activity. These studies define the landscape of single amino acid alterations that modulate the function of KRAS, providing a resource for the clinical interpretation of KRAS variants and elucidating mechanisms of oncogenic KRAS inactivation for therapeutic exploitation.

Deceased donor organs for transplantation are costly. Expenses include donor assessment, pre-operative care of acceptable donors, surgical organ recovery, preservation and transport, and other costs. US Organ Procurement Organizations (OPOs) serve defined geographic areas in which each OPO has exclusive organ recovery responsibilities including detailed reporting of costs. We sought to determine the costs of procuring deceased donor livers by examining reported organ acquisition costs from OPO cost reports. Using 6 years of US OPO cost report data for each OPO (2013-2018), we determined the average cost of recovering a viable (i.e., transplanted) liver for each of the 51 independent US OPOs. We examined predictors of these costs including the number of livers procured, the percent of nonviable livers, direct procurement costs, coordinator salaries, professional education, and local cost of living. A cost curve estimated the relationship between the cost of livers and the number of locally procured livers. The average cost of procured livers by individual OPO-year varied widely from $11 393 to $65 556 (average $31 659) over the six study years. An increase in the overall number of procured livers was associated with lower direct costs, administrative, and procurement overhead costs, but this association differed for imported livers. Cost per local liver decreased linearly for each additional liver, while importing more livers was only cost saving until 200 livers, with imported livers costing more ($39K vs. $31.7K). The largest predictor of variation in cost was the aggregate of direct costs (e.g., hospital costs) to recover the organ (57%). Cost increases were 2.5% per year (+$766/year). This information may be valuable in determining how OPOs might improve service to transplant centers and the patients they serve., (© 2024 The Author(s). Clinical Transplantation published by Wiley Periodicals LLC.)

Development of new targeted inhibitors for oncogenic KRAS mutants may benefit from insight into how a given mutation influences the accessibility of protein residues and how compounds interact with mutant or wild-type KRAS proteins. Targeted proteomic analysis, a key validation step in the KRAS inhibitor development process, typically involves both intact mass- and peptide-based methods to confirm compound localization or quantify binding. However, these methods may not always provide a clear picture of the compound binding affinity for KRAS, how specific the compound is to the target KRAS residue, and how experimental conditions may impact these factors. To address this, we have developed a novel top-down proteomic assay to evaluate in vitro KRAS4B-compound engagement while assessing relative quantitation in parallel. We present two applications to demonstrate the capabilities of our assay: maleimide-biotin labeling of a KRAS4B G12D cysteine mutant panel and treatment of three KRAS4B proteins (WT, G12C, and G13C) with small molecule compounds. Our results show the time- or concentration-dependence of KRAS4B-compound engagement in context of the intact protein molecule while directly mapping the compound binding site.

RAF kinases are integral to the RAS-MAPK signaling pathway, and proper RAF1 folding relies on its interaction with the chaperone HSP90 and the cochaperone CDC37. Understanding the intricate molecular interactions governing RAF1 folding is crucial for comprehending this process. Here, we present a cryo-EM structure of the closed-state RAF1-HSP90-CDC37 complex, where the C-lobe of the RAF1 kinase domain binds to one side of the HSP90 dimer, and an unfolded N-lobe segment of the RAF1 kinase domain threads through the center of the HSP90 dimer. CDC37 binds to the kinase C-lobe, mimicking the N-lobe with its HxNI motif. We also describe structures of HSP90 dimers without RAF1 and CDC37, displaying only N-terminal and middle domains, which we term the semi-open state. Employing 1 μs atomistic simulations, energetic decomposition, and comparative structural analysis, we elucidate the dynamics and interactions within these complexes. Our quantitative analysis reveals that CDC37 bridges the HSP90-RAF1 interaction, RAF1 binds HSP90 asymmetrically, and that HSP90 structural elements engage RAF1's unfolded region. Additionally, N- and C-terminal interactions stabilize HSP90 dimers, and molecular interactions in HSP90 dimers rearrange between the closed and semi-open states. Our findings provide valuable insight into the contributions of HSP90 and CDC37 in mediating client folding., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

KRAS , the most frequently mutated oncogene in human cancer, produces two isoforms, KRAS4a and KRAS4b, through alternative splicing. These isoforms differ in exon 4, which encodes the final 15 residues of the G-domain and hypervariable regions (HVRs), vital for trafficking and membrane localization. While KRAS4b has been extensively studied, KRAS4a has been largely overlooked. Our multidisciplinary study compared the structural and functional characteristics of KRAS4a and KRAS4b, revealing distinct structural properties and thermal stability. Position 151 influences KRAS4a's thermal stability, while position 153 affects binding to RAF1 CRD protein. Nuclear magnetic resonance analysis identified localized structural differences near sequence variations and provided a solution-state conformational ensemble. Notably, KRAS4a exhibits substantial transcript abundance in bile ducts, liver, and stomach, with transcript levels approaching KRAS4b in the colon and rectum. Functional disparities were observed in full-length KRAS variants, highlighting the impact of HVR variations on interaction with trafficking proteins and downstream effectors like RAF and PI3K within cells.

Individual oncogenic KRAS mutants confer distinct differences in biochemical properties and signaling for reasons that are not well understood. KRAS activity is closely coupled to protein dynamics and is regulated through two interconverting conformations: state 1 (inactive, effector binding deficient) and state 2 (active, effector binding enabled). Here, we use 31 P NMR to delineate the differences in state 1 and state 2 populations present in WT and common KRAS oncogenic mutants (G12C, G12D, G12V, G13D, and Q61L) bound to its natural substrate GTP or a commonly used nonhydrolyzable analog GppNHp (guanosine-5'-[(β,γ)-imido] triphosphate). Our results show that GppNHp-bound proteins exhibit significant state 1 population, whereas GTP-bound KRAS is primarily (90% or more) in state 2 conformation. This observation suggests that the predominance of state 1 shown here and in other studies is related to GppNHp and is most likely nonexistent in cells. We characterize the impact of this differential conformational equilibrium of oncogenic KRAS on RAF1 kinase effector RAS-binding domain and intrinsic hydrolysis. Through a KRAS G12C drug discovery, we have identified a novel small-molecule inhibitor, BBO-8956, which is effective against both GDP- and GTP-bound KRAS G12C. We show that binding of this inhibitor significantly perturbs state 1-state 2 equilibrium and induces an inactive state 1 conformation in GTP-bound KRAS G12C. In the presence of BBO-8956, RAF1-RAS-binding domain is unable to induce a signaling competent state 2 conformation within the ternary complex, demonstrating the mechanism of action for this novel and active-conformation inhibitor., Competing Interests: Conflict of interest F. M. is a consultant for the following companies: Amgen; Daiichi Ltd; Frontiers Medicine; Exuma Biotech, Ideaya Biosciences; Kura Oncology; PellePharm; Pfizer, Inc; PMV Pharma; and Quanta Therapeutics. F. M. is a consultant and cofounder for the following companies (with ownership interest including stock options): BridgeBio Pharma, Inc; DNAtrix Inc; Olema Pharmaceuticals, Inc; and Quartz. F. M. is the scientific advisor of the National Cancer Institute RAS Initiative at the Frederick National Laboratory for Cancer Research/Leidos Biomedical Research, Inc. F. M. has been recipient of research grants from Daiichi Sankyo and Gilead Sciences and has a current grant from Boehringer–Ingelheim. All the other authors declare that they have no conflicts of interest with the contents of this article., (Published by Elsevier Inc.)

