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Wang SM, Li M, Wu WS, Sun LL, Yan D. Methylation analysis of the SLC19A1 promoter region in Chinese children with acute lymphoblastic leukaemia. J Clin Pharm Ther 2020; 45:646-651. [PMID: 32403197 DOI: 10.1111/jcpt.13171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 03/18/2020] [Accepted: 04/20/2020] [Indexed: 11/30/2022]
Abstract
WHAT IS KNOWN AND OBJECTIVE Reduced folate carrier 1 (RFC1), which is encoded by the human solute carrier family 19 member 1 (SLC19A1) gene, plays an essential role in the cellular uptake of methotrexate (MTX). RFC1 expression is regulated by genetic variations and epigenetic modifications. The aim of the present study was to investigate the methylation status of the SLC19A1 promoter in peripheral blood and its association with MTX levels and toxicities in children with acute lymphoblastic leukaemia (ALL). METHODS Serum MTX concentrations were measured using a fluorescence polarization immunoassay. Methylation quantification for SLC19A1 promoter region #17 was performed by Sequenom MassARRAY in 52 paediatric ALL patients. RESULTS AND DISCUSSION Overall, the investigated region of the SLC19A1 promoter was in a hypermethylated state. No significant associations were detected between the methylation levels of six CpG units in the SLC19A1 promoter region #17 and clinical parameters of patients with ALL, including sex, age, immunotype and risk stratification. The methylation level of CpG_10 showed a significant positive correlation with MTX 24 hours after the initiation of infusion. No significant differences in the methylation levels of six CpG units were observed between patients with and without MTX toxicities. Due to the small sample size of this study, there was a high chance of false-positive results. A large-scale study would be required to confirm these preliminary results. WHAT IS NEW AND CONCLUSION Our preliminary results suggested the hypermethylated status of the SLC19A1 promoter in children with ALL. The methylation levels of the SLC19A1 promoter might affect MTX exposure. These findings have implications for the mechanisms underlying the variability of MTX responses in childhood ALL.
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Affiliation(s)
- Shu-Mei Wang
- Department of Pharmacy, Beijing Shijitan Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Bio-Characteristic Profiling for Evaluation of Rational Drug Use, Beijing, China.,International Cooperation & Joint Laboratory of Bio-Characteristic Profiling for Evaluation of Rational Drug Use, Beijing, China
| | - Miao Li
- Department of Pediatrics, Beijing Shijitan Hospital, Capital Medical University, Beijing, China
| | - Wan-Shui Wu
- Department of Pediatrics, Beijing Shijitan Hospital, Capital Medical University, Beijing, China
| | - Lu-Lu Sun
- Department of Pharmacy, Beijing Shijitan Hospital, Capital Medical University, Beijing, China
| | - Dan Yan
- Department of Pharmacy, Beijing Shijitan Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Bio-Characteristic Profiling for Evaluation of Rational Drug Use, Beijing, China.,International Cooperation & Joint Laboratory of Bio-Characteristic Profiling for Evaluation of Rational Drug Use, Beijing, China
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2
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Ludovini V, Antognelli C, Rulli A, Foglietta J, Pistola L, Eliana R, Floriani I, Nocentini G, Tofanetti FR, Piattoni S, Minenza E, Talesa VN, Sidoni A, Tonato M, Crinò L, Gori S. Influence of chemotherapeutic drug-related gene polymorphisms on toxicity and survival of early breast cancer patients receiving adjuvant chemotherapy. BMC Cancer 2017; 17:502. [PMID: 28747156 PMCID: PMC5530465 DOI: 10.1186/s12885-017-3483-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 07/12/2017] [Indexed: 12/18/2022] Open
Abstract
Background We investigated whether GSTT1 (“null” allele), GSTM1 (“null”allele), GSTP1 (A313G), RFC1 (G80A), MTHFR (C677T), TS (2R/3R) polymorphisms were associated with toxicity and survival in patients with early breast cancer (EBC) treated with adjuvant chemotherapy (CT). Methods This prospective trial included patients with stage I–III BC subjected to CT with CMF or FEC regimens. PCR-RFLP was performed for MTHFR, RFC1 and GSTP1, while PCR for TS, GSTT1 and GSTM1 genes. Results Among the 244 patients consecutively enrolled, 48.7% were treated with FEC and 51.3% with CMF. Patients with TS2R/3R genotype showed less frequently severe neutropenia (G3/G4) than those with TS2R/2R and 3R/3R genotype (p = 0.038). Patients with MTHFRCT genotype had a higher probability of developing severe neutropenia than those with MTHFR CC genotype (p = 0.043). Patients with RFC1GG or GSTT1-null genotype or their combination (GSTT1-null/RFC1GG) were significantly associated with a shorter disease free survival (DFS) (p = 0.009, p = 0.053, p = 0.003, respectively) and overall survival (OS) (p = 0.036, p = 0.015, p = 0.005, respectively). Multivariate analysis confirmed the association of RFC1GG genotype with a shorter DFS (p = 0.018) and of GSTT1-null genotype of a worse OS (p = 0.003), as well as for the combined genotypes GSTT1-null/RFC1GG, (DFS: p = 0.004 and OS: p = 0.003). Conclusions Our data suggest that TS2R/2R and 3R/3R or MTHFR CT genotypes have a potential role in identifying patients with greater risk of toxicity to CMF/FEC and that RFC1 GG and GSTT1-null genotypes alone or in combination could be important markers in predicting clinical outcome in EBC patients. Electronic supplementary material The online version of this article (doi:10.1186/s12885-017-3483-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Vienna Ludovini
- Medical Oncology Division, S. Maria della Misericordia Hospital, Azienda Ospedaliera of Perugia, Perugia, Italy.
| | - Cinzia Antognelli
- Department of Experimental Medicine, University of Perugia, Piazzale Menghini 8/9, 06156, Perugia, Italy
| | - Antonio Rulli
- Breast Unit, Department of Surgical, University of Perugia, Perugia, Italy
| | - Jennifer Foglietta
- Medical Oncology Division, S. Maria della Misericordia Hospital, Azienda Ospedaliera of Perugia, Perugia, Italy
| | - Lorenza Pistola
- Medical Oncology Division, S. Maria della Misericordia Hospital, Azienda Ospedaliera of Perugia, Perugia, Italy
| | - Rulli Eliana
- Oncology Department, IRCCS, Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy
| | - Irene Floriani
- Oncology Department, IRCCS, Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy
| | - Giuseppe Nocentini
- Section of Pharmacology, Department of Medicine, University of Perugia, Perugia, Italy
| | - Francesca Romana Tofanetti
- Medical Oncology Division, S. Maria della Misericordia Hospital, Azienda Ospedaliera of Perugia, Perugia, Italy
| | | | - Elisa Minenza
- Medical Oncology Division, "S. Maria" Hospital, Terni, Italy
| | - Vincenzo Nicola Talesa
- Department of Experimental Medicine, University of Perugia, Piazzale Menghini 8/9, 06156, Perugia, Italy
| | - Angelo Sidoni
- Department of Experimental Medicine, Section of Anatomic and Histology, Medical School, University of Perugia, Perugia, Italy
| | | | - Lucio Crinò
- Medical Oncology, Istituto Scientifico Romagnolo per lo studio e la cura dei tumori (IRST), IRCCS, Meldola, Italy
| | - Stefania Gori
- Medical Oncology, SacroCuore-Don Calabria Hospital, Negrar, Verona, Italy
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3
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Zaruma-Torres F, Lares-Asseff I, Lima A, Reyes-Espinoza A, Loera-Castañeda V, Sosa-Macías M, Galaviz-Hernández C, Arias-Peláez MC, Reyes-López MA, Quiñones LA. Genetic Polymorphisms Associated to Folate Transport as Predictors of Increased Risk for Acute Lymphoblastic Leukemia in Mexican Children. Front Pharmacol 2016; 7:238. [PMID: 27547186 PMCID: PMC4974492 DOI: 10.3389/fphar.2016.00238] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/21/2016] [Indexed: 01/25/2023] Open
Abstract
Acute lymphoblastic leukemia (ALL) is a frequent neoplasia occurring in children. The most commonly used drug for the treatment of ALL is methotrexate (MTX), an anti-folate agent. Previous studies suggest that folate transporters play a role in ALL prognosis and that genetic polymorphism of genes encoding folate transporters may increase the risk of ALL. Therefore, the main goal of this study was to determine the associations among six genetic polymorphisms in four genes related with the folate transporter pathway to determine a relationship with the occurrence of ALL in Mexican children. A case-control study was performed in 73 ALL children and 133 healthy children from Northern and Northwestern Mexico. COL18A1 (rs2274808), SLC19A1 (rs2838956), ABCB1 (rs1045642 and rs1128503), and ABCC5 (rs9838667 and rs3792585). Polymorphisms were assayed through qPCR. Our results showed an increased ALL risk in children carrying CT genotype (OR = 2.55, CI 95% 1.11–5.83, p = 0.0001) and TT genotype (OR = 21.05, CI 95% 5.62–78.87, p < 0.0001) of COL18A1 rs2274808; in SLC19A1 rs2838956 AG carriers (OR = 44.69, CI 95% 10.42–191.63, p = 0.0001); in ABCB1 rs1045642 TT carriers (OR = 13.76, CI 95% 5.94–31.88, p = 0.0001); in ABCC5 rs9838667 AC carriers (OR = 2.61, CI 95% 1.05–6.48, p < 0.05); and in ABCC5 rs3792585 CC carriers (OR = 9.99, CI 95% 3.19–31.28, p = 0.004). Moreover, several combinations of genetic polymorphisms were found to be significantly associated with a risk for ALL. Finally, two combinations of ABCC5 polymorphisms resulted in protection from this neoplasia. In conclusion, certain genetic polymorphisms related to the folate transport pathway, particularly COL18A1 rs2274808, SLC19A1 rs2838956, ABCB1 rs1045642, and ABCC5 rs3792585, were associated with an increased risk for ALL in Mexican children.
