bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract A14: Mutations in the ubiquitin ligase adaptor LZTR1 drive human disease by dysregulating RAS ubiquitination and signaling
Authors: Steklov Mikhail , Pandolfi Silvia , Baietti Maria Francesca , Carai Paolo , Zhang Mingzhen , Jang Hyunbum , Cai Yanyan , Legius Eric , Tavernier Jan , Gevaert Kris , Impens Francis , Heymans Stephane , Messiaen Ludwine , Nussimov Ruth , Eyckerman Sven , Sablina Anna 
Published: June 2021

Abstract
Genetic evidence explicitly points out a role for LZTR1, an adaptor for cullin 3 (CUL3) ubiquitin ligase complex, in human disease. Mutations in LZTR1 concurrent with loss of heterozygosity have been associated with glioblastoma and schwannomatosis. LZTR1 emerges as a predisposition gene for paediatric neoplasms. LZTR1 mutations are significantly higher than the background in liver cancers and testicular germ cell tumours. LZTR1 has been also recently added to the list of genes causing Noonan Syndrome, a RASopathy disorder. However, how LZTR1 contributes to human disease and whether it regulates the RAS/MAPK pathway are not known. We found that whereas Lztr1 knockout in mice is embryonically lethal, Lztr1 haploinsufficiency partially recapitulates Noonan syndrome phenotypes, including growth delay, craniofacial dysmorphism, and congenital heart defects. On the other hand, LZTR1 loss in primary Schwann cells drives their dedifferentiation into proliferating cells. By trapping LZTR1 complexes from intact mammalian cells, we identified RAS as a substrate for the LZTR1/CUL3 ubiquitin ligase complex. Immunoprecipitation experiments confirmed that endogenous LZTR1 is associated with endogenous RAS. Ubiquitome and proximity ligation analyses showed that Lztr1 loss abrogates ubiquitination of endogenous RAS specifically at lysine 170. Molecular simulations together with the analysis of Hras-K170R knock-in cells demonstrated that LZTR1-mediated ubiquitination at lysine 170 inhibits RAS signaling by attenuating its association with the membrane. Disease-associated LZTR1 mutations abolish RAS ubiquitination due to disruption of either the LZTR1/CUL3 complex formation, or the interaction with RAS proteins. In line with the work of Bigenzahn et al., Giulio Superti-Furga lab, CeMM (see separate abstract), our study implies LZTR1-mediated RAS ubiquitination as a key step in the control of the RAS GTPases. The discovered molecular mechanism provides a fundamental explanation for the role of LZTR1 in human disease.
Citation Format: Mikhail Steklov, Silvia Pandolfi, Maria Francesca Baietti, Paolo Carai, Mingzhen Zhang, Hyunbum Jang, Yanyan Cai, Eric Legius, Jan Tavernier, Kris Gevaert, Francis Impens, Stephane Heymans, Ludwine Messiaen, Ruth Nussimov, Sven Eyckerman, Anna Sablina. Mutations in the ubiquitin ligase adaptor LZTR1 drive human disease by dysregulating RAS ubiquitination and signaling [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A14.
Abstract A18: Characterization of K-RasG13D as a unique activating allele in a mouse model of colorectal cancer
Authors: Lin Yi-Jang , Dischinger Patrick , Graveel Carrie , Steensma Matthew , Haigis Kevin M. 
Published: June 2021

Abstract
The K-RAS (Kirsten rat sarcoma) oncoprotein is mutationally activated in ~40% of colorectal cancers (CRCs), and K-RAS mutation state is an excellent predictor of the failure of a cancer to respond to conventional chemotherapy or targeted therapy. The colonic epithelium provides a biologically interesting context in which to study the allele-specific characteristics of K-RAS, because CRC displays a broad spectrum of activating mutations that occur at lower frequencies than K-RAS-mutant tumors of other organs. Of particular interest to us, activating G&gt;D mutations in codon 13 of K-RAS occur in 10-20% of K-RAS-mutant CRC, are biochemically distinct from the G12D mutation in mechanism of RAS activation, and have a different epidemiologic profile in patient survival. We established a novel mouse model to compare the colon phenotype of the K-RasG13D allele to that of the previously characterized K-RasG12D allele. In the context of homeostasis and colorectal cancer, we characterized the murine colonic epithelium at histologic, proteomic and transcriptomic levels. Ultimately, we aim to elucidate mutant-specific drug sensitivities by deeply understanding K-Ras biology in the genetically controlled setting of our mouse models.
Citation Format: Yi-Jang Lin, Patrick Dischinger, Carrie Graveel, Matthew Steensma, Kevin M. Haigis. Characterization of K-RasG13D as a unique activating allele in a mouse model of colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A18.
Abstract A41: Nucleotide metabolism heterogeneity in mutant KRAS pancreatic cancer
Authors: Le Thuc M. , Kim Woosuk , Capri Joseph R. , Cabebe Anthony E. , Armstrong Wes , Abt Evan , Poddar Soumya , Xu Shili , Dawson Dave , Donahue Timothy R. , Radu Caius G. 
Published: June 2021

