1
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Nishizawa N, Kurasaka C, Ogino Y, Sato A. Regulation of 5-fluorodeoxyuridine monophosphate-thymidylate synthase ternary complex levels by autophagy confers resistance to 5-fluorouracil. FASEB Bioadv 2022; 5:43-51. [PMID: 36643896 PMCID: PMC9832531 DOI: 10.1096/fba.2022-00099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/27/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
5-Fluorouracil (5-FU) is a cornerstone drug used to treat colorectal cancer (CRC). However, the prolonged exposure of CRC cells to 5-FU results in acquired resistance. We have previously demonstrated that levels of the 5-fluorodeoxyuridylate (FdUMP) covalent complex with thymidylate synthase (FdUMP-TS) and free-TS (native enzyme) are higher in 5-FU-resistant CRC cells than in the parental cell line (HCT116). Accordingly, resistant cells may have an efficient system for trapping and removing FdUMP-TS, thus imparting resistance. In this study, using a model of 5-FU-resistant CRC cells generated by repeated exposure, the role of autophagy in the elimination of FdUMP-TS in resistant cells was investigated. The resistant cells showed greater sensitivity to autophagy inhibitors than that of parental cells. Autophagy inhibition increased 5-FU cytotoxicity more substantially in resistant cells than in parental cells. Furthermore, autophagy inhibition increased FdUMP-TS protein accumulation in resistant cells. Our findings suggest that resistance to 5-FU is mediated by autophagy as a system to eliminate FdUMP-TS and may guide the use and optimization of combination therapies involving autophagy inhibitors.
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Affiliation(s)
- Nana Nishizawa
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical SciencesTokyo University of ScienceChibaJapan
| | - Chinatsu Kurasaka
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical SciencesTokyo University of ScienceChibaJapan,Present address:
Kowa Company Ltd.Nihonbashi‐HonchoTokyoJapan
| | - Yoko Ogino
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical SciencesTokyo University of ScienceChibaJapan,Present address:
Department of Gene Regulation, Faculty of Pharmaceutical SciencesTokyo University of ScienceChibaJapan
| | - Akira Sato
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical SciencesTokyo University of ScienceChibaJapan
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2
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Kurasaka C, Nishizawa N, Ogino Y, Sato A. Trapping of 5-Fluorodeoxyuridine Monophosphate by Thymidylate Synthase Confers Resistance to 5-Fluorouracil. ACS OMEGA 2022; 7:6046-6052. [PMID: 35224365 PMCID: PMC8868108 DOI: 10.1021/acsomega.1c06394] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
The major metabolite of the anticancer agent 5-fluorouracil (5-FU) is 5-fluorodeoxyuridine monophosphate (FdUMP), which is a potent inhibitor of thymidylate synthase (TS). Recently, we hypothesized that 5-FU-resistant colorectal cancer (CRC) cells have increased levels of TS protein relative to 5-FU-sensitive CRC cells and use a fraction of their TS to trap FdUMP, which results in resistance to 5-FU. In this study, we analyzed the difference between the regulation of the balance of the free, active form of TS and the inactive FdUMP-TS form in 5-FU-resistant HCT116 cells and parental HCT116 cells. Silencing of TYMS, the gene that encodes TS, resulted in greater enhancement of the anticancer effect of 5-FU in the 5-FU-resistant HCT116RF10 cells than in the parental HCT116 cells. In addition, the trapping of FdUMP by TS was more effective in the 5-FU-resistant HCT116RF10 cells than in the parental HCT116 cells. Our observations suggest that the regulation of the balance between the storage of the active TS form and the accumulation of FdUMP-TS is responsible for direct resistance to 5-FU. The findings provide a better understanding of 5-FU resistance mechanisms and may enable the development of anticancer strategies that reverse the sensitivity of 5-FU resistance in CRC cells.
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Affiliation(s)
- Chinatsu Kurasaka
- Department
of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Nana Nishizawa
- Department
of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Yoko Ogino
- Department
of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
- Department
of Gene Regulation, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Akira Sato
- Department
of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
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3
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Costantino L, Ferrari S, Santucci M, Salo-Ahen OMH, Carosati E, Franchini S, Lauriola A, Pozzi C, Trande M, Gozzi G, Saxena P, Cannazza G, Losi L, Cardinale D, Venturelli A, Quotadamo A, Linciano P, Tagliazucchi L, Moschella MG, Guerrini R, Pacifico S, Luciani R, Genovese F, Henrich S, Alboni S, Santarem N, da Silva Cordeiro A, Giovannetti E, Peters GJ, Pinton P, Rimessi A, Cruciani G, Stroud RM, Wade RC, Mangani S, Marverti G, D'Arca D, Ponterini G, Costi MP. Destabilizers of the thymidylate synthase homodimer accelerate its proteasomal degradation and inhibit cancer growth. eLife 2022; 11:73862. [PMID: 36475542 PMCID: PMC9831607 DOI: 10.7554/elife.73862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 12/01/2022] [Indexed: 12/13/2022] Open
Abstract
Drugs that target human thymidylate synthase (hTS), a dimeric enzyme, are widely used in anticancer therapy. However, treatment with classical substrate-site-directed TS inhibitors induces over-expression of this protein and development of drug resistance. We thus pursued an alternative strategy that led us to the discovery of TS-dimer destabilizers. These compounds bind at the monomer-monomer interface and shift the dimerization equilibrium of both the recombinant and the intracellular protein toward the inactive monomers. A structural, spectroscopic, and kinetic investigation has provided evidence and quantitative information on the effects of the interaction of these small molecules with hTS. Focusing on the best among them, E7, we have shown that it inhibits hTS in cancer cells and accelerates its proteasomal degradation, thus causing a decrease in the enzyme intracellular level. E7 also showed a superior anticancer profile to fluorouracil in a mouse model of human pancreatic and ovarian cancer. Thus, over sixty years after the discovery of the first TS prodrug inhibitor, fluorouracil, E7 breaks the link between TS inhibition and enhanced expression in response, providing a strategy to fight drug-resistant cancers.
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Affiliation(s)
- Luca Costantino
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Stefania Ferrari
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Matteo Santucci
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Outi MH Salo-Ahen
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical StudiesHeidelbergGermany
| | - Emanuele Carosati
- Department of Chemistry, Biology and Biotechnology, University of PerugiaPerugiaItaly
| | - Silvia Franchini
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Angela Lauriola
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Cecilia Pozzi
- Department of Biotechnology, Chemistry and Pharmacy, University of SienaSienaItaly
| | - Matteo Trande
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Gaia Gozzi
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Puneet Saxena
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Giuseppe Cannazza
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Lorena Losi
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Daniela Cardinale
- Respiratory, Critical Care & Anesthesia UCL Great Ormond Street Institute of Child HealthLondonUnited Kingdom
| | - Alberto Venturelli
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Antonio Quotadamo
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Pasquale Linciano
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | | | - Maria Gaetana Moschella
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly,Clinical and Experimental Medicine PhD Program, University of Modena and Reggio Emilia, Modena, ItalyModenaItaly
| | - Remo Guerrini
- Department of Chemical and Pharmaceutical Science, University of FerraraFerraraItaly
| | - Salvatore Pacifico
- Department of Chemical and Pharmaceutical Science, University of FerraraFerraraItaly
| | - Rosaria Luciani
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Filippo Genovese
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Stefan Henrich
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical StudiesHeidelbergGermany
| | - Silvia Alboni
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | | | - Anabela da Silva Cordeiro
- IBMC I3SPortoPortugal,Department of Biological Sciences, Faculty of Pharmacy, University of PortoPortoPortugal
| | - Elisa Giovannetti
- Department of Medical Oncology, Amsterdam University Medical Center, Cancer Center Amsterdam, 1081HV, Vrije Universiteit AmsterdamAmsterdamNetherlands,CancerPharmacology Lab, Fondazione Pisana per la ScienzaPisaItaly
| | - Godefridus J Peters
- Department of Medical Oncology, Amsterdam University Medical Center, Cancer Center Amsterdam, 1081HV, Vrije Universiteit AmsterdamAmsterdamNetherlands
| | - Paolo Pinton
- Dept. of Medical Sciences and Laboratory for Technologies of Advanced Therapies (LTTA), University of FerraraFerraraItaly
| | - Alessandro Rimessi
- Dept. of Medical Sciences and Laboratory for Technologies of Advanced Therapies (LTTA), University of FerraraFerraraItaly
| | - Gabriele Cruciani
- Department of Chemistry, Biology and Biotechnology, University of PerugiaPerugiaItaly
| | - Robert M Stroud
- Biochemistry and Biophysics Department, University of California San FranciscoSan FranciscoUnited States
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical StudiesHeidelbergGermany,Interdisciplinary Center for Scientific Computing (IWR), Heidelberg UniversityHeidelbergGermany,Center for Molecular Biology (ZMBH), DKFZ-ZMBH Alliance, Heidelberg UniversityHeidelbergGermany
| | - Stefano Mangani
- Department of Biotechnology, Chemistry and Pharmacy, University of SienaSienaItaly
| | - Gaetano Marverti
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Domenico D'Arca
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Glauco Ponterini
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
| | - Maria Paola Costi
- Department of Life Sciences, University of Modena and Reggio EmiliaModenaItaly
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4
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Frost J, Rocha S, Ciulli A. Von Hippel-Lindau (VHL) small-molecule inhibitor binding increases stability and intracellular levels of VHL protein. J Biol Chem 2021; 297:100910. [PMID: 34174286 PMCID: PMC8313594 DOI: 10.1016/j.jbc.2021.100910] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/15/2021] [Accepted: 06/22/2021] [Indexed: 11/24/2022] Open
Abstract
Von Hippel-Lindau (VHL) disease is characterized by frequent mutation of VHL protein, a tumor suppressor that functions as the substrate recognition subunit of a Cullin2 RING E3 ligase complex (CRL2VHL). CRL2VHL plays important roles in oxygen sensing by targeting hypoxia-inducible factor-alpha (HIF-α) subunits for ubiquitination and degradation. VHL is also commonly hijacked by bifunctional molecules such as proteolysis-targeting chimeras to induce degradation of target molecules. We previously reported the design and characterization of VHL inhibitors VH032 and VH298 that block the VHL:HIF-α interaction, activate the HIF transcription factor, and induce a hypoxic response, which can be beneficial to treat anemia and mitochondrial diseases. How these compounds affect the global cellular proteome remains unknown. Here, we use unbiased quantitative MS to identify the proteomic changes elicited by the VHL inhibitor compared with hypoxia or the broad-spectrum prolyl-hydroxylase domain enzyme inhibitor IOX2. Our results demonstrate that VHL inhibitors selectively activate the HIF response similar to the changes induced in hypoxia and IOX2 treatment. Interestingly, VHL inhibitors were found to specifically upregulate VHL itself. Our analysis revealed that this occurs via protein stabilization of VHL isoforms and not via changes in transcript levels. Increased VHL levels upon VH298 treatment resulted in turn in reduced levels of HIF-1α protein. This work demonstrates the specificity of VHL inhibitors and reveals different antagonistic effects upon their acute versus prolonged treatment in cells. These findings suggest that therapeutic use of VHL inhibitors may not produce overt side effects from HIF stabilization as previously thought.
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Affiliation(s)
- Julianty Frost
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom; Center for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom; Department of Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Sonia Rocha
- Center for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom; Department of Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
| | - Alessio Ciulli
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom.