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Affiliation(s)
- Fausto Zaruma-Torres
- Pharmacogenomics Academia, National Polytechnic Institute-CIIDIRDurango, Mexico; School of Biochemistry and Pharmacy, University of CuencaCuenca, Ecuador
| | - Ismael Lares-Asseff
- Pharmacogenomics Academia, National Polytechnic Institute-CIIDIR Durango, Mexico
| | - Aurea Lima
- CESPU, Instituto de Investigação e Formação Avançada em Ciências e Tecnologias da Saúde Gandra, Portugal
| | | | | | - Martha Sosa-Macías
- Pharmacogenomics Academia, National Polytechnic Institute-CIIDIR Durango, Mexico
| | | | - María C Arias-Peláez
- Institute of Scientific Research of the University Juarez of State of Durango Durango, Mexico
| | - Miguel A Reyes-López
- Center of Biotechnology Genomics, National Polytechnic Institute Reynosa, Mexico
| | - Luis A Quiñones
- Pharmacological and Molecular Program, Laboratory of Chemical Carcinogenesis and Pharmacogenetics (CQF), Faculty of Medicine, ICBM, University of Chile Santiago, Chile
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Szabó I, Orbán E, Schlosser G, Hudecz F, Bánóczi Z. Cell-penetrating conjugates of pentaglutamylated methotrexate as potential anticancer drugs against resistant tumor cells. Eur J Med Chem 2016; 115:361-8. [PMID: 27031212 DOI: 10.1016/j.ejmech.2016.03.034] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 02/28/2016] [Accepted: 03/14/2016] [Indexed: 12/27/2022]
Abstract
The emerging resistance of tumor cells against methotrexate (MTX) is one of the major limitations of the MTX treatment of tumorous diseases. The disturbance in the polyglutamation which is a main step in the mechanism of methotrexate action is often the reason of the resistance. Delivery of polyglutamylated MTX into cells may evade the mechanisms that are responsible for drug resistance. In this study conjugates of methotrexate and its pentaglutamylated derivatives with cell-penetrating peptides - penetratin and octaarginine - were investigated. The cellular-uptake and in vitro cytostatic activity of conjugates were examined on breast cancer cell cultures (MDA-MB-231 as resistant and MCF-7 as sensitive cell culture). These cell cultures showed very different behaviour towards the conjugates. Although the presence of pentaglutamyl moiety significantly decreased the internalisation of conjugates, some of them were significantly active in vitro. All of the conjugates were able to penetrate in some extent into both cell types, but only the conjugates of penetratin showed in vitro cytostatic activity. The most effective conjugates were the MTX-Glu5-Penetratin(desMet) and MTX-Glu5-GFLG-Penetratin(desMet). The latter was effective on both cell cultures while the former was active only on the resistant tumor cells. Our results suggest that the translocation of polyglutamylated MTX may be a new way to treat sensitive and more importantly resistant tumors. While both penetratin and octaarginine peptides were successfully used to deliver several kinds of cargos earlier in our case the activity of penetratin conjugates was more pronounced.
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Affiliation(s)
- Ildikó Szabó
- MTA-ELTE Research Group of Peptide Chemistry, Budapest, Hungary
| | - Erika Orbán
- MTA-ELTE Research Group of Peptide Chemistry, Budapest, Hungary
| | - Gitta Schlosser
- MTA-ELTE Research Group of Peptide Chemistry, Budapest, Hungary
| | - Ferenc Hudecz
- MTA-ELTE Research Group of Peptide Chemistry, Budapest, Hungary; Department of Organic Chemistry, Eötvös L. University, Budapest, Hungary
| | - Zoltán Bánóczi
- MTA-ELTE Research Group of Peptide Chemistry, Budapest, Hungary; Department of Organic Chemistry, Eötvös L. University, Budapest, Hungary.
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5
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Yurgel VC, Oliveira CP, Begnini KR, Schultze E, Thurow HS, Leon PMM, Dellagostin OA, Campos VF, Beck RCR, Guterres SS, Collares T, Pohlmann AR, Seixas FK. Methotrexate diethyl ester-loaded lipid-core nanocapsules in aqueous solution increased antineoplastic effects in resistant breast cancer cell line. Int J Nanomedicine 2014; 9:1583-91. [PMID: 24741306 PMCID: PMC3970944 DOI: 10.2147/ijn.s56506] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Breast cancer is the most frequent cancer affecting women. Methotrexate (MTX) is an antimetabolic drug that remains important in the treatment of breast cancer. Its efficacy is compromised by resistance in cancer cells that occurs through a variety of mechanisms. This study evaluated apoptotic cell death and cell cycle arrest induced by an MTX derivative (MTX diethyl ester [MTX(OEt)2]) and MTX(OEt)2-loaded lipid-core nanocapsules in two MTX-resistant breast adenocarcinoma cell lines, MCF-7 and MDA-MB-231. The formulations prepared presented adequate granulometric profile. The treatment responses were evaluated through flow cytometry. Relying on the mechanism of resistance, we observed different responses between cell lines. For MCF-7 cells, MTX(OEt)2 solution and MTX(OEt)2-loaded lipid-core nanocapsules presented significantly higher apoptotic rates than untreated cells and cells incubated with unloaded lipid-core nanocapsules. For MDA-MB-231 cells, MTX(OEt)2-loaded lipid-core nanocapsules were significantly more efficient in inducing apoptosis than the solution of the free drug. S-phase cell cycle arrest was induced only by MTX(OEt)2 solution. The drug nanoencapsulation improved apoptosis induction for the cell line that presents MTX resistance by lack of transport receptors.
