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Zechner D, Bürtin F, Albert AC, Zhang X, Kumstel S, Schönrogge M, Graffunder J, Shih HY, Müller S, Radecke T, Jaster R, Vollmar B. Intratumoral heterogeneity of the therapeutical response to gemcitabine and metformin. Oncotarget 2016; 7:56395-56407. [PMID: 27486761 PMCID: PMC5302922 DOI: 10.18632/oncotarget.10892] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 07/18/2016] [Indexed: 12/15/2022] Open
Abstract
Cancer heterogeneity and microenvironmental aspects within a tumor are considered key factors influencing resistance of carcinoma cells to distinct chemotherapeutical agents. We evaluated a high concentration of metformin in combination with gemcitabine on a syngeneic orthotopic mouse model using 6606PDA cells. We observed reduced tumor size and reduced cancer cell proliferation after three weeks of chemotherapy with either compound and noticed an additive effect between gemcitabine and metformin on tumor weight. Interestingly, distinct areas of the carcinoma responded differently to either compound. Metformin inhibited the proliferation of cancer cells close to the desmoplastic reaction, whereas gemcitabine inhibited the proliferation of cancer cells mainly 360-570 μm distant to the desmoplastic reaction. Indeed, co-culture of pancreatic stellate cells with 6606PDA, 7265PDA or MIA PaCa-2 cells increased gemcitabine resistance. Metformin resistance, however, was increased by high glucose concentration in the medium. Other factors such as hypoxia or the pH of the medium had no influence on gemcitabine or metformin induced inhibition of cancer cell proliferation. These data demonstrate a spatial heterogeneity in drug resistance within pancreatic adenocarcinomas and that microenvironmental aspects such as supply of glucose and the presence of pancreatic stellate cells regulate cancer cell sensitivity towards metformin or gemcitabine.
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Affiliation(s)
- Dietmar Zechner
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Florian Bürtin
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Ann-Christin Albert
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Xianbin Zhang
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Simone Kumstel
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Maria Schönrogge
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Josefine Graffunder
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Hao-Yu Shih
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Sarah Müller
- Division of Gastroenterology, Department of Medicine II, Rostock University Medical Center, 18057 Rostock, Germany
| | - Tobias Radecke
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
| | - Robert Jaster
- Division of Gastroenterology, Department of Medicine II, Rostock University Medical Center, 18057 Rostock, Germany
| | - Brigitte Vollmar
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
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Aseervatham J, Tran L, Machaca K, Boudker O. The Role of Flexible Loops in Folding, Trafficking and Activity of Equilibrative Nucleoside Transporters. PLoS One 2015; 10:e0136779. [PMID: 26406980 PMCID: PMC4583308 DOI: 10.1371/journal.pone.0136779] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 08/07/2015] [Indexed: 11/25/2022] Open
Abstract
Equilibrative nucleoside transporters (ENTs) are integral membrane proteins, which reside in plasma membranes of all eukaryotic cells and mediate thermodynamically downhill transport of nucleosides. This process is essential for nucleoside recycling, and also plays a key role in terminating adenosine-mediated cellular signaling. Furthermore, ENTs mediate the uptake of many drugs, including anticancer and antiviral nucleoside analogues. The structure and mechanism, by which ENTs catalyze trans-membrane transport of their substrates, remain unknown. To identify the core of the transporter needed for stability, activity, and for its correct trafficking to the plasma membrane, we have expressed human ENT deletion mutants in Xenopus laevis oocytes and determined their localization, transport properties and susceptibility to inhibition. We found that the carboxyl terminal trans-membrane segments are essential for correct protein folding and trafficking. In contrast, the soluble extracellular and intracellular loops appear to be dispensable, and must be involved in the fine-tuning of transport regulation.