Abstract
Mutant KRAS orchestrates major metabolic adaptations critical for pancreatic ductal adenocarcinoma (PDAC) growth and survival, including changes in glucose, amino acid, lipid and energy metabolism. However, how nucleotide metabolism in PDAC is impacted by mutant KRAS has received much less attention, even though nucleotides play critical roles in major biologic processes including nucleic acid synthesis, phospholipid biosynthesis and protein glycosylation. Pyrimidine nucleotide metabolism is a highly complex and regulated system with multiple pathways contributing to its plasticity and robustness. Pyrimidine nucleotides can be produced via the de novo pathway (DNP) that utilizes glucose and amino acids, and the nucleoside scavenging pathway (NSP) that utilizes extracellular uridine and cytidine. We hypothesize that nucleotide products of RNA turnover can fuel a third route for pyrimidine biosynthesis, which we term the nucleotide recycling pathway (NRP). Among these three major pyrimidine nucleotide biosynthetic pathways, the DNP has been studied most extensively. The biologic and therapeutic significance of the NSP and NRP in PDAC, as well as their regulation and coordination with DNP in the context of mutant KRAS signaling, are poorly understood. We further hypothesize that since PDAC tumor microenvironment is characterized by insufficient supply of nutrients and oxygen, these tumors have limited DNP capacity and increased reliance on alternate pyrimidine biosynthetic pathways. Here, we describe a novel mass spectrometric (MS) method to measure the contributions of pyrimidine nucleotide convergent pathways to RNA and DNA synthesis in PDAC models. Applying this method to a panel of PDAC models, including patient-derived primary lines, revealed previously unappreciated pyrimidine biosynthetic heterogeneity, suggesting the existence of distinct pyrimidine nucleotide metabolic subtypes. Identifying and characterizing these subtypes in the context of oncogenic KRAS signaling may enable stratification of PDAC tumors and guide the development of novel therapeutic approaches.
Citation Format: Thuc M. Le, Woosuk Kim, Joseph R. Capri, Anthony E. Cabebe, Wes Armstrong, Evan Abt, Soumya Poddar, Shili Xu, Dave Dawson, Timothy R. Donahue, Caius G. Radu. Nucleotide metabolism heterogeneity in mutant KRAS pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A41.
Abstract B21: Cancer-specific intracellular delivery of therapeutic antibodies against KRAS
Authors: McGuire Michael J. , Li Susan , Venugopal Indu , Gormley Claire , Luebke Kevin J. , Allred Curtis A. , Brown Kathlynn C. 
Published: June 2021