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Affiliation(s)
- Virginia C Yurgel
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Catiuscia P Oliveira
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Karine R Begnini
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Eduarda Schultze
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Helena S Thurow
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Priscila M M Leon
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Odir A Dellagostin
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Vinicius F Campos
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Ruy C R Beck
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Silvia S Guterres
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Tiago Collares
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
| | - Adriana R Pohlmann
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil ; Departamento de Química Orgânica, Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil ; Centro de Nanociência e Nanotecnologia, CNANO-UFRGS, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Fabiana K Seixas
- Programa de Pós-Graduação em Biotecnologia (PPGB), Grupo de Pesquisa em Oncologia Celular e Molecular, Laboratório de Genômica Funcional, Biotecnologia/Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil
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Niedermeyer THJ, Daily A, Swiatecka-Hagenbruch M, Moscow JA. Selectivity and potency of microcystin congeners against OATP1B1 and OATP1B3 expressing cancer cells. PLoS One 2014; 9:e91476. [PMID: 24614281 PMCID: PMC3948918 DOI: 10.1371/journal.pone.0091476] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 02/13/2014] [Indexed: 11/19/2022] Open
Abstract
Microcystins are potent phosphatase inhibitors and cellular toxins. They require active transport by OATP1B1 and OATP1B3 transporters for uptake into human cells, and the high expression of these transporters in the liver accounts for their selective hepatic toxicity. Several human tumors have been shown to have high levels of expression of OATP1B3 but not OATP1B1, the main transporter in liver cells. We hypothesized that microcystin variants could be isolated that are transported preferentially by OATP1B3 relative to OATP1B1 to advance as anticancer agents with clinically tolerable hepatic toxicity. Microcystin variants have been isolated and tested for cytotoxicity in cancer cells stably transfected with OATP1B1 and OATP1B3 transporters. Microcystin variants with cytotoxic OATP1B1/OATP1B3 IC50 ratios that ranged between 0.2 and 32 were found, representing a 150-fold range in transporter selectivity. As microcystin structure has a significant impact on transporter selectivity, it is potentially possible to develop analogs with even more pronounced OATP1B3 selectivity and thus enable their development as anticancer drugs.
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Affiliation(s)
- Timo H. J. Niedermeyer
- Cyano Biotech GmbH, Berlin, Germany
- Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
- * E-mail:
| | - Abigail Daily
- Department of Pediatrics, University of Kentucky, Lexington, Kentucky, United States of America
| | | | - Jeffrey A. Moscow
- Department of Pediatrics, University of Kentucky, Lexington, Kentucky, United States of America
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7
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Assessment of the role of renal organic anion transporters in drug-induced nephrotoxicity. Toxins (Basel) 2010; 2:2055-82. [PMID: 22069672 PMCID: PMC3153278 DOI: 10.3390/toxins2082055] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 08/05/2010] [Accepted: 08/05/2010] [Indexed: 01/09/2023] Open
Abstract
In the present review we have attempted to assess the involvement of the organic anion transporters OAT1, OAT2, OAT3, and OAT4, belonging to the SLC22 family of polyspecific carriers, in drug-induced renal damage in humans. We have focused on drugs with widely recognized nephrotoxic potential, which have previously been reported to interact with OAT family members, and whose underlying pathogenic mechanism suggests the participation of tubular transport. Thus, only compounds generally believed to cause kidney injury either by means of direct tubular toxicity or crystal nephropathy have been considered. For each drug, or class of agents, the evidence for actual transport mediated by individual OATs under in vivo conditions is discussed. We have then examined their role in the context of other carriers present in the renal proximal tubule sharing certain substrates with OATs, as these are critical determinants of the overall contribution of OAT-dependent transport to intracellular accumulation and transepithelial drug secretion, and thus the impact it may have in drug-induced nephrotoxicity.
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8
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Begley DW, Zheng S, Varani G. Fragment-based discovery of novel thymidylate synthase leads by NMR screening and group epitope mapping. Chem Biol Drug Des 2010; 76:218-33. [PMID: 20626411 DOI: 10.1111/j.1747-0285.2010.01010.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Solution-state nuclear magnetic resonance (NMR) is a versatile tool for the study of binding interactions between small molecules and macromolecular targets. We applied ligand-based NMR techniques to the study of human thymidylate synthase (hTS) using known nanomolar inhibitors and a library of small molecule fragments. Screening by NMR led to the rapid identification of ligand pairs that bind in proximal sites within the cofactor-binding pocket of hTS. Screening hits were used as search criteria within commercially available sources, and a subset of catalog analogs were tested for potency by in vitro assay and binding affinity by quantitative saturation transfer difference (STD)-NMR titration. Two compounds identified by this approach possess low micromolar affinity and potency, as well as excellent binding efficiency against hTS. Relative binding orientations for both leads were modeled using AutoDock, and the most likely bound conformations were validated using experimentally derived STD-NMR binding epitope data. These ligands represent novel starting points for fragment-based drug design of non-canonical TS inhibitors, and their binding epitopes highlight important and previously unexploited interactions with conserved residues in the cofactor-binding site.
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Affiliation(s)
- Darren W Begley
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.
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9
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Stoeger SM, Cowan KH. Characterization of kinase suppressor of Ras-1 expression and anticancer drug sensitivity in human cancer cell lines. Cancer Chemother Pharmacol 2008; 63:807-18. [PMID: 18661133 DOI: 10.1007/s00280-008-0794-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2007] [Accepted: 07/07/2008] [Indexed: 01/08/2023]
Abstract
Previous studies have indicated that the ERK1/2 MAP kinase signaling pathway plays an important role not only in cell growth, cell cycle regulation, and differentiation, but also in determining the sensitivity of cells to anticancer agents as well. Furthermore, expression of kinase suppressor of Ras-1 (KSR1), a molecular scaffold that modulates signaling through the ERK1/2 MAP kinase pathway, has been shown to influence the cellular sensitivity to the anticancer agent cisplatin. To further define the role of KSR1 expression on drug sensitivity, the expression of KSR1 was examined in the NCI60 anticancer drug screen, a panel of cancer cell lines representing nine tissue types, established by the Developmental Therapeutics Program (DTP) at the National Cancer Institute (NCI). The expression of thousands of molecular targets has been examined in the NCI60 panel as well as the cellular toxicity for greater than 400,000 compounds. KSR1 expression varied almost 30-fold difference between the highest and lowest expressing cell lines in the NCI60. Using the COMPARE analysis algorithm, KSR1 expression was correlated with sensitivity of the compounds screened by DTP and several novel agents were identified whose sensitivity correlated with KSR1 expression in the NCI60 panel. Cytotoxicity of two agents, cytochalasin H and tunicamycin, identified through the COMPARE analysis of KSR1 expression and drug sensitivity, was also examined in wild type (KSR(+/+)) mouse embryo fibroblasts (MEFs) and MEFs deficient in KSR1 expression (KSR1(-/-)). These studies demonstrated enhanced sensitivity, as well as increased ERK activation, in KSR(-/-) MEFs following exposure to tunicamycin or cytochalasin H compared to KSR(+/+) MEFs. Furthermore, restoration of KSR1 expression in KSR(-/-) MEFs following stable transduction of cells with a KSR1 expression vector, enhanced sensitivity of cells to tunicamycin and cytochalasin H and decreased ERK1/2 activation following exposure to these drugs. In addition, the sensitivity to cytochalasin H and tunicamycin of breast cancer cell lines with low KSR1 expression, (HS578T and MDA-MB-231/ATCC), was increased relative to the sensitivity of breast cancer cells with higher levels of KSR1 (MCF7). These studies indicate that KSR1 may play an important role in the determination of cellular sensitivity to anticancer agents.
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Affiliation(s)
- Scott M Stoeger
- Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
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10
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Quantitative correlation between promoter methylation and messenger RNA levels of the reduced folate carrier. BMC Cancer 2008; 8:124. [PMID: 18452618 PMCID: PMC2387170 DOI: 10.1186/1471-2407-8-124] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 05/01/2008] [Indexed: 12/31/2022] Open
Abstract
Background Methotrexate (MTX) uptake is mediated by the reduced folate carrier (RFC). Defective drug uptake in association with decreased RFC expression is a common mechanism of MTX resistance in many tumor types. Heavy promoter methylation was previously identified as a basis for the complete silencing of RFC in MDA-MB-231 breast cancer cells, its role and prevalence in RFC transcription regulation are, however, not widely studied. Methods In the current study, RFC promoter methylation was assessed using methylation specific PCR in a panel of malignant cell lines (n = 8), including MDA-MB-231, and M805, a MTX resistant cell line directly established from the specimen of a patient with malignant fibrohistocytoma, whom received multiple doses of MTX. A quantitative approach of real-time PCR for measuring the extent of RFC promoter methylation was developed, and was validated by direct bisulfite genomic sequencing. RFC mRNA levels were determined by quantitative real-time RT-PCR and were related to the extent of promoter methylation in these cell lines. Results A partial promoter methylation and RFC mRNA down-regulation were observed in M805. Using the quantitative approach, a reverse correlation (correlation coefficient = -0.59, p < 0.05) was identified between the promoter methylation and RFC mRNA levels in this a panel of malignant cell lines. Conclusion This study further suggests that promoter methylation is a potential basis for MTX resistance. The quantitative correlation identified in this study implies that promoter methylation is possibly a mechanism involved in the fine regulation of RFC transcription.