Schwann cell tumors are the most common cancers of the peripheral nervous system and can arise in patients with neurofibromatosis type-1 (NF-1) or neurofibromatosis type-2 (NF-2). Functional interactions between NF1 and NF2 and broader mechanisms underlying malignant transformation of the Schwann lineage are unclear. Here we integrate bulk and single-cell genomics, biochemistry, and pharmacology across human samples, cell lines, and mouse allografts to identify cellular de-differentiation mechanisms driving malignant transformation and treatment resistance. We find DNA methylation groups of Schwann cell tumors can be distinguished by differentiation programs that correlate with response to the MEK inhibitor selumetinib. Functional genomic screening in NF1-mutant tumor cells reveals NF2 loss and PAK activation underlie selumetinib resistance, and we find that concurrent MEK and PAK inhibition is effective in vivo. These data support a de-differentiation paradigm underlying malignant transformation and treatment resistance of Schwann cell tumors and elucidate a functional link between NF1 and NF2., (© 2024. The Author(s).)

We present a novel method to determine engagement and specificity of KRAS4B-targeting compounds in vitro. By employing top-down mass spectrometry (MS), which analyzes intact and modified protein molecules (proteoforms), we can directly visualize and confidently characterize each KRAS4B species within compound-treated samples. Moreover, by employing targeted MS2 fragmentation, we can precisely localize each compound molecule to a specific residue on a given KRAS4B proteoform. This method allows us to comprehensively evaluate compound specificity, clearly detect nonspecific binding events, and determine the order and frequency with which they occur. We provide two proof-of-concept examples of our method employing publicly available compounds, along with detailed protocols for sample preparation, top-down MS data acquisition, targeted proteoform MS2 fragmentation, and analysis of the resulting data. Our results demonstrate the concentration dependence of KRAS4B-compound engagement and highlight the ability of top-down MS to directly map compound binding location(s) without disrupting the KRAS4B primary structure. Our hope is that this novel method may help accelerate the identification of new successful targeted inhibitors for KRAS4B and other RAS isoforms., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

RAS research has entered the world of translational and clinical science. Progress has been based on our appreciation of the role of RAS mutations in different types of cancer and the effects of these mutations on the biochemical, structural, and biophysical properties of the RAS proteins themselves, particularly KRAS, on which most attention has been focused. This knowledge base, while still growing, has enabled creative chemical approaches to targeting KRAS directly. Our understanding of RAS signaling pathways in normal and cancer cells plays an important role for developing RAS inhibitors but also continues to reveal new approaches to targeting RAS through disruption of signaling complexes and downstream pathways., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Virtually all clinicians agree that living donor renal transplantation is the optimal treatment for permanent loss of kidney function. Yet, living donor kidney transplantation has not grown in the United States for more than 2 decades. A virtual symposium gathered experts to examine this shortcoming and to stimulate and clarify issues salient to improving living donation. The ethical principles of rewarding kidney donors and the limits of altruism as the exclusive compelling stimulus for donation were emphasized. Concepts that donor incentives could save up to 40 000 lives annually and considerable taxpayer dollars were examined, and survey data confirmed voter support for donor compensation. Objections to rewarding donors were also presented. Living donor kidney exchanges and limited numbers of deceased donor kidneys were reviewed. Discussants found consensus that attempts to increase living donation should include removing artificial barriers in donor evaluation, expansion of living donor chains, affirming the safety of live kidney donation, and assurance that donors incur no expense. If the current legal and practice standards persist, living kidney donation will fail to achieve its true potential to save lives., Competing Interests: Declaration of Conflicting InterestsThe authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Dr Peters directs DCI Donor Services Research Fund and is a consultant for the Kidney Transplant Collaborative. Ms. Gershun is a Special Advisor to the Kidney Transplant Collaborative. The opinions expressed in this manuscript reflect those of the authors and not the institutions with which they are affiliated.

Cutaneous neurofibromas (cNFs) are the most common tumor in people with the rasopathy neurofibromatosis type 1. They number in hundreds or even thousands throughout the body, and currently, there are no effective interventions to prevent or treat these skin tumors. To facilitate the identification of novel and effective therapies, essential studies including a more refined understanding of cNF biology and the role of RAS signaling and downstream effector pathways responsible for cNF initiation, growth, and maintenance are needed. This review highlights the current state of knowledge of RAS signaling in cNF pathogenesis and therapeutic development for cNF treatment., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Biodiversity collections are experiencing a renaissance fueled by the intersection of informatics, emerging technologies, and the extended use and interpretation of specimens and archived databases. In this article, we explore the potential for transformative research in ecology integrating biodiversity collections, stable isotope analysis (SIA), and environmental informatics. Like genomic DNA, SIA provides a common currency interpreted in the context of biogeochemical principles. Integration of SIA data across collections allows for evaluation of long-term ecological change at local to continental scales. Challenges including the analysis of sparse samples, a lack of information about baseline isotopic composition, and the effects of preservation remain, but none of these challenges is insurmountable. The proposed research framework interfaces with existing databases and observatories to provide benchmarks for retrospective studies and ecological forecasting. Collections and SIA add historical context to fundamental questions in freshwater ecological research, reference points for ecosystem monitoring, and a means of quantitative assessment for ecosystem restoration.

RIT1 is a RAS guanosine triphosphatase (GTPase) that regulates different aspects of signal transduction and is mutated in lung cancer, leukemia, and in the germline of individuals with Noonan syndrome. Pathogenic RIT1 proteins promote mitogen-activated protein kinase (MAPK) hyperactivation; however, this mechanism remains poorly understood. Here, we show that RAF kinases are direct effectors of membrane-bound mutant RIT1 necessary for MAPK activation. We identify critical residues in RIT1 that facilitate interaction with membrane lipids and show that these are necessary for association with RAF kinases and MAPK activation. Although mutant RIT1 binds to RAF kinases directly, it fails to activate MAPK signaling in the absence of classical RAS proteins. Consistent with aberrant RAF/MAPK activation as a driver of disease, we show that pathway inhibition alleviates cardiac hypertrophy in a mouse model of RIT1 mutant Noonan syndrome. These data shed light on the function of pathogenic RIT1 and identify avenues for therapeutic intervention.