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Affiliation(s)
- Jaya Aseervatham
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Qatar foundation, Education City, Doha, Qatar
| | - Lucky Tran
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States of America
| | - Khaled Machaca
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Qatar foundation, Education City, Doha, Qatar
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States of America
- * E-mail:
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Dos Santos-Rodrigues A, Pereira MR, Brito R, de Oliveira NA, Paes-de-Carvalho R. Adenosine transporters and receptors: key elements for retinal function and neuroprotection. VITAMINS AND HORMONES 2015; 98:487-523. [PMID: 25817878 DOI: 10.1016/bs.vh.2014.12.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Adenosine is an important neuroactive substance in the central nervous system, including in the retina where subclasses of adenosine receptors and transporters are expressed since early stages of development. Here, we review some evidence showing that adenosine plays important functions in the mature as well as in the developing tissue. Adenosine transporters are divided into equilibrative and concentrative, and the major transporter subtype present in the retina is the ENT1. This transporter is responsible for a bidirectional transport of adenosine and the uptake or release of this nucleoside appears to be regulated by different signaling pathways that are also controlled by activation of adenosine receptors. Adenosine receptors are also key players in retina physiology regulating a variety of functions in the mature and developing tissue. Regulation of excitatory neurotransmitter release and neuroprotection are the main functions played be adenosine in the mature tissue, while regulation of cell survival and neurogenesis are some of the functions played by adenosine in developing retina. Since adenosine is neuroprotective against excitotoxic and metabolic dysfunctions observed in neurological and ocular diseases, the search for adenosine-related drugs regulating adenosine transporters and receptors can be important for advancement of therapeutic strategies against these diseases.
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Affiliation(s)
| | - Mariana R Pereira
- Program of Neurosciences, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil
| | - Rafael Brito
- Program of Neurosciences, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil
| | - Nádia A de Oliveira
- Program of Neurosciences, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil
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Dos Santos-Rodrigues A, Grañé-Boladeras N, Bicket A, Coe IR. Nucleoside transporters in the purinome. Neurochem Int 2014; 73:229-37. [PMID: 24704797 DOI: 10.1016/j.neuint.2014.03.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 03/23/2014] [Accepted: 03/24/2014] [Indexed: 01/20/2023]
Abstract
The purinome is a rich complex of proteins and cofactors that are involved in fundamental aspects of cellular homeostasis and cellular responses. The purinome is evolutionarily ancient and is made up of thousands of members. Our understanding of the mechanisms linking some parts of this complex network and the physiological relevance of the various connections is well advanced. However, our understanding of other parts of the purinome is less well developed. Our research focuses on the adenosine or nucleoside transporters (NTs), which are members of the membrane purinome. Nucleoside transporters are integral membrane proteins that are responsible for the flux of nucleosides, such as adenosine, and nucleoside analog drugs, used in a variety of anti-cancer, anti-viral and anti-parasite therapies, across cell membranes. Nucleoside transporters form the SLC28 and SLC29 families of solute carriers and the protein members of these families are widely distributed in human tissues including the central nervous system (CNS). NTs modulate purinergic signaling in the CNS primarily through their effects on modulating prevailing adenosine levels inside and outside the cell. By clearing the extracellular milieu of adenosine, NTs can terminate adenosine receptor-dependent signaling and this raises the possibility of regulatory feedback loops that tie together receptor signaling with transporter function. Despite the important role of NTs as modulators of purinergic signaling in the human body, very little is known about the nature or underlying mechanisms of regulation of either the SLC28 or SLC29 families, particularly within the context of the CNS purinome. Here we provide a brief overview of our current understanding of the regulation of members of the SLC29 family and highlight some interesting avenues for future research.
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Affiliation(s)
| | - Natalia Grañé-Boladeras
- Department of Chemistry and Biology, Faculty of Science, Ryerson University, Toronto, ON, Canada
| | - Alex Bicket
- Department of Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Imogen R Coe
- Department of Biology, Faculty of Science, York University, Toronto, ON, Canada; Department of Chemistry and Biology, Faculty of Science, Ryerson University, Toronto, ON, Canada.
