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Nair VS, Watson K. A Novel, Fully Automated, and Reagent-Agnostic Transient Transfection Protocol. Curr Protoc 2024; 4:e968. [PMID: 38314959 DOI: 10.1002/cpz1.968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Transfection is a potent technique to introduce foreign nucleic acids into eukaryotic cells. The capacity of the technique to alter the genetic content of host cells means it is useful for a wide range of applications, including the study of typical cellular processes, disease molecular mechanisms, and gene therapy effects. Here, we discuss a highly reliable and fully automated transient transfection protocol that utilizes an open-source liquid handler and accompanying HEPA Module. Two commonly used transfection reagents are employed to study the transfection efficiency in two cell lines with a GFP plasmid construct. The detailed method of the protocol, image acquisition, and analysis for evaluating transfection efficacy is provided. With HeLa cells, the transfection efficiency of the reagents ranges from 40.92% to 73.26%, while with the difficult-to-transfect A549 cells, the transfection efficiency is between 42.15% and 54%. The efficiency achieved is comparable to similar experiments performed manually. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Seeding of adherent cells (A549 and HeLa) for transient transfection on a Costar 6-well plate using a liquid handler on Day 0 Basic Protocol 2: Transfection of the cell lines using the transfection reagents Lipofectamine 3000 and FuGENE HD on Day 1 Support Protocol: Image acquisition and semi-quantitative analysis of transfection after 24 hr to calculate the transfection efficiency.
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Nair VS, Gu C, Janoshazi AK, Jessen HJ, Wang H, Shears SB. Inositol Pyrophosphate Synthesis by Diphosphoinositol Pentakisphosphate Kinase-1 is Regulated by Phosphatidylinositol(4,5)bisphosphate. Biosci Rep 2018; 38:BSR20171549. [PMID: 29459425 PMCID: PMC5857911 DOI: 10.1042/bsr20171549] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/14/2018] [Accepted: 02/17/2018] [Indexed: 11/17/2022] Open
Abstract
5-diphosphoinositol tetrakisphosphate (5-InsP7) and bisdiphosphoinositol tetrakisphosphate (InsP8) are 'energetic' inositol pyrophosphate signaling molecules that regulate bioenergetic homeostasis. Inositol pyrophosphate levels are regulated by diphosphoinositol pentakisphosphate kinases (PPIP5Ks); these are large modular proteins that host a kinase domain (which phosphorylates 5-InsP7 to InsP8), a phosphatase domain that catalyzes the reverse reaction, and a polyphosphoinositide-binding domain (PBD). Here, we describe new interactions between these three domains in the context of full-length human PPIP5K1. We determine that InsP7 kinase activity is dominant when PPIP5K1 is expressed in intact cells; in contrast, we found that InsP8 phosphatase activity prevails when the enzyme is isolated from its cellular environment. We approach a reconciliation of this disparity by showing that cellular InsP8 phosphatase activity is inhibited by C8-PtdIns(4,5)P2 (IC50 approx. 40 ìM). We recapitulate this phosphatase inhibition with natural PtdIns(4,5)P2 that was incorporated into large unilamellar vesicles. Additionally, PtdIns(4,5)P2 increases net InsP7 kinase activity 5-fold. We oftlinedemonstrate that PtdIns(4,5)P2 is not itself a phosphatase substrate; its inhibition of InsP8 phosphatase activity results from an unusual, functional overlap between the phosphatase domain and the PBD. Finally, we discuss the significance of PtdIns(4,5)P2 as a novel regulator of PPIP5K1, in relation to compartmentalization of InsP7/InsP8 signaling in vivo.