Localized dynamics of RAS, including regions distal to the nucleotide-binding site, is of high interest for elucidating the mechanisms by which RAS proteins interact with effectors and regulators and for designing inhibitors. Among several oncogenic mutants, methyl relaxation dispersion experiments reveal highly synchronized conformational dynamics in the active (GMPPNP-bound) KRAS G13D , which suggests an exchange between two conformational states in solution. Methyl and 31 P NMR spectra of active KRAS G13D in solution confirm a two-state ensemble interconverting on the millisecond timescale, with a major P γ atom peak corresponding to the dominant State 1 conformation and a secondary peak indicating an intermediate state different from the known State 2 conformation recognized by RAS effectors. High-resolution crystal structures of active KRAS G13D and KRAS G13D -RAF1 RBD complex provide snapshots of the State 1 and 2 conformations, respectively. We use residual dipolar couplings to solve and cross-validate the structure of the intermediate state of active KRAS G13D , showing a conformation distinct from those of States 1 and 2 outside the known flexible switch regions. The dynamic coupling between the conformational exchange in the effector lobe and the breathing motion in the allosteric lobe is further validated by a secondary mutation in the allosteric lobe, which affects the conformational population equilibrium., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Sprouty-related EVH-1 domain-containing (SPRED) proteins are a family of proteins that negatively regulate the RAS-Mitogen-Activated Protein Kinase (MAPK) pathway, which is involved in the regulation of the mitogenic response and cell proliferation. However, the mechanism by which these proteins affect RAS-MAPK signaling has not been elucidated. Patients with mutations in SPRED give rise to unique disease phenotypes; thus, we hypothesized that distinct interactions across SPRED proteins may account for alternative nodes of regulation. To characterize the SPRED interactome and evaluate how members of the SPRED family function through unique binding partners, we performed affinity purification mass spectrometry. We identified 90-kDa ribosomal S6 kinase 2 (RSK2) as a specific interactor of SPRED2 but not SPRED1 or SPRED3. We identified that the N-terminal kinase domain of RSK2 mediates the interaction between amino acids 123 to 201 of SPRED2. Using X-ray crystallography, we determined the structure of the SPRED2-RSK2 complex and identified the SPRED2 motif, F145A, as critical for interaction. We found that the formation of this interaction is regulated by MAPK signaling events. We also find that this interaction between SPRED2 and RSK2 has functional consequences, whereby the knockdown of SPRED2 resulted in increased phosphorylation of RSK substrates, YB1 and CREB. Furthermore, SPRED2 knockdown hindered phospho-RSK membrane and nuclear subcellular localization. We report that disruption of the SPRED2-RSK complex has effects on RAS-MAPK signaling dynamics. Our analysis reveals that members of the SPRED family have unique protein binding partners and describes the molecular and functional determinants of SPRED2-RSK2 complex dynamics., Competing Interests: Conflict of interest P. C is a founder and advisory board of Venthera, Inc. The other authors declare no competing interests. F. M. is a consultant for the following companies: Amgen; Daiichi Ltd, Frontier Medicines, Exuma Biotech, Ideaya Biosciences, Kura Oncology, Leidos Biomedical Research, Inc, PellePharm, Pfizer Inc, PMV Pharma and Quanta Therapeutics. F. M. is a consultant and co-founder for the following companies (with ownership interest including stock options): BridgeBio; DNAtrix Inc; Olema Pharmaceuticals, Inc; and Quartz. F. M. is the scientific director of the National Cancer Institute (NCI) RAS Initiative at the Frederick National Laboratory for Cancer Research/Leidos Biomedical Research, Inc. F. M. has been a recipient of research grants from Daiichi Sankyo, Gilead Sciences and has a current grant from Boehringer-Ingelheim., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

The majority of pathogenic mutations in the neurofibromatosis type I ( NF1 ) gene reduce total neurofibromin protein expression through premature truncation or microdeletion, but it is less well understood how loss-of-function missense variants drive NF1 disease. We have found that patient variants in codons 844 to 848, which correlate with a severe phenotype, cause protein instability and exert an additional dominant-negative action whereby wild-type neurofibromin also becomes destabilized through protein dimerization. We have used our neurofibromin cryogenic electron microscopy structure to predict and validate other patient variants that act through a similar mechanism. This provides a foundation for understanding genotype-phenotype correlations and has important implications for patient counseling, disease management, and therapeutics.

Objectives: The aim of this study was to show how the US government could save approximately 47 000 patients with chronic kidney failure each year from suffering on dialysis and premature death by compensating living kidney donors enough to completely end the kidney shortage., Methods: Supply and demand analysis was used to estimate the number of donated kidneys needed to end the kidney shortage and the level of compensation required to encourage this number of donations. These results were then input into a detailed cost-benefit analysis to estimate the economic value of kidney transplantation to (1) the average kidney recipient and their caregiver, (2) taxpayers, and (3) society in general., Results: We estimate half of patients diagnosed with kidney failure each year-approximately 62 000 patients-could be saved from suffering on dialysis and premature death if they could receive an average of 1½ kidney transplants. However, currently there are only enough donated kidneys to save approximately 15 000 patients. To encourage sufficient donations to save the other 47 000 patients, the government would have to compensate living kidney donors approximately $77 000 (±50%) per donor. The value of transplantation to an average kidney recipient (and caregiver) would be approximately $1.5 million, and the savings from the recipient not needing expensive dialysis treatments would be approximately $1.2 million., Conclusions: This analysis reveals the huge benefit that compensating living kidney donors would provide to patients with kidney failure and their caregivers and, conversely, the huge cost that is being imposed on these patients and their families by the current legal prohibition against such compensation., (Copyright © 2022. Published by Elsevier Inc.)

