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A multi-stage genome-wide association study of uterine fibroids in African Americans.
Hellwege JN, Jeff JM, Wise LA, Gallagher CS, Wellons M, Hartmann KE, Jones SF, Torstenson ES, Dickinson S, Ruiz-Narváez EA, Rohland N, Allen A, Reich D, Tandon A, Pasaniuc B, Mancuso N, Im HK, Hinds DA, Palmer JR, Rosenberg L, Denny JC, Roden DM, Stewart EA, Morton CC, Kenny EE, Edwards TL, Velez Edwards DR
(2017) Hum Genet 136: 1363-1373
MeSH Terms: Adult, African Americans, Alleles, Cell Adhesion Molecules, Female, Gene Expression Regulation, Neoplastic, Gene Frequency, Genetic Loci, Genome-Wide Association Study, Guanine Nucleotide Exchange Factors, Humans, Leiomyoma, Middle Aged, Neoplasm Proteins, Risk Factors, Uterine Neoplasms
Show Abstract · Added March 14, 2018
Uterine fibroids are benign tumors of the uterus affecting up to 77% of women by menopause. They are the leading indication for hysterectomy, and account for $34 billion annually in the United States. Race/ethnicity and age are the strongest known risk factors. African American (AA) women have higher prevalence, earlier onset, and larger and more numerous fibroids than European American women. We conducted a multi-stage genome-wide association study (GWAS) of fibroid risk among AA women followed by in silico genetically predicted gene expression profiling of top hits. In Stage 1, cases and controls were confirmed by pelvic imaging, genotyped and imputed to 1000 Genomes. Stage 2 used self-reported fibroid and GWAS data from 23andMe, Inc. and the Black Women's Health Study. Associations with fibroid risk were modeled using logistic regression adjusted for principal components, followed by meta-analysis of results. We observed a significant association among 3399 AA cases and 4764 AA controls at rs739187 (risk-allele frequency = 0.27) in CYTH4 (OR (95% confidence interval) = 1.23 (1.16-1.30), p value = 7.82 × 10). Evaluation of the genetic association results with MetaXcan identified lower predicted gene expression of CYTH4 in thyroid tissue as significantly associated with fibroid risk (p value = 5.86 × 10). In this first multi-stage GWAS for fibroids among AA women, we identified a novel risk locus for fibroids within CYTH4 that impacts gene expression in thyroid and has potential biological relevance for fibroids.
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16 MeSH Terms
Two distinct mTORC2-dependent pathways converge on Rac1 to drive breast cancer metastasis.
Morrison Joly M, Williams MM, Hicks DJ, Jones B, Sanchez V, Young CD, Sarbassov DD, Muller WJ, Brantley-Sieders D, Cook RS
(2017) Breast Cancer Res 19: 74
MeSH Terms: Animals, Breast Neoplasms, Cell Line, Tumor, Cell Movement, Disease Models, Animal, Female, Gene Amplification, Heterografts, Humans, Mechanistic Target of Rapamycin Complex 2, Mice, Mice, Transgenic, Neoplasm Metastasis, Neoplasm Staging, Prognosis, Proto-Oncogene Proteins c-akt, Rapamycin-Insensitive Companion of mTOR Protein, Receptor, ErbB-2, Signal Transduction, rac1 GTP-Binding Protein, rho Guanine Nucleotide Dissociation Inhibitor beta
Show Abstract · Added April 15, 2019
BACKGROUND - The importance of the mTOR complex 2 (mTORC2) signaling complex in tumor progression is becoming increasingly recognized. HER2-amplified breast cancers use Rictor/mTORC2 signaling to drive tumor formation, tumor cell survival and resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapy. Cell motility, a key step in the metastatic process, can be activated by mTORC2 in luminal and triple negative breast cancer cell lines, but its role in promoting metastases from HER2-amplified breast cancers is not yet clear.