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Affiliation(s)
- Vasudha S Nair
- NIEHS, Research Triangle Park, North Carolina, United States
| | - Chunfang Gu
- NIEHS, Research Triangle Park, North Carolina, United States
| | | | | | - Huanchen Wang
- NIEHS, Research Triangle Park, North Carolina, United States
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Shears SB, Baughman BM, Gu C, Nair VS, Wang H. The significance of the 1-kinase/1-phosphatase activities of the PPIP5K family. Adv Biol Regul 2016; 63:98-106. [PMID: 27776974 DOI: 10.1016/j.jbior.2016.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 10/13/2016] [Accepted: 10/15/2016] [Indexed: 01/29/2023]
Abstract
The inositol pyrophosphates (diphosphoinositol polyphosphates), which include 1-InsP7, 5-InsP7, and InsP8, are highly 'energetic' signaling molecules that play important roles in many cellular processes, particularly with regards to phosphate and bioenergetic homeostasis. Two classes of kinases synthesize the PP-InsPs: IP6Ks and PPIP5Ks. The significance of the IP6Ks - and their 5-InsP7 product - has been widely reported. However, relatively little is known about the biological significance of the PPIP5Ks. The purpose of this review is to provide an update on developments in our understanding of key features of the PPIP5Ks, which we believe strengthens the hypothesis that their catalytic activities serve important cellular functions. Central to this discussion is the recent discovery that the PPIP5K is a rare example of a single protein that catalyzes a kinase/phosphatase futile cycle.
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Affiliation(s)
- Stephen B Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, 101 T.W. Alexander Drive, Research Triangle Park, NC, 27709, USA.
| | - Brandi M Baughman
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, 101 T.W. Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - Chunfang Gu
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, 101 T.W. Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - Vasudha S Nair
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, 101 T.W. Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - Huanchen Wang
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, 101 T.W. Alexander Drive, Research Triangle Park, NC, 27709, USA
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Wang H, Nair VS, Holland AA, Capolicchio S, Jessen HJ, Johnson MK, Shears SB. Asp1 from Schizosaccharomyces pombe binds a [2Fe-2S](2+) cluster which inhibits inositol pyrophosphate 1-phosphatase activity. Biochemistry 2015; 54:6462-74. [PMID: 26422458 DOI: 10.1021/acs.biochem.5b00532] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-sulfur (Fe-S) clusters are widely distributed protein cofactors that are vital to cellular biochemistry and the maintenance of bioenergetic homeostasis, but to our knowledge, they have never been identified in any phosphatase. Here, we describe an iron-sulfur cluster in Asp1, a dual-function kinase/phosphatase that regulates cell morphogenesis in Schizosaccharomyces pombe. Full-length Asp1, and its phosphatase domain (Asp1(371-920)), were each heterologously expressed in Escherichia coli. The phosphatase activity is exquisitely specific: it hydrolyzes the 1-diphosphate from just two members of the inositol pyrophosphate (PP-InsP) signaling family, namely, 1-InsP7 and 1,5-InsP8. We demonstrate that Asp1 does not hydrolyze either InsP6, 2-InsP7, 3-InsP7, 4-InsP7, 5-InsP7, 6-InsP7, or 3,5-InsP8. We also recorded 1-phosphatase activity in a human homologue of Asp1, hPPIP5K1, which was heterologously expressed in Drosophila S3 cells with a biotinylated N-terminal tag, and then isolated from cell lysates with avidin beads. Purified, recombinant Asp1(371-920) contained iron and acid-labile sulfide, but the stoichiometry (0.8 atoms of each per protein molecule) indicates incomplete iron-sulfur cluster assembly. We reconstituted the Fe-S cluster in vitro under anaerobic conditions, which increased the stoichiometry to approximately 2 atoms of iron and acid-labile sulfide per Asp1 molecule. The presence of a [2Fe-2S](2+) cluster in Asp1(371-920) was demonstrated by UV-visible absorption, resonance Raman spectroscopy, and electron paramagnetic resonance spectroscopy. We determined that this [2Fe-2S](2+) cluster is unlikely to participate in redox chemistry, since it rapidly degraded upon reduction by dithionite. Biochemical and mutagenic studies demonstrated that the [2Fe-2S](2+) cluster substantially inhibits the phosphatase activity of Asp1, thereby increasing its net kinase activity.