Recently, screens for mediators of resistance to FLT3 and ABL kinase inhibitors in leukemia resulted in the discovery of LZTR1 as an adapter of a Cullin-3 RING E3 ubiquitin ligase complex responsible for the degradation of RAS GTPases. In parallel, dysregulated LZTR1 expression via aberrant splicing and mutations was identified in clonal hematopoietic conditions. Here we identify that loss of LZTR1, or leukemia-associated mutants in the LZTR1 substrate and RAS GTPase RIT1 that escape degradation, drives hematopoietic stem cell (HSC) expansion and leukemia in vivo. Although RIT1 stabilization was sufficient to drive hematopoietic transformation, transformation mediated by LZTR1 loss required MRAS. Proteolysis targeting chimeras (PROTAC) against RAS or reduction of GTP-loaded RAS overcomes LZTR1 loss-mediated resistance to FLT3 inhibitors. These data reveal proteolysis of noncanonical RAS proteins as novel regulators of HSC self-renewal, define the function of RIT1 and LZTR1 mutations in leukemia, and identify means to overcome drug resistance due to LZTR1 downregulation., Significance: Here we identify that impairing proteolysis of the noncanonical RAS GTPases RIT1 and MRAS via LZTR1 downregulation or leukemia-associated mutations stabilizing RIT1 enhances MAP kinase activation and drives leukemogenesis. Reducing the abundance of GTP-bound KRAS and NRAS overcomes the resistance to FLT3 kinase inhibitors associated with LZTR1 downregulation in leukemia. This article is highlighted in the In This Issue feature, p. 2221., (©2022 The Authors; Published by the American Association for Cancer Research.)

SHOC2 acts as a strong synthetic lethal interactor with MEK inhibitors in multiple KRAS cancer cell lines. SHOC2 forms a heterotrimeric complex with MRAS and PP1C that is essential for regulating RAF and MAPK-pathway activation by dephosphorylating a specific phosphoserine on RAF kinases. Here we present the high-resolution crystal structure of the SHOC2-MRAS-PP1C (SMP) complex and apo-SHOC2. Our structures reveal that SHOC2, MRAS, and PP1C form a stable ternary complex in which all three proteins synergistically interact with each other. Our results show that dephosphorylation of RAF substrates by PP1C is enhanced upon interacting with SHOC2 and MRAS. The SMP complex forms only when MRAS is in an active state and is dependent on SHOC2 functioning as a scaffolding protein in the complex by bringing PP1C and MRAS together. Our results provide structural insights into the role of the SMP complex in RAF activation and how mutations found in Noonan syndrome enhance complex formation, and reveal new avenues for therapeutic interventions., (© 2022. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Cancer cells utilize multiple nutrient scavenging mechanisms to support growth and survival in nutrient-poor, hypoxic tumor microenvironments. Among these mechanisms, macropinocytosis has emerged as an important pathway of extracellular nutrient acquisition in cancer cells, particularly in tumors with activated RAS signaling, such as pancreatic cancer. However, the absence of a clinically available inhibitor, as well as the gap of knowledge in macropinocytosis regulation, remain a hurdle for its use for cancer therapy. Here, we use the Informer set library to identify novel regulators of macropinocytosis-dependent growth in pancreatic cancer cells. Understanding how these regulators function will allow us to provide novel opportunities for therapeutic intervention.

Receptor tyrosine kinase (RTK)-RAS signalling through the downstream mitogen-activated protein kinase (MAPK) cascade regulates cell proliferation and survival. The SHOC2-MRAS-PP1C holophosphatase complex functions as a key regulator of RTK-RAS signalling by removing an inhibitory phosphorylation event on the RAF family of proteins to potentiate MAPK signalling 1 . SHOC2 forms a ternary complex with MRAS and PP1C, and human germline gain-of-function mutations in this complex result in congenital RASopathy syndromes 2-5 . However, the structure and assembly of this complex are poorly understood. Here we use cryo-electron microscopy to resolve the structure of the SHOC2-MRAS-PP1C complex. We define the biophysical principles of holoenzyme interactions, elucidate the assembly order of the complex, and systematically interrogate the functional consequence of nearly all of the possible missense variants of SHOC2 through deep mutational scanning. We show that SHOC2 binds PP1C and MRAS through the concave surface of the leucine-rich repeat region and further engages PP1C through the N-terminal disordered region that contains a cryptic RVXF motif. Complex formation is initially mediated by interactions between SHOC2 and PP1C and is stabilized by the binding of GTP-loaded MRAS. These observations explain how mutant versions of SHOC2 in RASopathies and cancer stabilize the interactions of complex members to enhance holophosphatase activity. Together, this integrative structure-function model comprehensively defines key binding interactions within the SHOC2-MRAS-PP1C holophosphatase complex and will inform therapeutic development ., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

RAF protein kinases are effectors of the GTP-bound form of small guanosine triphosphatase RAS and function by phosphorylating MEK. We showed here that the expression of ARAF activated RAS in a kinase-independent manner. Binding of ARAF to RAS displaced the GTPase-activating protein NF1 and antagonized NF1-mediated inhibition of RAS. This reduced ERK-dependent inhibition of RAS and increased RAS-GTP. By this mechanism, ARAF regulated the duration and consequences of RTK-induced RAS activation and supported the RAS output of RTK-dependent tumor cells. In human lung cancers with EGFR mutation, amplification of ARAF was associated with acquired resistance to EGFR inhibitors, which was overcome by combining EGFR inhibitors with an inhibitor of the protein tyrosine phosphatase SHP2 to enhance inhibition of nucleotide exchange and RAS activation., Competing Interests: Declaration of interests N.R. is on the scientific advisory board (SAB) and owns equity in Beigene, Zai Labs, MapKure, Ribon, and Effector. N.R. is also on the SAB of Astra Zeneca and Chugai and a past SAB member of Novartis, Millennium-Takeda, Kura, and Araxes. N.R. is a consultant to RevMed, Tarveda, Array-Pfizer, Boeringher Ingelheim, and Eli Lilly. He receives research funding from Revmed, Astra Zeneca, Array Pfizer, and Boerhinger Ingelheim and owns equity in Kura Oncology and Fortress. Z.Y. is a past SAB member of MapKure and currently an employee of Loxo Oncology at Lilly. R.Y. has received research support from Array BioPharma/Pfizer, Novartis, and Boehringer Ingelheim (Ingelheim, Germany) and served as an advisor for Array BioPharma/Pfizer, Mirati Therapeutics, and Natera. O.A.W. received research funding from H3B Biomedicine and personal fees from H3B Biomedicine, Foundation Medicine Inc, Merck, and Jansen. C.M.R. has consulted regarding cancer drug development with AbbVie, Amgen, Ascentage, Bicycle, Celgene, Daiichi Sankyo, Genentech/Roche, Ipsen, Loxo, and PharmaMar and serves on the SAB of Bridge Medicines and Harpoon Therapeutics. P.A.J. has received consulting fees from AstraZeneca, Boehringer Ingelheim, Pfizer, Roche/Genentech, Merrimack Pharmaceuticals, Chugai Pharmaceuticals, Ariad Pharmaceuticals, Eli Lilly and Company, Araxes Pharma, Ignyta, Novartis, Mirati Therapeutics, Takeda Oncology, Daiichi Sankyo, Biocartis, Voronoi, SFJ Pharmaceuticals, and Loxo Oncology; receives post-marketing royalties from DFCI-owned intellectual property on EGFR mutations licensed to Lab Corp; has sponsored research agreements with Astra Zeneca, Daichi Sankyo, Boehringer Ingelheim, PUMA, Eli Lilly, Astellas Pharmaceuticals, and Takeda Oncology; and has stock ownership in Gatekeeper Pharmaceuticals and Loxo Oncology. F.M. is shareholder in Olema, Opna, Kura, BridgeBio, Avidity, Quartz, Quadriga, and Wellspring and is a consultant for Amgen, Pfizer, Daiichi Sankyo, Ideaya, BridgeBio, PMV, Caris, and Aduro., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