METHODS - Because Rictor is an obligate cofactor of mTORC2, we genetically engineered Rictor ablation or overexpression in mouse and human HER2-amplified breast cancer models for modulation of mTORC2 activity. Signaling through mTORC2-dependent pathways was also manipulated using pharmacological inhibitors of mTOR, Akt, and Rac. Signaling was assessed by western analysis and biochemical pull-down assays specific for Rac-GTP and for active Rac guanine nucleotide exchange factors (GEFs). Metastases were assessed from spontaneous tumors and from intravenously delivered tumor cells. Motility and invasion of cells was assessed using Matrigel-coated transwell assays.
RESULTS - We found that Rictor ablation potently impaired, while Rictor overexpression increased, metastasis in spontaneous and intravenously seeded models of HER2-overexpressing breast cancers. Additionally, migration and invasion of HER2-amplified human breast cancer cells was diminished in the absence of Rictor, or upon pharmacological mTOR kinase inhibition. Active Rac1 was required for Rictor-dependent invasion and motility, which rescued invasion/motility in Rictor depleted cells. Rictor/mTORC2-dependent dampening of the endogenous Rac1 inhibitor RhoGDI2, a factor that correlated directly with increased overall survival in HER2-amplified breast cancer patients, promoted Rac1 activity and tumor cell invasion/migration. The mTORC2 substrate Akt did not affect RhoGDI2 dampening, but partially increased Rac1 activity through the Rac-GEF Tiam1, thus partially rescuing cell invasion/motility. The mTORC2 effector protein kinase C (PKC)α did rescue Rictor-mediated RhoGDI2 downregulation, partially rescuing Rac-guanosine triphosphate (GTP) and migration/motility.
CONCLUSION - These findings suggest that mTORC2 uses two coordinated pathways to activate cell invasion/motility, both of which converge on Rac1. Akt signaling activates Rac1 through the Rac-GEF Tiam1, while PKC signaling dampens expression of the endogenous Rac1 inhibitor, RhoGDI2.
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Bypass of DNA-Protein Cross-links Conjugated to the 7-Deazaguanine Position of DNA by Translesion Synthesis Polymerases.
Wickramaratne S, Ji S, Mukherjee S, Su Y, Pence MG, Lior-Hoffmann L, Fu I, Broyde S, Guengerich FP, Distefano M, Schärer OD, Sham YY, Tretyakova N
(2016) J Biol Chem 291: 23589-23603
MeSH Terms: Amination, Amino Acid Sequence, Base Sequence, DNA Adducts, DNA Replication, DNA-Directed DNA Polymerase, Guanine, Humans, Molecular Dynamics Simulation, Oxidation-Reduction, Peptides, Proteins, Recombinant Proteins
Show Abstract · Added March 14, 2018
DNA-protein cross-links (DPCs) are bulky DNA lesions that form both endogenously and following exposure to bis-electrophiles such as common antitumor agents. The structural and biological consequences of DPCs have not been fully elucidated due to the complexity of these adducts. The most common site of DPC formation in DNA following treatment with bis-electrophiles such as nitrogen mustards and cisplatin is the N7 position of guanine, but the resulting conjugates are hydrolytically labile and thus are not suitable for structural and biological studies. In this report, hydrolytically stable structural mimics of N7-guanine-conjugated DPCs were generated by reductive amination reactions between the Lys and Arg side chains of proteins/peptides and aldehyde groups linked to 7-deazaguanine residues in DNA. These model DPCs were subjected to in vitro replication in the presence of human translesion synthesis DNA polymerases. DPCs containing full-length proteins (11-28 kDa) or a 23-mer peptide blocked human polymerases η and κ. DPC conjugates to a 10-mer peptide were bypassed with nucleotide insertion efficiency 50-100-fold lower than for native G. Both human polymerase (hPol) κ and hPol η inserted the correct base (C) opposite the 10-mer peptide cross-link, although small amounts of T were added by hPol η. Molecular dynamics simulation of an hPol κ ternary complex containing a template-primer DNA with dCTP opposite the 10-mer peptide DPC revealed that this bulky lesion can be accommodated in the polymerase active site by aligning with the major groove of the adducted DNA within the ternary complex of polymerase and dCTP.