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Affiliation(s)
- Huanchen Wang
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health , 101 T. W. Alexander Drive, Research Triangle Park, North Carolina 27709, United States
| | - Vasudha S Nair
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health , 101 T. W. Alexander Drive, Research Triangle Park, North Carolina 27709, United States
| | - Ashley A Holland
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States
| | - Samanta Capolicchio
- Department of Chemistry, University of Zurich (UZH) , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Henning J Jessen
- Department of Chemistry, University of Zurich (UZH) , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Michael K Johnson
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States
| | - Stephen B Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health , 101 T. W. Alexander Drive, Research Triangle Park, North Carolina 27709, United States
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Marzook H, Li DQ, Nair VS, Mudvari P, Reddy SDN, Pakala SB, Santhoshkumar TR, Pillai MR, Kumar R. Metastasis-associated protein 1 drives tumor cell migration and invasion through transcriptional repression of RING finger protein 144A. J Biol Chem 2015; 290:6751. [PMID: 25770300 DOI: 10.1074/jbc.a114.314088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Sankaran D, Pakala SB, Nair VS, Sirigiri DNR, Cyanam D, Ha NH, Li DQ, Santhoshkumar T, Pillai MR, Kumar R. Withdrawal: Mechanism of MTA1 protein overexpression-linked invasion. MTA1 REGULATION OF HYALURONAN-MEDIATED MOTILITY RECEPTOR (HMMR) EXPRESSION AND FUNCTION. J Biol Chem 2013; 288:26177. [DOI: 10.1074/jbc.a111.324632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Li DQ, Nair SS, Ohshiro K, Kumar A, Nair VS, Pakala SB, Reddy SDN, Gajula RP, Eswaran J, Aravind L, Kumar R. MORC2 signaling integrates phosphorylation-dependent, ATPase-coupled chromatin remodeling during the DNA damage response. Cell Rep 2013; 2:1657-69. [PMID: 23260667 DOI: 10.1016/j.celrep.2012.11.018] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 07/25/2012] [Accepted: 11/27/2012] [Indexed: 12/23/2022] Open
Abstract
Chromatin dynamics play a central role in maintaining genome integrity, but how this is achieved remains largely unknown. Here, we report that microrchidia CW-type zinc finger 2 (MORC2), an uncharacterized protein with a derived PHD finger domain and a conserved GHKL-type ATPase module, is a physiological substrate of p21-activated kinase 1 (PAK1), an important integrator of extracellular signals and nuclear processes. Following DNA damage, MORC2 is phosphorylated on serine 739 in a PAK1-dependent manner, and phosphorylated MORC2 regulates its DNA-dependent ATPase activity to facilitate chromatin remodeling. Moreover, MORC2 associates with chromatin and promotes gamma-H2AX induction in a PAK1 phosphorylation-dependent manner. Consequently, cells expressing MORC2-S739A mutation displayed a reduction in DNA repair efficiency and were hypersensitive to DNA-damaging agent. These findings suggest that the PAK1-MORC2 axis is critical for orchestrating the interplay between chromatin dynamics and the maintenance of genomic integrity through sequentially integrating multiple essential enzymatic processes.
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Affiliation(s)
- Da-Qiang Li
- Department of Biochemistry and Molecular Biology, The George Washington University, Washington, DC 20037, USA.
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Pakala SB, Nair VS, Reddy SD, Kumar R. Signaling-dependent phosphorylation of mitotic centromere-associated kinesin regulates microtubule depolymerization and its centrosomal localization. J Biol Chem 2012; 287:40560-9. [PMID: 23055517 DOI: 10.1074/jbc.m112.399576] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Although PAK1 regulates cytoskeleton and microtubule dynamics, its role in controlling the functions of MCAK remains unknown. RESULTS PAK1 phosphorylates MCAK and thereby regulates both its localization and function. CONCLUSION MCAK is a cognate substrate of PAK1. SIGNIFICANCE This study provides a novel mechanistic insight into PAK1 regulation of MCAK functions. Although p21-activated kinase 1 (PAK1) and microtubule (MT) dynamics regulate numerous fundamental processes including cytoskeleton remodeling, directional motility, and mitotic functions, the significance of PAK1 signaling in regulating the functions of MT-destabilizing protein mitotic centromere-associated kinesin (MCAK) remains unknown. Here we found that MCAK is a cognate substrate of PAK1 wherein PAK1 phosphorylates MCAK on serines 192 and 111 both in vivo and in vitro. Furthermore, we found that PAK1 phosphorylation of MCAK on serines 192 and 111 preferentially regulates its microtubule depolymerization activity and localization to centrosomes, respectively, in the mammalian cells.
