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Slane EG, Tambrini SJ, Cummings BS. Therapeutic potential of lipin inhibitors for the treatment of cancer. Biochem Pharmacol 2024; 222:116106. [PMID: 38442792 DOI: 10.1016/j.bcp.2024.116106] [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: 12/18/2023] [Revised: 01/28/2024] [Accepted: 03/01/2024] [Indexed: 03/07/2024]
Abstract
Lipins are phosphatidic acid phosphatases (PAP) that catalyze the conversion of phosphatidic acid (PA) to diacylglycerol (DAG). Three lipin isoforms have been identified: lipin-1, -2 and -3. In addition to their PAP activity, lipin-1 and -2 act as transcriptional coactivators and corepressors. Lipins have been intensely studied for their role in regulation of lipid metabolism and adipogenesis; however, lipins are hypothesized to mediate several pathologies, such as those involving metabolic diseases, neuropathy and even cognitive impairment. Recently, an emerging role for lipins have been proposed in cancer. The study of lipins in cancer has been hampered by lack of inhibitors that have selectivity for lipins, that differentiate between lipin family members, or that are suitable for in vivo studies. Such inhibitors have the potential to be extremely useful as both molecular tools and therapeutics. This review describes the expression and function of lipins in various tissues and their roles in several diseases, but with an emphasis on their possible role in cancer. The mechanisms by which lipins mediate cancer cell growth are discussed and the potential usefulness of selective lipin inhibitors is hypothesized. Finally, recent studies reporting the crystallization of lipin-1 are discussed to facilitate rational design of novel lipin inhibitors.
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Affiliation(s)
- Elizabeth G Slane
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA
| | - Samantha J Tambrini
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA
| | - Brian S Cummings
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
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2
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Fixing the GAP: the role of RhoGAPs in cancer. Eur J Cell Biol 2022; 101:151209. [DOI: 10.1016/j.ejcb.2022.151209] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 01/29/2022] [Accepted: 02/08/2022] [Indexed: 12/12/2022] Open
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3
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Senyuz S, Jang H, Nussinov R, Keskin O, Gursoy A. Mechanistic Differences of Activation of Rac1 P29S and Rac1 A159V. J Phys Chem B 2021; 125:3790-3802. [PMID: 33848152 PMCID: PMC8154616 DOI: 10.1021/acs.jpcb.1c00883] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/31/2021] [Indexed: 12/26/2022]
Abstract
Rac1 is a small GTPase that plays key roles in actin reorganization, cell motility, and cell survival/growth as well as in various cancer types and neurodegenerative diseases. Similar to other Ras superfamily GTPases, Rac1 switches between active GTP-bound and inactive GDP-bound states. Switch I and II regions open and close during GDP/GTP exchange. P29S and A159V (paralogous to K-RasA146) mutations are the two most common somatic mutations of Rac1. Rac1P29S is a known hotspot for melanoma, whereas Rac1A159V most commonly occurs in head and neck cancer. To investigate how these substitutions induce the Rac1 dynamics, we used atomistic molecular dynamics simulations on the wild-type Rac1 and two mutant systems (P29S and A159V) in the GTP bound state, and on the wild-type Rac1 and P29S mutated system in the GDP bound state. Here, we show that P29S and A159V mutations activate Rac1 with different mechanisms. In Rac1P29S-GTP, the substitution increases the flexibility of Switch I based on RMSF and dihedral angle calculations and leads to an open conformation. We propose that the open Switch I conformation is one of the underlying reasons for rapid GDP/GTP exchange of Rac1P29S. On the other hand, in Rac1A159V-GTP, some of the contacts of the guanosine ring of GTP with Rac1 are temporarily lost, enabling the guanosine ring to move toward Switch I and subsequently close the switch. Rac1A159V-GTP adopts a Ras state 2 like conformation, where both switch regions are in closed conformation and Thr35 forms a hydrogen bond with the nucleotide.
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Affiliation(s)
- Simge Senyuz
- Computational
Science and Engineering, Koc University, Rumelifeneri Yolu, 34450 Sariyer, Istanbul, Turkey
| | - Hyunbum Jang
- Computational
Structural Biology Section, Frederick National Laboratory for Cancer
Research in the Laboratory of Cancer Immunometabolism, National Cancer Institute, Frederick, Maryland 21702, United States
| | - Ruth Nussinov
- Computational
Structural Biology Section, Frederick National Laboratory for Cancer
Research in the Laboratory of Cancer Immunometabolism, National Cancer Institute, Frederick, Maryland 21702, United States
- Department
of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ozlem Keskin
- Chemical
and Biological Engineering, Koc University, Rumelifeneri Yolu, 34450 Sariyer, Istanbul, Turkey
| | - Attila Gursoy
- Computer
Engineering, Koc University, Rumelifeneri Yolu, 34450 Sariyer, Istanbul, Turkey
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4
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Rho GTPases: Big Players in Breast Cancer Initiation, Metastasis and Therapeutic Responses. Cells 2020; 9:cells9102167. [PMID: 32992837 PMCID: PMC7600866 DOI: 10.3390/cells9102167] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/21/2020] [Accepted: 09/22/2020] [Indexed: 12/12/2022] Open
Abstract
Rho GTPases, a family of the Ras GTPase superfamily, are key regulators of the actin cytoskeleton. They were originally thought to primarily affect cell migration and invasion; however, recent advances in our understanding of the biology and function of Rho GTPases have demonstrated their diverse roles within the cell, including membrane trafficking, gene transcription, migration, invasion, adhesion, survival and growth. As these processes are critically involved in cancer initiation, metastasis and therapeutic responses, it is not surprising that studies have demonstrated important roles of Rho GTPases in cancer. Although the majority of data indicates an oncogenic role of Rho GTPases, tumor suppressor functions of Rho GTPases have also been revealed, suggesting a context and cell-type specific function for Rho GTPases in cancer. This review aims to summarize recent progresses in our understanding of the regulation and functions of Rho GTPases, specifically in the context of breast cancer. The potential of Rho GTPases as therapeutic targets and prognostic tools for breast cancer patients are also discussed.
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5
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P-REX1-Independent, Calcium-Dependent RAC1 Hyperactivation in Prostate Cancer. Cancers (Basel) 2020; 12:cancers12020480. [PMID: 32092966 PMCID: PMC7072377 DOI: 10.3390/cancers12020480] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 02/07/2020] [Accepted: 02/17/2020] [Indexed: 12/15/2022] Open
Abstract
The GTPase Rac1 is a well-established master regulator of cell motility and invasiveness contributing to cancer metastasis. Dysregulation of the Rac1 signaling pathway, resulting in elevated motile and invasive potential, has been reported in multiple cancers. However, there are limited studies on the regulation of Rac1 in prostate cancer. Here, we demonstrate that aggressive androgen-independent prostate cancer cells display marked hyperactivation of Rac1. This hyperactivation is independent of P-Rex1 activity or its direct activators, the PI3K product PIP3 and Gβγ subunits. Furthermore, we demonstrate that the motility and invasiveness of PC3 prostate cancer cells is independent of P-Rex1, supporting the analysis of publicly available datasets indicating no correlation between high P-Rex1 expression and cancer progression in patients. Rac1 hyperactivation was not related to the presence of activating Rac1 mutations and was insensitive to overexpression of a Rac-GAP or the silencing of specific Rac-GEFs expressed in prostate cancer cells. Interestingly, active Rac1 levels in these cells were markedly reduced by elevations in intracellular calcium or by serum stimulation, suggesting the presence of an alternative means of Rac1 regulation in prostate cancer that does not involve previously established paradigms.
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7
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Casado-Medrano V, Barrio-Real L, Gutiérrez-Miranda L, González-Sarmiento R, Velasco EA, Kazanietz MG, Caloca MJ. Identification of a truncated β1-chimaerin variant that inactivates nuclear Rac1. J Biol Chem 2019; 295:1300-1314. [PMID: 31871052 DOI: 10.1074/jbc.ra119.008688] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 12/14/2019] [Indexed: 12/11/2022] Open
Abstract
β1-chimaerin belongs to the chimaerin family of GTPase-activating proteins (GAPs) and is encoded by the CHN2 gene, which also encodes the β2- and β3-chimaerin isoforms. All chimaerin isoforms have a C1 domain that binds diacylglycerol as well as tumor-promoting phorbol esters and a catalytic GAP domain that inactivates the small GTPase Rac. Nuclear Rac has emerged as a key regulator of various cell functions, including cell division, and has a pathological role by promoting tumorigenesis and metastasis. However, how nuclear Rac is regulated has not been fully addressed. Here, using several approaches, including siRNA-mediated gene silencing, confocal microscopy, and subcellular fractionation, we identified a nuclear variant of β1-chimaerin, β1-Δ7p-chimaerin, that participates in the regulation of nuclear Rac1. We show that β1-Δ7p-chimaerin is a truncated variant generated by alternative splicing at a cryptic splice site in exon 7. We found that, unlike other chimaerin isoforms, β1-Δ7p-chimaerin lacks a functional C1 domain and is not regulated by diacylglycerol. We found that β1-Δ7p-chimaerin localizes to the nucleus via a nuclear localization signal in its N terminus. We also identified a key nuclear export signal in β1-chimaerin that is absent in β1-Δ7p-chimaerin, causing nuclear retention of this truncated variant. Functionally analyses revealed that β1-Δ7p-chimaerin inactivates nuclear Rac and negatively regulates the cell cycle. Our results provide important insights into the diversity of chimaerin Rac-GAP regulation and function and highlight a potential mechanism of nuclear Rac inactivation that may play significant roles in pathologies such as cancer.