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11
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Jansen G, Pieters R. The role of impaired transport in (pre)clinical resistance to methotrexate: insights on new antifolates. Drug Resist Updat 2007; 1:211-8. [PMID: 17092808 DOI: 10.1016/s1368-7646(98)80042-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/1997] [Revised: 01/20/1998] [Accepted: 01/20/1998] [Indexed: 11/17/2022]
Abstract
Impaired transport appears to be a common mechanism of resistance of neoplastic cells to the antifolate methotrexate. The extensive knowledge of the molecular, biochemical and functional properties of the membrane transport systems for folates, in particular the reduced folate carrier (RFC) and membrane folate receptors (MFR), has made an important contribution to the rational design of novel antifolates that are either more efficiently internalized via these transporters or can simply bypass these transport routes. The current status of exploiting the RFC and MFR for transport of novel antifolates active in preclinical model systems and a clinical setting will be reviewed, with a special reference to childhood acute lymphoblastic leukemia (ALL) and acute non-lymphoblastic leukemia (ANLL).
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Affiliation(s)
- G Jansen
- Department of Medical Oncology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
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12
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Abstract
Folates play a key role in one-carbon metabolism essential for the biosynthesis of purines, thymidylate and hence DNA replication. The antifolate methotrexate has been rationally-designed nearly 60 years ago to potently block the folate-dependent enzyme dihydrofolate reductase (DHFR) thereby achieving temporary remissions in childhood acute leukemia. Recently, the novel antifolates raltitrexed and pemetrexed that target thymidylate synthase (TS) and glycineamide ribonucleotide transformylase (GARTF) were introduced for the treatment of colorectal cancer and malignant pleural mesothelioma. (Anti)folates are divalent anions which predominantly use the reduced folate carrier (RFC) for their cellular uptake. (Anti)folates are retained intracellularly via polyglutamylation catalyzed by folylpoly-gamma-glutamate synthetase (FPGS). As the intracellular concentration of antifolates is critical for their pharmacologic activity, polyglutamylation is a key determinant of antifolate cytotoxicity. However, anticancer drug resistance phenomena pose major obstacles towards curative cancer chemotherapy. Pre-clinical and clinical studies have identified a plethora of mechanisms of antifolate-resistance; these are frequently associated with qualitative and/or quantitative alterations in influx and/or efflux transporters of (anti)folates as well as in folate-dependent enzymes. These include inactivating mutations and/or down-regulation of the RFC and various alterations in the target enzymes DHFR, TS and FPGS. Furthermore, it has been recently shown that members of the ATP-binding cassette (ABC) superfamily including multidrug resistance proteins (MRP/ABCC) and breast cancer resistance protein (BCRP/ABCG2) are low affinity, high capacity ATP-driven (anti)folate efflux transporters. This transport activity is in addition to their established facility to extrude multiple cytotoxic agents. Hence, by actively extruding antifolates, overexpressed MRPs and/or BCRP confer antifolate resistance. Moreover, down-regulation of MRPs and/or BCRP results in decreased folate efflux thereby leading to expansion of the intracellular folate pool and antifolate resistance. This chapter reviews and discusses the panoply of molecular modalities of antifolate-resistance in pre-clinical tumor cell systems in vitro and in vivo as well as in cancer patients. Currently emerging novel strategies for the overcoming of antifolate-resistance are presented. Finally, experimental evidence is provided that the identification and characterization of the molecular mechanisms of antifolate-resistance may prove instrumental in the future development of rationally-based novel antifolates and strategies that could conceivably overcome drug-resistance phenomena.
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Affiliation(s)
- Yehuda G Assaraf
- The Fred Wyszkowski Cancer Research Laboratory, Department of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel.
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13
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Yen WC, Lamph WW. The selective retinoid X receptor agonist bexarotene (LGD1069, Targretin) prevents and overcomes multidrug resistance in advanced breast carcinoma. Mol Cancer Ther 2005; 4:824-34. [PMID: 15897247 DOI: 10.1158/1535-7163.mct-05-0018] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Acquired drug resistance represents a major challenge in the therapeutic management of breast cancer patients. We reported previously that the retinoid X receptor-selective agonist bexarotene (LGD1069, Targretin) was efficacious in treating animal models of tamoxifen-resistant breast cancer. The goal of this study was to evaluate the effect of bexarotene on development of acquired drug resistance and its role in overcoming acquired drug resistance in advanced breast cancer. Paclitaxel, doxorubicin, and cisplatin were chosen as model compounds to determine the effect of bexarotene on the development of acquired drug resistance. Human breast cancer cells MDA-MB-231 were repeatedly treated in culture with a given therapeutic agent with or without bexarotene for 3 months. Thereafter, cells were isolated and characterized for their drug sensitivity. Compared with parental cells, cells treated with a single therapeutic agent became resistant to the therapeutic agent, whereas cells treated with the bexarotene combination remained chemosensitive. Cells with acquired drug resistance, when treated with the combination, showed increased sensitivity to the cytotoxic agent. Furthermore, cells treated with the combination regimen had reduced invasiveness and angiogenic potential than their resistant counterparts. These in vitro findings were further confirmed in an in vivo MDA-MB-231 xenograft model. Our results suggest a role for bexarotene in combination with chemotherapeutic agents in prevention and overcoming acquired drug resistance in advanced breast carcinoma.
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Affiliation(s)
- Wan-Ching Yen
- Department of Molecular Oncology, Ligand Pharmaceuticals, Inc., 10275 Science Center Drive, San Diego, CA 92121, USA
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14
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Zhao R, Zhang S, Hanscom M, Chattopadhyay S, Goldman ID. Loss of Reduced Folate Carrier Function and Folate Depletion Result in Enhanced Pemetrexed Inhibition of Purine Synthesis. Clin Cancer Res 2005. [DOI: 10.1158/1078-0432.1294.11.3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Abstract
Pemetrexed is a novel antifolate with polyglutamate derivatives that are potent inhibitors of thymidylate synthase (TS) and to a lesser extent glycinamide ribonucleotide formyltransferase (GARFT). Conditions that might modulate relative suppression of these sites were assessed by the pattern of hypoxanthine and thymidine protection. When grown with 25 nmol/L racemic 5-formyltetrahydrofolate, thymidine alone fully protected wild-type HeLa cells to at least 1 μmol/L pemetrexed, but protection of a reduced folate carrier (RFC)-null subline required both thymidine and hypoxanthine above a concentration of 30 nmol/L pemetrexed. As medium 5-formyltetrahydrofolate was decreased, protection by thymidine alone decreased, and was further diminished when HeLa cells were grown in dialyzed serum. There was little protection by thymidine of RFC-null HeLa cells under the latter conditions. Thymidine alone was not protective, and hypoxanthine alone produced only a small (2-fold) increase in IC50, in a HeLa-derived line 8-fold resistant to pemetrexed due to a modest increase in TS. Finally, in MCF-7 breast cancer cells there was greater protection with thymidine alone than in HeLa cells when cells were grown in medium containing a low concentration of 5-formyltetrahydrofolate. These observations indicate that as intracellular folates decrease in HeLa cells, due to decreased extracellular reduced folate, or loss of RFC function, pemetrexed inhibition of GARFT increases. These data support the concept that the contribution to pemetrexed activity by inhibition of GARFT, particularly at low folate levels, is a contributing factor to drug activity but relative inhibition of TS and GARFT may vary among human tumors and cell lines.