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
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13 MeSH Terms
The nucleoid-associated protein HU enhances 8-oxoguanine base excision by the formamidopyrimidine-DNA glycosylase.
Le Meur R, Culard F, Nadan V, Goffinont S, Coste F, Guerin M, Loth K, Landon C, Castaing B
(2015) Biochem J 471: 13-23
MeSH Terms: DNA Breaks, Double-Stranded, DNA Repair, DNA, Bacterial, DNA-Binding Proteins, DNA-Formamidopyrimidine Glycosylase, Escherichia coli, Escherichia coli Proteins, Guanine
Show Abstract · Added January 11, 2016
The nucleoid-associated protein HU is involved in numerous DNA transactions and thus is essential in DNA maintenance and bacterial survival. The high affinity of HU for SSBs (single-strand breaks) has suggested its involvement in DNA protection, repair and recombination. SSB-containing DNA are major intermediates transiently generated by bifunctional DNA N-glycosylases that initiate the BER (base excision repair) pathway. Enzyme kinetics and DNA-binding experiments demonstrate that HU enhances the 8-oxoguanine-DNA glycosylase activity of Fpg (formamidopyrimidine-DNA glycosylase) by facilitating the release of the enzyme from its final DNA product (one nucleoside gap). We propose that the displacement of Fpg from its end-DNA product by HU is an active mechanism in which HU recognizes the product when it is still bound by Fpg. Through DNA binding, the two proteins interplay to form a transient ternary complex Fpg/DNA/HU which results in the release of Fpg and the molecular entrapment of SSBs by HU. These results support the involvement of HU in BER in vivo.
© 2015 Authors; published by Portland Press Limited.
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8 MeSH Terms
Next-generation sequencing reveals the biological significance of the N(2),3-ethenoguanine lesion in vivo.
Chang SC, Fedeles BI, Wu J, Delaney JC, Li D, Zhao L, Christov PP, Yau E, Singh V, Jost M, Drennan CL, Marnett LJ, Rizzo CJ, Levine SS, Guengerich FP, Essigmann JM
(2015) Nucleic Acids Res 43: 5489-500
MeSH Terms: DNA Adducts, DNA Damage, DNA Polymerase beta, DNA Repair, DNA Repair Enzymes, Dioxygenases, Guanine, High-Throughput Nucleotide Sequencing, Mutagenesis, Mutation, Sequence Analysis, DNA, Sequence Deletion
Show Abstract · Added January 7, 2016
Etheno DNA adducts are a prevalent type of DNA damage caused by vinyl chloride (VC) exposure and oxidative stress. Etheno adducts are mutagenic and may contribute to the initiation of several pathologies; thus, elucidating the pathways by which they induce cellular transformation is critical. Although N(2),3-ethenoguanine (N(2),3-εG) is the most abundant etheno adduct, its biological consequences have not been well characterized in cells due to its labile glycosidic bond. Here, a stabilized 2'-fluoro-2'-deoxyribose analog of N(2),3-εG was used to quantify directly its genotoxicity and mutagenicity. A multiplex method involving next-generation sequencing enabled a large-scale in vivo analysis, in which both N(2),3-εG and its isomer 1,N(2)-ethenoguanine (1,N(2)-εG) were evaluated in various repair and replication backgrounds. We found that N(2),3-εG potently induces G to A transitions, the same mutation previously observed in VC-associated tumors. By contrast, 1,N(2)-εG induces various substitutions and frameshifts. We also found that N(2),3-εG is the only etheno lesion that cannot be repaired by AlkB, which partially explains its persistence. Both εG lesions are strong replication blocks and DinB, a translesion polymerase, facilitates the mutagenic bypass of both lesions. Collectively, our results indicate that N(2),3-εG is a biologically important lesion and may have a functional role in VC-induced or inflammation-driven carcinogenesis.
© The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.
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12 MeSH Terms
Differential repair of etheno-DNA adducts by bacterial and human AlkB proteins.