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5
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Kurasaka C, Ogino Y, Sato A. Molecular Mechanisms and Tumor Biological Aspects of 5-Fluorouracil Resistance in HCT116 Human Colorectal Cancer Cells. Int J Mol Sci 2021; 22:ijms22062916. [PMID: 33805673 PMCID: PMC8002131 DOI: 10.3390/ijms22062916] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/26/2021] [Accepted: 03/10/2021] [Indexed: 12/24/2022] Open
Abstract
5-Fluorouracil (5-FU) is a cornerstone drug used in the treatment of colorectal cancer (CRC). However, the development of resistance to 5-FU and its analogs remain an unsolved problem in CRC treatment. In this study, we investigated the molecular mechanisms and tumor biological aspects of 5-FU resistance in CRC HCT116 cells. We established an acquired 5-FU-resistant cell line, HCT116RF10. HCT116RF10 cells were cross-resistant to the 5-FU analog, fluorodeoxyuridine. In contrast, HCT116RF10 cells were collaterally sensitive to SN-38 and CDDP compared with the parental HCT16 cells. Whole-exome sequencing revealed that a cluster of genes associated with the 5-FU metabolic pathway were not significantly mutated in HCT116 or HCT116RF10 cells. Interestingly, HCT116RF10 cells were regulated by the function of thymidylate synthase (TS), a 5-FU active metabolite 5-fluorodeoxyuridine monophosphate (FdUMP) inhibiting enzyme. Half of the TS was in an active form, whereas the other half was in an inactive form. This finding indicates that 5-FU-resistant cells exhibited increased TS expression, and the TS enzyme is used to trap FdUMP, resulting in resistance to 5-FU and its analogs.
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Affiliation(s)
- Chinatsu Kurasaka
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan; (C.K.); (Y.O.)
| | - Yoko Ogino
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan; (C.K.); (Y.O.)
- Department of Gene Regulation, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Akira Sato
- Department of Biochemistry and Molecular Biology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan; (C.K.); (Y.O.)
- Correspondence: ; Tel.: +81-4-7121-3620
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6
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Choi YM, Yeo HK, Park YW, Lee JY. Structural Analysis of Thymidylate Synthase from Kaposi's Sarcoma-Associated Herpesvirus with the Anticancer Drug Raltitrexed. PLoS One 2016; 11:e0168019. [PMID: 27936107 PMCID: PMC5148040 DOI: 10.1371/journal.pone.0168019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 11/25/2016] [Indexed: 01/07/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is a highly infectious human herpesvirus that causes Kaposi's sarcoma. KSHV encodes functional thymidylate synthase, which is a target for anticancer drugs such as raltitrexed or 5-fluorouracil. Thymidylate synthase catalyzes the conversion of 2'-deoxyuridine-5'-monophosphate (dUMP) to thymidine-5'-monophosphate (dTMP) using 5,10-methylenetetrahydrofolate (mTHF) as a co-substrate. The crystal structures of thymidylate synthase from KSHV (apo), complexes with dUMP (binary), and complexes with both dUMP and raltitrexed (ternary) were determined at 1.7 Å, 2.0 Å, and 2.4 Å, respectively. While the ternary complex structures of human thymidylate synthase and E. coli thymidylate synthase had a closed conformation, the ternary complex structure of KSHV thymidylate synthase was observed in an open conformation, similar to that of rat thymidylate synthase. The complex structures of KSHV thymidylate synthase did not have a covalent bond between the sulfhydryl group of Cys219 and C6 atom of dUMP, unlike the human thymidylate synthase. The catalytic Cys residue demonstrated a dual conformation in the apo structure, and its sulfhydryl group was oriented toward the C6 atom of dUMP with no covalent bond upon ligand binding in the complex structures. These structural data provide the potential use of antifolates such as raltitrexed as a viral induced anticancer drug and structural basis to design drugs for targeting the thymidylate synthase of KSHV.
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Affiliation(s)
- Yong Mi Choi
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Hyun Ku Yeo
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Young Woo Park
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Jae Young Lee
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
- * E-mail:
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7
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Antosiewicz A, Jarmuła A, Przybylska D, Mosieniak G, Szczepanowska J, Kowalkowska A, Rode W, Cieśla J. Human dihydrofolate reductase and thymidylate synthase form a complex in vitro and co-localize in normal and cancer cells. J Biomol Struct Dyn 2016; 35:1474-1490. [PMID: 27187663 DOI: 10.1080/07391102.2016.1186560] [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: 12/30/2022]
Abstract
Enzymes involved in thymidylate biosynthesis, thymidylate synthase (TS), and dihydrofolate reductase (DHFR) are well-known targets in cancer chemotherapy. In this study, we demonstrated for the first time, that human TS and DHFR form a strong complex in vitro and co-localize in human normal and colon cancer cell cytoplasm and nucleus. Treatment of cancer cells with methotrexate or 5-fluorouracil did not affect the distribution of either enzyme within the cells. However, 5-FU, but not MTX, lowered the presence of DHFR-TS complex in the nucleus by 2.5-fold. The results may suggest the sequestering of TS by FdUMP in the cytoplasm and thereby affecting the translocation of DHFR-TS complex to the nucleus. Providing a strong likelihood of DHFR-TS complex formation in vivo, the latter complex is a potential new drug target in cancer therapy. In this paper, known 3D structures of human TS and human DHFR, and some protozoan bifunctional DHFR-TS structures as templates, are used to build an in silico model of human DHFR-TS complex structure, consisting of one TS dimer and two DHFR monomers. This complex structure may serve as an initial 3D drug target model for prospective inhibitors targeting interfaces between the DHFR and TS enzymes.
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Affiliation(s)
- Anna Antosiewicz
- a Faculty of Chemistry , Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw , Poland
| | - Adam Jarmuła
- b Nencki Institute of Experimental Biology , Polish Academy of Sciences , Pasteura 3, 02-093 , Warsaw , Poland
| | - Dorota Przybylska
- b Nencki Institute of Experimental Biology , Polish Academy of Sciences , Pasteura 3, 02-093 , Warsaw , Poland
| | - Grażyna Mosieniak
- b Nencki Institute of Experimental Biology , Polish Academy of Sciences , Pasteura 3, 02-093 , Warsaw , Poland
| | - Joanna Szczepanowska
- b Nencki Institute of Experimental Biology , Polish Academy of Sciences , Pasteura 3, 02-093 , Warsaw , Poland
| | - Anna Kowalkowska
- a Faculty of Chemistry , Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw , Poland
| | - Wojciech Rode
- b Nencki Institute of Experimental Biology , Polish Academy of Sciences , Pasteura 3, 02-093 , Warsaw , Poland
| | - Joanna Cieśla
- a Faculty of Chemistry , Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw , Poland
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8
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Inside the biochemical pathways of thymidylate synthase perturbed by anticancer drugs: Novel strategies to overcome cancer chemoresistance. Drug Resist Updat 2015; 23:20-54. [PMID: 26690339 DOI: 10.1016/j.drup.2015.10.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 10/08/2015] [Accepted: 10/23/2015] [Indexed: 12/11/2022]
Abstract
Our current understanding of the mechanisms of action of antitumor agents and the precise mechanisms underlying drug resistance is that these two processes are directly linked. Moreover, it is often possible to delineate chemoresistance mechanisms based on the specific mechanism of action of a given anticancer drug. A more holistic approach to the chemoresistance problem suggests that entire metabolic pathways, rather than single enzyme targets may better explain and educate us about the complexity of the cellular responses upon cytotoxic drug administration. Drugs, which target thymidylate synthase and folate-dependent enzymes, represent an important therapeutic arm in the treatment of various human malignancies. However, prolonged patient treatment often provokes drug resistance phenomena that render the chemotherapeutic treatment highly ineffective. Hence, strategies to overcome drug resistance are primarily designed to achieve either enhanced intracellular drug accumulation, to avoid the upregulation of folate-dependent enzymes, and to circumvent the impairment of DNA repair enzymes which are also responsible for cross-resistance to various anticancer drugs. The current clinical practice based on drug combination therapeutic regimens represents the most effective approach to counteract drug resistance. In the current paper, we review the molecular aspects of the activity of TS-targeting drugs and describe how such mechanisms are related to the emergence of clinical drug resistance. We also discuss the current possibilities to overcome drug resistance by using a molecular mechanistic approach based on medicinal chemistry methods focusing on rational structural modifications of novel antitumor agents. This paper also focuses on the importance of the modulation of metabolic pathways upon drug administration, their analysis and the assessment of their putative roles in the networks involved using a meta-analysis approach. The present review describes the main pathways that are modulated by TS-targeting anticancer drugs starting from the description of the normal functioning of the folate metabolic pathway, through the protein modulation occurring upon drug delivery to cultured tumor cells as well as cancer patients, finally describing how the pathways are modulated by drug resistance development. The data collected are then analyzed using network/netwire connecting methods in order to provide a wider view of the pathways involved and of the importance of such information in identifying additional proteins that could serve as novel druggable targets for efficacious cancer therapy.
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9
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Tochowicz A, Santucci M, Saxena P, Guaitoli G, Trande M, Finer-Moore J, Stroud RM, Costi MP. Alanine mutants of the interface residues of human thymidylate synthase decode key features of the binding mode of allosteric anticancer peptides. J Med Chem 2014; 58:1012-8. [PMID: 25427005 DOI: 10.1021/jm5011176] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Allosteric peptide inhibitors of thymidylate synthase (hTS) bind to the dimer interface and stabilize the inactive form of the protein. Four interface residues were mutated to alanine, and interaction studies were employed to decode the key role of these residues in the peptide molecular recognition. This led to the identification of three crucial interface residues F59, L198, and Y202 that impart activity to the peptide inhibitors and suggest the binding area for further inhibitor design.
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Affiliation(s)
- Anna Tochowicz
- Department of Biochemistry and Biophysics, University of California-San Francisco , 600 16th Street, San Francisco, California 94158, United States
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10
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Abstract
Expression of hTS (human thymidylate synthase), a key enzyme in thymidine biosynthesis, is regulated on the translational level through a feedback mechanism that is rarely found in eukaryotes. At low substrate concentrations, the ligand-free enzyme binds to its own mRNA and stabilizes a hairpin structure that sequesters the start codon. When in complex with dUMP (2'-deoxyuridine-5'-monophosphate) and a THF (tetrahydrofolate) cofactor, the enzyme adopts a conformation that is unable to bind and repress expression of mRNA. Here, we have used a combination of X-ray crystallography, RNA mutagenesis and site-specific cross-linking studies to investigate the molecular recognition of TS mRNA by the hTS enzyme. The interacting mRNA region was narrowed to the start codon and immediately flanking sequences. In the hTS enzyme, a helix-loop-helix domain on the protein surface was identified as the putative RNA-binding site.