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Affiliation(s)
- Rongbao Zhao
- Departments of Medicine and Molecular Pharmacology, the Albert Einstein College of Medicine and Cancer Research Center, Bronx, New York
| | - Shubing Zhang
- Departments of Medicine and Molecular Pharmacology, the Albert Einstein College of Medicine and Cancer Research Center, Bronx, New York
| | - Marie Hanscom
- Departments of Medicine and Molecular Pharmacology, the Albert Einstein College of Medicine and Cancer Research Center, Bronx, New York
| | - Shrikanta Chattopadhyay
- Departments of Medicine and Molecular Pharmacology, the Albert Einstein College of Medicine and Cancer Research Center, Bronx, New York
| | - I. David Goldman
- Departments of Medicine and Molecular Pharmacology, the Albert Einstein College of Medicine and Cancer Research Center, Bronx, New York
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15
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Holbeck SL. Update on NCI in vitro drug screen utilities. Eur J Cancer 2004; 40:785-93. [PMID: 15120034 DOI: 10.1016/j.ejca.2003.11.022] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2003] [Revised: 10/20/2003] [Accepted: 11/17/2003] [Indexed: 11/19/2022]
Abstract
Development of new anti-cancer drugs is a costly and risky proposition. The Developmental Therapeutics Program (DTP) of the National Cancer Institutes of the United States (U.S.) facilitates the drug development process by providing access to preclinical screening services. Since the early 1990's, DTP has screened tens of thousands of compounds against a panel of 60 human tumour cell lines representing nine tissue sites. At the same time, DTP began to accumulate information on the expression of molecular entities in the same 60 cell line panel. Many of these data are freely available to the public at. More recently, additional, more focused screens have entered the picture, with data also available through the web site. These include screening of roughly 100000 compounds against a panel of yeast mutants, and screening of the NCI Diversity Set in assays designed to detect effects on Molecular Targets of interest.
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Affiliation(s)
- S L Holbeck
- National Cancer Institute, Developmental Therapeutics Program, Information Technology Branch, Rockville, MD 20892-7444, USA.
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16
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Serra M, Reverter-Branchat G, Maurici D, Benini S, Shen JN, Chano T, Hattinger CM, Manara MC, Pasello M, Scotlandi K, Picci P. Analysis of dihydrofolate reductase and reduced folate carrier gene status in relation to methotrexate resistance in osteosarcoma cells. Ann Oncol 2004; 15:151-60. [PMID: 14679136 DOI: 10.1093/annonc/mdh004] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND To evaluate the impact of dihydrofolate reductase (DHFR) and reduced folate carrier (RFC) genes on methotrexate (MTX) resistance in osteosarcoma cells in relation to retinoblastoma (RB1) gene status. MATERIALS AND METHODS A series of human osteosarcoma cell lines-either sensitive or resistant to MTX-and 16 osteosarcoma tumour samples were used in this study. RESULTS In U-2OS MTX-resistant variants, and in other RB1-positive cell lines, MTX resistance was associated with increased levels of DHFR and with a slight decrease of RFC gene expression. In Saos-2 MTX-resistant variants, and in another RB1-negative cell line, development of MTX resistance was associated with a decrease in expression of RFC, without any significant involvement of DHFR. In osteosarcoma clinical samples, amplification of the DHFR gene at clinical onset appeared to be more frequent in RB1-positive compared with RB1-negative tumours. CONCLUSIONS Amplification of the DHFR gene may occur more frequently in the presence of RB1-mediated negative regulation of its activity and can be present at clinical onset in osteosarcoma patients. Simultaneous evaluation of RFC, DHFR and RB1 gene status at the time of diagnosis may become the basis for the identification of potentially MTX-unresponsive osteosarcoma patients, who could benefit from treatment protocols with alternative antifolate drugs.
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Affiliation(s)
- M Serra
- Laboratorio di Ricerca Oncologica, Istituti Ortopedici Rizzoli, Bologna, Italy.
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17
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Levy AS, Sather HN, Steinherz PG, Sowers R, La M, Moscow JA, Gaynon PS, Uckun FM, Bertino JR, Gorlick R. Reduced folate carrier and dihydrofolate reductase expression in acute lymphocytic leukemia may predict outcome: a Children's Cancer Group Study. J Pediatr Hematol Oncol 2003; 25:688-95. [PMID: 12972803 DOI: 10.1097/00043426-200309000-00004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Methotrexate is a major component of current treatment regimens for children with acute lymphocytic leukemia (ALL). Potential mechanisms of methotrexate resistance include impaired drug uptake, decreased drug retention, and dihydrofolate reductase (DHFR) amplification. The purpose of this study was to assess whether reduced folate carrier (RFC) and DHFR expression in untreated leukemic blasts correlated with outcome. METHODS Quantitative real-time RT-PCR was used to measure RFC and DHFR mRNA expression in leukemic blasts from 40 newly diagnosed patients with ALL obtained in a blinded fashion from Children's Cancer Group studies. RESULTS Low RFC expression at diagnosis correlated significantly with an unfavorable event free survival. Surprisingly, low, not high, DHFR expression correlated significantly with an unfavorable event-free survival. Proliferative cell nuclear antigen (PCNA) expression demonstrated a weak inverse relationship between sample PCNA and DHFR or RFC expression, suggesting that DHFR and RFC expression may be markers for factors other than drug resistance. CONCLUSIONS These results suggest that impaired transport may be an important mechanism of intrinsic methotrexate resistance in ALL, and DHFR expression also may be an important prognostic factor in ALL. Additional studies are necessary to clarify the mechanism for the correlation of low DHFR expression with poor outcome.
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Affiliation(s)
- Adam S Levy
- Department of Pediatrics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
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18
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Belzile JP, Karatzas A, Shiu HY, Létourneau S, Palerme JS, Cournoyer D. Increased resistance to nitrogen mustards and antifolates following in vitro selection of murine fibroblasts and primary hematopoietic cells transduced with a bicistronic retroviral vector expressing the rat glutathione S-transferase A3 and a mutant dihydrofolate reductase. Cancer Gene Ther 2003; 10:637-46. [PMID: 12872145 DOI: 10.1038/sj.cgt.7700619] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have constructed a retroviral bicistronic vector, MFG/GID, that transduces the expression of both the A3 isoform of the rat glutathione S-transferase (GST A3), and the tyr-22 variant of the human dihydrofolate reductase (DHFR(L22Y)). Transduction of murine 3T3 fibroblasts with this vector increased their in vitro resistance to chlorambucil (1.8-fold) and trimetrexate (TMTX) (748-fold). TMTX selection of a mixed population of 20% GID-transduced NIH 3T3 cells and 80% control cells resulted in a marked increase in the GST peroxidase activity associated with the GST A3 isoform (17.7-fold). MFG/GID-transduced primary clonogenic murine hematopoietic progenitor cells were likewise more resistant to TMTX and chlorambucil than control beta-gal-transduced cells. Selecting GID-transduced hematopoietic cells with a combination of TMTX and a nucleoside transport inhibitor resulted in a marked increase in resistance upon re-exposure to TMTX (99% survival). Similarly, GID-transduced hematopoietic cells selected with TMTX were more resistant to chlorambucil, with 40% survival at a drug concentration that killed practically all control cells. These results suggest that antifolate-mediated selection of MFG/GID-transduced hematopoietic cells could be used as a mean to enrich the population of transduced cells prior to or following transplantation, thus potentially conferring in vivo chemoprotection to nitrogen mustards and antifolates.
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Affiliation(s)
- Jean-Philippe Belzile
- Department of Human Genetics, Montreal General Hospital and Research Institute, McGill University, Montreal, Quebec, Canada.
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19
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Oyewumi MO, Liu S, Moscow JA, Mumper RJ. Specific association of thiamine-coated gadolinium nanoparticles with human breast cancer cells expressing thiamine transporters. Bioconjug Chem 2003; 14:404-11. [PMID: 12643751 DOI: 10.1021/bc0340013] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Thiamine (vitamin B(1)) was investigated as a tumor-specific ligand for gadolinium nanoparticles. Solid nanoparticles containing gadolinium hexanedione (1.5 mg/mL) were engineered from oil-in-water microemulsion templates and coated with thiamine ligands. Thiamine ligands were synthesized by conjugating thiamine to either distearoylphosphatidylethanolamine (DSPE) or fluorescein via a poly(ethylene glycol) (PEG) spacer (Mw 3350). The efficiency of thiamine ligand attachment to nanoparticles was evaluated using gel permeation chromatography (GPC). Cell association studies were carried using a methotrexate-resistant breast cancer cell line, MTX(R)ZR75, transfected with thiamine transporter genes (THTR1 and THTR2). Thiamine-coated nanoparticle association with THTR1 and THTR2 cells was significantly greater than that with control breast cancer cells (MTX(R)ZR75 transfected with the empty expression vector pREP4) (p < 0.01; t-test). The nanoparticle cell association was significantly dependent on the extent of thiamine ligand coating on nanoparticles, expression of thiamine transporters in cells, temperature of incubation, and the concentration of competitive inhibitor (free thiamine). Further studies are warranted to assess the potential of the engineered thiamine-coated gadolinium (Gd) nanoparticles in neutron capture therapy of tumors.