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Affiliation(s)
- Victoria Casado-Medrano
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
| | - Laura Barrio-Real
- Molecular Medicine Unit and Institute of Molecular and Cellular Biology of Cancer, Biomedical Research Institute of Salamanca, University of Salamanca, 37007 Salamanca, Spain
| | - Laura Gutiérrez-Miranda
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
| | - Rogelio González-Sarmiento
- Molecular Medicine Unit and Institute of Molecular and Cellular Biology of Cancer, Biomedical Research Institute of Salamanca, University of Salamanca, 37007 Salamanca, Spain
| | - Eladio A Velasco
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
| | - Marcelo G Kazanietz
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - María J Caloca
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
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8
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Wang Z, Lin HP, Li Y, Tao H, Yang P, Xie J, Maddy D, Kondo K, Yang C. Chronic Hexavalent Chromium Exposure Induces Cancer Stem Cell-Like Property and Tumorigenesis by Increasing c-Myc Expression. Toxicol Sci 2019; 172:252-264. [PMID: 31504995 PMCID: PMC6876261 DOI: 10.1093/toxsci/kfz196] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Hexavalent chromium [Cr(VI)] is one of the most common environmental carcinogen causing lung cancer in humans; however, the mechanism of Cr(VI) carcinogenesis remains elusive. Cancer stem cells (CSCs) are considered as cancer initiating and maintaining cells. Ours and other recent studies showed that chronic Cr(VI) exposure induces CSC-like property representing an important mechanism of Cr(VI) carcinogenesis. However, how Cr(VI) exposure induces CSC-like property remains largely unknown. In this study, we found that stably knocking down the expression of c-Myc, a proto-oncogene and one of key stemness factors playing critical roles in cancer initiation and progression, in Cr(VI)-transformed human bronchial epithelial cells [BEAS-2B-Cr(VI)] significantly decreased their CSC-like property and tumorigenicity in mice. Moreover, stably knocking down c-Myc expression in parental nontransformed BEAS-2B cells significantly impaired the capability of chronic Cr(VI) exposure to induce CSC-like property and cell transformation. It was also found that stably overexpressing c-Myc alone in parental nontransformed BEAS-2B cells is capable of causing CSC-like property and cell transformation. Mechanistic studies showed that chronic Cr(VI) exposure increases c-Myc expression by down-regulating the level of microRNA-494 (miR-494). It was further determined that overexpressing miR-494 significantly reduces Cr(VI)-induced CSC-like property, cell transformation, and tumorigenesis mainly through down-regulating c-Myc expression. Together, these findings indicate that chronic low dose Cr(VI) exposure induces CSC-like property and tumorigenesis by increasing c-Myc expression through down-regulating the level of miR-494, revealing an important role of the proto-oncogene c-Myc in Cr(VI) carcinogenesis.
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Affiliation(s)
- Zhishan Wang
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
| | - Hsuan-Pei Lin
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
| | - Yunfei Li
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
| | - Hua Tao
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
| | - Ping Yang
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
- School of Public Health, Guangzhou Medical University, Guangzhou, Guangdong 511436, P.R. China
| | - Jie Xie
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
- School of Health Sciences, Wuhan University, Wuhan, Hubei 430071, P.R. China
| | - Drew Maddy
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
| | - Kazuya Kondo
- Department of Oncological Medical Services, Graduate School of Biomedical Sciences, Tokushima University Graduate School, Tokushima City 770-8509, Japan
| | - Chengfeng Yang
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
- Center for Research on Environmental Disease, University of Kentucky College of Medicine, Lexington, Kentucky 40536
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9
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Zhou Y, Shi WY, He W, Yan ZW, Liu MH, Chen J, Yang YS, Wang YQ, Chen GQ, Huang Y. FAM122A supports the growth of hepatocellular carcinoma cells and its deletion enhances Doxorubicin-induced cytotoxicity. Exp Cell Res 2019; 387:111714. [PMID: 31711919 DOI: 10.1016/j.yexcr.2019.111714] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 11/02/2019] [Accepted: 11/05/2019] [Indexed: 12/29/2022]
Abstract
FAM122A is a highly conserved protein in mammals, however its function is still largely unknown so far. In this study, we investigated the potential role of FAM122A in hepatocellular carcinoma (HCC). By analyzing HCC patient cohorts from RNA sequencing datasets, we found the expression level of FAM122A mRNA is significantly upregulated in HCC patients. Moreover, this abnormally higher expression pattern of FAM122A protein was also found in partial HCC tumor tissues, compared with the normal parts. Further, we demonstrated that CRISPR/Cas9-mediated FAM122A knockout significantly inhibits the growth, clonogenic potential and xenografts of HCC cells, induces cell cycle arrest and reduces the expression of proliferation-related genes. Interestingly, FAM122A deletion significantly enhances the cytotoxicity effect of Doxorubicin (Dox), a drug used in standard chemotherapy in HCC patients. In contrary, overexpression of FAM122A not only promotes HCC cell growth, but also inhibits Dox-induced DNA damage and cell death. Considering that FAM122A is previously identified as an endogenous inhibitor of PP2A, we asked whether FAM122A regulating HCC cell growth is associated with PP2A. The results showed FAM122A can also modulate PP2A activity in HCC cells although the modulated effect is relatively slight, however, treatment with a PP2A inhibitor okadaic acid did not rescue the inhibitory effects of cell growth and proliferation in FAM122A deletion cells, indicating that FAM122A may support HCC cell growth independent of its ability to modulate PP2A. Collectively, these results suggest that FAM122A is required for maintaining HCC cell growth, and its elimination combined with chemotherapy may represent a potential novel therapeutic strategy for HCC patients.
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Affiliation(s)
- Yong Zhou
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Wen-Yang Shi
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Wei He
- Department of Pathology, Ren-Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200027, China
| | - Zhao-Wen Yan
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Man-Hua Liu
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jing Chen
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yun-Sheng Yang
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yin-Qi Wang
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Guo-Qiang Chen
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Ying Huang
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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10
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Li Y, Xiao Y, Lin HP, Reichel D, Bae Y, Lee EY, Jiang Y, Huang X, Yang C, Wang Z. In vivo β-catenin attenuation by the integrin α5-targeting nano-delivery strategy suppresses triple negative breast cancer stemness and metastasis. Biomaterials 2019; 188:160-172. [DOI: 10.1016/j.biomaterials.2018.10.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 10/16/2018] [Accepted: 10/17/2018] [Indexed: 12/13/2022]
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11
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Integrin α5 down-regulation by miR-205 suppresses triple negative breast cancer stemness and metastasis by inhibiting the Src/Vav2/Rac1 pathway. Cancer Lett 2018; 433:199-209. [PMID: 29964204 DOI: 10.1016/j.canlet.2018.06.037] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 06/21/2018] [Accepted: 06/26/2018] [Indexed: 01/06/2023]
Abstract
Triple negative breast cancer (TNBC) usually displays more aggressive metastasis, the underlying mechanism is unclear. Previous studies showed that microRNA-205 (miR-205) has controversial roles in cancer, however, its role in TNBC metastasis and the underlying mechanism have not been well-understood. In this study we found that miR-205 expression level is extremely low in basal mesenchymal-like highly migratory and invasive TNBC cells. Stably re-expressing miR-205 in TNBC cells significantly reduced their migration, invasion capability and cancer stem cell (CSC)-like property. Nude mouse orthotopic mammary xenograft tumor model study revealed that miR-205 re-expression greatly decreases TNBC tumor growth and abolishes spontaneous lung metastasis. Mechanistic studies demonstrated that miR-205 inhibits TNBC cell metastatic traits and tumor metastasis by down-regulating integrin α5 (ITGA5). Moreover, ITGA5 knockout using the CRISPR/Cas9 technique achieved the same strong inhibitory effect on TNBC cell CSC-like property and tumor metastasis as re-expressing miR-205 did. Further mechanistic studies indicated that ITGA5 down-regulation by miR-205 re-expression impairs TNBC cell metastatic traits by inhibiting the Src/Vav2/Rac1 pathway. Together, our findings suggest that miR-205 and ITGA5 may serve as potential targets for developing effective therapies for metastatic TNBC.
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12
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Elaimy AL, Guru S, Chang C, Ou J, Amante JJ, Zhu LJ, Goel HL, Mercurio AM. VEGF-neuropilin-2 signaling promotes stem-like traits in breast cancer cells by TAZ-mediated repression of the Rac GAP β2-chimaerin. Sci Signal 2018; 11:11/528/eaao6897. [PMID: 29717062 DOI: 10.1126/scisignal.aao6897] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The role of vascular endothelial growth factor (VEGF) signaling in cancer is not only well known in the context of angiogenesis but also important in the functional regulation of tumor cells. Autocrine VEGF signaling mediated by its co-receptors called neuropilins (NRPs) appears to be essential for sustaining the proliferation and survival of cancer stem cells (CSCs), which are implicated in mediating tumor growth, progression, and drug resistance. Therefore, understanding the mechanisms involved in VEGF-mediated support of CSCs is critical to successfully treating cancer patients. The expression of the Hippo effector TAZ is associated with breast CSCs and confers stem cell-like properties. We found that VEGF-NRP2 signaling contributed to the activation of TAZ in various breast cancer cells, which mediated a positive feedback loop that promoted mammosphere formation. VEGF-NRP2 signaling activated the GTPase Rac1, which inhibited the Hippo kinase LATS, thus leading to TAZ activity. In a complex with the transcription factor TEAD, TAZ then bound and repressed the promoter of the gene encoding the Rac GTPase-activating protein (Rac GAP) β2-chimaerin. By activating GTP hydrolysis, Rac GAPs effectively turn off Rac signaling; hence, the TAZ-mediated repression of β2-chimaerin resulted in sustained Rac1 activity in CSCs. Depletion of β2-chimaerin in non-CSCs increased Rac1 activity, TAZ abundance, and mammosphere formation. Analysis of a breast cancer patient database revealed an inverse correlation between β2-chimaerin and TAZ expression in tumors. Our findings highlight an unexpected role for β2-chimaerin in a feed-forward loop of TAZ activation and the acquisition of CSC properties.
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Affiliation(s)
- Ameer L Elaimy
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.,Medical Scientist Training Program, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01605, USA
| | - Santosh Guru
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Cheng Chang
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Jianhong Ou
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - John J Amante
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Lihua Julie Zhu
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.,Department of Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.,Department of Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Hira Lal Goel
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Arthur M Mercurio
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
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A new role of the Rac-GAP β2-chimaerin in cell adhesion reveals opposite functions in breast cancer initiation and tumor progression. Oncotarget 2017; 7:28301-19. [PMID: 27058424 PMCID: PMC5053728 DOI: 10.18632/oncotarget.8597] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 03/27/2016] [Indexed: 01/06/2023] Open
Abstract
β2-chimaerin is a Rac1-specific negative regulator and a candidate tumor suppressor in breast cancer but its precise function in mammary tumorigenesis in vivo is unknown. Here, we study for the first time the role of β2-chimaerin in breast cancer using a mouse model and describe an unforeseen role for this protein in epithelial cell-cell adhesion. We demonstrate that expression of β2-chimaerin in breast cancer epithelial cells reduces E-cadherin protein levels, thus loosening cell-cell contacts. In vivo, genetic ablation of β2-chimaerin in the MMTV-Neu/ErbB2 mice accelerates tumor onset, but delays tumor progression. Finally, analysis of clinical databases revealed an inverse correlation between β2-chimaerin and E-cadherin gene expressions in Her2+ breast tumors. Furthermore, breast cancer patients with low β2-chimaerin expression have reduced relapse free survival but develop metastasis at similar times. Overall, our data redefine the role of β2-chimaerin as tumor suppressor and provide the first in vivo evidence of a dual function in breast cancer, suppressing tumor initiation but favoring tumor progression.