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11
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Wilson PM, Danenberg PV, Johnston PG, Lenz HJ, Ladner RD. Standing the test of time: targeting thymidylate biosynthesis in cancer therapy. Nat Rev Clin Oncol 2014; 11:282-98. [PMID: 24732946 DOI: 10.1038/nrclinonc.2014.51] [Citation(s) in RCA: 257] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Over the past 60 years, chemotherapeutic agents that target thymidylate biosynthesis and the enzyme thymidylate synthase (TS) have remained among the most-successful drugs used in the treatment of cancer. Fluoropyrimidines, such as 5-fluorouracil and capecitabine, and antifolates, such as methotrexate and pemetrexed, induce a state of thymidylate deficiency and imbalances in the nucleotide pool that impair DNA replication and repair. TS-targeted agents are used to treat numerous solid and haematological malignancies, either alone or as foundational therapeutics in combination treatment regimens. We overview the pivotal discoveries that led to the rational development of thymidylate biosynthesis as a chemotherapeutic target, and highlight the crucial contribution of these advances to driving and accelerating drug development in the earliest era of cancer chemotherapy. The function of TS as well as the mechanisms and consequences of inhibition of this enzyme by structurally diverse classes of drugs with distinct mechanisms of action are also discussed. In addition, breakthroughs relating to TS-targeted therapies that transformed the clinical landscape in some of the most-difficult-to-treat cancers, such as pancreatic, colorectal and non-small-cell lung cancer, are highlighted. Finally, new therapeutic agents and novel mechanism-based strategies that promise to further exploit the vulnerabilities and target resistance mechanisms within the thymidylate biosynthesis pathway are reviewed.
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Affiliation(s)
- Peter M Wilson
- Department of Pathology, University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA
| | - Peter V Danenberg
- Department of Biochemistry and Molecular Biology, University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA
| | - Patrick G Johnston
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast BT9 7AE, UK
| | - Heinz-Josef Lenz
- Division of Medical Oncology, University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA
| | - Robert D Ladner
- Department of Pathology, University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA
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12
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Pelà M, Saxena P, Luciani R, Santucci M, Ferrari S, Marverti G, Marraccini C, Martello A, Pirondi S, Genovese F, Salvadori S, D’Arca D, Ponterini G, Costi MP, Guerrini R. Optimization of Peptides That Target Human Thymidylate Synthase to Inhibit Ovarian Cancer Cell Growth. J Med Chem 2014; 57:1355-67. [DOI: 10.1021/jm401574p] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Michela Pelà
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17-19, 44100 Ferrara, Italy
| | - Puneet Saxena
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Rosaria Luciani
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Matteo Santucci
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Stefania Ferrari
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Gaetano Marverti
- Department of Biomedical Sciences, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, via Campi 287, 41125 Modena, Italy
| | - Chiara Marraccini
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Andrea Martello
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Silvia Pirondi
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Filippo Genovese
- C.I.G.S. (Centro Interdipartimentale Grandi Strumenti), University of Modena and Reggio Emilia, via Campi 213/A, 41125 Modena, Italy
| | - Severo Salvadori
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17-19, 44100 Ferrara, Italy
- LTTA (Laboratorio per le Tecnologie delle Terapie Avanzate), via Fossato di Mortara 17-19, 44100 Ferrara, Italy
| | - Domenico D’Arca
- Department of Biomedical Sciences, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, via Campi 287, 41125 Modena, Italy
| | - Glauco Ponterini
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Maria Paola Costi
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 183, 41125 Modena, Italy
| | - Remo Guerrini
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17-19, 44100 Ferrara, Italy
- LTTA (Laboratorio per le Tecnologie delle Terapie Avanzate), via Fossato di Mortara 17-19, 44100 Ferrara, Italy
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13
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Erales J, Coffino P. Ubiquitin-independent proteasomal degradation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:216-21. [PMID: 23684952 DOI: 10.1016/j.bbamcr.2013.05.008] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 10/26/2022]
Abstract
Most proteasome substrates are marked for degradation by ubiquitin conjugation, but some are targeted by other means. The properties of these exceptional cases provide insights into the general requirements for proteasomal degradation. Here the focus is on three ubiquitin-independent substrates that have been the subject of detailed study. These are Rpn4, a transcriptional regulator of proteasome homeostasis, thymidylate synthase, an enzyme required for production of DNA precursors and ornithine decarboxylase, the initial enzyme committed to polyamine biosynthesis. It can be inferred from these cases that proteasome association and the presence of an unstructured region are the sole prerequisites for degradation. Based on that inference, artificial substrates have been designed to test the proteasome's capacity for substrate processing and its limitations. Ubiquitin-independent substrates may in some cases be a remnant of the pre-ubiquitome world, but in other cases could provide optimized regulatory solutions. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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Affiliation(s)
- Jenny Erales
- Department of Microbiology & Immunology, University of California, San Francisco, San Francisco, CA 94127, USA
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14
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Characterization of the bipartite degron that regulates ubiquitin-independent degradation of thymidylate synthase. Biosci Rep 2013. [PMID: 23181752 PMCID: PMC3549573 DOI: 10.1042/bsr20120112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
TS (thymidylate synthase) is a key enzyme in the de novo biosynthesis of dTMP, and is indispensable for DNA replication. Previous studies have shown that intracellular degradation of the human enzyme [hTS (human thymidylate synthase)] is mediated by the 26S proteasome, and occurs in a ubiquitin-independent manner. Degradation of hTS is governed by a degron that is located at the polypeptide's N-terminus that is capable of promoting the destabilization of heterologous proteins to which it is attached. The hTS degron is bipartite, consisting of two subdomains: an IDR (intrinsically disordered region) that is highly divergent among mammalian species, followed by a conserved amphipathic α-helix (designated hA). In the present report, we have characterized the structure and function of the hTS degron in more detail. We have conducted a bioinformatic analysis of interspecies sequence variation exhibited by the IDR, and find that its hypervariability is not due to diversifying (or positive) selection; rather, it has been subjected to purifying (or negative) selection, although the intensity of such selection is relaxed or weakened compared with that exerted on the rest of the molecule. In addition, we have verified that both subdomains of the hTS degron are required for full activity. Furthermore, their co-operation does not necessitate that they are juxtaposed, but is maintained when they are physically separated. Finally, we have identified a 'cryptic' degron at the C-terminus of hTS, which is activated by the N-terminal degron and appears to function only under certain circumstances; its role in TS metabolism is not known.
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15
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Carosati E, Tochowicz A, Marverti G, Guaitoli G, Benedetti P, Ferrari S, Stroud RM, Finer-Moore J, Luciani R, Farina D, Cruciani G, Costi MP. Inhibitor of Ovarian Cancer Cells Growth by Virtual Screening: A New Thiazole Derivative Targeting Human Thymidylate Synthase. J Med Chem 2012; 55:10272-6. [DOI: 10.1021/jm300850v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Emanuele Carosati
- Dipartimento
di Chimica, Università degli Studi di Perugia, Via Elce
di Sotto 10, 06123, Perugia, Italy
| | - Anna Tochowicz
- Department of Biochemistry and
Biophysics, University of California—San Francisco, 600 16th Street, San Francisco 94158, California, United States
| | - Gaetano Marverti
- Dipartimento di Scienze Biomediche,
Metaboliche e Neuroscienze, Università degli Studi di Modena e Reggio Emilia, Via Campi 287, 41125 Modena,
Italy
| | - Giambattista Guaitoli
- Dipartimento di Scienze
Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41125 Modena, Italy
| | - Paolo Benedetti
- Molecular Discovery Limited, 215 Marsh Road, Pinner, Middlesex, London HA5
5NE, U.K
| | - Stefania Ferrari
- Dipartimento di Scienze
Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41125 Modena, Italy
| | - Robert M. Stroud
- Department of Biochemistry and
Biophysics, University of California—San Francisco, 600 16th Street, San Francisco 94158, California, United States
| | - Janet Finer-Moore
- Department of Biochemistry and
Biophysics, University of California—San Francisco, 600 16th Street, San Francisco 94158, California, United States
| | - Rosaria Luciani
- Dipartimento di Scienze
Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41125 Modena, Italy
| | - Davide Farina
- Dipartimento di Scienze
Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41125 Modena, Italy
| | - Gabriele Cruciani
- Dipartimento
di Chimica, Università degli Studi di Perugia, Via Elce
di Sotto 10, 06123, Perugia, Italy
| | - M. Paola Costi
- Dipartimento di Scienze
Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41125 Modena, Italy
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16
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Ligabue A, Marverti G, Liebl U, Myllykallio H. Transcriptional activation and cell cycle block are the keys for 5-fluorouracil induced up-regulation of human thymidylate synthase expression. PLoS One 2012; 7:e47318. [PMID: 23056627 PMCID: PMC3467224 DOI: 10.1371/journal.pone.0047318] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 09/14/2012] [Indexed: 12/27/2022] Open
Abstract
Background 5-fluorouracil, a commonly used chemotherapeutic agent, up-regulates expression of human thymidylate synthase (hTS). Several different regulatory mechanisms have been proposed to mediate this up-regulation in distinct cell lines, but their specific contributions in a single cell line have not been investigated to date. We have established the relative contributions of these previously proposed regulatory mechanisms in the ovarian cancer cell line 2008 and the corresponding cisplatin-resistant and 5-FU cross-resistant-subline C13*. Methodology/Principal Findings Using RNA polymerase II inhibitor DRB treated cell cultures, we showed that 70–80% of up-regulation of hTS results from transcriptional activation of TYMS mRNA. Moreover, we report that 5-FU compromises the cell cycle by blocking the 2008 and C13* cell lines in the S phase. As previous work has established that TYMS mRNA is synthesized in the S and G1 phase and hTS is localized in the nuclei during S and G2-M phase, the observed cell cycle changes are also expected to affect the intracellular regulation of hTS. Our data also suggest that the inhibition of the catalytic activity of hTS and the up-regulation of the hTS protein level are not causally linked, as the inactivated ternary complex, formed by hTS, deoxyuridine monophosphate and methylenetetrahydrofolate, was detected already 3 hours after 5-FU exposure, whereas substantial increase in global TS levels was detected only after 24 hours. Conclusions/Significance Altogether, our data indicate that constitutive TYMS mRNA transcription, cell cycle-induced hTS regulation and hTS enzyme stability are the three key mechanisms responsible for 5-fluorouracil induced up-regulation of human thymidylate synthase expression in the two ovarian cancer cell lines studied. As these three independent regulatory phenomena occur in a precise order, our work provides a feasible rationale for earlier observed synergistic combinations of 5-FU with other drugs and may suggest novel therapeutic strategies.
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Affiliation(s)
- Alessio Ligabue
- INSERM U696, Palaiseau, France
- Laboratoire d'Optique et Biosciences, CNRS, Ecole Polytechnique, Palaiseau, France
| | - Gaetano Marverti
- Dipartimento di Scienze Biomediche, Sezione di Chimica Biologica, University of Modena and Reggio Emilia, Modena, Italy
| | - Ursula Liebl
- INSERM U696, Palaiseau, France
- Laboratoire d'Optique et Biosciences, CNRS, Ecole Polytechnique, Palaiseau, France
| | - Hannu Myllykallio
- INSERM U696, Palaiseau, France
- Laboratoire d'Optique et Biosciences, CNRS, Ecole Polytechnique, Palaiseau, France
- * E-mail:
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17
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Galvani E, Peters GJ, Giovannetti E. Thymidylate synthase inhibitors for non-small cell lung cancer. Expert Opin Investig Drugs 2011; 20:1343-56. [PMID: 21905922 DOI: 10.1517/13543784.2011.617742] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
INTRODUCTION The folate-dependent enzyme thymidylate synthase (TS) plays a pivotal role in DNA replication/repair and cancer cell proliferation, and represents a valid target for the treatment of several tumor types, including NSCLC. NSCLC is the leading cause of cancer-related mortality, and several TS inhibitors have gone into preclinical and clinical testing, with pemetrexed emerging for its approval and widespread use as first-/second-line and maintenance therapy for this disease. AREAS COVERED This review summarizes the therapeutic options in NSCLC, as well as the background and rationale for targeting TS. The authors also review recent pharmacogenetic studies and data from clinical trials evaluating novel TS inhibitors, hoping that the reader will gain a comprehensive overview of the field of TS inhibition, specifically relating to drugs used or being developed for lung cancer patients. EXPERT OPINION TS is a validated target in NSCLC. However, benefits from conventional chemotherapy in NSCLC have plateaued, and more cost-effective results should be obtained with individualized treatment. Accordingly, the clinical success for TS inhibitors may depend on our ability to correctly administer these agents following biomarker-driven patient selection, including TS genotype and expression, and using the right combination therapy.