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Affiliation(s)
- Moses O Oyewumi
- Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington 40536-0082, USA
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20
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Laverdière C, Chiasson S, Costea I, Moghrabi A, Krajinovic M. Polymorphism G80A in the reduced folate carrier gene and its relationship to methotrexate plasma levels and outcome of childhood acute lymphoblastic leukemia. Blood 2002; 100:3832-4. [PMID: 12411325 DOI: 10.1182/blood.v100.10.3832] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methotrexate (MTX) is a key compound of chemotherapeutic regimens used in the treatment of childhood acute lymphoblastic leukemia (ALL). Resistance to this drug may arise by, among other factors, altered cellular uptake that may hamper the efficacy of the treatment. Recently, a G(80)A polymorphism has been described in the reduced folate carrier gene (RFC1), which encodes the major MTX transporter. Here, we assessed the association between the genetic polymorphisms G(80)A and both MTX plasma levels and childhood ALL outcome. Children with the A(80) variant had worse prognoses than patients with the GG genotype (P =.04), as shown by event-free survival estimates. Patients homozygous for A(80) had higher levels of MTX (P =.004) than the other genotype groups. Possible explanations for observed associations are discussed; however, additional experiments are required to achieve understanding of the underlying mechanism.
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21
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Gong S, Lu X, Xu Y, Swiderski CF, Jordan CT, Moscow JA. Identification of OCT6 as a novel organic cation transporter preferentially expressed in hematopoietic cells and leukemias. Exp Hematol 2002; 30:1162-9. [PMID: 12384147 DOI: 10.1016/s0301-472x(02)00901-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Human organic cation transporters (OCTs) play a critical role in the cellular uptake and efflux of endogenous cationic substrates and hydrophilic exogenous xenobiotics. We sought to identify OCT genes preferentially expressed in hematopoietic cells. MATERIALS AND METHODS We isolated a novel OCT, named OCT6, by data-mining human expressed sequence tag databases for sequences homologous to known OCT genes. We developed a quantitative reverse transcriptase polymerase chain reaction assay to determine the relative expression of this gene in 50 cancer cell lines and in tissues. RESULTS The two highest expressing cell lines were the leukemia cell lines HL-60 and MOLT4. Quantitative reverse transcriptase polymerase chain reaction analysis using a normal tissue cDNA panel demonstrated that this transport gene is highly expressed in testis and fetal liver, with detectable RNA levels in bone marrow and peripheral blood leukocytes. Unlike other OCT genes, RNA levels were not detectable in placenta, liver, or kidney. To further define the expression of OCT6 in hematopoietic tissues, we measured OCT6 RNA levels in sorted peripheral blood cell populations and found a clear enrichment of OCT6-expressing cells in purified CD34(+) cells. To determine if OCT6 was highly expressed in leukemias, we examined circulating leukemia cells from 25 patients and found high levels of OCT6 RNA in all specimens in comparison with liver, kidney, and placenta. CONCLUSIONS The results demonstrate the existence of a novel OCT preferentially expressed in human hematopoietic tissues, including CD34(+) cells and leukemia cells. Its narrow tissue distribution, potential for substrate specificity, and close homology to other cell membrane transporters make OCT6 an attractive target for the treatment of leukemia.
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Affiliation(s)
- Shimei Gong
- Department of Pediatrics, University of Kentucky, Lexington, KY 40536, USA
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22
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Liu S, Song L, Bevins R, Birhiray O, Moscow JA. The murine-reduced folate carrier gene can act as a selectable marker and a suicide gene in hematopoietic cells in vivo. Hum Gene Ther 2002; 13:1777-82. [PMID: 12396629 DOI: 10.1089/104303402760293600] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Increased expression of the reduced folate carrier confers sensitivity to the antifolate drug methotrexate because it results in increased cellular uptake of this drug, and increased resistance to trimetrexate, a lipid-soluble antifolate drug, because it enables cells to take up exogenous folates that rescue cells from antifolate cytotoxicity. We therefore hypothesized that the reduced folate carrier could act as a suicide gene after treatment with methotrexate and as a selectable marker after exposure to trimetrexate. To test this hypothesis, we constructed replication-defective retroviruses containing the murine-reduced folate carrier (mRFC). Murine bone marrow cells transduced with the mRFC-containing retrovirus showed increased sensitivity to methotrexate and increased resistance to trimetrexate compared to empty vector-transduced controls in colony forming assays. Furthermore, colonies surviving trimetrexate and methotrexate treatment showed an enrichment of the mRFC gene after exposure to trimetrexate and a decrease after exposure to methotrexate. Lethally irradiated mice transplanted with bone marrow cells transduced with the mRFC-retrovirus and treated with the antifolate drugs after hematopoietic recovery demonstrated a relative increase in the number of cells containing the mRFC transgene after trimetrexate treatment and a decrease after methotrexate treatment. Therefore, these studies demonstrate the potential of the reduced folate carrier gene to play a dual role in gene therapy applications.
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Affiliation(s)
- Shuqian Liu
- Department of Pediatrics, University of Kentucky, Lexington, KY 40536, USA
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23
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Lu X, Gong S, Monks A, Zaharevitz D, Moscow JA. Correlation of nucleoside and nucleobase transporter gene expression with antimetabolite drug cytotoxicity. JOURNAL OF EXPERIMENTAL THERAPEUTICS AND ONCOLOGY 2002; 2:200-12. [PMID: 12416024 DOI: 10.1046/j.1359-4117.2002.01035.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Antimetabolite drugs that inhibit nucleic acid metabolism are widely used in cancer chemotherapy. Nucleoside and nucleobase transporters are important for the cellular uptake of nucleic acids and their corresponding anticancer analogue drugs. Thus, these transporters may play a role both in antimetabolite drug sensitivity, by mediating the uptake of nucleoside analogues, and in antimetabolite drug resistance, by mediating the uptake of endogenous nucleosides that may rescue cells from toxicity. Therefore, we examined the relation of the expression of nucleoside and nucleobase transporters to antimetabolite cytotoxicity. We measured the RNA levels of all eight known nucleoside and nucleobase transporters in 50 cell lines included in the National Cancer Institute's Anticancer Drug Screen panel. RNA levels of concentrative nucleoside transporters (CNTs), equilibrative nucleoside transporters (ENTs) and nucleobase transporters (NCBTs) were determined by quantitative RT-PCR using real-time fluorescence acquisition. This method was validated by measuring the expression of the MDR1 gene, and correlating our results with independently determined measurements of MDR1 RNA levels and protein function in these cell lines. We then correlated the pattern of RNA levels to the pattern of cytotoxicity of anticancer drugs in the NCI drug screen database using the COMPARE analysis. Several hypothesized relations between transporter gene expression and cytotoxicity, based upon known interactions between certain nucleoside analogues and transporter proteins, were not observed, suggesting that expression of individual transporters may not be a significant determinant of the cytotoxicity of these drugs. The most closely correlated drug cytotoxicity patterns to transporter gene expression patterns (where increased expression corresponds to increase sensitivity) included those between CNT1 and O6-methylguanine and between ENT2 and hydroxyurea. We also observed that p53 status influenced correlations between ENT1 transporter gene RNA levels and sensitivity to the drugs tiazafurin, AZQ and 3-deazauridine. One of three drugs identified by correlation of cytotoxicity patterns with ENT1 RNA levels, 3-deazauridine, inhibited uptake of the classic ENT1 substrate uridine, demonstrating a physical interaction between an identified drug and the transporter. These studies demonstrate that it is possible to correlate genetic information to functional databases to determine the influence of transport gene expression on drug sensitivity and to identify transporter-drug interactions.