Abstract
Antibodies and peptides directed against the switch regions of RAS can disrupt interactions with its downstream effector proteins, blocking downstream protumorigenic signaling. However, these biologic therapies are unable to reach the intracellular environment. We have overcome this problem using peptidic molecular guidance system (MGSs) that have the unique ability to bind specifically to epithelial-derived cancer cells, and upon binding, trigger rapid internalization and trafficking to a specific subcellular location. Using an unbiased phage display approach, we have identified a series of cancer-specific MGSs that deliver cargo to discrete subcellular locations. Chemical optimization results in MGSs with 1-10 nM affinity for their cellular target, serum stability &gt;48 hours, and 50- to 1000-fold specificity for cancer cells compared to normal control cells. The rate of MGS internalization is rapid with t1/2 of 10-30 minutes, achieving intracellular concentrations up to 1.5 μM. Using these MGSs as delivery agents, we have delivered a function-blocking RAS antibody (Y13-259), resulting in a reduction of p-ERK and apoptosis in KRAS mutant cell lines. The effect is MGS dependent, and confocal microscopy indicates co-localization of KRAS and the antibody indicating target engagement. The MGS-antibody homes to tumors in an animal model, resulting in significant suppression in tumor growth compared to untreated animals. Free MAb does not impact tumor growth. Using MGSs to delivery MAb for intracellular targets is a paradigm change for immunotherapy and represents a new approach for controlling intracellular protein-protein interactions. Combination of these cancer-specific delivery agents with effectors of RAS signaling, such as antibodies and other biologics, has therapeutic potential for KRAS-driven cancers.
Citation Format: Michael J. McGuire, Susan Li, Indu Venugopal, Claire Gormley, Kevin J. Luebke, Curtis A. Allred, Kathlynn C. Brown. Cancer-specific intracellular delivery of therapeutic antibodies against KRAS [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B21.
Abstract B34: Targeted destruction of endogenous K-RAS using an Affinity directed PROtein Missile (AdPROM)
Authors: Roth Sascha O. M. , Macartney Thomas J. , Konopacka Agnieszka , Queisser Markus , Sapkota Gopal P. 
Published: June 2021

Abstract
K-RAS is one of the most frequently mutated oncogenes in cancer. Yet there are no effective strategies to target K-RAS for inhibition. Our laboratory has developed an Affinity-directed PROtein Missile (AdPROM) system for targeted proteolysis of endogenous proteins. Here, we show that we can achieve a robust degradation of endogenous K-RAS and mutant K-RAS from different cell lines in a targeted manner using our AdPROM system. We are currently assessing the impact of the targeted destruction of K-RAS and mutant K-RAS in cell signaling and proliferation.
Citation Format: Sascha O. M. Roth, Thomas J. Macartney, Agnieszka Konopacka, Markus Queisser, Gopal P. Sapkota. Targeted destruction of endogenous K-RAS using an Affinity directed PROtein Missile (AdPROM) [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B34.
Abstract B50: ERK MAPK inhibition enhances the immunogenicity of KRAS-mutant colorectal cancer
Authors: Ryan Meagan B. , Fece de la Cruz Ferran , Ahronian Leanne G. , Phat Sarah , Myers David T. , Shahzade Heather A. , Hong Catriona , Corcoran Ryan B. 
Published: June 2021

Abstract
The three RAS genes are the most commonly mutated oncogenes in cancer and are refractory to conventional therapies. Oncogenic mutation of KRAS in 44% of colorectal cancers (CRC) leads to aberrant activation of downstream effector pathways, including the ERK MAPK signaling cascade, which can lead to an immunosuppressive tumor microenvironment. Single-agent therapies targeting the ERK MAPK cascade or immune checkpoint (PD-1/PD-L1) have been mostly unsuccessful in KRAS-mutant CRC, and efforts are under way to identify effective combination strategies. We employed an unbiased RNA-seq approach to identify gene signatures significantly upregulated upon ERK MAPK pathway inhibition in a panel of KRAS-mutant CRC cell lines. We found that treatment with either the MEK inhibitor trametinib or ERK inhibitor Vx-11e induced upregulation of interferon gene signatures and JAK/STAT pathway signaling components. Inhibition of MEK or ERK also transcriptionally increased levels of MHC Class I and antigen presentation machinery. Upregulation of MHC Class I was reversed with either pharmacologic inhibition of JAK/STAT signaling or genetic knockdown of the transcription factor IRF1. We propose that combining MAPK inhibition with checkpoint immunotherapy may provide an effective treatment in KRAS-mutant CRC tumors in vivo and that potential synergy may be due to enhancing the immunogenicity of tumors through priming of interferon response pathways and antigen presentation machinery.
Citation Format: Meagan B. Ryan, Ferran Fece de la Cruz, Leanne G. Ahronian, Sarah Phat, David T. Myers, Heather A. Shahzade, Catriona Hong, Ryan B. Corcoran. ERK MAPK inhibition enhances the immunogenicity of KRAS-mutant colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B50.
Abstract IA07: KRAS4b’s unique diffusion behavior is defined by plasma membrane and effector interactions
Authors: Goswami Debanjan , Chen De , Columbus John , Yang Yue , Lightstone Felice , Turbyville Thomas 
Published: June 2021