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Affiliation(s)
- Elena Galvani
- VU University Medical Center, Department of Medical Oncology, Amsterdam, The Netherlands
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18
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Protein-protein interface-binding peptides inhibit the cancer therapy target human thymidylate synthase. Proc Natl Acad Sci U S A 2011; 108:E542-9. [PMID: 21795601 DOI: 10.1073/pnas.1104829108] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Human thymidylate synthase is a homodimeric enzyme that plays a key role in DNA synthesis and is a target for several clinically important anticancer drugs that bind to its active site. We have designed peptides to specifically target its dimer interface. Here we show through X-ray diffraction, spectroscopic, kinetic, and calorimetric evidence that the peptides do indeed bind at the interface of the dimeric protein and stabilize its di-inactive form. The "LR" peptide binds at a previously unknown binding site and shows a previously undescribed mechanism for the allosteric inhibition of a homodimeric enzyme. It inhibits the intracellular enzyme in ovarian cancer cells and reduces cellular growth at low micromolar concentrations in both cisplatin-sensitive and -resistant cells without causing protein overexpression. This peptide demonstrates the potential of allosteric inhibition of hTS for overcoming platinum drug resistance in ovarian cancer.
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19
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Di Cresce C, Figueredo R, Ferguson PJ, Vincent MD, Koropatnick J. Combining small interfering RNAs targeting thymidylate synthase and thymidine kinase 1 or 2 sensitizes human tumor cells to 5-fluorodeoxyuridine and pemetrexed. J Pharmacol Exp Ther 2011; 338:952-63. [PMID: 21673071 DOI: 10.1124/jpet.111.183178] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Thymidylate synthase (TS) is the only de novo source of thymidylate (dTMP) for DNA synthesis and repair. Drugs targeting TS protein are a mainstay in cancer treatment, but off-target effects and toxicity limit their use. Cytosolic thymidine kinase (TK1) and mitochondrial thymidine kinase (TK2) contribute to an alternative dTMP-producing pathway, by salvaging thymidine from the tumor milieu, and may modulate resistance to TS-targeting drugs. Combined down-regulation of these enzymes is an attractive strategy to enhance cancer therapy. We have shown previously that antisense-targeting TS enhanced tumor cell sensitivity to TS-targeting drugs in vitro and in vivo. Because both TS and TKs contribute to increased cellular dTMP, we hypothesized that TKs mediate resistance to the capacity of TS small interfering RNA (siRNA) to sensitize tumor cells to TS-targeting anticancer drugs. We assessed the effects of targeting TK1 or TK2 with siRNA alone and in combination with siRNA targeting TS and/or TS-protein targeting drugs on tumor cell proliferation. Down-regulation of TK with siRNA enhanced the capacity of TS siRNA to sensitize tumor cells to traditional TS protein-targeting drugs [5-fluorodeoxyuridine (5FUdR) and pemetrexed]. The sensitization was greater than that observed in response to any siRNA used alone and was specific to drugs targeting TS. Up-regulation of TK1 in response to combined 5FUdR and TS siRNA suggests that TK knockdown may be therapeutically useful in combination with these agents. TKs may be useful targets for cancer therapy when combined with molecules targeting TS mRNA and TS protein.
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Affiliation(s)
- C Di Cresce
- London Regional Cancer Program and Lawson Health Research Institute, London, Ontario, Canada
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20
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Luo B, Repalli J, Yousef AM, Johnson SR, Lebioda L, Berger SH. Human thymidylate synthase with loop 181-197 stabilized in an inactive conformation: ligand interactions, phosphorylation, and inhibition profiles. Protein Sci 2011; 20:87-94. [PMID: 21064161 DOI: 10.1002/pro.539] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Thymidylate synthase (TS) is a well-validated cancer target that undergoes conformational switching between active and inactive states. Two mutant human TS (hTS) proteins are predicted from crystal structures to be stabilized in an inactive conformation to differing extents, with M190K populating the inactive conformation to a greater extent than A191K. Studies of intrinsic fluorescence and circular dichroism revealed that the structures of the mutants differ from those of hTS. Inclusion of the substrate dUMP was without effect on M190K but induced structural changes in A191K that are unique, relative to hTS. The effect of strong stabilization in an inactive conformation on protein phosphorylation by casein kinase 2 (CK2) was investigated. M190K was highly phosphorylated by CK2 relative to an active-stabilized mutant, R163K hTS. dUMP had no detectable effect on phosphorylation of M190K; however, dUMP inhibited phosphorylation of hTS and R163K. Studies of temperature dependence of catalysis revealed that the E(act) and temperature optimum are higher for A191K than hTS. The potency of the active-site inhibitor, raltitrexed, was lower for A191K than hTS. The response of A191K to the allosteric inhibitor, propylene diphosphonate (PDPA) was concentration dependent. Mixed inhibition was observed at low concentrations; at higher concentrations, A191K exhibited nonhyperbolic behavior with respect to dUMP and inhibition of catalysis was reversed by substrate saturation. In summary, inactive-stabilized mutants differ from hTS in thermal stability and response to substrates and PDPA. Importantly, phosphorylation of hTS by CK2 is selective for the inactive conformation, providing the first indication of physiological relevance for conformational switching.
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Affiliation(s)
- BeiBei Luo
- Department of Pharmaceutical Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
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21
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Garg D, Henrich S, Salo-Ahen OMH, Myllykallio H, Costi MP, Wade RC. Novel approaches for targeting thymidylate synthase to overcome the resistance and toxicity of anticancer drugs. J Med Chem 2010; 53:6539-49. [PMID: 20527892 DOI: 10.1021/jm901869w] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Divita Garg
- Molecular and Cellular Modeling Group, Heidelberg Institute of Theoretical Studies gGmbH, Heidelberg, Germany
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22
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Boni V, Bitarte N, Cristobal I, Zarate R, Rodriguez J, Maiello E, Garcia-Foncillas J, Bandres E. miR-192/miR-215 influence 5-fluorouracil resistance through cell cycle-mediated mechanisms complementary to its post-transcriptional thymidilate synthase regulation. Mol Cancer Ther 2010; 9:2265-75. [PMID: 20647341 DOI: 10.1158/1535-7163.mct-10-0061] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Thymidylate synthase (TYMS) is a target of the most widely used chemotherapeutic agents against gastrointestinal malignancies, the fluoropyrimidine-based therapy. TYMS expression levels have been identified as predictive biomarkers for 5-fluoruracil (FU) response in colorectal cancer, but their clinical utility remains controversial. The complexity of fluoropyrimidine response must require more mechanisms that currently have not been completely elucidated. In this context, microRNAs (miRNA) may play a role in modulating chemosensitivity. By carrying out an in silico analysis coupled to experimental validation, we detected that miR-192 and miR-215 target TYMS expression in colorectal cancer cell lines. However, downregulation of TYMS by these miRNAs does not sensitize colorectal cancer cell lines to FU treatment. The overexpression of miR-192/215 significantly reduces cell proliferation by targeting cell cycle progression. This effect was partially associated with p53 status, because reduction of cell proliferation and cell cycle arrest was associated with p21 and p27 induction. The decrease of S-phase cells by these miRNAs mitigates the effects of S phase-specific drugs and suggests that other mechanisms different from TYMS overexpression are essential to direct FU resistance. Finally, ectopic expression of miR-192/215 might have stronger impact to predict FU response than TYMS inhibition. Prospective studies to elucidate the role of these miRNAs as predictive biomarkers to FU are necessary.
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Affiliation(s)
- Valentina Boni
- Oncology Unit, Casa Sollievo Sofferenza, S. Giovanni Rotondo, Italy
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23
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Zhang Y, Yang S, Liu M, Song C, Wu N, Ling P, Chu E, Lin X. Interaction between thymidylate synthase and its cognate mRNA in zebrafish embryos. PLoS One 2010; 5:e10618. [PMID: 20485548 PMCID: PMC2868900 DOI: 10.1371/journal.pone.0010618] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 04/14/2010] [Indexed: 02/06/2023] Open
Abstract
Thymidylate synthase (TS), which catalyzes the de novo synthesis of dUMP, is an important target for cancer therapy. In this report, the effects of 5-fluorouracil (5-FU) and ZD1694 on the regulation of TS gene expression were evaluated in zebrafish embryos. Our results revealed that the expression of TS was increased by about six-fold when embryos were treated with 1.0 µM 5-FU and there was a greater than 10-fold increase in the TS protein level after treatment with 0.4 µM ZD1694. Northern blot analysis confirmed that expression of TS mRNA was identical in treated or untreated embryos. Gel shift and immunoprecipitation assays revealed that zebrafish TS was specifically bound with its cognate mRNA in vitro and in vivo. We identified a 20 nt RNA sequence, TS:N20, localized to the 5′-UTR of TS mRNA, which corresponded to nt 13–32; TS:N20 bound to the TS protein with an affinity similar to that of the full-length TS mRNA. The MFold program predicted that TS:N20 formed a stable stem-loop structure similar to that of the cis-acting element found in human TS mRNA. Variant RNAs with either a deletion or mutation in the core motif of TS:N20 were unable to bind to the TS protein. In vitro translation experiments, using the rabbit lysate system, confirmed that zebrafish TS mRNA translation was significantly repressed when an excess amount of TS protein was included in the system. Additionally, a TS stability experiment confirmed that treatment of zebrafish embryos with 5-FU could increase the TS stability significantly, and the half life of TS protein was about 2.7 times longer than in untreated embryos. Our study revealed a structural requirement for the interaction of TS RNA with TS protein. These findings also demonstrated that the increase in TS protein induced by 5-FU occurs at the post-transcriptional level and that increased stability and translation efficiency both contributed to the increase in TS protein levels induced by TS inhibitors.
