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  • 1
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 12, No. 1 ( 2021-07-16)
    Abstract: DNMDP and related compounds, or velcrins, induce complex formation between the phosphodiesterase PDE3A and the SLFN12 protein, leading to a cytotoxic response in cancer cells that express elevated levels of both proteins. The mechanisms by which velcrins induce complex formation, and how the PDE3A-SLFN12 complex causes cancer cell death, are not fully understood. Here, we show that PDE3A and SLFN12 form a heterotetramer stabilized by binding of DNMDP. Interactions between the C-terminal alpha helix of SLFN12 and residues near the active site of PDE3A are required for complex formation, and are further stabilized by interactions between SLFN12 and DNMDP. Moreover, we demonstrate that SLFN12 is an RNase, that PDE3A binding increases SLFN12 RNase activity, and that SLFN12 RNase activity is required for DNMDP response. This new mechanistic understanding will facilitate development of velcrin compounds into new cancer therapies.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
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  • 2
    In: Cancer Cell, Elsevier BV, Vol. 32, No. 6 ( 2017-12), p. 884-
    Type of Medium: Online Resource
    ISSN: 1535-6108
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
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  • 3
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 81, No. 13_Supplement ( 2021-07-01), p. 1219-1219
    Abstract: PDE3A-SLFN12 complex formation is induced by a class of compounds, now called “velcrins”, exemplified by the small molecule, DNMDP. Cancer cells that express elevated levels of PDE3A and SLFN12 are sensitive to a velcrin-mediated cytotoxic response, which is independent of PDE3A inhibition. However, the details of complex formation have not yet been revealed. We solved the crystal structure of PDE3A with a series of ligands bound to the active site and found that PDE3A exists as a dimer, and velcrin binding does not cause any obvious structural changes in the PDE3A protein structure. Hydrogen-deuterium exchange (HDX-MS) experiments with velcrin-bound PDE3A in the absence and presence of SLFN12 identified three regions of PDE3A that are shielded from solvent as a result of velcrin-induced SLFN12 binding. Two of these regions are near the velcrin binding site, and the third region lies at the PDE3A homodimerization interface. In order to further investigate the structural relationship between PDE3A, DNMDP, and SLFN12, we took a deep-mutation scanning (DMS) approach to identify residues of PDE3A that impact DNMDP sensitivity. A library of PDE3A alleles was developed in which the sequence encoding amino acids 668-1141, including the PDE3A catalytic domain, was substituted with a codon for every other possible amino acid or a stop codon in the context of the full-length cDNA. The library was transduced into PDE3A-knockout GB1 glioblastoma cells and assessed for survival in the presence of DMSO or DNMDP. Corroborating the HDX-MS data, we identified three regions of PDE3A in which missense mutations abrogated DNMDP response: the active site, the homodimerization surface, and an alpha helix containing amino acid F914. We confirmed that mutations of F914 and the homodimer interface retain the ability to bind resin-conjugated compound but fail to complex with SLFN12. Taken together, the HDX and DMS results suggest that PDE3A dimerization is required to stabilize velcrin-induced SLFN12 binding and implicate the alpha helix containing F914 as the SLFN12 binding interface of PDE3A. Citation Format: Xiaoyun Wu, Malvina Papanastasiou, Gavin Schnitzler, Colin Garvie, Stephanie Hoyt, Terry Zhang, James Mullahoo, Andrew Baker, Joseph McGaunn, Bethany Kaplan, Sooncheol Lee, Martin Lange, Steven Carr, Xiaoping Yang, Federica Piccioni, Andrew Cherniack, Matthew Meyerson, Heidi Greulich. Deep mutational scanning of PDE3A identifies residues required for DNMDP response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1219.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2021
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  • 4
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 77, No. 13_Supplement ( 2017-07-01), p. 394-394
    Abstract: KRAS is the most commonly mutated oncogenes and is a major driver of tumor initiation and progression. Understanding the functional consequences of cancer-associated KRAS variants may have important clinical implications. For example, KRAS mutation status defines those that are likely to respond to EGFR-directed therapy in KRAS-mutant metastatic colorectal cancer. A compendium of all possible oncogenic KRAS alleles would serve as a roadmap for future therapeutic strategies directed at KRAS itself or downstream signaling effectors. Comprehensive mutagenesis of KRAS may also elucidate structure-function relationships that reveal novel biochemical properties that may be exploited for therapeutic gain. We performed saturation mutagenesis of both a wild-type (WT) and a G12D mutant form of KRAS cDNA and generated lentiviral expression libraries of 3,553 and 3,534 single amino acid substitution mutants of each backbone. We utilized these WT and G12D mutagenesis libraries for functional genetic screening to identify gain- and loss-of-function missense variants that alter critical oncogenic properties of KRAS. First, we sought to comprehensively identify all possible oncogenic missense mutations in KRAS that mediate oncogenic transformation. We stably transduced the WT library into immortalized human epithelial cells and evaluated growth in low attachment (GILA), an assay that is highly correlated with in vivo tumor formation. We identified all previously known hotspot oncogenic alleles of KRAS as well as many functionally relevant alleles that are also discovered at lower