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Affiliation(s)
- Xin Lu
- Division of Hematology and Oncology, Department of Pediatrics, University of Kentucky, Lexington, Kentucky 40536, USA
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24
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Worm J, Kirkin AF, Dzhandzhugazyan KN, Guldberg P. Methylation-dependent silencing of the reduced folate carrier gene in inherently methotrexate-resistant human breast cancer cells. J Biol Chem 2001; 276:39990-40000. [PMID: 11509559 DOI: 10.1074/jbc.m103181200] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular basis of methotrexate resistance was studied in human MDA-MB-231 breast cancer cells, which are inherently defective in methotrexate uptake and lack expression of the reduced folate carrier (RFC). Transfection of MDA-MB-231 cells with RFC cDNA restored methotrexate uptake and increased methotrexate sensitivity by approximately 50-fold. A CpG island in the promoter region of RFC was found to be methylated in MDA-MB-231 cells, but was unmethylated in RFC expressing, methotrexate-sensitive MCF-7 breast cancer cells. Chromatin immunoprecipitation with antibodies against acetylated histones H3 and H4 showed that the RFC promoter was enriched for acetylated histones on expressed, unmethylated alleles only. Treatment of MDA-MB-231 cells with 5-aza-2'-deoxycytidine restored RFC expression but also led to increased methotrexate efflux and did not reverse methotrexate resistance. This suggests that 5-aza-2'-deoxycytidine up-regulates both methotrexate uptake and some methotrexate-resistance mechanism(s). Reverse transcription-polymerase chain reaction analysis showed increased expression levels of several ATP-dependent efflux pumps in response to 5-aza-2'-deoxycytidine treatment, including P-glycoprotein and members of the multidrug resistance-associated protein family. Up-regulation of P-glycoprotein in response to 5-aza-2'-deoxycytidine was associated with demethylation of a CpG island in the MDR1 promoter, whereas the mechanism(s) for 5-aza-2'-deoxycytidine-induced up-regulation of multidrug resistance-associated proteins is probably indirect. Dipyridamole inhibited methotrexate efflux and reversed methotrexate resistance in 5-aza-2'-deoxycytidine-treated MDA-MB-231 cells.
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Affiliation(s)
- J Worm
- Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
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Ma D, Huang H, Moscow JA. Down-regulation of reduced folate carrier gene (RFC1) expression after exposure to methotrexate in ZR-75-1 breast cancer cells. Biochem Biophys Res Commun 2000; 279:891-7. [PMID: 11162445 DOI: 10.1006/bbrc.2000.4019] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Methotrexate (MTX) is administered in intervals of one week or longer in the treatment of cancer and autoimmune disease. Early studies suggested that daily MTX administration was associated with decreased effectiveness and increased toxicity, leading to schedules of administration that include periodic intervals of rest during chronic MTX therapy. We hypothesized that these observations may be the result of the down-regulation of the reduced folate carrier, the major route of cellular uptake of both MTX and the endogenous folates, after MTX exposure. We exposed folate-depleted ZR-75-1 breast cancer cells to low-dose MTX in the presence of hypoxanthine, adenosine and thymidine. After 72 h, the initial rate of MTX uptake had decreased to 22% of the Day 0 value. Western blot analysis showed down-regulation of RFC1 protein expression, and Northern blot analysis showed a corresponding decrease in RFC1 RNA levels. Using an RT-PCR assay, we found that levels of RNA transcripts containing each of the three RFC1 5' noncoding exons were decreased after exposure to MTX, suggesting that MTX exposure causes transcriptional down-regulation of RFC1. Promoter-reporter construct assays demonstrated decreased activity of RFC1 promoter elements upstream of these exons after MTX exposure. Preexposure of the ZR-75-1 cells to 5-azacytidine, a DNA methylation inhibitor, further decreased MTX uptake rather than reverse the inhibition of RFC1 activity, indicating that RFC1 down-regulation after MTX exposure is not the result of methylation of the RFC1 promoter. In summary, these studies demonstrate that MTX exposure can down-regulate RFC1 expression and activity. These acute, inducible, epigenetic changes in RFC1 expression may ultimately be molded into the more permanent genetic changes that result in the transport-mediated MTX resistance that have been observed in MTX-resistant cell lines.
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Affiliation(s)
- D Ma
- Department of Pediatrics, University of Kentucky, Lexington 40502, USA
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Kelland LR, Sharp SY, Rogers PM, Myers TG, Workman P. DT-Diaphorase expression and tumor cell sensitivity to 17-allylamino, 17-demethoxygeldanamycin, an inhibitor of heat shock protein 90. J Natl Cancer Inst 1999; 91:1940-9. [PMID: 10564678 DOI: 10.1093/jnci/91.22.1940] [Citation(s) in RCA: 293] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND To our knowledge, 17-allylamino,17-demethoxygeldanamycin (17AAG) is the first inhibitor of heat shock protein 90 (Hsp90) to enter a phase I clinical trial in cancer. Inhibition of Hsp90, a chaperone protein (a protein that helps other proteins avoid misfolding pathways that produce inactive or aggregated states), leads to depletion of important oncogenic proteins, including Raf-1 and mutant p53 (also known as TP53). Given its ansamycin benzoquinone structure, we questioned whether the antitumor activity of 17AAG was affected by expression of the NQO1 gene, which encodes the quinone-metabolizing enzyme DT-diaphorase. METHODS The antitumor activity of 17AAG and other Hsp90 inhibitors was determined by use of a sulforhodamine B-based cell growth inhibition assay in culture and by the arrest of xenograft tumor growth in nude mice. DT-diaphorase activity was determined by use of a spectrophotometric assay, and protein expression was determined by means of western immunoblotting. RESULTS In two independent in vitro human tumor cell panels, we observed a positive relationship between DT-diaphorase expression level and growth inhibition by 17AAG. Stable, high-level expression of the active NQO1 gene transfected into the DT-diaphorase-deficient (by NQO1 mutation) BE human colon carcinoma cell line resulted in a 32-fold increase in 17AAG growth-inhibition activity. Increased sensitivity to 17AAG in the transfected cell line was also confirmed in xenografts. The extent of depletion of Raf-1 and mutant p53 protein confirmed that the Hsp90 inhibition mechanism was maintained in cells with high and low levels of DT-diaphorase. 17AAG was shown to be a substrate for purified human DT-diaphorase. CONCLUSION These results suggest that the antitumor activity and possibly the toxicologic properties of 17AAG in humans may be influenced by the expression of DT-diaphorase. Careful monitoring for NQO1 polymorphism and the level of tumor DT-diaphorase activity is therefore recommended in clinical trials with 17AAG.
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Affiliation(s)
- L R Kelland
- L. R. Kelland, S. Y. Sharp, P. M. Rogers, P. Workman, Cancer Research Campaign Centre for Cancer Therapeutics, The Institute of Cancer Research, Surrey, U.K
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Ouellette M, Leblanc E, Kündig C, Papadopoulou B. Antifolate resistance mechanisms from bacteria to cancer cells with emphasis on parasites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 456:99-113. [PMID: 10549365 DOI: 10.1007/978-1-4615-4897-3_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- M Ouellette
- Département de Microbiologie, Université Laval, Québec, Canada
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Gong M, Cowan KH, Gudas J, Moscow JA. Isolation and characterization of genomic sequences involved in the regulation of the human reduced folate carrier gene (RFC1). Gene 1999; 233:21-31. [PMID: 10375617 DOI: 10.1016/s0378-1119(99)00166-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Decreased reduced folate carrier (RFC) activity has been associated with MTX resistance in experimental models of transport-mediated MTX resistance, and has been attributed to changes in the expression of RFC1, the gene that encodes a protein with this activity. RNA transcripts of RFC1 may contain any one of four distinct 5' untranslated regions (UTRs). We cloned a human genomic DNA fragment upstream from the RFC1 translation start site and determined the nucleotide sequence of a 4.8kb region that contained the exons corresponding to each of the reported UTRs. To identify regulatory elements that may be involved in RFC1 transcription, we first developed a semi-quantitative RT-PCR assay using primers specific for each of the 5' UTRs to amplify RNA transcripts containing each of the RFC1 5' exons, and found evidence for differential transcription of RFC1 non-coding exons in tissues, during development, and in MTX-resistant, transport-deficient cells. We also found that RFC1 RNA levels are cell cycle regulated and peak at the G1 to S transition. Then, using a series of RFC1 promoter-reporter fusion constructs, we identified genomic sequences that may be involved in the regulation of expression of exons 1b and 1c of the RFC1 gene. These studies therefore identify regulatory regions of RFC1 promoters and potential models of regulation in which these regions may exert control.