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Affiliation(s)
- Yuyan Zhang
- Institute of Oceanology, Chinese Academy of Science, Qingdao, People's Republic of China
- Graduate School of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Shaoli Yang
- Institute of Oceanology, Chinese Academy of Science, Qingdao, People's Republic of China
| | - Ming Liu
- Institute of Oceanology, Chinese Academy of Science, Qingdao, People's Republic of China
| | - Chunxia Song
- Institute of Oceanology, Chinese Academy of Science, Qingdao, People's Republic of China
| | - Ning Wu
- Institute of Oceanology, Chinese Academy of Science, Qingdao, People's Republic of China
- Graduate School of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Peixue Ling
- Institute of Biopharmaceuticals of Shandong Province, Jinan, People's Republic of China
| | - Edward Chu
- Yale Cancer Center, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Xiukun Lin
- Institute of Oceanology, Chinese Academy of Science, Qingdao, People's Republic of China
- * E-mail:
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24
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Collateral sensitivity to novel thymidylate synthase inhibitors correlates with folate cycle enzymes impairment in cisplatin-resistant human ovarian cancer cells. Eur J Pharmacol 2009; 615:17-26. [DOI: 10.1016/j.ejphar.2009.04.062] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 03/20/2009] [Accepted: 04/27/2009] [Indexed: 12/16/2022]
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25
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Fazzone W, Wilson PM, Labonte MJ, Lenz HJ, Ladner RD. Histone deacetylase inhibitors suppress thymidylate synthase gene expression and synergize with the fluoropyrimidines in colon cancer cells. Int J Cancer 2009; 125:463-73. [PMID: 19384949 DOI: 10.1002/ijc.24403] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Despite recent therapeutic advances, the response rates to chemotherapy for patients with metastatic colon cancer remain at approximately 50% with the fluoropyrimidine, 5-fluorouracil (5-FU), continuing to serve as the foundation chemotherapeutic agent for the treatment of this disease. Previous studies have demonstrated that overexpression of thymidylate synthase (TS) is a key determinant of resistance to 5-FU-based chemotherapy. Therefore, there is a significant need to develop alternative therapeutic strategies to overcome TS-mediated resistance. In this study, we demonstrate that the histone deacetylase inhibitors (HDACi) vorinostat and LBH589 significantly downregulate TS gene expression in a panel of colon cancer cell lines. Downregulation of TS was independent of p53, p21 and HDAC2 expression and was achievable in vivo as demonstrated by mouse xenograft models. We provide evidence that HDACi treatment leads to a potent transcriptional repression of the TS gene. Combination of the fluoropyrimidines 5-FU or FUdR with both vorinostat and LBH589 enhanced cell cycle arrest and growth inhibition. Importantly, the downstream effects of TS inhibition were significantly enhanced by this combination including the inhibition of acute TS induction and the enhanced accumulation of the cytotoxic nucleotide intermediate dUTP. These data demonstrate that HDACi repress TS expression at the level of transcription and provides the first evidence suggesting a direct mechanistic link between TS downregulation and the synergistic interaction observed between HDACi and 5-FU. This study provides rationale for the continued clinical evaluation of HDACi in combination with 5-FU-based therapies as a strategy to overcome TS-mediated resistance.
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Affiliation(s)
- William Fazzone
- Department of Pathology, Norris Comprehensive Cancer Center/University of Southern California, Keck School of Medicine, Los Angeles, CA 90033, USA
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26
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Brody JR, Hucl T, Costantino CL, Eshleman JR, Gallmeier E, Zhu H, van der Heijden MS, Winter JM, Wikiewicz AK, Yeo CJ, Kern SE. Limits to thymidylate synthase and TP53 genes as predictive determinants for fluoropyrimidine sensitivity and further evidence for RNA-based toxicity as a major influence. Cancer Res 2009; 69:984-91. [PMID: 19155291 DOI: 10.1158/0008-5472.can-08-3610] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The major determinants of 5-flurouracil (5-FU) response would seem, based on accumulated literature, to be thymidylate synthase (TYMS, TS) expression levels, TS gene modifications, and TP53 status. We tested 5-FU sensitivity in yeast and human cancer cell models in which TS or TP53 alleles and expression were varied. Polymorphic TS tandem repeat status, TS expression levels reported, TS intragenic mutations, and TP53 status in outbred and experimental cancer cell lines did not predict 5-FU sensitivity or resistance. Novel observations included a dose-resistant persistence of unbound TS protein in many cancers and, upon 5-FU treatment of the colon cancer cell line, HCT116, evidence of allelic switching favoring transcripts of the mutant TS allele. The reported alleles having an intragenic mutation could not be causally associated with major degrees of 5-FU sensitivity. In yeast, TS protein was altered upon treatment with FdUMP, but 5-FU toxicity seemed to be largely RNA-based, being rescued by uridine rather than by thymidine. Cancer cell lines were also rescued from 5-FU toxicity with uridine rather than thymidine. Additionally, a TS (CDC21) knockout yeast strain, obviating any potential role for TS protein as a target, was hypersensitive to 5-FU. When denatured proteins from cancer cells treated with radiolabeled 5-FU were labeled, species with alternative molecular weights other than TS were visualized, providing further evidence for alternative 5-FU protein targets. These data emphasize that TS and TP53 status do not consistently explain the variance in responses of fluoropyrimidine-treated cancer cells, in part due to RNA-based toxicity.
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Affiliation(s)
- Jonathan R Brody
- Department of Surgery and Pathology, Jefferson Pancreas, Biliary, and Related Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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Sato A, Hiramoto A, Uchikubo Y, Miyazaki E, Satake A, Naito T, Hiraoka O, Miyake T, Kim HS, Wataya Y. Gene expression profiles of necrosis and apoptosis induced by 5-fluoro-2'-deoxyuridine. Genomics 2008; 92:9-17. [PMID: 18572099 DOI: 10.1016/j.ygeno.2008.02.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Revised: 02/07/2008] [Accepted: 02/08/2008] [Indexed: 01/31/2023]
Abstract
5-Fluoro-2'-deoxyuridine (FUdR), a potent anticancer agent, exerts its effects by inhibiting thymidylate synthase, an essential machinery for DNA synthesis in cell proliferation. Also, cell death is caused by FUdR, primarily due to an imbalance in the nucleotide pool resulting from this enzyme inhibition. We have investigated the cancer cell death induced by FUdR, focusing on its molecular mechanisms. Using mouse mammary tumor FM3A cell lines, the original clone F28-7 and its variant F28-7-A cells, we previously reported an interesting observation that FUdR induces a necrotic morphology in F28-7, but induces, in contrast, an apoptotic morphology in F28-7-A cells. In the present study, to understand the molecular mechanisms underlying these differential cell deaths, i.e., necrosis and apoptosis, we investigated the gene expression changes occurring in these processes. Using the cDNA microarray technology, we found 215 genes being expressed differentially in the necrosis and apoptosis. Further analysis revealed differences between these cell lines in terms of the expressions of both a cluster of heat shock protein (HSP)-related genes and a cluster of apoptosis-related genes. Notably, inhibition of HSP90 in F28-7 cells caused a shift from the FUdR-induced necrosis into apoptosis. These findings are expected to lead to a better understanding of this anticancer drug FUdR for its molecular mechanisms and also of the general biological issue, necrosis and apoptosis.
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Affiliation(s)
- Akira Sato
- Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan
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Jariel-Encontre I, Bossis G, Piechaczyk M. Ubiquitin-independent degradation of proteins by the proteasome. Biochim Biophys Acta Rev Cancer 2008; 1786:153-77. [PMID: 18558098 DOI: 10.1016/j.bbcan.2008.05.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 05/15/2008] [Accepted: 05/15/2008] [Indexed: 02/08/2023]
Abstract
The proteasome is the main proteolytic machinery of the cell and constitutes a recognized drugable target, in particular for treating cancer. It is involved in the elimination of misfolded, altered or aged proteins as well as in the generation of antigenic peptides presented by MHC class I molecules. It is also responsible for the proteolytic maturation of diverse polypeptide precursors and for the spatial and temporal regulation of the degradation of many key cell regulators whose destruction is necessary for progression through essential processes, such as cell division, differentiation and, more generally, adaptation to environmental signals. It is generally believed that proteins must undergo prior modification by polyubiquitin chains to be addressed to, and recognized by, the proteasome. In reality, however, there is accumulating evidence that ubiquitin-independent proteasomal degradation may have been largely underestimated. In particular, a number of proto-oncoproteins and oncosuppressive proteins are privileged ubiquitin-independent proteasomal substrates, the altered degradation of which may have tumorigenic consequences. The identification of ubiquitin-independent mechanisms for proteasomal degradation also poses the paramount question of the multiplicity of catabolic pathways targeting each protein substrate. As this may help design novel therapeutic strategies, the underlying mechanisms are critically reviewed here.
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Affiliation(s)
- Isabelle Jariel-Encontre
- Institut de Génétique Moléculaire de Montpellier, CNRS, UMR5535, IFR122, 1919 Route de Mende, Montpellier, F-34293, France
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Abstract
Tetrahydrofolate (THF) polyglutamates are a family of cofactors that carry and chemically activate one-carbon units for biosynthesis. THF-mediated one-carbon metabolism is a metabolic network of interdependent biosynthetic pathways that is compartmentalized in the cytoplasm, mitochondria, and nucleus. One-carbon metabolism in the cytoplasm is required for the synthesis of purines and thymidylate and the remethylation of homocysteine to methionine. One-carbon metabolism in the mitochondria is required for the synthesis of formylated methionyl-tRNA; the catabolism of choline, purines, and histidine; and the interconversion of serine and glycine. Mitochondria are also the primary source of one-carbon units for cytoplasmic metabolism. Increasing evidence indicates that folate-dependent de novo thymidylate biosynthesis occurs in the nucleus of certain cell types. Disruption of folate-mediated one-carbon metabolism is associated with many pathologies and developmental anomalies, yet the biochemical mechanisms and causal metabolic pathways responsible for the initiation and/or progression of folate-associated pathologies have yet to be established. This chapter focuses on our current understanding of mammalian folate-mediated one-carbon metabolism, its cellular compartmentation, and knowledge gaps that limit our understanding of one-carbon metabolism and its regulation.
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Affiliation(s)
- Jennifer T Fox
- Graduate Field of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York 14853, USA
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Brody JR, Hucl T, Gallmeier E, Winter JM, Kern SE, Murphy KM. Genomic copy number changes affecting the thymidylate synthase (TYMS) gene in cancer: a model for patient classification to aid fluoropyrimidine therapy. Cancer Res 2007; 66:9369-73. [PMID: 17018589 DOI: 10.1158/0008-5472.can-06-2165] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Thymidylate synthase (TS) is an important target for 5-fluorouracil (5FU)-based therapy. The TS polymorphic 5'-untranslated region tandem repeat sequence is under investigation to guide 5FU treatment, yet current protocols omit consideration of copy number changes at the TS locus. We surveyed the TS tandem repeat sequence and found copy number changes in gastrointestinal cancers. Ten of 12 informative cases had loss of heterozygosity (LOH), whereas two others and an additional cell line had a novel TS genotype, allelic imbalance at the TS locus due to polysomy. Experimentally, we studied a diploid colorectal cancer line heterozygous at TS to mimic three common TS genotypes of cancers. Using genetic engineering, we deleted the short tandem repeat (two repeats) allele and retained the long (three repeats) allele to produce artificial LOH at the TS gene; the TS(+/-) line had a reduced TS protein expression and was hypersensitive to 5FU and 5-fluoro-2'-deoxyuridine in vitro as compared with syngeneic control lines. We linked this sensitivity directly to the reduced TS expression by introducing exogenous TS cDNA expression into the TS(+/-) line (i.e., increased TS copies). Our model predicts that the 5FU sensitivity of a tumor is modified by aneuploidy producing copy number changes of TS alleles by one or more of the following: LOH, amplification, and, as presented here, copy number changes due to polysomy. The data suggest that TS copy number in a patient's tumor may be a dominating variable affecting 5FU responsiveness.