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Affiliation(s)
- Suresh B Pakala
- Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
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Marzook H, Li DQ, Nair VS, Mudvari P, Reddy SDN, Pakala SB, Santhoshkumar T, Pillai MR, Kumar R. Metastasis-associated protein 1 drives tumor cell migration and invasion through transcriptional repression of RING finger protein 144A. J Biol Chem 2012. [DOI: 10.1074/jbc.a111.314088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Marzook H, Li DQ, Nair VS, Mudvari P, Reddy SDN, Pakala SB, Santhoshkumar TR, Pillai MR, Kumar R. Metastasis-associated protein 1 drives tumor cell migration and invasion through transcriptional repression of RING finger protein 144A. J Biol Chem 2012; 287:5615-26. [PMID: 22184113 PMCID: PMC3285335 DOI: 10.1074/jbc.m111.314088] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 12/16/2011] [Indexed: 01/01/2023] Open
Abstract
Metastasis-associated protein 1 (MTA1), a component of the nucleosome-remodeling and histone deacetylase complex, is widely up-regulated in human cancers and significantly correlated with tumor invasion and metastasis, but the mechanisms involved remain largely unknown. Here, we report that MTA1 transcriptionally represses the expression of RING finger protein 144A (RNF144A), an uncharacterized gene whose protein product possesses potential E3 ubiquitin ligase activity, by recruiting the histone deacetylase 2 (HDAC2) and CCAAT/enhancer-binding protein α (c/EBPα) co-repressor complex onto human RNF144A promoter. Furthermore, an inverse correlation between the expression levels of MTA1 and RNF144A was demonstrated in publicly available breast cancer microarray datasets and the MCF10 breast cancer progression model system. To address functional aspects of MTA1 regulation of RNF144A, we demonstrate that RNF144A is a novel suppressor of cancer migration and invasion, two requisite steps of metastasis in vivo, and knockdown of endogenous RNF144A by small interfering RNAs accelerates the migration and invasion of MTA1-overexpressing cells. These results suggest that RNF144A is partially responsible for MTA1-mediated migration and invasion and that MTA1 overexpression in highly metastatic cancer cells drives cell migration and invasion by, at least in part, interfering with the suppressive function of RNF144A through transcriptional repression of RNF144A expression. Together, these findings provide novel mechanistic insights into regulation of tumor progression and metastasis by MTA1 and highlight a previously unrecognized role of RNF144A in MTA1-driven cancer cell migration and invasion.
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Affiliation(s)
- Hezlin Marzook
- From the Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, India and
| | - Da-Qiang Li
- the Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, George Washington University, Washington, D. C. 20037
| | - Vasudha S. Nair
- the Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, George Washington University, Washington, D. C. 20037
| | - Prakriti Mudvari
- the Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, George Washington University, Washington, D. C. 20037
| | - Sirigiri Divijendra Natha Reddy
- the Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, George Washington University, Washington, D. C. 20037
| | - Suresh B. Pakala
- the Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, George Washington University, Washington, D. C. 20037
| | - T. R. Santhoshkumar
- From the Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, India and
| | - M. Radhakrishna Pillai
- From the Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, India and
| | - Rakesh Kumar
- From the Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, India and
- the Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, George Washington University, Washington, D. C. 20037
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Sankaran D, Pakala SB, Nair VS, Sirigiri DNR, Cyanam D, Ha NH, Li DQ, Santhoshkumar TR, Pillai MR, Kumar R. Mechanism of MTA1 protein overexpression-linked invasion: MTA1 regulation of hyaluronan-mediated motility receptor (HMMR) expression and function. J Biol Chem 2012; 287:5483-91. [PMID: 22203674 PMCID: PMC3285325 DOI: 10.1074/jbc.m111.324632] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 12/27/2011] [Indexed: 11/06/2022] Open
Abstract
Even though the hyaluronan-mediated motility receptor (HMMR), a cell surface oncogenic protein, is widely up-regulated in human cancers and correlates well with cell motility and invasion, the underlying molecular and nature of its putative upstream regulation remain unknown. Here, we found for the first time that MTA1 (metastatic tumor antigen 1), a master chromatin modifier, regulates the expression of HMMR and, consequently, its function in breast cancer cell motility and invasiveness. We recognized a positive correlation between the levels of MTA1 and HMMR in human cancer. Furthermore, MTA1 is required for optimal expression of HMMR. The underlying mechanism includes interaction of the MTA1·RNA polymerase II·c-Jun coactivator complex with the HMMR promoter to stimulates its transcription. Accordingly, selective siRNA-mediated knockdown of HMMR in breast cancer cells substantially reduces the invasion and migration of cells. These findings reveal a regulatory role for MTA1 as an upstream coactivator of HMMR expression and resulting biological phenotypes.