RAS GTPases are highly conserved proteins involved in the regulation of mitogenic signaling. We have previously described a novel Cullin 3 RING E3 ubiquitin ligase complex formed by the substrate adaptor protein LZTR1 that binds, ubiquitinates, and promotes proteasomal degradation of the RAS GTPase RIT1. In addition, others have described that this complex is also responsible for the ubiquitination of classical RAS GTPases. Here, we have analyzed the phenotypes of Lztr1 loss-of-function mutants in both fruit flies and mice and have demonstrated a biochemical preference for their RIT1 orthologs. Moreover, we show that Lztr1 is haplosufficient in mice and that embryonic lethality of the homozygous null allele can be rescued by deletion of Rit1 . Overall, our results indicate that, in model organisms, RIT1 orthologs are the preferred substrates of LZTR1., Competing Interests: AC, LR, JG, AC, KR, AU, GJ No competing interests declared, FM is a consultant for Ideaya Biosciences, Kura Oncology, Leidos Biomedical Research, Pfizer, Daiichi Sankyo, Amgen, PMV Pharma, OPNA-IO, and Quanta Therapeutics and has received research grants from Boehringer-Ingelheim and is a consultant for and cofounder of BridgeBio Pharma, PC PC is a founder and advisory board of Venthera, (© 2022, Cuevas-Navarro et al.)

CD70 is a member of the tumor necrosis factor receptor superfamily. Emerging data indicate that CD70 may be a suitable target for various malignancies. We investigated the expression of CD70 in cutaneous and systemic T-cell lymphomas and conducted preclinical studies of SGN-CD70A, a CD70-directed antibody-drug conjugate (ADC), using patient-derived xenograft cutaneous T-cell lymphoma (CTCL PDX) models. CD70 expression was examined by immunohistochemical (IHC) stains in 49 diagnostic specimens of T-cell lymphomas. The activities of SGN-CD70A in growth inhibition and apoptosis induction were examined in CTCL cell lines and primary CTCL tumor cells. Using previously established CTCL PDXs, we conducted a dose-finding trial followed by a phase 2-like trial to evaluate the optimal dosing and the efficacy of SGN-CD70A in tumor-bearing PDX animals. The therapeutic efficacy of SGN-CD70A was measured by tumor-associated cell-free DNA (cfDNA) and survival of treated PDXs. We found that CD70 is highly expressed in T-cell lymphomas, especially in CTCL. SGN-CD70A inhibited cell growth and induced apoptosis in CD70-expressing CTCL cell lines and primary tumors cells. Additionally, SGN-CD70A at 100 μg/kg and 300 μg/kg prolonged the survival of PDXs in a dose-dependent manner. Finally, treatment with 3 doses of SGN-CD70A at 300 μg/kg was superior to a single-dose treatment in survival prolongation (median survival: 111 days vs 39 days; P = .017). Most importantly, multiple dosing of SGN-CD70A induced complete eradication of established tumors in PDXs measured by cfDNA. Our results demonstrated marked antitumor activity of SGN-CD70A in CTCL PDXs, providing compelling support for its clinical investigation., (© 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Despite the discovery of RAS oncogenes in human tumor DNA 40 years ago, the development of effective targeted therapies directed against RAS has lagged behind those more successful advancements in the field of therapeutic tyrosine kinase inhibitors targeting other oncogenes such as EGFR , ALK , and ROS1 . The discoveries that (1) malignant RAS oncogenes differ from their wild-type counterparts by only a single amino acid change and (2) covalent inhibition of the cysteine residue at codon 12 of KRAS G12C in its inactive GDP-bound state resulted in effective inhibition of oncogenic RAS signaling and have catalyzed a dramatic shift in mindset toward KRAS -driven cancers. Although the development of allele-selective KRAS G12C inhibitors has changed a treatment paradigm, the clinical activity of these agents is more modest than tyrosine kinase inhibitors targeting other oncogene-driven cancers. Heterogeneous resistance mechanisms generally result in the restoration of RAS/mitogen-activated protein kinase pathway signaling. Many approaches are being evaluated to overcome this resistance, with many combinatorial clinical trials ongoing. Furthermore, because KRAS G12D and KRAS G12V are more prevalent than KRAS G12C , there remains an unmet need for additional therapeutic strategies for these patients. Thus, our current translational standing could be described as "the end of the beginning," with additional discovery and research innovation needed to address the enormous disease burden imposed by RAS -mutant cancers. Here, we describe the development of KRAS G12C inhibitors, the challenges of resistance to these inhibitors, strategies to mitigate that resistance, and new approaches being taken to address other RAS -mutant cancers.

Summary: The RAS Initiative was launched in 2013 to address unmet clinical needs of patients with KRAS-driven cancers. The Initiative is based at Frederick National Laboratory for Cancer Research in Frederick, MD, and involves multiple collaborations with the RAS research community in academia and industry with the shared goal of developing RAS therapies., (©2022 American Association for Cancer Research.)