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Affiliation(s)
- Jonathan R Brody
- The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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31
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Mauritz R, van Groeningen CJ, Smid K, Jansen G, Pinedo HM, Peters GJ. Thymidylate synthase and dihydropyrimidine dehydrogenase mRNA expression after administration of 5-fluorouracil to patients with colorectal cancer. Int J Cancer 2007; 120:2609-12. [PMID: 17330233 DOI: 10.1002/ijc.22626] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This study explores the effect of 5-fluorouracil (5FU) exposure on mRNA levels of its target enzyme thymidylate synthase (TS) and the rate-limiting catabolic enzyme dihydropyrimidine dehydrogenase (DPD) in tumors of colorectal cancer patients. TS and DPD mRNA levels were determined in primary tumor and liver metastasis samples from patients who were either not pretreated (n = 29) or given one presurgery bolus of 5FU (n = 67). In both groups a wide variation in TS mRNA levels was observed. Median TS mRNA expression in 17 primary tumors of exposed patients was 3.0-fold higher than in 19 primary tumors of unexposed patients (p = 0.015). TS mRNA expression in liver metastasis samples of exposed patients (n = 16) was also higher (5.2-fold) than that of unexposed patients (n = 48; p < 0.001). Also DPD mRNA expression displayed a large degree of interpatient variation. No difference in DPD expression in liver metastasis samples was observed between exposed and unexposed patients. However, median DPD mRNA expression in 15 primary tumors of exposed patients was 3.2-fold lower than in 18 primary tumors of unexposed patients (p = 0.027). In conclusion, administration of 5FU in vivo influences the gene expression of TS and DPD.
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Affiliation(s)
- Robert Mauritz
- Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands
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32
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Lovelace LL, Gibson LM, Lebioda L. Cooperative inhibition of human thymidylate synthase by mixtures of active site binding and allosteric inhibitors. Biochemistry 2007; 46:2823-30. [PMID: 17297914 PMCID: PMC2516748 DOI: 10.1021/bi061309j] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thymidylate synthase (TS) is a target in the chemotherapy of colorectal cancer and some other neoplasms. It catalyzes the transfer of a methyl group from methylenetetrahydrofolate to dUMP to form dTMP. On the basis of structural considerations, we have introduced 1,3-propanediphosphonic acid (PDPA) as an allosteric inhibitor of human TS (hTS); it is proposed that PDPA acts by stabilizing an inactive conformer of loop 181-197. Kinetic studies showed that PDPA is a mixed (noncompetitive) inhibitor versus dUMP. In contrast, versus methylenetrahydrofolate at concentrations lower than 0.25 microM, PDPA is an uncompetitive inhibitor, while at PDPA concentrations higher than 1 microM the inhibiton is noncompetive, as expected. At the concentrations corresponding to uncompetitive inhibition, PDPA shows positive cooperativity with an antifolate inhibitor, ZD9331, which binds to the active conformer. PDPA binding leads to the formation of hTS tetramers, but not higher oligomers. These data are consistent with a model in which hTS exists preferably as an asymmetric dimer with one subunit in the active conformation of loop 181-197 and the other in the inactive conformation.
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Affiliation(s)
- Leslie L. Lovelace
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Lydia M. Gibson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Lukasz Lebioda
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
- Center for Colon Cancer Research, University of South Carolina, Columbia, South Carolina 29208
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Yang Z, Cloud A, Hughes D, Johnson LF. Stable inhibition of human thymidylate synthase expression following retroviral introduction of an siRNA gene. Cancer Gene Ther 2006; 13:107-14. [PMID: 16052228 DOI: 10.1038/sj.cgt.7700880] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Thymidylate synthase (TS) is an essential enzyme that synthesizes thymidylic acid in the de novo biosynthetic pathway. Inhibiting TS enzyme activity with substrate or cofactor analogs leads to inhibition of DNA replication and cell death. For this reason, TS is an important target enzyme for cancer chemotherapeutic drugs. We describe an alternative approach to reducing cellular TS enzyme activity using short interfering RNA (siRNA) technology to lower TS mRNA levels. Plasmids that direct the synthesis of siRNAs that target nucleotides 898-916 and 965-983 (relative to the A of the translational start codon) of human TS mRNA were highly effective at reducing TS enzyme levels in transient transfection assays. Infection of HeLa cells with retroviruses that contain the effective siRNA genes led to a stable 80-95% reduction of TS enzyme and mRNA. A similar percent reduction in TS expression was observed in a cell line that overproduces TS enzyme 100-fold due to TS gene amplification. Cells that exhibited the greatest reduction in TS enzyme level grew poorly in medium that lacked thymidine. These observations suggest that siRNA approaches may provide an alternative therapeutic strategy to reduce TS enzyme levels.
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Affiliation(s)
- Z Yang
- Department of Molecular Genetics, The Ohio State University, Columbus, 43210, USA
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35
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Peña M, Xing Y, Koli S, Berger F. Role of N-terminal residues in the ubiquitin-independent degradation of human thymidylate synthase. Biochem J 2006; 394:355-63. [PMID: 16259621 PMCID: PMC1386034 DOI: 10.1042/bj20051479] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Thymidylate synthase (TS) catalyses the reductive methylation of dUMP to form dTMP, a reaction that is essential for maintenance of nucleotide pools during cell growth. Because the enzyme is indispensable for DNA replication in actively dividing cells, it is an important target for cytotoxic drugs used in cancer chemotherapy, including fluoropyrimidines (e.g. 5-fluorouracil and 5-fluoro-2'-deoxyuridine) and anti-folates (e.g. raltitrexed, LY231514, ZD9331 and BW1843U89). These drugs generate metabolites that bind to the enzyme's active site and inhibit catalytic activity, leading to thymidylate deprivation and cellular apoptosis. Ligand binding to TS results in stabilization of the enzyme and an increase in its intracellular concentration. Previously, we showed that degradation of the TS polypeptide is carried out by the 26 S proteasome in a ubiquitin-independent manner. Such degradation is directed by the disordered N-terminal region of the TS polypeptide, and is abrogated by ligand binding. In the present study, we have verified the ubiquitin-independent nature of TS proteolysis by showing that a 'lysine-less' polypeptide, in which all lysine residues were replaced by arginine, is still subject to proteasome-mediated degradation. In addition, we have mapped the structural determinants of intracellular TS degradation in more detail and show that residues at the N-terminal end of the molecule, particularly the penultimate amino acid Pro2, play an important role in governing the half-life of the enzyme. This region is capable on its own of destabilizing an evolutionarily distinct TS molecule that normally lacks this domain, indicating that it functions as a degradation signal. Interestingly, degradation of an intrinsically unstable mutant form of TS, containing a Pro-->Leu substitution at residue 303, is directed by C-terminal, rather than N-terminal, sequences. The implications of these findings for the control of TS expression, and for the regulation of protein degradation in general, are discussed.
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Affiliation(s)
- Maria Marjorette O. Peña
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
| | - Yang Yang Xing
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
| | - Sangita Koli
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
| | - Franklin G. Berger
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
- To whom correspondence should be addressed (email )
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36
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Cao W, Chau B, Hunter R, Strnatka D, McQueen CA, Erickson RP. Only low levels of exogenous N-acetyltransferase can be achieved in transgenic mice. THE PHARMACOGENOMICS JOURNAL 2005; 5:255-61. [PMID: 16041393 DOI: 10.1038/sj.tpj.6500319] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Therapeutic and environmental aromatic amines and hydrazines are substrates for the arylamine N-acetyltransferases (NAT). In all, 10 transgenic lines containing either the human NAT1 or NAT2 transgene were developed using multiple promoters. The presence of the transgene was confirmed by determining copy number, mRNA and enzyme activity. Despite some lines having high copy numbers of the transgene, only modest or no increases in enzymatic activity could be found in a variety of tissues. The NAT1 transgene could not be bred to homozygosity. The cytomegalovirus (CMV)-promoted NAT1 transgene increased endogenous Nat1 mRNA levels in liver and had little effect on endogenous Nat2 mRNA levels. The presence of the CMV-promoted NAT2 transgene appeared to suppress endogenous hepatic Nat2 mRNA, but did not alter Nat1 mRNA levels. The failure to achieve high expression of any of the transgenes suggests that overexpression of NAT genes may have harmful effects during development.
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Affiliation(s)
- W Cao
- Department of Pediatrics, Colleges of Medicine and Pharmacy, University of Arizona, Tucson, AZ 85724-5073, USA
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37
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Vincenzi B, Cesa AL, Santini D, Schiavon G, Grilli C, Graziano F, Tonini G. Predictive factors for response to chemotherapy in colorectal cancer patients. Crit Rev Oncol Hematol 2005; 52:45-60. [PMID: 15363466 DOI: 10.1016/j.critrevonc.2004.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2004] [Indexed: 02/06/2023] Open
Abstract
Colorectal cancer represents a major health problem in the western world. A lot of drugs have been employed in treatment of this disease, but only few data are available about predictive factors for response to anticancer treatments in colorectal cancer. Aim of this paper is to review the main data about this investigation field. Using a Medline database search (1966-2003) we reviewed all the relevant papers that investigate clinical and molecular predictors for response to the main drugs used in the treatment of colorectal cancer patients, both in adjuvant and in advanced setting. Moreover we comprehensively reviewed all the data published in abstract form during the most significant international meetings. Our review put in evidence the most important predictive factors for response in colorectal cancer patients treated with anticancer chemotherapy both in adjuvant and in advanced setting. The predictive factors are clustered on the basis of the different anticancer drugs. The results of this review provide the rationale basis for personalizing anticancer treatment in colorectal cancer patients by molecular and clinical features, aiming to improve response rate and reduce toxicities.
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Affiliation(s)
- Bruno Vincenzi
- Medical Oncology, Campus Bio-Medico University, Via Emilio Longoni, 69, 00155 Rome, Italy
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38
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Nirmalan N, Sims PFG, Hyde JE. Translational up-regulation of antifolate drug targets in the human malaria parasite Plasmodium falciparum upon challenge with inhibitors. Mol Biochem Parasitol 2004; 136:63-70. [PMID: 15138068 DOI: 10.1016/j.molbiopara.2004.02.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2003] [Revised: 02/11/2004] [Accepted: 02/29/2004] [Indexed: 11/30/2022]
Abstract
The thymidylate cycle in Plasmodium falciparum is essential for cell growth and replication, and dihydrofolate reductase (DHFR), a key enzyme in this cycle, is the target of important antimalarial drugs such as pyrimethamine and cycloguanil. Following previous work, where we found no evidence of upregulation of the dhfr-ts gene upon challenge with pyrimethamine, we investigated the expression at the protein level of the bifunctional gene product, which also carries thymidylate synthase (TS) activity. Challenge of parasite cultures with fluoro-substituted bases that are specific TS inhibitors at levels close to the IC(50) resulted in five to seven-fold increases in enzyme level, as monitored by both DHFR and TS activities, while pyrimethamine and another DHFR-binding inhibitor, WR99210, induced smaller but still significant increases of approximately three-fold. However, when parasites were challenged with tetracycline, an antimalarial not directed at the folate pathway, although an increase was consistently seen above untreated controls, this was at a level of approximately 1.8-fold. These increases reflect enhanced synthesis of the DHFR-TS enzyme, rather than liberation of a latent activity, as they were completely abolished if cultures were pre-incubated with cycloheximide to block de novo protein synthesis. Moreover, none of the above antimalarial drugs was found to significantly alter absolute levels of the dhfr-ts mRNA under the conditions of challenge used. We conclude that, in common with mammalian systems, where a similar phenomenon has been reported, malaria parasites are able to significantly relieve translational constraint when faced with antifolate drug challenge. The data indicate that there is a specific component in addition to a low-level non-specific increment, and that binding to the TS domain of the DHFR-TS protein appears to be better able to relieve this constraint than binding to the DHFR domain.