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Cardama GA, Gonzalez N, Maggio J, Menna PL, Gomez DE. Rho GTPases as therapeutic targets in cancer (Review). Int J Oncol 2017; 51:1025-1034. [PMID: 28848995 PMCID: PMC5592879 DOI: 10.3892/ijo.2017.4093] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 07/17/2017] [Indexed: 12/20/2022] Open
Abstract
Rho GTPases are key molecular switches controlling the transduction of external signals to cytoplasmic and nuclear effectors. In the last few years, the development of genetic and pharmacological tools has allowed a more precise definition of the specific roles of Rho GTPases in cancer. The aim of the present review is to describe the cellular functions regulated by these proteins with focus in deregulated signals present in malignant tumors. Finally, we describe the state of the art in search of different experimental therapeutic strategies with Rho GTPases as molecular targets.
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Affiliation(s)
- G A Cardama
- Laboratory of Molecular Oncology, Department of Science and Technology, Quilmes National University, Bernal B1876BXD, Buenos Aires, Argentina
| | - N Gonzalez
- Laboratory of Molecular Oncology, Department of Science and Technology, Quilmes National University, Bernal B1876BXD, Buenos Aires, Argentina
| | - J Maggio
- Laboratory of Molecular Oncology, Department of Science and Technology, Quilmes National University, Bernal B1876BXD, Buenos Aires, Argentina
| | - P Lorenzano Menna
- Laboratory of Molecular Oncology, Department of Science and Technology, Quilmes National University, Bernal B1876BXD, Buenos Aires, Argentina
| | - D E Gomez
- Laboratory of Molecular Oncology, Department of Science and Technology, Quilmes National University, Bernal B1876BXD, Buenos Aires, Argentina
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Humphries B, Wang Z, Li Y, Jhan JR, Jiang Y, Yang C. ARHGAP18 Downregulation by miR-200b Suppresses Metastasis of Triple-Negative Breast Cancer by Enhancing Activation of RhoA. Cancer Res 2017; 77:4051-4064. [PMID: 28619708 DOI: 10.1158/0008-5472.can-16-3141] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 02/13/2017] [Accepted: 06/05/2017] [Indexed: 11/16/2022]
Abstract
Rho GTPases activated in cancer cells drive proliferation, migration, and metastasis. Thus, RhoGAP proteins, which negatively regulate Rho GTPases, are generally thought to function as tumor suppressors. Here this expectation was challenged by characterization of ARHGAP18, a RhoGAP family member that is selectively overexpressed in highly migratory triple-negative breast cancer (TNBC) cells. In human breast tumors, higher ARHGAP18 levels associated with worse overall survival, recurrence-free survival, and metastasis-free survival. In TNBC cells, ARHGAP18 deletion increased RhoA activation but reduced growth, migration, and metastatic capacity. Mechanistic investigations revealed that ARHGAP18 levels were controlled by miR-200b, the enforced expression of which was sufficient to activate RhoA, enhanced formation of focal adhesions and actin stress fibers, and reduced migration and metastasis. Enforced elevation of ARHGAP18 where miR-200b was stably expressed reduced RhoA activity but increased cell migration. Pharmacologic inhibition of the Rho effector kinase ROCK blocked RhoA signaling and reversed the inhibitory effect of miR-200b on cell migration. Finally, ARHGAP18 overexpression or ROCK inhibition was sufficient to overcome metastatic blockade by miR-200b. Taken together, these results define opposing roles for oncogenic ARHGAP18 and tumor suppressive miR-200b in determining TNBC cell migration and metastatic prowess. Cancer Res; 77(15); 4051-64. ©2017 AACR.
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Affiliation(s)
- Brock Humphries
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - Zhishan Wang
- Department of Physiology, Michigan State University, East Lansing, Michigan
- Department of Toxicology and Cancer Biology, Center for Research on Environmental Diseases, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Yunfei Li
- Department of Physiology, Michigan State University, East Lansing, Michigan
- Department of Toxicology and Cancer Biology, Center for Research on Environmental Diseases, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Jing-Ru Jhan
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - Yiguo Jiang
- Institute for Chemical Carcinogenesis, State Key Laboratory of Respiratory Diseases, Guangzhou Medical University, Guangzhou, Guangdong, P.R. China
| | - Chengfeng Yang
- Department of Physiology, Michigan State University, East Lansing, Michigan.
- Department of Toxicology and Cancer Biology, Center for Research on Environmental Diseases, College of Medicine, University of Kentucky, Lexington, Kentucky
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Cooke M, Magimaidas A, Casado-Medrano V, Kazanietz MG. Protein kinase C in cancer: The top five unanswered questions. Mol Carcinog 2017; 56:1531-1542. [PMID: 28112438 DOI: 10.1002/mc.22617] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 01/04/2017] [Accepted: 01/20/2017] [Indexed: 12/29/2022]
Abstract
Few kinases have been studied as extensively as protein kinase C (PKC), particularly in the context of cancer. As major cellular targets for the phorbol ester tumor promoters and diacylglycerol (DAG), a second messenger generated by stimulation of membrane receptors, PKC isozymes play major roles in the control of signaling pathways associated with proliferation, migration, invasion, tumorigenesis, and metastasis. However, despite decades of research, fundamental questions remain to be answered or are the subject of intense controversy. Primary among these unresolved issues are the role of PKC isozymes as either tumor promoter or tumor suppressor kinases and the incomplete understanding on isozyme-specific substrates and effectors. The involvement of PKC isozymes in cancer progression needs to be reassessed in the context of specific oncogenic and tumor suppressing alterations. In addition, there are still major hurdles in addressing isozyme-specific function due to the limited specificity of most pharmacological PKC modulators and the lack of validated predictive biomarkers for response, which impacts the translation of these agents to the clinic. In this review we focus on key controversial issues and upcoming challenges, with the expectation that understanding the intricacies of PKC function will help fulfill the yet unsuccessful promise of targeting PKCs for cancer therapeutics.
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Affiliation(s)
- Mariana Cooke
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Andrew Magimaidas
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Victoria Casado-Medrano
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Marcelo G Kazanietz
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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Kazanietz MG, Barrio-Real L, Casado-Medrano V, Baker MJ, Lopez-Haber C. The P-Rex1/Rac signaling pathway as a point of convergence for HER/ErbB receptor and GPCR responses. Small GTPases 2016; 9:297-303. [PMID: 27588611 DOI: 10.1080/21541248.2016.1221273] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Guanine nucleotide Exchange Factors (GEFs) are responsible for mediating GDP/GTP exchange for specific small G proteins, such as Rac. There has been substantial evidence for the involvement of Rac-GEFs in the control of cancer cell migration and metastatic progression. We have previously established that the Rac-GEF P-Rex1 is a mediator of actin cytoskeleton rearrangements and cell motility in breast cancer cells downstream of HER/ErbB receptors and the G-Protein Coupled Receptor (GPCR) CXCR4. P-Rex1 is highly expressed in luminal A and B breast cancer compared to normal mammary tissue, whereas expression is very low in basal breast cancer, and its expression correlates with the appearance of metastasis in patients. Here, we discuss the involvement of P-Rex1 as an effector of oncogenic/metastatic receptors in breast cancer and underscore its relevance in the convergence of receptor-triggered motile signals. In addition, we provide an overview of our recent findings describing a cross-talk between HER/ErbB receptors and CXCR4, and how this impacts on the activation of P-Rex1/Rac1 signaling, as well as highlight challenges that lie ahead. We propose a model in which P-Rex1 acts as a crucial node for the integration of upstream inputs from HER/ErbB receptors and CXCR4 in luminal breast cancer cells.
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Affiliation(s)
- Marcelo G Kazanietz
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Laura Barrio-Real
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Victoria Casado-Medrano
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Martin J Baker
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Cynthia Lopez-Haber
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
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Heregulin/ErbB3 Signaling Enhances CXCR4-Driven Rac1 Activation and Breast Cancer Cell Motility via Hypoxia-Inducible Factor 1α. Mol Cell Biol 2016; 36:2011-26. [PMID: 27185877 DOI: 10.1128/mcb.00180-16] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 05/06/2016] [Indexed: 01/11/2023] Open
Abstract
The growth factor heregulin (HRG), a ligand of ErbB3 and ErbB4 receptors, contributes to breast cancer development and the promotion of metastatic disease, and its expression in breast tumors has been associated with poor clinical outcome and resistance to therapy. In this study, we found that breast cancer cells exposed to sustained HRG treatment show markedly enhanced Rac1 activation and migratory activity in response to the CXCR4 ligand SDF-1/CXCL12, effects mediated by P-Rex1, a Rac-guanine nucleotide exchange factor (GEF) aberrantly expressed in breast cancer. Notably, HRG treatment upregulates surface expression levels of CXCR4, a G protein-coupled receptor (GPCR) implicated in breast cancer metastasis and an indicator of poor prognosis in breast cancer patients. A detailed mechanistic analysis revealed that CXCR4 upregulation and sensitization of the Rac response/motility by HRG are mediated by the transcription factor hypoxia-inducible factor 1α (HIF-1α) via ErbB3 and independently of ErbB4. HRG caused prominent induction in the nuclear expression of HIF-1α, which transcriptionally activates the CXCR4 gene via binding to a responsive element located in positions -1376 to -1372 in the CXCR4 promoter, as revealed by mutagenesis analysis and chromatin immunoprecipitation (ChIP). Our results uncovered a novel function for ErbB3 in enhancing breast cancer cell motility and sensitization of the P-Rex1/Rac1 pathway through HIF-1α-mediated transcriptional induction of CXCR4.
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Alvi MA, McArt DG, Kelly P, Fuchs MA, Alderdice M, McCabe CM, Bingham V, McGready C, Tripathi S, Emmert-Streib F, Loughrey MB, McQuaid S, Maxwell P, Hamilton PW, Turkington R, James JA, Wilson RH, Salto-Tellez M. Comprehensive molecular pathology analysis of small bowel adenocarcinoma reveals novel targets with potential for clinical utility. Oncotarget 2016; 6:20863-74. [PMID: 26315110 PMCID: PMC4673235 DOI: 10.18632/oncotarget.4576] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 07/20/2015] [Indexed: 01/22/2023] Open
Abstract
Small bowel accounts for only 0.5% of cancer cases in the US but incidence rates have been rising at 2.4% per year over the past decade. One-third of these are adenocarcinomas but little is known about their molecular pathology and no molecular markers are available for clinical use. Using a retrospective 28 patient matched normal-tumor cohort, next-generation sequencing, gene expression arrays and CpG methylation arrays were used for molecular profiling. Next-generation sequencing identified novel mutations in IDH1, CDH1, KIT, FGFR2, FLT3, NPM1, PTEN, MET, AKT1, RET, NOTCH1 and ERBB4. Array data revealed 17% of CpGs and 5% of RNA transcripts assayed to be differentially methylated and expressed respectively (p < 0.01). Merging gene expression and DNA methylation data revealed CHN2 as consistently hypermethylated and downregulated in this disease (Spearman −0.71, p < 0.001). Mutations in TP53 which were found in more than half of the cohort (15/28) and Kazald1 hypomethylation were both were indicative of poor survival (p = 0.03, HR = 3.2 and p = 0.01, HR = 4.9 respectively). By integrating high-throughput mutational, gene expression and DNA methylation data, this study reveals for the first time the distinct molecular profile of small bowel adenocarcinoma and highlights potential clinically exploitable markers.