RAS proteins cycling between the active-form (GTP-bound) and inactive-form (GDP-bound) play a key role in cell signaling pathways that control cell survival, proliferation, and differentiation. Mutations at codon 12, 13, and 61 in RAS are known to attenuate its GTPase activity favoring the RAS active state and constitutively active downstream signaling. This hyperactivation accounts for various malignancies including pancreatic, lung, and colorectal cancers. Active KRAS is found to exist in equilibrium between two rapidly interconverting conformational states (State1-State2) in solution. Due to this dynamic feature of the protein, the 1 H- 15 N correlation cross-peak signals of several amino acid (AA) residues of KRAS belonging to the flexible loop regions are absent from its 2D 1 H- 15 N HSQC spectrum within and near physiological solution pH. A threonine to serine mutation at position 35 (T35S) shifts the interconverting equilibrium to State1 conformation and enables the emergence of such residues in the 2D 1 H- 15 N HSQC spectrum due to gained conformational rigidity. We report here the 1 H N , 15 N, and 13 C backbone resonance assignments for the 19.2 kDa (AA 1-169) protein constructs of KRAS-GppNHp harboring T35S mutation (KRAS T35S/C118S -GppNHp) and of its oncogenic counterpart harboring the Q61L mutation (KRAS T35S/Q61L/C118S -GppNHp) using heteronuclear, multidimensional NMR spectroscopy at 298 K. High resolution NMR data allowed the unambiguous assignments of 1 H- 15 N correlation cross-peaks for all the residues except for Met1. Furthermore, 2D 1 H- 15 N HSQC overlay of two proteins assisted in determination of Q61L mutation-induced chemical shift perturbations for select residues in the regions of P-loop, Switch-II, and helix α3., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

KRAS is the most frequently mutated RAS protein in cancer patients, and it is estimated that about 20% of the cancer patients in the United States carried mutant RAS proteins. To accelerate therapeutic development, structures and dynamics of RAS proteins had been extensively studied by various biophysical techniques for decades. Although 31 P NMR studies revealed population equilibrium of the two major states in the active GMPPNP-bound form, more complex conformational dynamics in RAS proteins and oncogenic mutants subtly modulate the interactions with their downstream effectors. We established a set of customized NMR relaxation dispersion techniques to efficiently and systematically examine the ms-μs conformational dynamics of RAS proteins. This method allowed us to observe varying synchronized motions that connect the effector and allosteric lobes in KRAS. We demonstrated the role of conformational dynamics of KRAS in controlling its interaction with the Ras-binding domain of the downstream effector RAF1, the first kinase in the MAPK pathway. This allows one to explain, as well as to predict, the altered binding affinities of various KRAS mutants, which was neither previously reported nor apparent from the structural perspective.

RAF inhibitors unexpectedly induce ERK signaling in normal and tumor cells with elevated RAS activity. Paradoxical activation is believed to be RAS dependent. In this study, we showed that LY3009120, a pan-RAF inhibitor, can unexpectedly cause paradoxical ERK activation in KRAS G12C -dependent lung cancer cell lines, when KRAS is inhibited by ARS1620, a KRAS G12C inhibitor. Using H/N/KRAS-less mouse embryonic fibroblasts, we discovered that classical RAS proteins are not essential for RAF inhibitor-induced paradoxical ERK signaling. In their absence, RAF inhibitors can induce ERK phosphorylation, ERK target gene transcription, and cell proliferation. We further showed that the MRAS/SHOC2 complex is required for this process. This study highlights the complexity of the allosteric RAF regulation by RAF inhibitors, and the importance of other RAS-related proteins in this process., Competing Interests: Competing interest statement: F.M. is a consultant for the following companies: Amgen; Daiichi Ltd., Frontiers Med, Exuma Biotech, Ideaya Biosciences, Kura Oncology, Leidos Biomedical Research, Inc., PellePharm, Pfizer Inc., PMV Pharma and Quanta Therapeutics. F.M. is a consultant for and cofounder of the following companies (with ownership interest including stock options): BridgeBio; DNAtrix Inc., Olema Pharmaceuticals, Inc., and Quartz. F.M. is the scientific director of the National Cancer Institute RAS Initiative at the Frederick National Laboratory for Cancer Research/Leidos Biomedical Research, Inc. F.M. has been a recipient of research grants from Daiichi Sankyo and Gilead Sciences and has a current grant from Boehringer-Ingelheim., (Copyright © 2022 the Author(s). Published by PNAS.)

RAS is a signaling protein associated with the cell membrane that is mutated in up to 30% of human cancers. RAS signaling has been proposed to be regulated by dynamic heterogeneity of the cell membrane. Investigating such a mechanism requires near-atomistic detail at macroscopic temporal and spatial scales, which is not possible with conventional computational or experimental techniques. We demonstrate here a multiscale simulation infrastructure that uses machine learning to create a scale-bridging ensemble of over 100,000 simulations of active wild-type KRAS on a complex, asymmetric membrane. Initialized and validated with experimental data (including a new structure of active wild-type KRAS), these simulations represent a substantial advance in the ability to characterize RAS-membrane biology. We report distinctive patterns of local lipid composition that correlate with interfacially promiscuous RAS multimerization. These lipid fingerprints are coupled to RAS dynamics, predicted to influence effector binding, and therefore may be a mechanism for regulating cell signaling cascades., (Copyright © 2021 the Author(s). Published by PNAS.)

In this review, I provide a brief history of the discovery of RAS and the GAPs and GEFs that regulate its activity from a personal perspective. Much of this history has been driven by technological breakthroughs that occurred concurrently, such as molecular cloning, cDNA expression to analyze RAS proteins and their structures, and application of PCR to detect mutations. I discuss the RAS superfamily and RAS proteins as therapeutic targets, including recent advances in developing RAS inhibitors. I also describe the role of the RAS Initiative at Frederick National Laboratory for Cancer Research in advancing development of RAS inhibitors and providing new insights into signaling complexes and interaction of RAS proteins with the plasma membrane., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: The goal is to provide a national analysis of organ procurement organization (OPO) costs., Methods: Five years of data, for 51 of the 58 OPOs (2013-2017, a near census) were obtained under a FOIA. OPOs are not-for-profit federal contractors with a geographic monopoly. A generalized 15-factor cost regression model was estimated with adjustments to precision of estimates (P) for repeated observations. Selected measures were validated by comparison to IRS forms., Results: Decease donor organ procurement is a $1B/y operation with over 26 000 transplants/y. Over 60% of the cost of an organ is overhead. Profits are $2.3M/OPO/y. Total assets are $45M/OPO and growing at 9%/y. "Tissue" (skin, bones) generates $2-3M profit/OPO/y. A comparison of the highest with the lower costing OPOs showed our model explained 75% of the cost difference. Comparing costs across OPOs showed that highest-cost OPOs are smaller, import 44% more kidneys, face 6% higher labor costs, report 98% higher compensation for support personnel, spend 46% more on professional education, have 44% fewer assets, compensate their Executive Director 36% less, and have a lower procurement performance (SDRR) score., Conclusions: Profits and assets suggest that OPOs are fiscally secure and OPO finances are not a source of the organ shortage. Asset accumulation ($45M/OPO) of incumbents suggests establishing a competitive market with new entrants is unlikely. Kidney-cost allocations support tissue procurements. Professional education spending does not reduce procurement costs. OPO importing of organs from other OPOs is a complex issue possibly increasing cost ($6K/kidney)., Competing Interests: The authors declare no funding or conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