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Affiliation(s)
- Niroshini Nirmalan
- Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology (UMIST), P.O. Box 88, Manchester M60 1QD, UK
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39
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Berger SH, Berger FG, Lebioda L. Effects of ligand binding and conformational switching on intracellular stability of human thymidylate synthase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1696:15-22. [PMID: 14726200 DOI: 10.1016/j.bbapap.2003.09.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Thymidylate synthase (TS) is the target in colon cancer therapeutic protocols utilizing such drugs as 5-fluorouracil and raltitrexed. The effectiveness of these treatments is hampered by emerging drug resistance, usually related to increased levels of TS. Human TS (hTS) is unique among thymidylate synthases from all species examined as its loop 181-197 can assume two main conformations related by rotation of 180 degrees. In one conformation, "active", the catalytic Cys-195 is positioned in the active site; in the other conformation, "inactive", it is at the subunit interface. Also, in the active conformation, region 107-128 has one well-defined conformation while in the inactive conformation this region assumes multiple conformations and is disordered in crystals. The native protein exists in apparent equilibrium between the two conformational states, while the enzyme liganded with TS inhibitors assumes the active conformation. The native protein has been reported to bind to several mRNAs, including its own mRNA, but upon ligation, RNA binding activity is lost. Ligation of TS by inhibitors also stabilizes it to turnover. Since currently used TS-directed drugs stabilize the active conformation and slow down the enzyme degradation, it is postulated that inhibitors of hTS stabilizing the inactive conformation of hTS should cause a down-regulation in enzyme levels as well as inactivate the enzyme.
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Affiliation(s)
- Sondra H Berger
- Center for Colon Cancer Research, University of South Carolina, Columbia, SC 29208, USA.
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40
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Schmitz JC, Chen TM, Chu E. Small interfering double-stranded RNAs as therapeutic molecules to restore chemosensitivity to thymidylate synthase inhibitor compounds. Cancer Res 2004; 64:1431-5. [PMID: 14973067 DOI: 10.1158/0008-5472.can-03-1203] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RNA interference is a post-transcriptional mechanism by which double-stranded RNA specifically silence expression of a corresponding gene. Small interfering double-stranded RNA (siRNA) of 21-23 nucleotides can induce the process of RNA interference. Studies from our laboratory have shown that translation of thymidylate synthase (TS) mRNA is controlled by its own protein end-product TS in a negative autoregulatory manner. Disruption of this process gives rise to increased synthesis of TS and leads to the development of cellular drug resistance to TS-targeted compounds. As a strategy to inhibit TS expression at the mRNA level, siRNAs were designed to target nucleotides 1058-1077 on human TS mRNA. Transfection of TS1058 siRNA into human colon cancer RKO cells resulted in a dose-dependent inhibition of TS expression with an IC(50) value of 10 pM but had no effect on the expression of alpha-tubulin or topoisomerase I. Inhibition of TS expression by TS1058 was maximal at 48 h and remained suppressed for up to 5 days. Pretreatment of RKO cells with TS1058 siRNA suppressed TS protein induction following exposure to raltitrexed. In addition, TS1058 restored chemosensitivity of the resistant RKO-HTStet cell line to various TS inhibitor compounds. On treatment with TS1058, IC(50) values for raltitrexed, 1843U89, and 5-fluoro-2'-deoxyuridine decreased by approximately 15-16-fold. These studies suggest that TS-targeted siRNAs are effective inhibitors of TS expression and may have therapeutic potential by themselves or as chemosensitizers in combination with TS inhibitor compounds.
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Affiliation(s)
- John C Schmitz
- Department of Medicine and Pharmacology, Yale Cancer Center, Yale University School of Medicine and VACT Cancer Center IIID, VACT Healthcare System, 950 Campbell Avenue, West Haven, CT 06516, USA.
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Abstract
The antifolates were the first class of antimetabolites to enter the clinics more than 50 years ago. Over the following decades, a full understanding of their mechanisms of action and chemotherapeutic potential evolved along with the mechanisms by which cells develop resistance to these drugs. These principals served as a basis for the subsequent exploration and understanding of the mechanisms of resistance to a variety of diverse antineoplastics with different cellular targets. This section describes the bases for intrinsic and acquired antifolate resistance within the context of the current understanding of the mechanisms of actions and cytotoxic determinants of these agents. This encompasses impaired drug transport into cells, augmented drug export, impaired activation of antifolates through polyglutamylation, augmented hydrolysis of antifolate polyglutamates, increased expression and mutation of target enzymes, and the augmentation of cellular tetrahydrofolate-cofactor pools in cells. This chapter also describes how these insights are being utilized to develop gene therapy approaches to protect normal bone marrow progenitor cells as a strategy to improve the efficacy of bone marrow transplantation. Finally, clinical studies are reviewed that correlate the cellular pharmacology of methotrexate with the clinical outcome in children with neoplastic diseases treated with this antifolate.
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Affiliation(s)
- Rongbao Zhao
- Departments of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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42
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Kamm YJL, Peters GJ, Hull WE, Punt CJA, Heerschap A. Correlation between 5-fluorouracil metabolism and treatment response in two variants of C26 murine colon carcinoma. Br J Cancer 2003; 89:754-62. [PMID: 12915890 PMCID: PMC2376920 DOI: 10.1038/sj.bjc.6601162] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Following an i.p. dose of 150 mg x kg(-1) 5-fluorouracil (5-FU), drug uptake and metabolism over a 2-h period were studied by in vivo (19)F magnetic resonance spectroscopy (MRS) for the murine colon carcinoma lines C26-B (5-FU-insensitive; n=11) and C26-10 (5-FU-sensitive; n=15) implanted s.c. in Balb/C mice. Time courses for tumour growth, intracellular levels of FdUMP, thymidylate synthase (TS) activity, and 5-FU in RNA were also determined, and the effects of a 9.5-min period of carbogen breathing, starting 1 min before drug administration, on MRS-detected 5-FU metabolism and tumour growth curves were examined. Both tumour variants generated MRS-detectable 5-FU nucleotides and showed similar initial growth inhibition after treatment. However, the growth rate of C26-B tumours returned to normal, while the sensitive C26-10 tumours, which produced larger fluoronucleotide pools, still showed moderate growth inhibition. Carbogen breathing did not significantly influence 5-FU uptake or fluoronucleotide production but did significantly enhance growth inhibition in C26-10 tumours. While both tumour variants exhibited incorporation of 5-FU into RNA and inhibition of TS via FdUMP, clearance of 5-FU from RNA and recovery of TS activity were greater for the insensitive C26-B line, indicating that these processes, in addition to 5-FU uptake and metabolism, may be important determinants of drug sensitivity and treatment response.
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Affiliation(s)
- Y J L Kamm
- Department of Medical Oncology 550, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
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Voeller DM, Zajac-Kaye M, Fisher RJ, Allegra CJ. The identification of thymidylate synthase peptide domains located in the interface region that bind thymidylate synthase mRNA. Biochem Biophys Res Commun 2002; 297:24-31. [PMID: 12220503 DOI: 10.1016/s0006-291x(02)02080-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Thymidylate synthase (TS) is a critical chemotherapeutic target and intracellular levels of TS are an important determinant of sensitivity to TS inhibitors. Translational autoregulation represents one cellular mechanism for controlling the level of expression of TS. This mechanism involves the binding of TS protein to its own messenger RNA (mRNA), thus, repressing translational efficiency. The presence of excess substrate or inhibitors of TS leads to derepression of protein binding to mRNA, resulting in increased translational efficiency and ultimately increased levels of TS protein. TS protein has been shown to bind to two distinct areas on its mRNA. The goal of the present work is to define the TS domains responsible for this interaction. Using a separate series of overlapping 17-mer peptides spanning the length of both the human and Escherichia coli TS sequences, we have identified six potential domains located in the interface region of the TS protein that bind TS mRNA. The identified domains that bind TS mRNA include three concordant regions in both the human and E. coli peptide series. Five of the six binding peptides contain at least one invariant arginine residue, which has been shown to be critical in other well-defined protein-RNA interactions. These data suggest that the identified highly conserved protein domains, which occur at the homodimeric interface of TS, represent potential participating sites for binding of TS protein to its mRNA.
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Affiliation(s)
- Donna M Voeller
- Center for Cancer Research, Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Building 37 Room 6050D, 37 Convent Drive MSC 4255, Bethesda, MD 20892, USA.
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Codacci-Pisanelli G, Van der Wilt CL, Smid K, Noordhuis P, Voorn D, Pinedo HM, Peters GJ. High-dose 5-Fluorouracil with uridine-diphosphoglucose rescue increases thymidylate synthase inhibition but not 5-Fluorouracil incorporation into RNA in murine tumors. Oncology 2002; 62:363-70. [PMID: 12138245 DOI: 10.1159/000065069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
5-Fluorouracil (5FU) shows a steep dose response curve in several experimental systems, but the clinical use of high doses is hampered by the toxic side effects of this drug. Uridine diphosphoglucose (UDPG) rescue allows an increase in the maximum tolerated dose of 5FU in mice from 100 (FU(100)) to 150 mg/kg (5FU(150)+UDPG) and the higher dose is more effective than the standard treatment against several tumors. In the present paper we report on the effect of high-dose 5FU on thymidylate synthase (TS) levels and on 5FU incorporation into RNA. In the resistant murine tumor (Colon 26A) high-dose 5FU inhibited TS catalytic activity 8 h after treatment (4-fold; p = 0.00041) and the inhibition persisted until day 3 (p < 10(-4)). Standard-dose 5FU did not significantly inhibit TS activity. In a relatively sensitive tumor (Colon 26-10), there was no difference in the initial extent of TS inhibition by the two 5FU doses, but TS was still inhibited (2-fold) on day 3 after (5FU(150)+UDPG) while it was within the normal range after 5FU(100). In both tumor types TS activity showed an impressive rebound (3-fold) on days 3-7, and this occurred after both 5FU doses. In Colon 26A, however, a new 5FU injection on day 7 was still able to inhibit TS but not as effectively as the first dose. 5FU incorporation into RNA reached similar peak values (8 pmol/microg RNA) after the two 5FU doses, but the clearance was faster in mice receiving UDPG rescue. We conclude that UDPG does not interfere with the extent of TS inhibition by 5FU, but UDPG allows the use of a higher dose of 5FU resulting in enhanced TS inhibition. UDPG, however, increases 5FU clearance from RNA. In this experimental system the inhibition of TS seems essential in order to obtain a good antitumor activity, while 5FU incorporation into RNA does not seem to play a role in the antitumor activity of 5FU. Since preliminary results indicate that UDPG is well tolerated by patients, the use of higher 5FU doses may improve the response rate of human tumors.