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Affiliation(s)
- Muhammad A Alvi
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Darragh G McArt
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Paul Kelly
- Tissue Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK
| | - Marc-Aurel Fuchs
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Matthew Alderdice
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Clare M McCabe
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Victoria Bingham
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Claire McGready
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Shailesh Tripathi
- Computational Biology and Machine Learning Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Frank Emmert-Streib
- Computational Biology and Machine Learning Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Maurice B Loughrey
- Tissue Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK
| | - Stephen McQuaid
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK.,Tissue Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK
| | - Perry Maxwell
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK.,Tissue Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK
| | - Peter W Hamilton
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Richard Turkington
- Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Jacqueline A James
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK.,Tissue Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK
| | - Richard H Wilson
- Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Manuel Salto-Tellez
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, UK.,Tissue Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK
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20
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Ning L, Guo-Chun Z, Sheng-Li A, Xue-Rui L, Kun W, Jian Z, Chong-Yang R, Ling-Zhu W, Hai-Tong L. Inhibition of autophagy induced by PTEN loss promotes intrinsic breast cancer resistance to trastuzumab therapy. Tumour Biol 2015; 37:5445-54. [DOI: 10.1007/s13277-015-4392-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 11/05/2015] [Indexed: 12/19/2022] Open
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Abstract
INTRODUCTION Rho GTPases are master regulators of actomyosin structure and dynamics and play pivotal roles in a variety of cellular processes including cell morphology, gene transcription, cell cycle progression, and cell adhesion. Because aberrant Rho GTPase signaling activities are widely associated with human cancer, key components of Rho GTPase signaling pathways have attracted increasing interest as potential therapeutic targets. Similar to Ras, Rho GTPases themselves were, until recently, deemed "undruggable" because of structure-function considerations. Several approaches to interfere with Rho GTPase signaling have been explored and show promise as new ways for tackling cancer cells. AREAS COVERED This review focuses on the recent progress in targeting the signaling activities of three prototypical Rho GTPases, that is, RhoA, Rac1, and Cdc42. The authors describe the involvement of these Rho GTPases, their key regulators and effectors in cancer. Furthermore, the authors discuss the current approaches for rationally targeting aberrant Rho GTPases along their signaling cascades, upstream and downstream of Rho GTPases, and posttranslational modifications at a molecular level. EXPERT OPINION To date, while no clinically effective drugs targeting Rho GTPase signaling for cancer treatment are available, tool compounds and lead drugs that pharmacologically inhibit Rho GTPase pathways have shown promise. Small-molecule inhibitors targeting Rho GTPase signaling may add new treatment options for future precision cancer therapy, particularly in combination with other anti-cancer agents.
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Affiliation(s)
- Yuan Lin
- Division of Experimental Hematology and Cancer Biology, Children’s Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio 45229, USA
| | - Yi Zheng
- Division of Experimental Hematology and Cancer Biology, Children’s Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio 45229, USA
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22
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Gutierrez-Uzquiza A, Lopez-Haber C, Jernigan DL, Fatatis A, Kazanietz MG. PKCε Is an Essential Mediator of Prostate Cancer Bone Metastasis. Mol Cancer Res 2015; 13:1336-46. [PMID: 26023164 DOI: 10.1158/1541-7786.mcr-15-0111] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/20/2015] [Indexed: 11/16/2022]
Abstract
UNLABELLED The bone is a preferred site for metastatic homing of prostate cancer cells. Once prostate cancer patients develop skeletal metastases, they eventually succumb to the disease; therefore, it is imperative to identify key molecular drivers of this process. This study examines the involvement of protein kinase C epsilon (PKCε), an oncogenic protein that is abnormally overexpressed in human tumor specimens and cell lines, on prostate cancer cell bone metastasis. PC3-ML cells, a highly invasive prostate cancer PC3 derivative with bone metastatic colonization properties, failed to induce skeletal metastatic foci upon inoculation into nude mice when PKCε expression was silenced using shRNA. Interestingly, while PKCε depletion had only marginal effects on the proliferative, adhesive, and migratory capacities of PC3-ML cells in vitro or in the growth of xenografts upon s.c. inoculation, it caused a significant reduction in cell invasiveness. Notably, PKCε was required for transendothelial cell migration (TEM) as well as for the growth of PC3-ML cells in a bone biomimetic environment. At a mechanistic level, PKCε depletion abrogates the expression of IL1β, a cytokine implicated in skeletal metastasis. Taken together, PKCε is a key factor for driving the formation of bone metastasis by prostate cancer cells and is a potential therapeutic target for advanced stages of the disease. IMPLICATIONS This study uncovers an important new function of PKCε in the dissemination of cancer cells to the bone; thus, highlighting the promising potential of this oncogenic kinase as a therapeutic target for skeletal metastasis.
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Affiliation(s)
- Alvaro Gutierrez-Uzquiza
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Cynthia Lopez-Haber
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Danielle L Jernigan
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Alessandro Fatatis
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania. Program in Biology of Prostate Cancer, Sidney Kimmel Cancer Center, Philadelphia, Pennsylvania
| | - Marcelo G Kazanietz
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
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Cardama GA, Comin MJ, Hornos L, Gonzalez N, Defelipe L, Turjanski AG, Alonso DF, Gomez DE, Menna PL. Preclinical development of novel Rac1-GEF signaling inhibitors using a rational design approach in highly aggressive breast cancer cell lines. Anticancer Agents Med Chem 2015; 14:840-51. [PMID: 24066799 PMCID: PMC4104455 DOI: 10.2174/18715206113136660334] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 06/21/2013] [Accepted: 09/15/2013] [Indexed: 11/22/2022]
Abstract
Rho GTPases play a key role in the regulation of multiple essential cellular processes, including actin dynamics, gene transcription and cell cycle progression. Aberrant activation of Rac1, a member of Rho family of small GTPases, is associated with tumorigenesis, cancer progression, invasion and metastasis. Particularly, Rac1 is overexpressed and hyperactivated in highly aggressive breast cancer. Thus, Rac1 appears to be a promising and relevant target for the development of novel anticancer drugs. We identified the novel Rac1 inhibitor ZINC69391 through a docking-based virtual library screening targeting Rac1 activation by GEFs. This compound was able to block Rac1 interaction with its GEF Tiam1, prevented EGF-induced Rac1 activation and inhibited cell proliferation, cell migration and cell cycle progression in highly aggressive breast cancer cell lines. Moreover, ZINC69391 showed an in vivo antimetastatic effect in a syngeneic animal model. We further developed the novel analog 1A-116 by rational design and showed to be specific and more potent than the parental compound in vitro and interfered Rac1-P-Rex1 interaction. We also showed an enhanced in vivo potency of 1A-116 analog. These results show that we have developed novel Rac1 inhibitors that may be used as a novel anticancer therapy.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Pablo Lorenzano Menna
- Laboratorio de Oncología Molecular, Universidad Nacional de Quilmes. Roque Saenz Pena 352, Bernal B1876BXD Buenos Aires, Argentina.
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24
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Barrio-Real L, Benedetti LG, Engel N, Tu Y, Cho S, Sukumar S, Kazanietz MG. Subtype-specific overexpression of the Rac-GEF P-REX1 in breast cancer is associated with promoter hypomethylation. Breast Cancer Res 2014; 16:441. [PMID: 25248717 PMCID: PMC4303123 DOI: 10.1186/s13058-014-0441-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 09/01/2014] [Indexed: 01/30/2023] Open
Abstract
Introduction The Rac-GEF P-REX1 is a key mediator of ErbB signaling in breast cancer recently implicated in mammary tumorigenesis and metastatic dissemination. Although P-REX1 is essentially undetectable in normal human mammary epithelial tissue, this Rac-GEF is markedly upregulated in human breast carcinomas, particularly of the luminal subtype. The mechanisms underlying P-REX1 upregulation in breast cancer are unknown. Toward the goal of dissecting the mechanistic basis of P-REX1 overexpression in breast cancer, in this study we focused on the analysis of methylation of the PREX1 gene promoter. Methods To determine the methylation status of the PREX1 promoter region, we used bisulfite genomic sequencing and pyrosequencing approaches. Re-expression studies in cell lines were carried out by treatment of breast cancer cells with the demethylating agent 5-aza-2′-deoxycitidine. PREX1 gene methylation in different human breast cancer subtypes was analyzed from the TCGA database. Results We found that the human PREX1 gene promoter has a CpG island located between -1.2 kb and +1.4 kb, and that DNA methylation in this region inversely correlates with P-REX1 expression in human breast cancer cell lines. A comprehensive analysis of human breast cancer cell lines and tumors revealed significant hypomethylation of the PREX1 promoter in ER-positive, luminal subtype, whereas hypermethylation occurs in basal-like breast cancer. Treatment of normal MCF-10A or basal-like cancer cells, MDA-MB-231 with the demethylating agent 5-aza-2′-deoxycitidine in combination with the histone deacetylase inhibitor trichostatin A restores P-REX1 levels to those observed in luminal breast cancer cell lines, suggesting that aberrant expression of P-REX1 in luminal breast cancer is a consequence of PREX1 promoter demethylation. Unlike PREX1, the pro-metastatic Rho/Rac-GEF, VAV3, is not regulated by methylation. Notably, PREX1 gene promoter hypomethylation is a prognostic marker of poor patient survival. Conclusions Our study identified for the first time gene promoter hypomethylation as a distinctive subtype-specific mechanism for controlling the expression of a key regulator of Rac-mediated motility and metastasis in breast cancer. Electronic supplementary material The online version of this article (doi:10.1186/s13058-014-0441-7) contains supplementary material, which is available to authorized users.
