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Bannoura SF, Khan HY, Uddin MH, Mohammad RM, Pasche BC, Azmi AS. Targeting guanine nucleotide exchange factors for novel cancer drug discovery. Expert Opin Drug Discov 2024; 19:949-959. [PMID: 38884380 DOI: 10.1080/17460441.2024.2368242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 06/10/2024] [Indexed: 06/18/2024]
Abstract
INTRODUCTION Guanine nucleotide exchange factors (GEFs) regulate the activation of small GTPases (G proteins) of the Ras superfamily proteins controlling cellular functions. Ras superfamily proteins act as 'molecular switches' that are turned 'ON' by guanine exchange. There are five major groups of Ras family GTPases: Ras, Ran, Rho, Rab and Arf, with a variety of different GEFs regulating their GTP loading. GEFs have been implicated in various diseases including cancer. This makes GEFs attractive targets to modulate signaling networks controlled by small GTPases. AREAS COVERED In this review, the roles and mechanisms of GEFs in malignancy are outlined. The mechanism of guanine exchange activity by GEFs on a small GTPase is illustrated. Then, some examples of GEFs that are significant in cancer are presented with a discussion on recent progress in therapeutic targeting efforts using a variety of approaches. EXPERT OPINION Recently, GEFs have emerged as potential therapeutic targets for novel cancer drug development. Targeting small GTPases is challenging; thus, targeting their activation by GEFs is a promising strategy. Most GEF-targeted drugs are still in preclinical development. A deeper biological understanding of the underlying mechanisms of GEF activity and utilizing advanced technology are necessary to enhance drug discovery for GEFs in cancer.
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Affiliation(s)
- Sahar F Bannoura
- Department of Oncology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA
| | - Husain Yar Khan
- Department of Oncology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA
| | - Md Hafiz Uddin
- Department of Oncology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA
| | - Ramzi M Mohammad
- Department of Oncology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA
| | - Boris C Pasche
- Department of Oncology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA
| | - Asfar S Azmi
- Department of Oncology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA
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Vav2 pharmaco-mimetic mice reveal the therapeutic value and caveats of the catalytic inactivation of a Rho exchange factor. Oncogene 2020; 39:5098-5111. [PMID: 32528129 PMCID: PMC7610363 DOI: 10.1038/s41388-020-1353-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 05/29/2020] [Accepted: 06/03/2020] [Indexed: 11/20/2022]
Abstract
The current paradigm holds that the inhibition of Rho guanosine nucleotide exchange factors (GEFs), the enzymes that stimulate Rho GTPases, can be a valuable therapeutic strategy to treat Rho-dependent tumors. However, formal validation of this idea using in vivo models is still missing. In this context, it is worth remembering that many Rho GEFs can mediate both catalysis-dependent and independent responses, thus raising the possibility that the inhibition of their catalytic activities might not be sufficient per se to block tumorigenic processes. On the other hand, the inhibition of these enzymes can trigger collateral side effects that could preclude the practical implementation of anti-GEF therapies. To address those issues, we have generated mouse models to mimic the effect of the systemic application of an inhibitor for the catalytic activity of the Rho GEF Vav2 at the organismal level. Our results indicate that lowering the catalytic activity of Vav2 below specific thresholds is sufficient to block skin tumor initiation, promotion, and progression. They also reveal that the negative side effects typically induced by the loss of Vav2 can be bypassed depending on the overall level of Vav2 inhibition achieved in vivo. These data underscore the pros and cons of anti-Rho GEF therapies for cancer treatment. They also support the idea that Vav2 could represent a viable drug target.