The spindle assembly checkpoint (SAC) functions as a sensor of unattached kinetochores that delays mitotic progression into anaphase until proper chromosome segregation is guaranteed. 1 , 2 Disruptions to this safety mechanism lead to genomic instability and aneuploidy, which serve as the genetic cause of embryonic demise, congenital birth defects, intellectual disability, and cancer. 3 , 4 However, despite the understanding of the fundamental mechanisms that control the SAC, it remains unknown how signaling pathways directly interact with and regulate the mitotic checkpoint activity. In response to extracellular stimuli, a diverse network of signaling pathways involved in cell growth, survival, and differentiation are activated, and this process is prominently regulated by the Ras family of small guanosine triphosphatases (GTPases). 5 Here we show that RIT1, a Ras-related GTPase that regulates cell survival and stress response, 6 is essential for timely progression through mitosis and proper chromosome segregation. RIT1 dissociates from the plasma membrane (PM) during mitosis and interacts directly with SAC proteins MAD2 and p31 comet in a process that is regulated by cyclin-dependent kinase 1 (CDK1) activity. Furthermore, pathogenic levels of RIT1 silence the SAC and accelerate transit through mitosis by sequestering MAD2 from the mitotic checkpoint complex (MCC). Moreover, SAC suppression by pathogenic RIT1 promotes chromosome segregation errors and aneuploidy. Our results highlight a unique function of RIT1 compared to other Ras GTPases and elucidate a direct link between a signaling pathway and the SAC through a novel regulatory mechanism., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Acute myeloid leukemia patients refractory to induction therapy or relapsed within one year have poor outcomes. Autocrine production of hepatocyte growth factor by myeloid blasts drives leukemogenesis in pre-clinical models. A phase Ib trial evaluated ficlatuzumab, a first-in-class anti-HGF antibody, in combination with cytarabine in this high-risk population. Dose-limiting toxicities were not observed, and 20 mg/kg was established as the recommended phase II dose. The most frequent treatment-related adverse event was febrile neutropenia. Among 17 evaluable patients, the overall response rate was 53%, all complete remissions. Phospho-proteomic mass cytometry showed potent on-target suppression of p-MET after ficlatuzumab treatment and that attenuation of p-S6 was associated with clinical response. Multiplexed single cell RNA sequencing using prospectively acquired patient specimens identified interferon response genes as adverse predictive factors. The ficlatuzumab and cytarabine combination is well-tolerated with favorable efficacy. High-dimensional analyses at single-cell resolution represent promising approaches for identifying biomarkers of response and mechanisms of resistance in prospective clinical studies., Competing Interests: Conflict of Interests: The authors declare no potential conflicts of interest.

RAS proteins are molecular switches that interact with effector proteins when bound to guanosine triphosphate, stimulating downstream signaling in response to multiple stimuli. Although several canonical downstream effectors have been extensively studied and tested as potential targets for RAS-driven cancers, many of these remain poorly characterized. In this study, we undertook a biochemical and structural approach to further study the role of Sin1 as a RAS effector. Sin1 interacted predominantly with KRAS isoform 4A in cells through an atypical RAS-binding domain that we have characterized by X-ray crystallography. Despite the essential role of Sin1 in the assembly and activity of mTORC2, we find that the interaction with RAS is not required for these functions. Cells and mice expressing a mutant of Sin1 that is unable to bind RAS are proficient for activation and assembly of mTORC2. Our results suggest that Sin1 is a bona fide RAS effector that regulates downstream signaling in an mTORC2-independent manner., Competing Interests: Competing interest statement: F.M. is a consultant for Ideaya Biosciences, Kura Oncology, Leidos Biomedical Research, Pfizer, Daiichi Sankyo, Amgen, PMV Pharma, OPNA-IO, and Quanta Therapeutics and has received research grants from Boehringer-Ingelheim and is a consultant for and cofounder of BridgeBio Pharma. P.C. is a cofounder and advisory board member of Venthera.

UDP-glucose pyrophosphorylase 2 (UGP2), the enzyme that synthesizes uridine diphosphate (UDP)-glucose, rests at the convergence of multiple metabolic pathways, however, the role of UGP2 in tumor maintenance and cancer metabolism remains unclear. Here, we identify an important role for UGP2 in the maintenance of pancreatic ductal adenocarcinoma (PDAC) growth in both in vitro and in vivo tumor models. We found that transcription of UGP2 is directly regulated by the Yes-associated protein 1 (YAP)-TEA domain transcription factor (TEAD) complex, identifying UGP2 as a bona fide YAP target gene. Loss of UGP2 leads to decreased intracellular glycogen levels and defects in N-glycosylation targets that are important for the survival of PDACs, including the epidermal growth factor receptor (EGFR). These critical roles of UGP2 in cancer maintenance, metabolism, and protein glycosylation may offer insights into therapeutic options for otherwise intractable PDACs., Competing Interests: Competing interest statement: A.L.W. has received research funding from Oncogenuity. M.S. has received research funds from Puma Biotechnology, AstraZeneca, Daiichi-Sankyo, Immunomedics, Targimmune, and Menarini Ricerche. He is on the scientific advisory board of Menarini Ricerche and the Bioscience Institute, a cofounder of medendi.org, and an employee and stockholder of AstraZeneca. F.M. is a consultant for Daiichi-Sankyo, Pfizer, Amgen, BridgeBio, Olema, OPNA-IO, PMV, Quanta, and Remedy Plan and has received research funding from Daiichi-Sankyo., (Copyright © 2021 the Author(s). Published by PNAS.)