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Chen M, Lin WR, Lu CH, Chen CC, Huang YC, Liao WL, Tsai FJ. Chimerin 2 genetic polymorphisms are associated with non-proliferative diabetic retinopathy in Taiwanese type 2 diabetic patients. J Diabetes Complications 2014; 28:460-3. [PMID: 24854763 DOI: 10.1016/j.jdiacomp.2014.04.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 04/01/2014] [Accepted: 04/11/2014] [Indexed: 12/12/2022]
Abstract
AIM To investigate whether chimerin 2 (CHN2) genetic polymorphisms were associated with the susceptibility to diabetic retinopathy (DR) in Taiwanese individuals with type 2 diabetes. METHODS This case-control study comprised of 171 individuals with DR and 548 without DR. Four rs39059, rs2023908, rs1002630 and rs1362363 polymorphism of CHN2 were genotyped for each subjects. All subjects underwent a complete ophthalmologic examination, and basic information (age, gender, age at diagnosis of diabetes, and ocular history of the patient) was record. Several clinical parameters (systolic and diastolic blood pressure, waist and hip circumferences, body mass index levels, fasting glucose and HbA1c) were measured. RESULTS Logistic regressions were used to analyze odds ratios between SNPs and DR after controlling for gender, systolic blood pressure, waist and hip ratio, duration of diabetes, serum HbA1c levels and nephropathy classification. A protective effect of rs1002630 (GA+AA) and rs1362363 (AG+GG) [odds ratio (OR) (95% confidence interval)=0.45 (0.22-0.88), 0.66 (0.44-0.99), respectively) was observed. Furthermore, the protective effect of rs1002630 was observed when compared subjects with non-proliferative DR with subjects without DR [OR=0.25 (95%C.I. = 0.09-0.73)]. CONCLUSIONS This study showed that the rs1002630 of CHN2 were associated with DR risk and non-proliferative DR risk in Taiwanese individuals with type 2 diabetes. Variations at this locus may contribute to the pathogenesis of DR.
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Affiliation(s)
- Marcelo Chen
- Department of Urology, Mackay Memorial Hospital, Taipei, Taiwan; Mackay Medicine, Nursing and Management College, Taipei, Taiwan; School of Medicine, Mackay Medical College, New Taipei City, Taiwan
| | - Wun-Rong Lin
- Department of Urology, Mackay Memorial Hospital, Taipei, Taiwan
| | - Chieh-Hsiang Lu
- Division of Endocrinology and Metabolism of Internal Medicine, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chia-Yi, Taiwan
| | - Ching-Chu Chen
- Division of Endocrinology and Metabolism, Department of Medicine, China Medical University Hospital, Taichung, Taiwan; School of Chinese Medicine, China Medical University, Taichung, Taiwan
| | - Yu-Chuen Huang
- School of Chinese Medicine, China Medical University, Taichung, Taiwan; Genetics Center, Department of Medical Research, China Medical University Hospital, Taichung, Taiwan
| | - Wen-Ling Liao
- Center for Personalized Medicine, China Medical University Hospital, Taichung, Taiwan; Graduate Institute of Integrate Medicine, School of Chinese Medicine, China Medical University, Taichung, Taiwan.
| | - Fuu-Jen Tsai
- School of Chinese Medicine, China Medical University, Taichung, Taiwan; Genetics Center, Department of Medical Research, China Medical University Hospital, Taichung, Taiwan.
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Humphries B, Wang Z, Oom AL, Fisher T, Tan D, Cui Y, Jiang Y, Yang C. MicroRNA-200b targets protein kinase Cα and suppresses triple-negative breast cancer metastasis. Carcinogenesis 2014; 35:2254-63. [PMID: 24925028 DOI: 10.1093/carcin/bgu133] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with poor prognosis and lacks effective targeted therapies. The microRNA-200 (miR-200) family is found to inhibit or promote breast cancer metastasis; however, the underlying mechanism is not well understood. This study was performed to investigate the effect and mechanism of miR-200b on TNBC metastasis and identify targets for developing more efficient treatment for TNBC. We found that miR-200 family expression levels are significantly lower in highly migratory TNBC cells and metastatic TNBC tumors than other types of breast cancer cells and tumors. Ectopically expressing a single member (miR-200b) of the miR-200 family drastically reduces TNBC cell migration and inhibits tumor metastasis in an orthotopic mouse mammary xenograft tumor model. We identified protein kinase Cα (PKCα) as a new direct target of miR-200b and found that PKCα protein levels are inversely correlated with miR-200b levels in 12 kinds of breast cancer cells. Inhibiting PKCα activity or knocking down PKCα levels significantly reduces TNBC cell migration. In contrast, forced expression of PKCα impairs the inhibitory effect of miR-200b on cell migration and tumor metastasis. Further mechanistic studies revealed that PKCα downregulation by miR-200b results in a significant decrease of Rac1 activation in TNBC cells. These results show that loss of miR-200b expression plays a crucial role in TNBC aggressiveness and that miR-200b suppresses TNBC cell migration and tumor metastasis by targeting PKCα. Our findings suggest that miR-200b and PKCα may serve as promising therapeutic targets for metastatic TNBC.
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Affiliation(s)
- Brock Humphries
- Department of Physiology and Cellular and Molecular Biology Graduate Program, Michigan State University, East Lansing, MI 48824, USA
| | | | | | | | - Dongfeng Tan
- Department of Pathology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Yuehua Cui
- Department of Statistics and Probability, Michigan State University, East Lansing, MI 48824, USA
| | - Yiguo Jiang
- Institute for Chemical Carcinogenesis, State Key Laboratory of Respiratory Diseases, Guangzhou Medical University, Guangzhou, Guangdong 510182, People's Republic of China and
| | - Chengfeng Yang
- Department of Physiology and Cellular and Molecular Biology Graduate Program, Michigan State University, East Lansing, MI 48824, USA, Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, USA
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Wang Z, Humphries B, Xiao H, Jiang Y, Yang C. MicroRNA-200b suppresses arsenic-transformed cell migration by targeting protein kinase Cα and Wnt5b-protein kinase Cα positive feedback loop and inhibiting Rac1 activation. J Biol Chem 2014; 289:18373-86. [PMID: 24841200 DOI: 10.1074/jbc.m114.554246] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
MicroRNA-200b (miR-200b) is a member of miR-200 family that has been found to inhibit cell migration and cancer metastasis; however, the underlying mechanism is not well understood. We previously reported that miR-200 expression is depleted in arsenic-transformed human bronchial epithelial cells with highly migratory and invasive characteristics, whereas stably re-expressing miR-200b strongly suppresses arsenic-transformed cell migration. This study was performed to investigate how miR-200b inhibits arsenic-transformed cell migration. We found that protein kinase Cα (PKCα) is significantly up-regulated in arsenic-transformed cells. Combining bioinformatics analysis with PKCα 3'-untranslated region vector luciferase reporter assays, we showed that PKCα is a direct target of miR-200b. Inhibiting PKCα activity or knocking down PKCα expression drastically reduced cell migration, phenocoping the inhibitory effect of overexpressing miR-200b. In contrast, forced expression of PKCα in miR-200b overexpressing cells impaired the inhibitory effect of miR-200b on cell migration. In addition, we also found a positive feedback loop between Wnt5b and PKCα in arsenic-transformed cells. Knocking down Wnt5b expression reduced phospho-PKC levels and cell migration; and knocking down PKCα expression decreased Wnt5b level and cell migration. Moreover, forced expression of PKCα increased Wnt5b and phospho-PKC levels and cell migration. Further mechanistic studies revealed that Rac1 is highly activated in arsenic-transformed cells and stably expressing miR-200b abolishes Rac1 activation changing actin cytoskeleton organization. Manipulating PKCα or Wnt5b expression levels significantly altered the level of active Rac1. Together, these findings indicate that miR-200b suppresses arsenic-transformed cell migration by targeting PKCα and Wnt5b-PKCα positive feedback loop and subsequently inhibiting Rac1 activation.
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Affiliation(s)
- Zhishan Wang
- From the Department of Physiology, Michigan State University, East Lansing, Michigan 48824
| | - Brock Humphries
- From the Department of Physiology, Michigan State University, East Lansing, Michigan 48824
| | - Hua Xiao
- From the Department of Physiology, Michigan State University, East Lansing, Michigan 48824
| | - Yiguo Jiang
- the Institute for Chemical Carcinogenesis, State Key Laboratory of Respiratory Diseases, Guangzhou Medical University, Guangzhou 510182, China, and
| | - Chengfeng Yang
- From the Department of Physiology, Michigan State University, East Lansing, Michigan 48824, the Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
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Hallare AV, Ruiz PLS, Cariño JCED. Assessment of Jatropha curcas L. biodiesel seed cake toxicity using the zebrafish (Danio rerio) embryo toxicity (ZFET) test. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:6044-6056. [PMID: 24464135 DOI: 10.1007/s11356-014-2539-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Accepted: 01/08/2014] [Indexed: 06/03/2023]
Abstract
Consequent to the growing demand for alternative sources of energy, the seeds from Jatropha curcas remain to be the favorite for biodiesel production. However, a significant volume of the residual organic mass (seed cake) is produced during the extraction process, which raises concerns on safe waste disposal. In the present study, we assessed the toxicity of J. curcas seed cake using the zebrafish (Danio rerio) embryotoxicity test. Within 1-h post-fertilization (hpf), the fertilized eggs were exposed to five mass concentrations of J. curcas seed cake and were followed through 24, 48, and 72 hpf. Toxicity was evaluated based on lethal endpoints induced on zebrafish embryos namely egg coagulation, non-formation of somites, and non-detachment of tail. The lowest concentration tested, 1 g/L, was not able to elicit toxicity on embryos whereas 100 % mortality (based also on lethal endpoints) was recorded at the highest concentration at 2.15 g/L. The computed LC50 for the J. curcas seed cake was 1.61 g/L. No further increase in mortality was observed in the succeeding time points (48 and 72 hpf) indicating that J. curcas seed cake exerted acute toxicity on zebrafish embryos. Sublethal endpoints (yolk sac and pericardial edema) were noted at 72 hpf in zebrafish embryos exposed to higher concentrations. The observed lethal endpoints induced on zebrafish embryos were discussed in relation to the active principles, notably, phorbol esters that have remained in the seed cake even after extraction.