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Peters GJ, Backus HHJ, Freemantle S, van Triest B, Codacci-Pisanelli G, van der Wilt CL, Smid K, Lunec J, Calvert AH, Marsh S, McLeod HL, Bloemena E, Meijer S, Jansen G, van Groeningen CJ, Pinedo HM. Induction of thymidylate synthase as a 5-fluorouracil resistance mechanism. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1587:194-205. [PMID: 12084461 DOI: 10.1016/s0925-4439(02)00082-0] [Citation(s) in RCA: 267] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Thymidylate synthase (TS) is a key enzyme in the de novo synthesis of 2'-deoxythymidine-5'-monophosphate (dTMP) from 2'-deoxyuridine-5'-monophosphate (dUMP), for which 5,10-methylene-tetrahydrofolate (CH(2)-THF) is the methyl donor. TS is an important target for chemotherapy; it is inhibited by folate and nucleotide analogs, such as by 5-fluoro-dUMP (FdUMP), the active metabolite of 5-fluorouracil (5FU). FdUMP forms a relatively stable ternary complex with TS and CH(2)THF, which is further stabilized by leucovorin (LV). 5FU treatment can induce TS expression, which might bypass dTMP depletion. An improved efficacy of 5FU might be achieved by increasing and prolonging TS inhibition, a prevention of dissociation of the ternary complex, and prevention of TS induction. In a panel of 17 colon cancer cells, including several variants with acquired resistance to 5FU, sensitivity was related to TS levels, but exclusion of the resistant variants abolished this relation. For antifolates, polyglutamylation was more important than the intrinsic TS level. Cells with low p53 levels were more sensitive to 5FU and the antifolate raltitrexed (RTX) than cells with high, mutated p53. Free TS protein down-regulates its own translation, but its transcription is regulated by E2F, a cell cycle checkpoint regulator. Together, this results in low TS levels in stationary phase cells. Although cells with a low TS might theoretically be more sensitive to 5FU, the low proliferation rate prevents induction of DNA damage and 5FU toxicity. TS levels were not related to polymorphisms of the TS promoter. Treatment with 5FU or RTX rapidly induced TS levels two- to five-fold. In animal models, 5FU treatment resulted in TS inhibition followed by a two- to three-fold TS induction. Both LV and a high dose of 5FU not only enhanced TS inhibition, but also prevented TS induction and increased the antitumor effect. In patients, TS levels as determined by enzyme activity assays, immunohistochemistry and mRNA expression, were related to a response to 5FU. 5FU treatment initially decreased TS levels, but this was followed by an induction, as seen with an increased ratio of TS protein over TS-mRNA. The clear retrospective relation between TS levels and response now forms the basis for a prospective study, in which TS levels are measured before treatment in order to determine the treatment protocol.
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MESH Headings
- Animals
- Antimetabolites, Antineoplastic/metabolism
- Antimetabolites, Antineoplastic/pharmacology
- Drug Resistance, Neoplasm/physiology
- Enzyme Induction/drug effects
- Fluorouracil/metabolism
- Fluorouracil/pharmacology
- Folic Acid Antagonists/pharmacology
- Humans
- In Vitro Techniques
- Neoplasms/drug therapy
- Neoplasms/enzymology
- Neoplasms/genetics
- Polymorphism, Genetic
- Promoter Regions, Genetic
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- Thymidylate Synthase/antagonists & inhibitors
- Thymidylate Synthase/biosynthesis
- Thymidylate Synthase/genetics
- Tumor Cells, Cultured
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- G J Peters
- Department of Medical Oncology, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands.
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Banerjee D, Mayer-Kuckuk P, Capiaux G, Budak-Alpdogan T, Gorlick R, Bertino JR. Novel aspects of resistance to drugs targeted to dihydrofolate reductase and thymidylate synthase. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1587:164-73. [PMID: 12084458 DOI: 10.1016/s0925-4439(02)00079-0] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Drug resistance is often a limiting factor in successful chemotherapy. Our laboratory has been interested in studying mechanisms of resistance to drugs that are targeted to the thymidylate biosynthesis pathway especially those that target thymidylate synthase (TS) and dihydrofolate reductase (DHFR). We have used leukemia as a model system to study resistance to methotrexate (MTX) and colorectal cancer as the model system to study 5-fluorouracil (5-FU) resistance. In leukemias, we and others have shown that transport, efflux, polyglutamylation and hydrolase activities are major determinants of MTX resistance. We have further reported that some leukemic cells have an increase in DHFR gene copy number possibly contributing to the resistant phenotype. Recently, we have begun to study in detail the molecular mechanisms that govern translational regulation of DHFR in response to MTX as an additional resistance mechanism. Studies thus far involving colorectal tumors obtained from patients have focused predominantly on the predictive value of levels of TS expression and p53 mutations in determining response to 5-FU. Although the predictive value of these two measures appears to be significant, given the variety of resistance to 5-FU observed in cell lines, it is not likely that these are the only measures predictive of response or responsible for acquired resistance to this drug. The enzyme uridine-cytidine monophosphate kinase (UMPK) is an essential and rate-limiting enzyme in 5-FU activation while dihydropyrimidine dehydrogenase (DPD) is a catabolic enzyme that inactivates 5-FU. Alterations in UMPK and DPD may therefore explain failure of 5-FU response in the absence of alterations in TS or p53. Transcription factors that regulate TS may also influence drug sensitivity. We have found that mRNA levels of the E2F family of transcription factors correlates with TS message levels and are higher in lung metastases than in liver metastases of colorectal cancers. Moreover, gene copy number of the E2F-1 gene appears to be increased in a significant number of samples obtained from metastases of colorectal cancer. We have also generated mutants of both DHFR and TS that confer resistance to MTX as well as 5-FU by random as well as site-directed mutagenesis. These mutants used alone or as fusion cDNAs of the mutants have proven to be useful in transplant studies where transfer of these mutant cDNAs to bone marrow cells have been shown to confer drug resistance to recipients. The fusion cDNAs of DHFR such as the DHFR-herpes simplex virus type 1 thymidine kinase (HSVTK) are also useful for regulation of gene expression in vivo using MTX as the small molecule regulator that can be monitored by positron emission tomography (PET) scanning or by optical imaging using a fusion construct such as DHFR-EGFP.
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Affiliation(s)
- Debabrata Banerjee
- Program of Molecular Pharmacology and Experimental Therapeutics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
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Liu J, Schmitz JC, Lin X, Tai N, Yan W, Farrell M, Bailly M, Chen TM, Chu E. Thymidylate synthase as a translational regulator of cellular gene expression. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1587:174-82. [PMID: 12084459 DOI: 10.1016/s0925-4439(02)00080-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Studies from our laboratory have shown that the folate-dependent enzyme, thymidylate synthase (TS), functions as an RNA binding protein. There is evidence that TS, in addition to interacting with its own TS mRNA, forms a ribonucleoprotein complex with a number of other cellular mRNAs, including those corresponding to the p53 tumor suppressor gene and the myc family of transcription factors. Using both in vitro and in vivo model systems, we have demonstrated that the functional consequence of binding of TS protein to its own cognate mRNA, as well as binding of TS to the p53 mRNA, is translational repression. Herein, we review current work on the translational autoregulatory control of TS expression and discuss the molecular elements that are required for the TS protein-TS mRNA interaction. TS may play a critical role in regulating the cell cycle and the process of apoptosis through its regulatory effects on expression of p53 and perhaps other cell cycle related proteins. Finally, the ability of TS to function as a translational regulator may have important consequences with regard to the development of cellular resistance to various anticancer drugs.
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Affiliation(s)
- Jun Liu
- Department of Medicine and Pharmacology, Yale Cancer Center, Yale University School of Medicine, USA
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Mayer-Kuckuk P, Banerjee D, Malhotra S, Doubrovin M, Iwamoto M, Akhurst T, Balatoni J, Bornmann W, Finn R, Larson S, Fong Y, Gelovani Tjuvajev J, Blasberg R, Bertino JR. Cells exposed to antifolates show increased cellular levels of proteins fused to dihydrofolate reductase: a method to modulate gene expression. Proc Natl Acad Sci U S A 2002; 99:3400-5. [PMID: 11891321 PMCID: PMC122535 DOI: 10.1073/pnas.062036899] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human cells exposed to antifolates show a rapid increase in the levels of the enzyme dihydrofolate reductase (DHFR). We hypothesized that this adaptive response mechanism can be used to elevate cellular levels of proteins fused to DHFR. In this study, mouse cells transfected to express a green fluorescent protein-DHFR fusion protein and subsequently exposed to the antifolate trimetrexate (TMTX) showed a specific and time-dependent increase in cellular levels of the fusion protein. Next, human HCT-8 and HCT-116 colon cancer cells retrovirally transduced to express a DHFR-herpes simplex virus 1 thymidine kinase (HSV1 TK) fusion protein and treated with the DHFR inhibitor TMTX exhibited increased levels of the DHFR-HSV1 TK fusion protein and an increase in ganciclovir sensitivity by 250-fold. The level of fusion protein in antifolate-treated human tumor cells was increased in response to a 24-h exposure of methotrexate, trimetrexate, as well as dihydrofolate. This effect depended on the antifolate concentration and was independent of the fusion-protein mRNA levels, consistent with this increase occurring at a translational level. In a xenograft model, nude rats bearing DHFR-HSV1 TK-transduced HCT-8 tumors and treated with TMTX showed, after 24 h, a 2- to 4-fold increase of fusion-protein levels in tumor tissue from treated animals compared with controls, as determined by Western blotting. The fusion-protein increase was imaged with positron-emission tomography, where a substantially enhanced signal of the transduced tumor was detected in animals after antifolate administration. Drug-mediated elevation of cellular DHFR-fused proteins is a very useful method to modulate gene expression in vivo for imaging as well as therapeutic purposes.
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Affiliation(s)
- Philipp Mayer-Kuckuk
- Molecular Pharmacology and Therapeutics Program, Department of Surgery, Nuclear Medicine Service, Radiochemistry/ Cyclotron, and Preparative Synthesis Chemistry Core Facilities, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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Grem JL, Danenberg KD, Kao V, Danenberg PV, Nguyen D. Biochemical and molecular effects of UCN-01 in combination with 5-fluorodeoxyuridine in A431 human epidermoid cancer cells. Anticancer Drugs 2002; 13:259-70. [PMID: 11984070 DOI: 10.1097/00001813-200203000-00008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Concurrent and pre-exposure of A431 human epidermoid cancer cells to UCN-01, an investigational anticancer drug, with 5-fluoro--2'-deoxyuridine (FdUrd), which targets thymidylate synthase, produced more than additive cytotoxicty. A 24-h exposure to 10 nM FdUrd led to inhibition of TS, a 2.5-fold increase in total thymidylate synthase protein content, profound dTTP depletion and a 6.3-fold increase in the ratio of dATP to dTTP, but did not cause single-strand breaks in DNA. However, FdUrd enhanced UCN-01-associated DNA strand breaks. Concurrent thymidine exposure led to repletion of dTTP pools, and cytoprotection against FdUrd alone and with UCN-01. UCN-01 arrested cells in G1, decreased the percentage of FdUrd-treated cells in S phase and reduced FdUrd-DNA incorporation, suggesting the latter was not important for cytotoxicity. Delayed induction of high molecular mass DNA fragmentation and poly(ADP-ribose) polymerase cleavage was observed with the combination of UCN-01 and FdUrd. These findings suggest that while FdUrd-mediated deoxynucleotide imbalance alone was insufficient to induce apoptosis in this p53-mutant cell line, it magnified UCN-01's effects, most likely by interfering with DNA repair. The clinical evaluation of UCN-01 combined with 5-fluoropyrimidines may be of interest.
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Affiliation(s)
- Jean L Grem
- Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute-Navy Medical Oncology, National Naval Medical Center, Bethesda, MD 20889-5105, USA.
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Abstract
Folate catabolism has been assumed to result from the nonenzymatic oxidative degradation of labile folate cofactors. Increased rates of folate catabolism and simultaneous folate deficiency occur in several physiological states, including pregnancy, cancer, and when anticonvulsant drugs are used. These studies have introduced the possibility that folate catabolism may be a regulated cellular process that influences intracellular folate concentrations. Recent studies have demonstrated that the iron storage protein ferritin can catabolize folate in vitro and in vivo, and increased heavy-chain ferritin synthesis decreases intracellular folate concentrations independent of exogenous folate levels in cell culture models. Ferritin levels are elevated in most physiological states associated with increased folate catabolism. Therefore, folate catabolism is emerging as an important component in the regulation of intracellular folate concentrations and whole-body folate status.
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Affiliation(s)
- J R Suh
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA.
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