Zdżalik D, Domańska A, Prorok P, Kosicki K, van den Born E, Falnes PØ, Rizzo CJ, Guengerich FP, Tudek B
(2015) DNA Repair (Amst) 30: 1-10
MeSH Terms: Adenine, AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase, AlkB Homolog 3, Alpha-Ketoglutarate-Dependent Dioxygenase, Bacteria, Bacterial Proteins, Cytosine, DNA, DNA Adducts, DNA Glycosylases, DNA Repair, DNA Repair Enzymes, DNA, Single-Stranded, Dioxygenases, Escherichia coli, Escherichia coli Proteins, Guanine, Humans, Mixed Function Oxygenases, Mycobacterium tuberculosis, Rhizobium etli, Streptomyces, Substrate Specificity, Xanthomonas campestris
Show Abstract · Added January 7, 2016
AlkB proteins are evolutionary conserved Fe(II)/2-oxoglutarate-dependent dioxygenases, which remove alkyl and highly promutagenic etheno(ɛ)-DNA adducts, but their substrate specificity has not been fully determined. We developed a novel assay for the repair of ɛ-adducts by AlkB enzymes using oligodeoxynucleotides with a single lesion and specific DNA glycosylases and AP-endonuclease for identification of the repair products. We compared the repair of three ɛ-adducts, 1,N(6)-ethenoadenine (ɛA), 3,N(4)-ethenocytosine (ɛC) and 1,N(2)-ethenoguanine (1,N(2)-ɛG) by nine bacterial and two human AlkBs, representing four different structural groups defined on the basis of conserved amino acids in the nucleotide recognition lid, engaged in the enzyme binding to the substrate. Two bacterial AlkB proteins, MT-2B (from Mycobacterium tuberculosis) and SC-2B (Streptomyces coelicolor) did not repair these lesions in either double-stranded (ds) or single-stranded (ss) DNA. Three proteins, RE-2A (Rhizobium etli), SA-2B (Streptomyces avermitilis), and XC-2B (Xanthomonas campestris) efficiently removed all three lesions from the DNA substrates. Interestingly, XC-2B and RE-2A are the first AlkB proteins shown to be specialized for ɛ-adducts, since they do not repair methylated bases. Three other proteins, EcAlkB (Escherichia coli), SA-1A, and XC-1B removed ɛA and ɛC from ds and ssDNA but were inactive toward 1,N(2)-ɛG. SC-1A repaired only ɛA with the preference for dsDNA. The human enzyme ALKBH2 repaired all three ɛ-adducts in dsDNA, while only ɛA and ɛC in ssDNA and repair was less efficient in ssDNA. ALKBH3 repaired only ɛC in ssDNA. Altogether, we have shown for the first time that some AlkB proteins, namely ALKBH2, RE-2A, SA-2B and XC-2B can repair 1,N(2)-ɛG and that ALKBH3 removes only ɛC from ssDNA. Our results also suggest that the nucleotide recognition lid is not the sole determinant of the substrate specificity of AlkB proteins.
Copyright © 2015 Elsevier B.V. All rights reserved.
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2 Members
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23 MeSH Terms
The guanine nucleotide exchange factor (GEF) Asef2 promotes dendritic spine formation via Rac activation and spinophilin-dependent targeting.