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Affiliation(s)
- Arnold V Hallare
- Department of Biology, CAS, University of the Philippines, Manila, Padre Faura St., Manila, 1000, Philippines,
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29
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Zubeldia-Brenner L, Gutierrez-Uzquiza A, Barrio-Real L, Wang H, Kazanietz MG, Leskow FC. β3-chimaerin, a novel member of the chimaerin Rac-GAP family. Mol Biol Rep 2014; 41:2067-76. [PMID: 24430297 DOI: 10.1007/s11033-014-3055-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 01/04/2014] [Indexed: 12/11/2022]
Abstract
Chimaerins are a family of diacylglycerol- and phorbol ester-regulated GTPase activating proteins (GAPs) for the small G-protein Rac. Extensive evidence indicates that these proteins play important roles in development, axon guidance, metabolism, cell motility, and T cell activation. Four isoforms have been reported to-date, which are products of CHN1 (α1- and α2-chimaerins) and CHN2 (β1- and β2-chimaerins) genes. Although these gene products are assumed to be generated by alternative splicing, bioinformatics analysis of the CHN2 gene revealed that β1- and β2-chimaerins are the products of alternative transcription start sites (TSSs) in different promoter regions. Furthermore, we found an additional TSS in CHN2 gene that leads to a novel product, which we named β3-chimaerin. Expression profile analysis revealed predominantly low levels for the β3-chimaerin transcript, with higher expression levels in epididymis, plasma blood leucocytes, spleen, thymus, as well as various areas of the brain. In addition to the prototypical SH2, C1, and Rac-GAP domains, β3-chimaerin has a unique N-terminal domain. Studies in cells established that β3-chimaerin has Rac-GAP activity and is responsive to phorbol esters. The enhanced responsiveness of β3-chimaerin for phorbol ester-induced translocation relative to β2-chimaerin suggests differential ligand accessibility to the C1 domain.
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Affiliation(s)
- Lautaro Zubeldia-Brenner
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, IQUIBICEN-CONICET, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
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30
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Gutierrez-Uzquiza A, Colon-Gonzalez F, Leonard TA, Canagarajah BJ, Wang H, Mayer BJ, Hurley JH, Kazanietz MG. Coordinated activation of the Rac-GAP β2-chimaerin by an atypical proline-rich domain and diacylglycerol. Nat Commun 2013; 4:1849. [PMID: 23673634 PMCID: PMC3700536 DOI: 10.1038/ncomms2834] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/04/2013] [Indexed: 02/08/2023] Open
Abstract
Chimaerins, a family of GTPase activating proteins (GAPs) for the small G-protein Rac, have been implicated in development, neuritogenesis, and cancer. These Rac-GAPs are regulated by the lipid second messenger diacylglycerol (DAG) generated by tyrosine-kinases such as the epidermal growth factor receptor (EGFR). Here we identify an atypical Pro-rich motif in chimaerins that binds to the adaptor protein Nck1. Unlike most Nck1 partners, chimaerins bind to the third SH3 domain of Nck1. This association is mediated by electrostatic interactions of basic residues within the Pro-rich motif with acidic clusters in the SH3 domain. EGF promotes the binding of β2-chimaerin to Nck1 in the cell periphery in a DAG-dependent manner. Moreover, β2-chimaerin translocation to the plasma membrane and its peripheral association with Rac1 requires Nck1. Our studies underscore a coordinated mechanism for β2-chimaerin activation that involves lipid interactions via the C1 domain and protein-protein interactions via the N-terminal Pro-rich region.
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Affiliation(s)
- Alvaro Gutierrez-Uzquiza
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA
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31
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Dipaolo BC, Davidovich N, Kazanietz MG, Margulies SS. Rac1 pathway mediates stretch response in pulmonary alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2013; 305:L141-53. [PMID: 23686855 DOI: 10.1152/ajplung.00298.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alveolar epithelial cells (AECs) maintain the pulmonary blood-gas barrier integrity with gasketlike intercellular tight junctions (TJ) that are anchored internally to the actin cytoskeleton. We have previously shown that AEC monolayers stretched cyclically and equibiaxially undergo rapid magnitude- and frequency-dependent actin cytoskeletal remodeling to form perijunctional actin rings (PJARs). In this work, we show that even 10 min of stretch induced increases in the phosphorylation of Akt and LIM kinase (LIMK) and decreases in cofilin phosphorylation, suggesting that the Rac1/Akt pathway is involved in these stretch-mediated changes. We confirmed that Rac1 inhibitors wortmannin or EHT-1864 decrease stretch-stimulated Akt and LIMK phosphorylation and that Rac1 agonists PIP3 or PDGF increase phosphorylation of these proteins in unstretched cells. We also confirmed that Rac1 pathway inhibition during stretch modulated stretch-induced changes in occludin content and monolayer permeability, actin remodeling and PJAR formation, and cell death. As further validation, overexpression of Rac GTPase-activating protein β2-chimerin also preserved monolayer barrier properties in stretched monolayers. In summary, our data suggest that constitutive activity of Rac1, which is necessary for stretch-induced activation of the Rac1 downstream proteins, mediates stretch-induced increases in permeability and PJAR formation.
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Affiliation(s)
- Brian C Dipaolo
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
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32
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Lopez-Haber C, Kazanietz MG. Cucurbitacin I inhibits Rac1 activation in breast cancer cells by a reactive oxygen species-mediated mechanism and independently of Janus tyrosine kinase 2 and P-Rex1. Mol Pharmacol 2013; 83:1141-54. [PMID: 23478800 DOI: 10.1124/mol.112.084293] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The small GTPase Rac1 has been widely implicated in mammary tumorigenesis and metastasis. Previous studies established that stimulation of ErbB receptors in breast cancer cells activates Rac1 and enhances motility via the Rac-guanine nucleotide exchange factor P-Rex1. As the Janus tyrosine kinase 2 (Jak2)/signal transducer and activator of transcription 3 (Stat3) pathway has been shown to be functionally associated with ErbB receptors, we asked if this pathway could mediate P-Rex1/Rac1 activation in response to ErbB ligands. Here we found that the anticancer agent cucurbitacin I, a Jak2 inhibitor, reduced the activation of Rac1 and motility in response to the ErbB3 ligand heregulin in breast cancer cells. However, Rac1 activation was not affected by Jak2 or Stat3 RNA interference, suggesting that the effect of cucurbitacin I occurs through a Jak2-independent mechanism. Cucurbitacin I also failed to affect the activation of P-Rex1 by heregulin. Subsequent analysis revealed that cucurbitacin I strongly activates RhoA and the Rho effector Rho kinase (ROCK) in breast cancer cells and induces the formation of stress fibers. Interestingly, disruption of the RhoA-ROCK pathway prevented the inhibitory effect of cucurbitacin I on Rac1 activation by heregulin. Lastly, we found that RhoA activation by cucurbitacin I is mediated by reactive oxygen species (ROS). The ROS scavenger N-acetyl L-cysteine and the mitochondrial antioxidant Mito-TEMPO rescued the inhibitory effect of cucurbitacin I on Rac1 activation. In conclusion, these results indicate that ErbB-driven Rac1 activation in breast cancer cells proceeds independently of the Jak2 pathway. Moreover, they established that the inhibitory effect of cucurbitacin I on Rac1 activity involves the alteration of the balance between Rho and Rac.
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Affiliation(s)
- Cynthia Lopez-Haber
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA
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33
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Katz E, Sims AH, Sproul D, Caldwell H, Dixon MJ, Meehan RR, Harrison DJ. Targeting of Rac GTPases blocks the spread of intact human breast cancer. Oncotarget 2013; 3:608-19. [PMID: 22689141 PMCID: PMC3442288 DOI: 10.18632/oncotarget.520] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
High expression of Rac small GTPases in invasive breast ductal carcinoma is associated with poor prognosis, but its therapeutic value in human cancers is not clear. The aim of the current study was to determine the response of human primary breast cancers to Rac-based drug treatments ex vivo. Three-dimensional organotypic cultures were used to assess candidate therapeutic avenues in invasive breast cancers. Uniquely, in these primary cultures, the tumour is not disaggregated, with both epithelial and mesenchymal components maintained within a three-dimensional matrix of type I collagen. EHT 1864, a small molecule inhibitor of Rac GTPases, prevents spread of breast cancers in this setting, and also reduces proliferation at the invading edge. Rac1+ epithelial cells in breast tumours also contain high levels of the phosphorylated form of the transcription factor STAT3. The small molecule Stattic inhibits activation of STAT3 and induces effects similar to those seen with EHT 1864. Pan-Rac inhibition of proliferation precedes down-regulation of STAT3 activity, defining it as the last step in Rac activation during human breast cancer invasion. Our data highlights the potential use of Rac and STAT3 inhibition in treatment of invasive human breast cancer and the benefit of studying novel cancer treatments using three-dimensional primary tumour tissue explant cultures.
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Affiliation(s)
- Elad Katz
- Breakthrough Breast Cancer Research Unit, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom.
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34
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Chimaerin suppresses Rac1 activation at the apical membrane to maintain the cyst structure. PLoS One 2012; 7:e52258. [PMID: 23284959 PMCID: PMC3527519 DOI: 10.1371/journal.pone.0052258] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 11/09/2012] [Indexed: 02/06/2023] Open
Abstract
Epithelial organs are made of a well-polarized monolayer of epithelial cells, and their morphology is maintained strictly for their proper functions. Previously, we showed that Rac1 activation is suppressed at the apical membrane in the mature organoid, and that such spatially biased Rac1 activity is required for the polarity maintenance. Here we identify Chimaerin, a GTPase activating protein for Rac1, as a suppressor of Rac1 activity at the apical membrane. Depletion of Chimaerin causes over-activation of Rac1 at the apical membrane in the presence of hepatocyte growth factor (HGF), followed by luminal cell accumulation. Importantly, Chimaerin depletion did not inhibit extension formation at the basal membrane. These observations suggest that Chimaerin functions as the apical-specific Rac1 GAP to maintain epithelial morphology.
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35
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Wertheimer E, Gutierrez-Uzquiza A, Rosemblit C, Lopez-Haber C, Sosa MS, Kazanietz MG. Rac signaling in breast cancer: a tale of GEFs and GAPs. Cell Signal 2012; 24:353-362. [PMID: 21893191 PMCID: PMC3312797 DOI: 10.1016/j.cellsig.2011.08.011] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 08/20/2011] [Indexed: 11/28/2022]
Abstract
Rac GTPases, small G-proteins widely implicated in tumorigenesis and metastasis, transduce signals from tyrosine-kinase, G-protein-coupled receptors (GPCRs), and integrins, and control a number of essential cellular functions including motility, adhesion, and proliferation. Deregulation of Rac signaling in cancer is generally a consequence of enhanced upstream inputs from tyrosine-kinase receptors, PI3K or Guanine nucleotide Exchange Factors (GEFs), or reduced Rac inactivation by GTPase Activating Proteins (GAPs). In breast cancer cells Rac1 is a downstream effector of ErbB receptors and mediates migratory responses by ErbB1/EGFR ligands such as EGF or TGFα and ErbB3 ligands such as heregulins. Recent advances in the field led to the identification of the Rac-GEF P-Rex1 as an essential mediator of Rac1 responses in breast cancer cells. P-Rex1 is activated by the PI3K product PIP3 and Gβγ subunits, and integrates signals from ErbB receptors and GPCRs. Most notably, P-Rex1 is highly overexpressed in human luminal breast tumors, particularly those expressing ErbB2 and estrogen receptor (ER). The P-Rex1/Rac signaling pathway may represent an attractive target for breast cancer therapy.