Abstract
RAS proteins are GTP-dependent switches that control and regulate signaling pathways involved in cell fate and are frequently mutated in cancer. RAS association with the plasma membrane, or with certain endomembrane compartments, is a required step for its activity. Why precisely this is so remains an open question. One possibility is that RAS is merely required for recruitment of RAF and other effectors to the membrane where it can associate with key regulatory molecules that lead to signaling activation. However, four isoforms exist in humans (HRAS, NRAS, and two splice variants, KRAS4b and KRAS4a) and their differences lie within 22 amino acids in the C-terminal hypervariable region (HVR, aa 167-189). These differences in the domain responsible for membrane association result in the recruitment and organization of RAS into distinct membrane nanodomains, and it is thought that this results in differential signaling behavior from RAS isoforms. Isoform-specific RAS nanodomains are thought to both be highly dynamic, differentially composed of a variety of lipids and proteins, and supported by interactions with cytoskeletal structures. How these domains are regulated, and how they influence isoform-specific RAS signaling, remains unclear. Here, we report the molecular mobility of RAS variants in the plasma membrane of living cancer cells using single-molecule tracking methods. Detailed analysis of tracks revealed that KRAS4b molecules exhibit confined mobility with three diffusive states in the active plasma membrane of living cells. This diffusion characteristic was unique to KRAS4b and influenced by both the hypervariable region and globular domain of the protein, compared to all the other Ras isoforms. Importantly, the occupancy of each diffusive states was altered for the oncogenic mutant of KRAS4b, suggesting that the diffusive states we observe are related to signaling events. Our working hypothesis is that the HVR of KRAS4b may be directly involved in assembling the membrane lipid and protein nanodomain necessary for KRAS4b signaling activity. In addition, using two-color single-molecule tracking studies, we are beginning to characterize the interactions of KRAS4b with its major effector RAF. From these studies, we are learning about the kinetics of RAS/RAF interactions in the membrane of living cells. Understanding the underlying principle of KRAS4b functionality on cell membranes is useful for developing novel therapeutic strategies for targeting oncogenic KRAS4b.
Citation Format: Debanjan Goswami, De Chen, John Columbus, Yue Yang, Felice Lightstone, Thomas Turbyville. KRAS4b’s unique diffusion behavior is defined by plasma membrane and effector interactions [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr IA07.
Abstract IA08: Lipid dependence of KRAS plasma membrane interactions
Authors: Hancock John F. 
Published: June 2021

Abstract
RAS proteins must localize to the plasma membrane (PM) in order to function. We have examined how different RAS PM anchors select and assemble highly specific phospholipids into signaling platforms called nanoclusters, how these transient lipid assemblies impact signal transmission, and in consequence how the lipid composition of the PM can operate as high-level regulator of RAS signal transmission. For example, the KRAS polybasic domain (PBD)-farnesyl membrane anchor exhibits exquisite specificity for phosphatidylserine (PtdSer) over other anionic phospholipids by virtue of defined structural dynamics of the C-terminal polybasic domain and farnesyl group. This specificity extends to PtdSer with specific combinations of lipid side chains. PtdSer binding is therefore essential for stable KRAS PM binding and the spatial organization of KRAS into nanoclusters. These and complementary results with RAC1 highlight the critical role of specific anionic PM lipids in the biologic function of small GTPases. In this context for KRAS we have now shown that the PM levels and lateral availability of PtdSer are critically dependent on sphingomyelin metabolism such that multiple perturbations of sphingomyelin content or distribution, or endolysosmal lipid trafficking, profoundly affect KRAS plasma membrane localization, nanoclustering, and function. Concordantly, directly targeting the molecular machinery that maintains PtdSer on the PM also abrogates KRAS function in multiple pancreatic cancer cell lines. These new observations suggest multiple new potential therapeutic targets to abrogate oncogenic KRAS signaling, which we are evaluating in model systems.
Citation Format: John F. Hancock. Lipid dependence of KRAS plasma membrane interactions [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr IA08.
Abstract IA14: Exploiting the metabolic dependencies of mutant Kras lung tumors
Authors: Martins Carla P. 
Published: June 2021