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Affiliation(s)
- Deivendran Sankaran
- From the Integrated Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, Kerala, India and
| | - Suresh B. Pakala
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
| | - Vasudha S. Nair
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
| | - Divijendra Natha Reddy Sirigiri
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
| | - Dinesh Cyanam
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
| | - Ngoc-Han Ha
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
| | - Da-Qiang Li
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
| | - T. R. Santhoshkumar
- From the Integrated Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, Kerala, India and
| | - M. Radhakrishna Pillai
- From the Integrated Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, Kerala, India and
| | - Rakesh Kumar
- From the Integrated Cancer Research Program, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, Kerala, India and
- the Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, D. C. 20037
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Ha NH, Nair VS, Reddy DNS, Mudvari P, Ohshiro K, Ghanta KS, Pakala SB, Li DQ, Costa L, Lipton A, Badwe RA, Fuqua S, Wallon M, Prendergast GC, Kumar R. Lactoferrin-endothelin-1 axis contributes to the development and invasiveness of triple-negative breast cancer phenotypes. Cancer Res 2011; 71:7259-69. [PMID: 22006997 DOI: 10.1158/0008-5472.can-11-1143] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Triple-negative breast cancer (TNBC) is characterized by the lack of expression of estrogen receptor-α (ER-α), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2). However, pathways responsible for downregulation of therapeutic receptors, as well as subsequent aggressiveness, remain unknown. In this study, we discovered that lactoferrin (Lf) efficiently downregulates levels of ER-α, PR, and HER-2 in a proteasome-dependent manner in breast cancer cells, and it accounts for the loss of responsiveness to ER- or HER-2-targeted therapies. Furthermore, we found that lactoferrin increases migration and invasiveness of both non-TNBC and TNBC cell lines. We discovered that lactoferrin directly stimulates the transcription of endothelin-1 (ET-1), a secreted proinvasive polypeptide that acts through a specific receptor, ET(A)R, leading to secretion of the bioactive ET-1 peptide. Interestingly, a therapeutic ET-1 receptor-antagonist blocked lactoferrin-dependent motility and invasiveness of breast cancer cells. The physiologic significance of this newly discovered Lf-ET-1 axis in the manifestation of TNBC phenotypes is revealed by elevated plasma and tissue lactoferrin and ET-1 levels in patients with TNBC compared with those in ER(+) cases. These findings describe the first physiologically relevant polypeptide as a functional determinant in downregulating all three therapeutic receptors in breast cancer, which uses another secreted ET-1 system to confer invasiveness. Results presented in this article provide proof-of-principle evidence in support of the therapeutic effectiveness of ET-1 receptor antagonist to completely block the lactoferrin-induced motility and invasiveness of the TNBC as well as non-TNBC cells, and thus, open a remarkable opportunity to treat TNBC by targeting the Lf-ET-1 axis using an approved developmental drug.
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Affiliation(s)
- Ngoc-Han Ha
- Department of Biochemistry and Molecular Biology and Global Cancer Genomic Consortium, The George Washington University, Washington, District of Columbia 20037, USA
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Abstract
A woman developed peripheral neuropathy and optic neuritis while receiving ethambutol in the retreatment of drug-resistant pulmonary tuberculosis. There was prompt improvement in peripheral neuropathy and the ocular symptoms following the withdrawal of the drug. The clinical events in this case suggest that occasionally symptoms of peripheral neuropathy may precede the development of optic neuritis by several months, and thus serve as a warning for the subsequent development of the more serious visual toxicity.
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