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Affiliation(s)
- Eva Wertheimer
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Alvaro Gutierrez-Uzquiza
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Cinthia Rosemblit
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Cynthia Lopez-Haber
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Maria Soledad Sosa
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Marcelo G Kazanietz
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA.
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36
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Ligeti E, Welti S, Scheffzek K. Inhibition and Termination of Physiological Responses by GTPase Activating Proteins. Physiol Rev 2012; 92:237-72. [DOI: 10.1152/physrev.00045.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Physiological processes are strictly organized in space and time. However, in cell physiology research, more attention is given to the question of space rather than to time. To function as a signal, environmental changes must be restricted in time; they need not only be initiated but also terminated. In this review, we concentrate on the role of one specific protein family involved in biological signal termination. GTPase activating proteins (GAPs) accelerate the endogenously low GTP hydrolysis rate of monomeric guanine nucleotide-binding proteins (GNBPs), limiting thereby their prevalence in the active, GTP-bound form. We discuss cases where defective or excessive GAP activity of specific proteins causes significant alteration in the function of the nervous, endocrine, and hemopoietic systems, or contributes to development of infections and tumors. Biochemical and genetic data as well as observations from human pathology support the notion that GAPs represent vital elements in the spatiotemporal fine tuning of physiological processes.
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Affiliation(s)
- Erzsébet Ligeti
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Stefan Welti
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Klaus Scheffzek
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
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37
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Halpert M, Abu-Abied M, Avisar D, Moskovitz Y, Altshuler O, Cohen A, Weissberg M, Riov J, Gottlieb HE, Perl A, Sadot E. Rac-dependent doubling of HeLa cell area and impairment of cell migration and cell cycle by compounds from Iris germanica. PROTOPLASMA 2011; 248:785-797. [PMID: 21207085 DOI: 10.1007/s00709-010-0254-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 12/06/2010] [Indexed: 05/30/2023]
Abstract
Plants are an infinite source of bioactive compounds. We screened the Israeli flora for compounds that interfere with the organization of the actin cytoskeleton. We found an activity in lipidic extract from Iris germanica that was able to increase HeLa cell area and adhesion and augment the formation of actin stress fibers. This effect was not observed when Ref52 fibroblasts were tested and was not the result of disruption of microtubules. Further, the increase in cell area was Rac1-dependent, and the iris extract led to slight Rac activation. Inhibitor of RhoA kinase did not interfere with the ability of the iris extract to increase HeLa cell area. The increase in HeLa cell area in the presence of iris extract was accompanied by impairment of cell migration and arrest of the cell cycle at G1 although the involvement of Rac1 in these processes is not clear. Biochemical verification of the extract based on activity-mediated fractionation and nuclear magnetic resonance analysis revealed that the active compounds belong to the group of iridals, a known group of triterpenoid. Purified iripallidal was able to increase cell area of both HeLa and SW480 cells.
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Affiliation(s)
- Michal Halpert
- The Institute of Plant Sciences, Volcani Center, P.O. Box 6, Bet-Dagan, 50250, Israel
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38
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Zhao Y, Wang Z, Jiang Y, Yang C. Inactivation of Rac1 reduces Trastuzumab resistance in PTEN deficient and insulin-like growth factor I receptor overexpressing human breast cancer SKBR3 cells. Cancer Lett 2011; 313:54-63. [PMID: 21943825 DOI: 10.1016/j.canlet.2011.08.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 08/21/2011] [Accepted: 08/22/2011] [Indexed: 12/17/2022]
Abstract
Drug resistance remains to be a big challenge in applying anti-HER2 monoclonal antibody Trastuzumab for treating breast cancer with HER2 overexpression. Amplification of insulin-like growth factor I receptor (IGF-IR) and deletion of tumor suppressor phosphatase and tensin homolog (PTEN) are implicated in Trastuzumab resistance, however, the underlying mechanisms have not been clearly defined. Activation of Rac1, a member of Rho GTPase family, is capable of causing cytoskeleton reorganization, regulating gene expression and promoting cell proliferation. To investigate the mechanism of Trastuzumab resistance, PTEN knockdown and IGF-IR overexpressing stable cell lines were generated in HER2 overexpression human breast cancer SKBR3 cells. Rac1 was highly activated in PTEN deficient and IGF-IR overexpressing Trastuzumab-resistant cells in a HER2-independent manner. Inactivation of Rac1 by using a Rac1 inhibitor NSC23766 or siRNA knocking down the expression of Tiam1, a guanine nucleotide exchange factor for Rac, significantly reduced Trastuzumab resistance in SKBR3 cells. Inhibition of Rac1 had no effect on the levels of phosphor-HER2 and phosphor-Akt, but significantly decreased the levels of cyclin D1 in Trastuzumab-resistant cells. Inhibition of Akt with an Akt inhibitor also significantly reduced Trastuzumab resistance. However, simultaneous inhibition of both Rac1 and Akt resulted in a significantly more decrease of Trastuzumab resistance than inactivation of Rac1 or Akt alone. These results suggest that Rac1 activation is critically involved in Trastuzumab resistance caused by PTEN deletion or IGF-IR overexpression. Simultaneous inhibition of Rac1 and Akt may represent a promising strategy in reducing Trastuzumab resistance in HER2 overexpression breast cancer.
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Affiliation(s)
- Yong Zhao
- Department of Physiology, Michigan State University, 2201 Biomedical Physical Sciences, East Lansing, MI 48824, United States
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39
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Wertheimer E, Kazanietz MG. Rac1 takes center stage in pancreatic cancer and ulcerative colitis: quantity matters. Gastroenterology 2011; 141:427-30. [PMID: 21704620 DOI: 10.1053/j.gastro.2011.06.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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40
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Polizio AH, Chinchilla P, Chen X, Kim S, Manning DR, Riobo NA. Heterotrimeric Gi proteins link Hedgehog signaling to activation of Rho small GTPases to promote fibroblast migration. J Biol Chem 2011; 286:19589-96. [PMID: 21474452 DOI: 10.1074/jbc.m110.197111] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Evidence supporting the functionality of Smoothened (SMO), an essential transducer in most pathways engaged by Hedgehog (Hh), as a G(i)-coupled receptor contrasts with the lack of an apparently consistent requirement for G(i) in Hh signal transduction. In the present study, we sought to evaluate the role of SMO-G(i) coupling in fibroblast migration induced by Sonic Hedgehog (Shh). Our results demonstrate an absolute requirement for G(i) in Shh-induced fibroblast migration. We found that Shh acutely stimulates the small Rho GTPases Rac1 and RhoA via SMO through a G(i) protein- and PI3K-dependent mechanism, and that these are required for cell migration. These responses were independent of transcription by Gli and of the C-terminal domain of SMO, as we show using a combination of molecular and genetic tools. Our findings provide a mechanistic model for fibroblast migration in response to Shh and underscore the role of SMO-G(i) coupling in non-canonical Hh signaling.
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Affiliation(s)
- Ariel H Polizio
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 1910, USA
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41
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Identification of the Rac-GEF P-Rex1 as an essential mediator of ErbB signaling in breast cancer. Mol Cell 2010; 40:877-92. [PMID: 21172654 DOI: 10.1016/j.molcel.2010.11.029] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 08/21/2010] [Accepted: 10/18/2010] [Indexed: 02/08/2023]
Abstract
While the small GTPase Rac1 and its effectors are well-established mediators of mitogenic and motile signaling by tyrosine kinase receptors and have been implicated in breast tumorigenesis, little is known regarding the exchange factors (Rac-GEFs) that mediate ErbB receptor responses. Here, we identify the PIP(3)-Gβγ-dependent Rac-GEF P-Rex1 as an essential mediator of Rac1 activation, motility, cell growth, and tumorigenesis driven by ErbB receptors in breast cancer cells. Notably, activation of P-Rex1 in breast cancer cells requires the convergence of inputs from ErbB receptors and a Gβγ- and PI3Kγ-dependent pathway. Moreover, we identified the GPCR CXCR4 as a crucial mediator of P-Rex1/Rac1 activation in response to ErbB ligands. P-Rex1 is highly overexpressed in human breast cancers and their derived cell lines, particularly those with high ErbB2 and ER expression. In addition to the prognostic and therapeutic implications, our findings reveal an ErbB effector pathway that is crucial for breast cancer progression.
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42
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McHenry PR, Vargo-Gogola T. Pleiotropic functions of Rho GTPase signaling: a Trojan horse or Achilles' heel for breast cancer treatment? Curr Drug Targets 2010; 11:1043-58. [PMID: 20545614 PMCID: PMC3188943 DOI: 10.2174/138945010792006852] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 05/01/2010] [Indexed: 01/05/2023]
Abstract
Rho GTPase signaling is altered in human breast tumors, and elevated expression and activation of Rho GTPases correlate with tumor progression, metastasis, and poor prognosis. Here we review the evidence that Rho signaling functions as a key regulator of cell cycle, mitosis, apoptosis, and invasion during breast cancer growth and progression and discuss whether these pleiotropic actions enhance or limit the targetability of this network. We propose that depending on the stage and subtype of breast cancer, targeting Rho signaling may have chemopreventative, anti-tumor, and anti-metastatic efficacy. An understanding of how Rho signaling is perturbed in specific stages and subtypes of breast cancer and how it functions in the context of the complex in vivo environment during the stochastic process of tumor formation and progression are necessary in order to effectively target this signaling network for breast cancer treatment.
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Affiliation(s)
- P R McHenry
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, South Bend, IN 46617, USA
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Griner EM, Caino MC, Sosa MS, Colón-González F, Chalmers MJ, Mischak H, Kazanietz MG. A novel cross-talk in diacylglycerol signaling: the Rac-GAP beta2-chimaerin is negatively regulated by protein kinase Cdelta-mediated phosphorylation. J Biol Chem 2010; 285:16931-41. [PMID: 20335173 DOI: 10.1074/jbc.m109.099036] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the family of chimaerin Rac-GAPs has recently gained significant attention for their involvement in development, cancer, and neuritogenesis, little is known about their molecular regulation. Chimaerins are activated by the lipid second messenger diacylglycerol via their C1 domain upon activation of tyrosine kinase receptors, thereby restricting the magnitude of Rac signaling in a receptor-regulated manner. Here we identified a novel regulatory mechanism for beta2-chimaerin via phosphorylation. Epidermal growth factor or the phorbol ester phorbol 12-myristate 13-acetate caused rapid phosphorylation of beta2-chimaerin on Ser(169) located in the SH2-C1 domain linker region via protein kinase Cdelta, which retained beta2-chimaerin in the cytosol and prevented its C1 domain-mediated translocation to membranes. Furthermore, despite the fact that Ser(169) phosphorylation did not alter intrinsic Rac-GAP activity in vitro, a non-phosphorylatable beta2-chimaerin mutant was highly sensitive to translocation, and displayed enhanced association with activated Rac, enhanced Rac-GAP activity, and anti-migratory properties when expressed in cells. Our results not only revealed a novel regulatory mechanism that facilitates Rac activation, but also identified a novel mechanism of cross-talk between diacylglycerol receptors that restricts beta2-chimaerin relocalization and activation.