Abstract
Lung adenocarcinoma (LUAD) is a major cause of cancer-related death worldwide. Kras and TP53 (p53) are the most frequently mutated genes in LUAD (~30% and ~50% of LUAD cases, respectively). Since mutations in these genes cannot be currently targeted in the clinic, alternative approaches to target these aggressive and largely therapy-resistant tumors are needed. To identify new vulnerabilities associated with these tumors, our lab is characterizing the alterations that promote the development, and enable the maintenance, of mutant Kras, p53-deficient lung tumors. Using mouse models that closely recapitulate human LUAD, we have recently shown that low- and high-grade tumors exhibit distinct genetic, transcriptional, and metabolic signatures, which in turn influence their therapeutic susceptibilities. In particular, we have shown that mutant Kras gene dosage and the type of p53 mutation present have a major impact on lung tumor metabolism in vivo, creating unique dependencies that can be exploited to selectively target specific mutant Kras lung tumor subsets. This phenotypic heterogeneity is also present in the human disease and may have contributed to the poor therapeutic responses often associated with mutant Kras LUAD. We will discuss these findings and how unique metabolic signatures can be potentially exploited to improve lung cancer targeting in the clinic.
Citation Format: Carla P. Martins. Exploiting the metabolic dependencies of mutant Kras lung tumors [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr IA14.
Abstract IA16: The interplay between RAS/MAPK signaling and tumor immunology
Authors: Hegde Priti 
Published: June 2021

Abstract
The role of MAPK in regulating the expression of pathways important for immune recognition of tumors such as modulation of the antigen presenting machinery and MHC Class I expression is now well studied preclinically. The clinical experience of the combination of MAPK inhibition with checkpoint inhibition (anti-PD-L1/PD-1) in cancer, however, has been less understood. Here, we will review the clinical data for checkpoint inhibitors and correlation with outcomes in the context of KRAS mutations in lung cancer and melanoma. In addition, the clinical activity of combinations of checkpoint inhibitors with MAPK inhibitors will be reviewed for both inflamed cancers such as melanoma and noninflamed cancers such as colorectal cancer.
Citation Format: Priti Hegde. The interplay between RAS/MAPK signaling and tumor immunology [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr IA16.
Abstract IA20: Unlocked groove—developing covalent inhibitors of KRASG12C
Authors: Lipford J. Russell , Cee Victor , Lanman Brian , Saiki Anne , Rex Karen , Volak Laurie , Shimanovich Roman , Hinkle Beth 
Published: June 2021

Abstract
KRAS is one of the most frequently mutated oncogenes in human cancer, with KRASp.G12D, p.G12V, and p.G12C constituting the major mutational subtypes across lung, colon, and pancreatic cancers. Despite over three decades of research, indirect approaches targeting KRAS mutant cancers have largely failed to show clinical benefit, and direct approaches have been limited by the apparent “undruggable” nature of KRAS. Recently, remarkable progress has been reported for targeting KRASG12C with small molecules that bind to the shallow, highly flexible P2 pocket of KRAS and form covalent adducts with the adjacent mutant cysteine. This class of inhibitors has demonstrated robust blockade of KRAS signaling and cell viability with substantial selectivity for KRASp.G12C tumors. Clinical validation of this approach is eagerly awaited. We have used iterative covalent library design and screening to develop unique inhibitors of KRASG12C. In one series, co-crystal structures of improved hit molecules revealed that side-chain motion exposed an undescribed shallow groove that was occupied by ligand atoms. This series was optimized to generate inhibitors with promising cellular activities (cellular IC50 ~100-200 nM and selectivity &gt;200-fold vs. non-G12C lines). To further enhance potency, selectivity, and drug-like properties, scaffold hopping was employed. After extensive optimization, potent and selective inhibitors were identified that potently suppressed KRAS-MAPK signaling (cellular phospho-ERK IC50 ~30 nM) and impaired cell viability (IC50 ~2 nM). In mouse xenograft tumor models, these inhibitors induce tumor regressions when dosed orally, once daily at a dose of 30 mg/kg. The results obtained with these inhibitors have critically informed our efforts to develop KRASG12C inhibitors suitable for clinical testing.
Citation Format: J. Russell Lipford, Victor Cee, Brian Lanman, Anne Saiki, Karen Rex, Laurie Volak, Roman Shimanovich, Beth Hinkle. Unlocked groove—developing covalent inhibitors of KRASG12C [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr IA20.