Evans JC, Robinson CM, Shi M, Webb DJ
(2015) J Biol Chem 290: 10295-308
MeSH Terms: Actin Cytoskeleton, Amino Acid Sequence, Animals, Dendritic Spines, Embryo, Mammalian, Gene Expression Regulation, Developmental, Guanine Nucleotide Exchange Factors, Hippocampus, Microfilament Proteins, Molecular Sequence Data, Nerve Tissue Proteins, Neurogenesis, Primary Cell Culture, Proto-Oncogene Proteins c-akt, RNA, Small Interfering, Rats, Receptors, N-Methyl-D-Aspartate, Signal Transduction, Synapses
Show Abstract · Added February 5, 2016
Dendritic spines are actin-rich protrusions that establish excitatory synaptic contacts with surrounding neurons. Reorganization of the actin cytoskeleton is critical for the development and plasticity of dendritic spines, which is the basis for learning and memory. Rho family GTPases are emerging as important modulators of spines and synapses, predominantly through their ability to regulate actin dynamics. Much less is known, however, about the function of guanine nucleotide exchange factors (GEFs), which activate these GTPases, in spine and synapse development. In this study we show that the Rho family GEF Asef2 is found at synaptic sites, where it promotes dendritic spine and synapse formation. Knockdown of endogenous Asef2 with shRNAs impairs spine and synapse formation, whereas exogenous expression of Asef2 causes an increase in spine and synapse density. This effect of Asef2 on spines and synapses is abrogated by expression of GEF activity-deficient Asef2 mutants or by knockdown of Rac, suggesting that Asef2-Rac signaling mediates spine development. Because Asef2 interacts with the F-actin-binding protein spinophilin, which localizes to spines, we investigated the role of spinophilin in Asef2-promoted spine formation. Spinophilin recruits Asef2 to spines, and knockdown of spinophilin hinders spine and synapse formation in Asef2-expressing neurons. Furthermore, inhibition of N-methyl-d-aspartate receptor (NMDA) activity blocks spinophilin-mediated localization of Asef2 to spines. These results collectively point to spinophilin-Asef2-Rac signaling as a novel mechanism for the development of dendritic spines and synapses.
© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
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19 MeSH Terms
The Rho family GEF Asef2 regulates cell migration in three dimensional (3D) collagen matrices through myosin II.
Jean L, Yang L, Majumdar D, Gao Y, Shi M, Brewer BM, Li D, Webb DJ
(2014) Cell Adh Migr 8: 460-7
MeSH Terms: Cell Line, Cell Movement, Collagen, Guanine Nucleotide Exchange Factors, Heterocyclic Compounds, 4 or More Rings, Humans, Immunohistochemistry, Myosin Type II
Show Abstract · Added January 20, 2015
Cell migration is fundamental to a variety of physiological processes, including tissue development, homeostasis, and regeneration. Migration has been extensively studied with cells on 2-dimensional (2D) substrates, but much less is known about cell migration in 3D environments. Tissues and organs are 3D, which is the native environment of cells in vivo, pointing to a need to understand migration and the mechanisms that regulate it in 3D environments. To investigate cell migration in 3D environments, we developed microfluidic devices that afford a controlled, reproducible platform for generating 3D matrices. Using these devices, we show that the Rho family guanine nucleotide exchange factor (GEF) Asef2 inhibits cell migration in 3D type I collagen (collagen I) matrices. Treatment of cells with the myosin II (MyoII) inhibitor blebbistatin abolished the decrease in migration by Asef2. Moreover, Asef2 enhanced MyoII activity as shown by increased phosphorylation of serine 19 (S19). Furthermore, Asef2 increased activation of Rac, which is a Rho family small GTPase, in 3D collagen I matrices. Inhibition of Rac activity by treatment with the Rac-specific inhibitor NSC23766 abrogated the Asef2-promoted increase in S19 MyoII phosphorylation. Thus, our results indicate that Asef2 regulates cell migration in 3D collagen I matrices through a Rac-MyoII-dependent mechanism.
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8 MeSH Terms
The Cdc15 and Imp2 SH3 domains cooperatively scaffold a network of proteins that redundantly ensure efficient cell division in fission yeast.