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Affiliation(s)
- M Gong
- Medical Breast Cancer Section, Medicine Branch, NCI, Bethesda, MD 20892, USA
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Reduced Folate Carrier Expression in Acute Lymphoblastic Leukemia: A Mechanism for Ploidy but not Lineage Differences in Methotrexate Accumulation. Blood 1999. [DOI: 10.1182/blood.v93.5.1643.405k06_1643_1650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methotrexate (MTX) is one of the most active and widely used agents for the treatment of acute lymphoblastic leukemia (ALL). To elucidate the mechanism for higher accumulation of MTX polyglutamates (MTX-PG) in hyperdiploid ALL and lower accumulation in T-lineage ALL, expression of the reduced folate carrier (RFC) was assessed by reverse transcription-polymerase chain reaction in ALL blasts isolated from newly diagnosed patients. RFC expression exhibited a 60-fold range among 29 children, with significantly higher expression in hyperdiploid B-lineage ALL (median, 11.3) compared with nonhyperdiploid ALL (median, 2.1; P < .0006), but no significant difference between nonhyperdiploid B-lineage and T-lineage ALL. Furthermore, mRNA levels of RFC (mapped by FISH to chromosome 21) were significantly related to chromosome 21 copy number (P = .0013), with the highest expression in hyperdiploid ALL blasts with 4 copies of chromosome 21. To assess the functional significance of gene copy number, MTX-PG accumulation was compared in ALL blasts isolated from 121 patients treated with either low-dose MTX (LDMTX; n = 60) or high-dose MTX (HDMTX; n = 61). After LDMTX, MTX-PG accumulation was highest in hyperdiploid B-lineage ALL with 4 copies of chromosome 21 (P = .011), but MTX-PG accumulation was not significantly related to chromosome 21 copy number after HDMTX (P = .24). These data show higher RFC expression as a mechanism for greater MTX accumulation in hyperdiploid B-lineage ALL and indicate that lineage differences in MTX-PG accumulation are not due to lower RFC expression in T-lineage ALL.
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Reduced Folate Carrier Expression in Acute Lymphoblastic Leukemia: A Mechanism for Ploidy but not Lineage Differences in Methotrexate Accumulation. Blood 1999. [DOI: 10.1182/blood.v93.5.1643] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractMethotrexate (MTX) is one of the most active and widely used agents for the treatment of acute lymphoblastic leukemia (ALL). To elucidate the mechanism for higher accumulation of MTX polyglutamates (MTX-PG) in hyperdiploid ALL and lower accumulation in T-lineage ALL, expression of the reduced folate carrier (RFC) was assessed by reverse transcription-polymerase chain reaction in ALL blasts isolated from newly diagnosed patients. RFC expression exhibited a 60-fold range among 29 children, with significantly higher expression in hyperdiploid B-lineage ALL (median, 11.3) compared with nonhyperdiploid ALL (median, 2.1; P < .0006), but no significant difference between nonhyperdiploid B-lineage and T-lineage ALL. Furthermore, mRNA levels of RFC (mapped by FISH to chromosome 21) were significantly related to chromosome 21 copy number (P = .0013), with the highest expression in hyperdiploid ALL blasts with 4 copies of chromosome 21. To assess the functional significance of gene copy number, MTX-PG accumulation was compared in ALL blasts isolated from 121 patients treated with either low-dose MTX (LDMTX; n = 60) or high-dose MTX (HDMTX; n = 61). After LDMTX, MTX-PG accumulation was highest in hyperdiploid B-lineage ALL with 4 copies of chromosome 21 (P = .011), but MTX-PG accumulation was not significantly related to chromosome 21 copy number after HDMTX (P = .24). These data show higher RFC expression as a mechanism for greater MTX accumulation in hyperdiploid B-lineage ALL and indicate that lineage differences in MTX-PG accumulation are not due to lower RFC expression in T-lineage ALL.
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Rosowsky A, Wright JE, Vaidya CM, Bader H, Forsch RA, Mota CE, Pardo J, Chen CS, Chen YN. Synthesis and potent antifolate activity and cytotoxicity of B-ring deaza analogues of the nonpolyglutamatable dihydrofolate reductase inhibitor Nalpha-(4-amino-4-deoxypteroyl)-Ndelta-hemiphthaloyl- L-ornithine (PT523). J Med Chem 1998; 41:5310-9. [PMID: 9857098 DOI: 10.1021/jm980477+] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Six new B-ring analogues of the nonpolyglutamatable antifolate Nalpha-(4-amino-4-deoxypteroyl)-Ndelta-hemiphthaloy l-L-ornithine (PT523, 3) were synthesized with a view to determining the effect of modifications at the 5- and/or 8-position on dihydrofolate reductase (DHFR) binding and tumor cell growth inhibition. The 5- and 8-deaza analogues were prepared from methyl 2-L-amino-5-phthalimidopentanoate and 4-amino-4-deoxy-N10-formyl-5-deaza- and -8-deazapteroic acid, respectively. The 5,8-dideaza analogues were prepared from methyl 2-L-[(4-aminobenzoyl)amino]-5-phthalimidopentanoate and 2, 4-diaminoquinazoline-6-carbonitriles. The Ki for inhibition of human DHFR by the 5-deaza and 5-methyl-5-deaza analogues was about the same as that of 3 (0.35 pM), 11-fold lower than that of aminopterin (AMT, 1), and 15-fold lower than that of methotrexate (MTX, 2). However the Ki of the 8-deaza analogue was 27-fold lower than that of 1, and that of the 5,8-dideaza, 5-methyl-5,8-dideaza, and 5-chloro-5,8-dideaza analogues was approximately 50-fold lower. This trend was consistent with the published literature on the corresponding DHFR inhibitors with a glutamate side chain. In colony formation assays against the human head and neck squamous carcinoma cell line SCC25 after 72 h of treatment, the 5- and 8-deaza analogues were approximately as potent as 3, whereas the 5,8-dideaza analogue was 3 times more potent. 5-Methyl and 5-chloro substitution was also favorable, with the 5-methyl-5-deaza analogue being 2. 5-fold more potent than the 5-deaza analogue. However the effect of 5-methyl substitution was less pronounced in the 5,8-dideaza analogues than in the 5-deaza analogues. The 5-chloro-5,8-dideaza analogue of 3 was the most active member of the series, with an IC50 = 0.33 nM versus 1.8 nM for 3 and 15 nM for MTX. The 5-methyl-5-deaza analogue of 3 was also tested at the National Cancer Institute against a panel of 50 human tumor cell lines in culture and was consistently more potent than 3, with IC50 values in the low-nanomolar to subnanomolar range against most of the tumors. Leukemia and colorectal carcinoma cell lines were generally most sensitive, though good activity was also observed against CNS tumors and carcinomas of the breast and prostate. The results of this study demonstrate that B-ring analogues of 3 inhibit DHFR activity and tumor cell colony formation as well as, or better than, the parent compound. In view of the fact that 3 and its B-ring analogues cannot form polyglutamates, their high cytotoxicity relative to the corresponding B-ring analogues of AMT is noteworthy.
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Affiliation(s)
- A Rosowsky
- Dana-Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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Abstract
Methotrexate (MTX), the antifolate drug widely used as both an anticancer chemotherapeutic drug and as an immunosuppressive agent, mimics natural folates to inhibit critical cellular biosynthetic pathways. One of the most important determinants of cellular sensitivity to MTX is the degree to which this drug is internalized by cancer cells, and one of the major pathways of folate uptake results from the activity of the reduced folate carrier (RFC). Decreased RFC activity has been associated with several models of transport-mediated MTX resistance. Recently, the rodent and human genes which encode this protein have been isolated (RFC1), and defects in the expression of RFC1 genes have been identified in transport-deficient, MTX-resistant cell lines. Therefore, these studies have demonstrated the importance of RFC1 expression in transport-mediated antifolate drug resistance. In addition, however, studies of both MTX uptake in cancer cells and of folate transport in physiologic systems indicate that there are other proteins with uptake characteristics similar to RFC, and which maybe encoded by genes other than RFC1.
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Affiliation(s)
- J A Moscow
- Department of Pediatrics, University of Kentucky Medical Center, Lexington 40536, USA
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