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Maldonado MDM, Medina JI, Velazquez L, Dharmawardhane S. Targeting Rac and Cdc42 GEFs in Metastatic Cancer. Front Cell Dev Biol 2020; 8:201. [PMID: 32322580 PMCID: PMC7156542 DOI: 10.3389/fcell.2020.00201] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/09/2020] [Indexed: 12/20/2022] Open
Abstract
The Rho family GTPases Rho, Rac, and Cdc42 have emerged as key players in cancer metastasis, due to their essential roles in regulating cell division and actin cytoskeletal rearrangements; and thus, cell growth, migration/invasion, polarity, and adhesion. This review will focus on the close homologs Rac and Cdc42, which have been established as drivers of metastasis and therapy resistance in multiple cancer types. Rac and Cdc42 are often dysregulated in cancer due to hyperactivation by guanine nucleotide exchange factors (GEFs), belonging to both the diffuse B-cell lymphoma (Dbl) and dedicator of cytokinesis (DOCK) families. Rac/Cdc42 GEFs are activated by a myriad of oncogenic cell surface receptors, such as growth factor receptors, G-protein coupled receptors, cytokine receptors, and integrins; consequently, a number of Rac/Cdc42 GEFs have been implicated in metastatic cancer. Hence, inhibiting GEF-mediated Rac/Cdc42 activation represents a promising strategy for targeted metastatic cancer therapy. Herein, we focus on the role of oncogenic Rac/Cdc42 GEFs and discuss the recent advancements in the development of Rac and Cdc42 GEF-interacting inhibitors as targeted therapy for metastatic cancer, as well as their potential for overcoming cancer therapy resistance.
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Affiliation(s)
- Maria Del Mar Maldonado
- Department of Biochemistry, School of Medicine, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Julia Isabel Medina
- Department of Biochemistry, School of Medicine, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Luis Velazquez
- Department of Biochemistry, School of Medicine, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Suranganie Dharmawardhane
- Department of Biochemistry, School of Medicine, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
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Prieto-Dominguez N, Parnell C, Teng Y. Drugging the Small GTPase Pathways in Cancer Treatment: Promises and Challenges. Cells 2019; 8:E255. [PMID: 30884855 PMCID: PMC6468615 DOI: 10.3390/cells8030255] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 03/08/2019] [Accepted: 03/13/2019] [Indexed: 02/07/2023] Open
Abstract
Small GTPases are a family of low molecular weight GTP-hydrolyzing enzymes that cycle between an inactive state when bound to GDP and an active state when associated to GTP. Small GTPases regulate key cellular processes (e.g., cell differentiation, proliferation, and motility) as well as subcellular events (e.g., vesicle trafficking), making them key participants in a great array of pathophysiological processes. Indeed, the dysfunction and deregulation of certain small GTPases, such as the members of the Ras and Arf subfamilies, have been related with the promotion and progression of cancer. Therefore, the development of inhibitors that target dysfunctional small GTPases could represent a potential therapeutic strategy for cancer treatment. This review covers the basic biochemical mechanisms and the diverse functions of small GTPases in cancer. We also discuss the strategies and challenges of inhibiting the activity of these enzymes and delve into new approaches that offer opportunities to target them in cancer therapy.
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Affiliation(s)
- Néstor Prieto-Dominguez
- Department of Oral Biology and Diagnostic Sciences, Dental College of Georgia, Augusta University, Augusta, GA 30912, USA.
- Institute of Biomedicine (IBIOMED), University of León, León 24010, Spain.
| | | | - Yong Teng
- Department of Oral Biology and Diagnostic Sciences, Dental College of Georgia, Augusta University, Augusta, GA 30912, USA.
- Medical College of Georgia, Augusta University, Augusta, GA 30912, USA.
- Department of Medical laboratory, Imaging and Radiologic Sciences, College of Allied Health, Augusta University, Augusta, GA 30912, USA.
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Bustelo XR. RHO GTPases in cancer: known facts, open questions, and therapeutic challenges. Biochem Soc Trans 2018; 46:741-760. [PMID: 29871878 PMCID: PMC7615761 DOI: 10.1042/bst20170531] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 04/17/2018] [Accepted: 05/03/2018] [Indexed: 02/06/2023]
Abstract
RHO GTPases have been traditionally associated with protumorigenic functions. While this paradigm is still valid in many cases, recent data have unexpectedly revealed that RHO proteins can also play tumor suppressor roles. RHO signaling elements can also promote both pro- and antitumorigenic effects using GTPase-independent mechanisms, thus giving an extra layer of complexity to the role of these proteins in cancer. Consistent with these variegated roles, both gain- and loss-of-function mutations in RHO pathway genes have been found in cancer patients. Collectively, these observations challenge long-held functional archetypes for RHO proteins in both normal and cancer cells. In this review, I will summarize these data and discuss new questions arising from them such as the functional and clinical relevance of the mutations found in patients, the mechanistic orchestration of those antagonistic functions in tumors, and the pros and cons that these results represent for the development of RHO-based anticancer drugs.