Ren L, Willet AH, Roberts-Galbraith RH, McDonald NA, Feoktistova A, Chen JS, Huang H, Guillen R, Boone C, Sidhu SS, Beckley JR, Gould KL
(2015) Mol Biol Cell 26: 256-69
MeSH Terms: Amino Acid Sequence, Cell Cycle Proteins, Cell Division, Cytokinesis, Cytoskeletal Proteins, GTP-Binding Proteins, Gene Regulatory Networks, Guanine Nucleotide Exchange Factors, Immunoblotting, Luminescent Proteins, Microscopy, Confocal, Molecular Sequence Data, Mutation, Protein Binding, Proteome, Proteomics, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Sequence Homology, Amino Acid, Time-Lapse Imaging, src Homology Domains
Show Abstract · Added January 20, 2015
Schizosaccharomyces pombe cdc15 homology (PCH) family members participate in numerous biological processes, including cytokinesis, typically by bridging the plasma membrane via their F-BAR domains to the actin cytoskeleton. Two SH3 domain-containing PCH family members, Cdc15 and Imp2, play critical roles in S. pombe cytokinesis. Although both proteins localize to the contractile ring, with Cdc15 preceding Imp2, only cdc15 is an essential gene. Despite these distinct roles, the SH3 domains of Cdc15 and Imp2 cooperate in the essential process of recruiting other proteins to stabilize the contractile ring. To better understand the connectivity of this SH3 domain-based protein network at the CR and its function, we used a biochemical approach coupled to proteomics to identify additional proteins (Rgf3, Art1, Spa2, and Pos1) that are integrated into this network. Cell biological and genetic analyses of these SH3 partners implicate them in a range of activities that ensure the fidelity of cell division, including promoting cell wall metabolism and influencing cell morphogenesis.
© 2015 Ren et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
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21 MeSH Terms
P-REX1 creates a positive feedback loop to activate growth factor receptor, PI3K/AKT and MEK/ERK signaling in breast cancer.
Dillon LM, Bean JR, Yang W, Shee K, Symonds LK, Balko JM, McDonald WH, Liu S, Gonzalez-Angulo AM, Mills GB, Arteaga CL, Miller TW
(2015) Oncogene 34: 3968-76
MeSH Terms: Animals, Breast Neoplasms, Cell Survival, Feedback, Physiological, Female, Guanine Nucleotide Exchange Factors, Humans, MAP Kinase Signaling System, MCF-7 Cells, Mice, Inbred NOD, Mice, SCID, Mutation, Neoplasm Transplantation, Phosphatidylinositol 3-Kinases, Proto-Oncogene Proteins c-akt, Receptors, Growth Factor, rac GTP-Binding Proteins
Show Abstract · Added October 21, 2014
Phosphatidylinositol 3-kinase (PI3K) promotes cancer cell survival, migration, growth and proliferation by generating phosphatidylinositol 3,4,5-trisphosphate (PIP3) in the inner leaflet of the plasma membrane. PIP3 recruits pleckstrin homology domain-containing proteins to the membrane to activate oncogenic signaling cascades. Anticancer therapeutics targeting the PI3K/AKT/mTOR (mammalian target of rapamycin) pathway are in clinical development. In a mass spectrometric screen to identify PIP3-regulated proteins in breast cancer cells, levels of the Rac activator PIP3-dependent Rac exchange factor-1 (P-REX1) increased in response to PI3K inhibition, and decreased upon loss of the PI3K antagonist phosphatase and tensin homolog (PTEN). P-REX1 mRNA and protein levels were positively correlated with ER expression, and inversely correlated with PI3K pathway activation in breast tumors as assessed by gene expression and phosphoproteomic analyses. P-REX1 increased activation of Rac1, PI3K/AKT and MEK/ERK signaling in a PTEN-independent manner, and promoted cell and tumor viability. Loss of P-REX1 or inhibition of Rac suppressed PI3K/AKT and MEK/ERK, and decreased viability. P-REX1 also promoted insulin-like growth factor-1 receptor activation, suggesting that P-REX1 provides positive feedback to activators upstream of PI3K. In support of a model where PIP3-driven P-REX1 promotes both PI3K/AKT and MEK/ERK signaling, high levels of P-REX1 mRNA (but not phospho-AKT or a transcriptomic signature of PI3K activation) were predictive of sensitivity to PI3K inhibitors among breast cancer cell lines. P-REX1 expression was highest in estrogen receptor-positive breast tumors compared with many other cancer subtypes, suggesting that neutralizing the P-REX1/Rac axis may provide a novel therapeutic approach to selectively abrogate oncogenic signaling in breast cancer cells.
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17 MeSH Terms