frequency in human tumors. Moreover, we also discovered a group of transforming KRAS variants that have not been well described in human tumors, thus revealing potentially novel activating mechanisms for oncogenic KRAS. In parallel, we utilized the G12D mutagenesis library to perform second-site suppressor screening to identify loss-of-function single amino acid changes that abrogate the transforming ability of oncogenic KRAS. We performed positive-selection screening in primary cell lines for variants that enable bypass of oncogene-induced senescence. Additionally, we conducted a negative-selection screen with the G12D library in a KRAS-dependent cancer cell line with inducible suppression of endogenous KRAS, thus identifying all possible second-site mutations that abolish KRAS-driven signaling necessary for maintenance of cellular proliferation and viability. Structure-function analysis of these data may reveal novel patterns of amino-acid changes that result in inactivation of oncogenic KRAS. In summary, this comprehensive dictionary of gain- and loss-of-function KRAS mutants will facilitate understanding of clinically important mutations and also yield novel insights into structure-function relationships that may improve our understanding of the KRAS oncogene. Citation Format: Eejung Kim, Seav Huong Ly, Nicole S. Persky, Belinda Wang, Xiaoping Yang, Federica Piccioni, Katherine Labella, Mihir Doshi, Robert E. Lintner, Cong Zhu, Scott Steelman, David E. Root, Cory M. Johannessen, Alex B. Burgin, Laura E. MacConaill, William C. Hahn, Andrew J. Aguirre. Saturation mutagenesis of KRAS reveals the functional landscape of missense variants [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 394. doi:10.1158/1538-7445.AM2017-394
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2017
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  • 5
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 78, No. 13_Supplement ( 2018-07-01), p. 1815-1815
    Abstract: Drug resistant mutations that arise in therapeutic targets often limit clinical responses. However, the discovery of such mutations has historically been performed one gene or mutation at a time, often over decades of experimental and clinical testing, limiting our understanding of conserved mechanisms of drug resistance. We hypothesized that deep mutational scanning of canonical kinases may expedite this process and identify novel conserved elements that cause drug resistance when mutated (similar to the well-studied “Gatekeeper” residue). To test this, we generated cDNA-expression libraries containing all possible amino acid substitutions in CDK6, CDK4, ERK2, and EGFR. We screened each library against clinically utilized, ATP-competitive small molecule inhibitors. We then mapped the phenotypic data for over 40,000 missense mutations onto the aligned crystal structures of each protein and searched for shared structural attributes associated with drug resistance. This analysis revealed 4 equivalent amino acid sites whose mutation conferred drug resistance to ATP-competitive inhibitors in all of our screens: the Gatekeeper residue, as well as three uncharacterized residues. One of these sites, which we have termed the “Keymaster”, was additionally found to cause resistance in published data sets of sub-saturation BRAF, HER2, BCR-ABL, and MEK1 mutagenesis screens against their respective inhibitors. We confirmed that drug resistant phenotypes are caused by these alterations utilizing growth assays and protein target phosphorylation detection assays. Mechanistically, we show preliminary evidence that Keymaster-mutant proteins are competent for drug binding, but may display elevated basal activity. Consistent with our findings, we additionally identified mutations at Keymaster residues in reported patient tumors in a number of oncogene kinases, suggesting that Keymaster mutations could be drivers of tumorigenesis, as well as drug resistance. These efforts may prove useful for characterizing somatic kinase mutations of unknown function, designing next-generation therapeutics and deepening our understanding of kinase regulation. Citation Format: Nicole S. Persky, Desiree Hernandez, Jonathon Cordova, Amanda Walker, Lisa Brenan, Federica Piccioni, Sasha Pantel, Yenarae Lee, Amy Goodale, Xiaoping Yang, Yoichiro Mitsuishi, Mariana Do Carmo, Cong Zhu, Aleksandr Andreev, David E. Root, Cory M. Johannessen. Massively parallel identification of conserved drug resistant mutations in kinases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1815.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2018
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  • 6
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 22, No. Supplement_3 ( 2020-12-04), p. iii471-iii471
    Abstract: The brain is the foremost non-gonadal tissue for expression of non-coding RNAs of unclear function. Yet, whether such transcripts are truly non-coding or rather the source of non-canonical protein translation is unknown. Here, we used functional genomic screens to establish the cellular bioactivity of non-canonical proteins located in putative non-coding RNAs or untranslated regions of protein-coding genes. We experimentally interrogated 553 open reading frames (ORFs) identified by ribosome profiling for three major phenotypes: 257 (46%) demonstrated protein translation when ectopically expressed in HEK293T cells, 401 (73%) induced gene expression changes following ectopic expression across 4 cancer cell types, and 57 (10%) induced a viability defect when the endogenous ORF was knocked out using CRISPR/Cas9 in 8 human cancer cell lines. CRISPR tiling and start codon mutagenesis indicated that the biological impact of these non-canonical ORFs required their translation as opposed to RNA-mediated effects. We functionally characterized one of these ORFs, G029442—renamed GREP1 (Glycine-Rich Extracellular Protein-1)—as a cancer-implicated gene with high expression in multiple cancer types, such as gliomas. GREP1 knockout in & gt;200 cancer cell lines reduced cell viability in multiple cancer types, including glioblastoma, in a cell-autonomous manner and produced cell cycle arrest via single-cell RNA sequencing. Analysis of the secretome of GREP1-expressing cells showed increased abundance of the oncogenic cytokine GDF15, and GDF15 supplementation mitigated the growth inhibitory effect of GREP1 knock-out. Taken together, these experiments suggest that the non-canonical ORFeome is surprisingly rich in biologically active proteins and potential cancer therapeutic targets deserving of further study.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