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Park JS, Hammond JR. Cysteine Residues in the Transmembrane (TM) 9 to TM11 Region of the Human Equilibrative Nucleoside Transporter Subtype 1 Play an Important Role in Inhibitor Binding and Translocation Function. Mol Pharmacol 2012; 82:784-94. [DOI: 10.1124/mol.112.079616] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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Reyes G, Nivillac NMI, Karim MZ, Desouza L, Siu KWM, Coe IR. The Equilibrative Nucleoside Transporter (ENT1) can be phosphorylated at multiple sites by PKC and PKA. Mol Membr Biol 2011; 28:412-26. [DOI: 10.3109/09687688.2011.604861] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Abstract
BACKGROUND Nucleoside/nucleobase transporters have been investigated since the 1960s. In particular, equilibrative nucleoside transporters were thought to be valuable drug targets, since they are involved in various kinds of viral and parasitic diseases as well as cancers. DISCUSSION In the postgenomic era multiple transporters, including different subtypes, have been cloned and characterized on the molecular level. In this article we summarize recent advances regarding structure, function and localization of nucleoside/nucleobase transporters as well as the pharmacological profile of selected drugs. CONCLUSION Knowledge of the different kinetic properties and structural features of nucleoside transporters can either be used for the rational design of therapeutics directly targeting the transporter itself or for the delivery of drugs using the transporter as a port of entry into the target cell. Equilibrative nucleoside transporters are of considerable pharmacological interest as drug targets for the development of drugs tailored to each patient's need for the treatment of cardiac disease, cancer and viral infections.
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Cano-Soldado P, Pastor-Anglada M. Transporters that translocate nucleosides and structural similar drugs: structural requirements for substrate recognition. Med Res Rev 2011; 32:428-57. [DOI: 10.1002/med.20221] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Pedro Cano-Soldado
- Departament de Bioquímica i Biologia Molecular; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona and CIBER EHD; Barcelona Spain
| | - Marçal Pastor-Anglada
- Departament de Bioquímica i Biologia Molecular; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona and CIBER EHD; Barcelona Spain
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Riegelhaupt PM, Frame IJ, Akabas MH. Transmembrane segment 11 appears to line the purine permeation pathway of the Plasmodium falciparum equilibrative nucleoside transporter 1 (PfENT1). J Biol Chem 2010; 285:17001-10. [PMID: 20335165 DOI: 10.1074/jbc.m110.115758] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Purine transport is essential for malaria parasites to grow because they lack the enzymes necessary for de novo purine biosynthesis. The Plasmodium falciparum Equilibrative Nucleoside Transporter 1 (PfENT1) is a member of the equilibrative nucleoside transporter (ENT) gene family. PfENT1 is a primary purine transport pathway across the P. falciparum plasma membrane because PfENT1 knock-out parasites are not viable at physiologic extracellular purine concentrations. Topology predictions and experimental data indicate that ENT family members have eleven transmembrane (TM) segments although their tertiary structure is unknown. In the current work, we showed that a naturally occurring polymorphism, F394L, in TM11 affects transport substrate K(m). We investigated the structure and function of the TM11 segment using the substituted cysteine accessibility method. We showed that mutation to Cys of two highly conserved glycine residues in a GXXXG motif significantly reduces PfENT1 protein expression levels. We speculate that the conserved TM11 GXXXG glycines may be critical for folding and/or assembly. Small, cysteine-specific methanethiosulfonate (MTS) reagents reacted with four TM11 Cys substitution mutants, L393C, I397C, T400C, and Y403C. Larger MTS reagents do not react with the more cytoplasmic positions. Hypoxanthine, a transported substrate, protected L393C, I397C, and T400C from covalent modification by the MTS reagents. Plotted on an alpha-helical wheel, Leu-393, Ile-397, and Thr-400 lie on one face of the helix in a 60 degrees arc suggesting that TM11 is largely alpha helical. We infer that they line a water-accessible surface, possibly the purine permeation pathway. These results advance our understanding of the ENT structure.
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Affiliation(s)
- Paul M Riegelhaupt
- Department of Physiology and Biophysics, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA
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