To predict whether the COVID-19 pandemic and transplant center responses could have resulted in preventable deaths, we analyzed registry information of the US end-stage renal disease (ESRD) patient population awaiting kidney transplantation. Data were from the Organ Procurement and Transplantation Network (OPTN), the US Centers for Disease Control and Prevention, and the United States Renal Data System. Based on 2019 OPTN reports, annualized reduction in kidney transplantation of 25%-100% could result in excess deaths of wait-listed (deceased donor) transplant candidates from 84 to 337 and living donor candidate excess deaths from 35 to 141 (total 119-478 potentially preventable deaths of transplant candidates). Changes in transplant activity due to COVID-19 varied with some centers shutting down while others simply heeded known or suspected pandemic risks. Understanding potential excess mortality for ESRD transplant candidates when circumstances compel curtailment of transplant activity may inform policy and procedural aspects of organ transplant systems allowing ways to best inform patients and families as to potential risks in shuttering organ transplant activity. Considering that more than 700 000 Americans have ESRD with 100 000 awaiting a kidney transplant, our highest annual estimate of 478 excess total deaths from postponing kidney transplantation seems modest., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Oncogenic forms of KRAS proteins are known to be drivers of pancreatic, colorectal, and lung cancers. The goal of this study is to identify chemical leads that inhibit oncogenic KRAS signaling. We first developed an isogenic panel of mouse embryonic fibroblast (MEF) cell lines that carry wild-type RAS, oncogenic KRAS, and oncogenic BRAF. We validated these cell lines by screening against a tool compound library of 1402 annotated inhibitors in an adenosine triphosphate (ATP)-based cell viability assay. Subsequently, this MEF panel was used to conduct a high-throughput phenotypic screen in a cell viability assay with a proprietary compound library. All 126 compounds that exhibited a selective activity against mutant KRAS were selected and prioritized based on their activities in secondary assays. Finally, five chemical clusters were chosen. They had specific activity against SW620 and LS513 over Colo320 colorectal cancer cell lines. In addition, they had no effects on BRAF V600E , MEK1, extracellular signal-regulated kinase 2 (ERK2), phosphoinositide 3-kinase alpha (PI3Kα), AKT1, or mammalian target of rapamycin (mTOR) as tested in in vitro enzymatic activity assays. Biophysical assays demonstrated that these compounds did not bind directly to KRAS. We further identified the mechanism of action and showed that three of them have CDK9 inhibitory activity. In conclusion, we have developed and validated an isogenic MEF panel that was used successfully to identify RAS oncogenic or wild-type allele-specific vulnerabilities. Furthermore, we identified sensitivity of oncogenic KRAS-expressing cells to CDK9 inhibitors, which warrants future studies of treating KRAS-driven cancers with CDK9 inhibitors.

Summary: A primary goal of the US National Cancer Institute's Ras initiative at the Frederick National Laboratory for Cancer Research is to develop methods to quantify RAS signaling to facilitate development of novel cancer therapeutics. We use targeted proteomics technologies to develop a community resource consisting of 256 validated multiple reaction monitoring (MRM)-based, multiplexed assays for quantifying protein expression and phosphorylation through the receptor tyrosine kinase, MAPK, and AKT signaling networks. As proof of concept, we quantify the response of melanoma (A375 and SK-MEL-2) and colorectal cancer (HCT-116 and HT-29) cell lines to BRAF inhibition by PLX-4720. These assays replace over 60 Western blots with quantitative mass spectrometry-based assays of high molecular specificity and quantitative precision, showing the value of these methods for pharmacodynamic measurements and mechanism of action studies. Methods, fit-for-purpose validation, and results are publicly available as a resource for the community at assays.cancer.gov., Motivation: A lack of quantitative, multiplexable assays for phosphosignaling limits comprehensive investigation of aberrant signaling in cancer and evaluation of novel treatments. To alleviate this limitation, we sought to develop assays using targeted mass spectrometry for quantifying protein expression and phosphorylation through the receptor tyrosine kinase, MAPK, and AKT signaling networks. The resulting assays provide a resource for replacing over 60 Western blots in examining cancer signaling and tumor biology with high molecular specificity and quantitative rigor., Competing Interests: DECLARATION OF INTERESTS The authors declare no competing interests.

Recently, the highly mutated oncoprotein K-Ras4B (hereafter K-Ras) was shown to drive cancer cell stemness in conjunction with calmodulin (CaM). We previously showed that the covalent CaM inhibitor ophiobolin A (OphA) can potently inhibit K-Ras stemness activity. However, OphA, a fungus-derived natural product, exhibits an unspecific, broad toxicity across all phyla. Here we identified a less toxic, functional analog of OphA that can efficiently inactivate CaM by covalent inhibition. We analyzed a small series of benzazulenones, which bear some structural similarity to OphA and can be synthesized in only six steps. We identified the formyl aminobenzazulenone 1 , here named Calmirasone1, as a novel and potent covalent CaM inhibitor. Calmirasone1 has a 4-fold increased affinity for CaM as compared to OphA and was active against K-Ras in cells within minutes, as compared to hours required by OphA. Calmirasone1 displayed a 2.5-4.5-fold higher selectivity for KRAS over BRAF mutant 3D spheroid growth than OphA, suggesting improved relative on-target activity. Importantly, Calmirasone1 has a 40-260-fold lower unspecific toxic effect on HRAS mutant cells, while it reaches almost 50% of the activity of novel K-RasG12C specific inhibitors in 3D spheroid assays. Our results suggest that Calmirasone1 can serve as a new tool compound to further investigate the cancer cell biology of the K-Ras and CaM associated stemness activities., Competing Interests: FM was employed by company Leidos Biomedical Research, Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Okutachi, Manoharan, Kiriazis, Laurini, Catillon, McCormick, Yli-Kauhaluoma and Abankwa.)

Most eukaryotes harbor two distinct pre-mRNA splicing machineries: the major spliceosome, which removes >99% of introns, and the minor spliceosome, which removes rare, evolutionarily conserved introns. Although hypothesized to serve important regulatory functions, physiologic roles of the minor spliceosome are not well understood. For example, the minor spliceosome component ZRSR2 is subject to recurrent, leukemia-associated mutations, yet functional connections among minor introns, hematopoiesis and cancers are unclear. Here, we identify that impaired minor intron excision via ZRSR2 loss enhances hematopoietic stem cell self-renewal. CRISPR screens mimicking nonsense-mediated decay of minor intron-containing mRNA species converged on LZTR1, a regulator of RAS-related GTPases. LZTR1 minor intron retention was also discovered in the RASopathy Noonan syndrome, due to intronic mutations disrupting splicing and diverse solid tumors. These data uncover minor intron recognition as a regulator of hematopoiesis, noncoding mutations within minor introns as potential cancer drivers and links among ZRSR2 mutations, LZTR1 regulation and leukemias.

To prepare for potential human infection challenge studies (HICS) involving SARS-CoV-2, we convened a multidisciplinary working group to address ethical questions regarding whether and how much SARS-CoV-2 HICS participants should be paid. Because the goals of paying HICS participants, as well as the relevant ethical concerns, are the same as those arising for other types of clinical research, the same basic framework for ethical payment can apply. This framework divides payment into reimbursement, compensation, and incentives, focusing on fairness and promoting adequate recruitment and retention as counterweights to concerns about undue inducement. Within the basic framework, several factors are especially salient for HICS, and for SARS-CoV-2 HICS in particular, including the nature of participant confinement, anticipated discomfort, risks and uncertainty, participant motivations, and trust. These factors are reflected in a payment worksheet created to help sponsors, researchers, and ethics reviewers systematically develop and assess ethically justifiable payment amounts.