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  • 7
    In: Nature Biotechnology, Springer Science and Business Media LLC, Vol. 39, No. 6 ( 2021-06), p. 697-704
    Type of Medium: Online Resource
    ISSN: 1087-0156 , 1546-1696
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
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  • 8
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 76, No. 14_Supplement ( 2016-07-15), p. 4368-4368
    Abstract: Recent cancer genome sequencing and analysis has identified millions of somatic mutations in cancer. However, the functional impact of most variants is poorly understood, limiting the use of this genetic knowledge for clinical decision-making. Here we describe a new high-throughput approach, expression-based variant impact phenotyping (eVIP), which uses gene expression changes to infer somatic mutation impact. We generated a lentiviral expression library representing 53 genes and 194 somatic mutations identified in primary lung adenocarcinomas. Next, we introduced this library into A549 lung adenocarcinoma cells and 96 hours later performed gene expression profiling using Luminex-based L1000 profiling. We built a computational pipeline, eVIP, to compare mutant and wild-type expression signatures to infer whether variants were gain-of-function, change-of-function, loss-of-function, or neutral. Overall, eVIP identified 69% of mutations as impactful whereas 31% appeared functionally neutral. A very high rate, 92%, of missense mutations in the KEAP1 and STK11 tumor suppressor genes were found to inactivate or diminish protein function. As a complementary approach, we assessed which mutations are epistatic to EGFR or capable of initiating xenograft tumor formation in vivo. A subset of the impactful mutations identified by eVIP could induce xenograft tumor formation in mice and/or confer resistance to cellular EGFR inhibition. Among these mutations were 20 rare or non-canonical somatic variants in clinically-actionable or -relevant oncogenes including EGFR S645C, ARAF S214C and S214F, ERBB2 S418T, and PIK3CA E600K. eVIP can, in principle, characterize any genetic variant, independent of prior knowledge of gene function. Further application of eVIP should significantly advance the pace of functional characterization of mutations identified from genome sequencing. Citation Format: Alice H. Berger, Angela N. Brooks, Xiaoyun Wu, Yashaswi Shrestha, Candace Chouinard, Federica Piccioni, Mukta Bagul, Atanas Kamburov, Marcin Imielinski, Larson Hogstrom, Cong Zhu, Xiaoping Yang, Sasha Pantel, Ryo Sakai, Nathan Kaplan, David Root, Rajiv Narayan, Ted Natoli, David Lahr, Itay Tirosh, Pablo Tamayo, Gad Getz, Bang Wong, John Doench, Aravind Subramanian, Todd R. Golub, Matthew Meyerson, Jesse S. Boehm. High-throughput phenotyping of lung cancer somatic mutations. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4368.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2016
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  • 9
    In: Cancer Discovery, American Association for Cancer Research (AACR), Vol. 6, No. 7 ( 2016-07-01), p. 714-726
    Abstract: Cancer genome characterization efforts now provide an initial view of the somatic alterations in primary tumors. However, most point mutations occur at low frequency, and the function of these alleles remains undefined. We have developed a scalable systematic approach to interrogate the function of cancer-associated gene variants. We subjected 474 mutant alleles curated from 5,338 tumors to pooled in vivo tumor formation assays and gene expression profiling. We identified 12 transforming alleles, including two in genes (PIK3CB, POT1) that have not been shown to be tumorigenic. One rare KRAS allele, D33E, displayed tumorigenicity and constitutive activation of known RAS effector pathways. By comparing gene expression changes induced upon expression of wild-type and mutant alleles, we inferred the activity of specific alleles. Because alleles found to be mutated only once in 5,338 tumors rendered cells tumorigenic, these observations underscore the value of integrating genomic information with functional studies. Significance: Experimentally inferring the functional status of cancer-associated mutations facilitates the interpretation of genomic information in cancer. Pooled in vivo screen and gene expression profiling identified functional variants and demonstrated that expression of rare variants induced tumorigenesis. Variant phenotyping through functional studies will facilitate defining key somatic events in cancer. Cancer Discov; 6(7); 714–26. ©2016 AACR. See related commentary by Cho and Collisson, p. 694. This article is highlighted in the In This Issue feature, p. 681
    Type of Medium: Online Resource
    ISSN: 2159-8274 , 2159-8290
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2016
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  • 10
    In: Cancer Cell, Elsevier BV, Vol. 30, No. 2 ( 2016-08), p. 214-228
    Type of Medium: Online Resource
    ISSN: 1535-6108
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2016
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