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Affiliation(s)
- Erin M Griner
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA
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Notcovich C, Diez F, Tubio MR, Baldi A, Kazanietz MG, Davio C, Shayo C. Histamine acting on H1 receptor promotes inhibition of proliferation via PLC, RAC, and JNK-dependent pathways. Exp Cell Res 2010; 316:401-11. [DOI: 10.1016/j.yexcr.2009.11.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 11/04/2009] [Accepted: 11/05/2009] [Indexed: 01/06/2023]
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Sosa MS, Lewin NE, Choi SH, Blumberg PM, Kazanietz MG. Biochemical characterization of hyperactive beta2-chimaerin mutants revealed an enhanced exposure of C1 and Rac-GAP domains. Biochemistry 2009; 48:8171-8. [PMID: 19618918 DOI: 10.1021/bi9010623] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent studies established that the Rac-GAP beta2-chimaerin plays important roles in development, neuritogenesis, and cancer progression. A unique feature of beta2-chimaerin is that it can be activated by phorbol esters and the lipid second messenger diacylglycerol (DAG), which bind with high affinity to its C1 domain and promote beta2-chimaerin translocation to membranes, leading to the inactivation of the small G-protein Rac. Crystallographic evidence and cellular studies suggest that beta2-chimaerin remains in an inactive conformation in the cytosol with the C1 domain inaccessible to ligands. We developed a series of beta2-chimaerin point mutants in which intramolecular contacts that occlude the C1 domain have been disrupted. These mutants showed enhanced translocation in response to phorbol 12-myristate 13-acetate (PMA) in cells. Binding assays using [(3)H]phorbol 12,13-dibutyrate ([(3)H]PDBu) revealed that internal contact mutants have a reduced acidic phospholipid requirement for phorbol ester binding. Moreover, disruption of intramolecular contacts enhances binding of beta2-chimaerin to acidic phospholipid vesicles and confers enhanced Rac-GAP activity in vitro. These studies suggest that beta2-chimaerin must undergo a conformational rearrangement in order to expose its lipid binding sites and become activated.
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Affiliation(s)
- Maria Soledad Sosa
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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Fournier AK, Campbell LE, Castagnino P, Liu WF, Chung BM, Weaver VM, Chen CS, Assoian RK. Rac-dependent cyclin D1 gene expression regulated by cadherin- and integrin-mediated adhesion. J Cell Sci 2008; 121:226-33. [PMID: 18187454 DOI: 10.1242/jcs.017012] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Integrin-mediated adhesion to substratum is required for cyclin D1 induction in mesenchymal cells, but we show here that the induction of cyclin D1 persists despite blockade of ECM-integrin signaling in MCF10A mammary epithelial cells. E-cadherin-mediated cell-cell adhesion also supports cyclin D1 induction in these cells, and the combined inhibition of both E-cadherin and integrin adhesion is required to prevent the expression of cyclin D1 mRNA and protein. Our previous studies described a pro-proliferative effect of E-cadherin in MCF10A cells, mediated by Rac, and we now show that Rac is required for cyclin D1 mRNA induction by both E-cadherin and integrin engagement. The levels of p21Cip1 and p27Kip1, Cdk inhibitors that are also targets of integrin signaling, are not affected by E-cadherin-mediated cell-cell adhesion. Finally, we show that the increased expression of cyclin D1 mRNA associated with E-cadherin-dependent cell-cell adhesion is causally linked to an increased entry into S phase. Our results identify Rac signaling to cyclin D1 as a crucial pro-proliferative effect of E-cadherin-mediated cell-cell adhesion.
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Affiliation(s)
- Alaina K Fournier
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
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Yin J, Lu J, Yu FSX. Role of small GTPase Rho in regulating corneal epithelial wound healing. Invest Ophthalmol Vis Sci 2008; 49:900-9. [PMID: 18326710 DOI: 10.1167/iovs.07-1122] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the role of small GTPase Rho and its relation with epidermal growth factor receptor (EGFR) in mediating corneal epithelial wound healing. METHODS Rho activity in THCE cells, an SV40-immortalized human corneal epithelial cell (HCEC) line, and primary HCECs was assessed by pull-down assay followed by Western blotting. Rho functions were inhibited with specific inhibitor exoenzyme C3 (C3) and confirmed by knockdown with small interference RNA (siRNA) transfection. Effects of Rho inhibition on wound healing were determined in porcine corneal organ culture and HCEC scratch wound models. Effects of C3 on cell proliferation and focal adhesion formation were determined by BrdU incorporation assay and immunocytochemistry, respectively. RESULTS Wounding, lysophosphatidic acid, and heparin-binding EGF-like growth factor (HB-EGF) induced rapid and strong RhoA activation. HB-EGF-, but not wounding-, enhanced RhoA activity was sensitive to EGFR inhibition. In corneal organ and cell culture models, C3 attenuated spontaneous and HB-EGF-induced wound closures, confirmed by delayed wound healing in cells transfected with RhoA siRNA. C3 also retarded spontaneous wound healing in the presence of hydroxyurea, a cell cycle blocker. C3 significantly reduced the number of BrdU-positive cells near the leading edge. Treatment with C3 resulted in the disruption of the cortical actin cytoskeleton and in the disappearance of paxillin-containing focal adhesion and lamellipodia. CONCLUSIONS Wounding induces RhoA activation through an EGFR-independent pathway. Rho activity is required for modulating cell migration and proliferation through cytoskeleton reorganization and focal adhesion formation in response to wounding.
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Affiliation(s)
- Jia Yin
- Department of Ophthalmology, Kresge Eye Institute, Wayne State UniversitySchool of Medicine, Detroit, Michigan 48201, USA
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Fortino V, Torricelli C, Capurro E, Sacchi G, Valacchi G, Maioli E. Antiproliferative and survival properties of PMA in MCF-7 breast cancer cell. Cancer Invest 2008; 26:13-21. [PMID: 18181040 DOI: 10.1080/07357900701637949] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Although PKCs are assumed to be the main targets of phorbol esters (PMA), additional PMA effectors, such as chimaerins (a family of RacGTPase activating proteins) and RasGRP (exchange factor for Ras/Rap1), can counteract or strengthen the PKC pathways. In this study, we evaluated the proliferative behavior of PMA-treated MCF-7 breast cancer cell and found that: PMA induced growth arrest and inhibited cell death; PMA activated ERKs, which, in turn, induced p21; and inhibitors of ERK (PD98059) and PKC (GF109203X) prevented p21 induction and abolished the PMA survival effect. We conclude that PMA inhibits MCF-7 cell growth and simultaneously stimulates cell survival; both responses are linked to ERK-dependent and p53-independent p21 induction.
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Affiliation(s)
- V Fortino
- Department of Physiology, University of Siena, Siena, Italy
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Heregulin β1 promotes breast cancer cell proliferation through Rac/ERK-dependent induction of cyclin D1 and p21Cip1. Biochem J 2008; 410:167-75. [DOI: 10.1042/bj20070781] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Accumulating evidence indicates that heregulins, EGF (epidermal growth factor)-like ligands, promote breast cancer cell proliferation and are involved in the progression of breast cancer towards an aggressive and invasive phenotype. However, there is limited information regarding the molecular mechanisms that mediate these effects. We have recently established that HRG (heregulin β1) promotes breast cancer cell proliferation and migration via cross-talk with EGFR (EGF receptor) that involves the activation of the small GTPase Rac1. In the present paper we report that Rac1 is an essential player for mediating the induction of cyclin D1 and p21Cip1 by HRG in breast cancer cells. Inhibition of Rac function by expressing either the Rac-GAP (GTPase-activating protein) β2-chimaerin or the dominant-negative Rac mutant N17Rac1, or Rac1 depletion using RNAi (RNA interference), abolished the cyclin D1 and p21Cip1 induction by HRG. Interestingly, the proliferative effect of HRG was impaired not only when the expression of Rac1 or cyclin D1 was inhibited, but also when cells were depleted of p21Cip1 using RNAi. Inhibition of EGFR, PI3K (phosphoinositide 3-kinase; kinases required for Rac activation by HRG) or MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] also blocked the up-regulation of cyclin D1 and p21Cip1 by HRG. In addition, we found that HRG activates NF-κB (nuclear factor κB) in a Rac1- and MEK-dependent fashion, and inhibition of NF-κB abrogates cyclin D1/p21Cip1 induction and proliferation by HRG. Taken together, these findings establish a central role for Rac1 in the control of HRG-induced breast cancer cell-cycle progression and proliferation through up-regulating the expression of cyclin D1 and p21Cip1.
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Friedland JC, Lakins JN, Kazanietz MG, Chernoff J, Boettiger D, Weaver VM. alpha6beta4 integrin activates Rac-dependent p21-activated kinase 1 to drive NF-kappaB-dependent resistance to apoptosis in 3D mammary acini. J Cell Sci 2007; 120:3700-12. [PMID: 17911169 DOI: 10.1242/jcs.03484] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Malignant transformation and multidrug resistance are linked to resistance to apoptosis, yet the molecular mechanisms that mediate tumor survival remain poorly understood. Because the stroma can influence tumor behavior by regulating the tissue phenotype, we explored the role of extracellular matrix signaling and tissue organization in epithelial survival. We report that elevated (alpha6)beta4 integrin-dependent Rac-Pak1 signaling supports resistance to apoptosis in mammary acini by permitting stress-dependent activation of the p65 subunit of NF-kappaB through Pak1. We found that inhibiting Pak1 through expression of N17Rac or PID compromises NF-kappaB activation and renders mammary acini sensitive to death, but that resistance to apoptosis could be restored to these structures by overexpressing wild-type NF-kappaB p65. We also observed that acini expressing elevated levels of Pak1 can activate p65 and survive death treatments, even in the absence of activated Rac, yet will die if activation of NF-kappaB is simultaneously inhibited through expression of IkappaBalphaM. Thus, mammary tissues can resist apoptotic stimuli by activating NF-kappaB through alpha6beta4 integrin-dependent Rac-Pak1 signaling. Our data emphasize the importance of the extracellular matrix stroma in tissue survival and suggest that alpha6beta4 integrin-dependent Rac stimulation of Pak1 could be an important mechanism mediating apoptosis-resistance in some breast tumors.
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Affiliation(s)
- Julie C Friedland
- Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104, USA
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