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Affiliation(s)
- Xosé R Bustelo
- Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, and Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Consejo Superior de Investigaciones Científicas (CSIC)-University of Salamanca, 37007 Salamanca, Spain
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Abstract
Nucleic acid aptamers are promising alternatives to antibodies in analytics. They are generally obtained through an iterative SELEX protocol that enriches a population of synthetic oligonucleotides to a subset that can recognize the chosen target molecule specifically and avidly. A wide range of targets is recognized by aptamers. Once identified and optimized for performance, aptamers can be reproducibly synthesized and offer other key features, like small size, low cost, sensitivity, specificity, rapid response, stability, and reusability. This makes them excellent options for sensory units in a variety of analytical platforms including those with electrochemical, optical, and mass sensitive transduction detection. Many novel sensing strategies have been developed by rational design to take advantage of the tendency of aptamers to undergo conformational changes upon target/analyte binding and employing the principles of base complementarity that can drive the nucleic acid structure. Despite their many advantages over antibodies, surprisingly few aptamers have yet been integrated into commercially available analytical devices. In this review, we discuss how to select and engineer aptamers for their identified application(s), some of the challenges faced in developing aptamers for analytics and many examples of their reported successful performance as sensors in a variety of analytical platforms.
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Affiliation(s)
- Muslum Ilgu
- Roy J Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames IA 50011, USA. and Aptalogic Inc., Ames IA 50014, USA
| | - Marit Nilsen-Hamilton
- Roy J Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames IA 50011, USA. and Aptalogic Inc., Ames IA 50014, USA and Ames Laboratory, US DOE, Ames IA 50011, USA
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Ouellet E, Lagally ET, Cheung KC, Haynes CA. A simple method for eliminating fixed-region interference of aptamer binding during SELEX. Biotechnol Bioeng 2014; 111:2265-79. [PMID: 24895227 DOI: 10.1002/bit.25294] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 05/07/2014] [Accepted: 05/12/2014] [Indexed: 01/20/2023]
Abstract
Standard libraries for systematic evolution of ligands by exponential enrichment (SELEX) typically utilize flanking regions that facilitate amplification of aptamers recovered from each selection round. Here, we show that these flanking sequences can bias the selection process, due in part to their ability to interfere with the fold or function of aptamers localized within the random region of the library sequence. We then address this problem by investigating the use of complementary oligonucleotides as a means to block aptamer interference by each flanking region. Isothermal titration calorimetry (ITC) studies are combined with fold predictions to both define the various interference mechanisms and assess the ability of added complementary oligonucleotides to ameliorate them. The proposed blocking strategy is thereby refined and then applied to standard library forms of benchmark aptamers against human α-thrombin, streptavidin, and vascular endothelial growth factor (VEGF). In each case, ITC data show that the new method effectively removes fixed-region mediated interference effects so that the natural binding affinity of the benchmark aptamer is completely restored. We further show that the binding affinities of properly functioning aptamers within a selection library are not affected by the blocking protocol, and that the method can be applied to various common library formats comprised of different flanking region sequences. Finally, we present a rapid and inexpensive qPCR-based method for determining the mean binding affinity of retained aptamer pools and use it to show that introduction of the pre-blocking method into the standard SELEX protocol results in retention of high-affinity aptamers that would otherwise be lost during the first round of selection. Significant enrichment of the available pool of high-affinity aptamers is thereby achieved in the first few rounds of selection. By eliminating single-strand (aptamer-like) structures within or involving the fixed regions, the technique is therefore shown to isolate aptamer sequence and function within the desired random region of the library members, and thereby provide a new selection method that is complementary to other available SELEX protocols.
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Affiliation(s)
- Eric Ouellet
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4; Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3; Biomedical Engineering Program, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3
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