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Ahmed Juvale II, Abdul Hamid AA, Abd Halim KB, Che Has AT. P-glycoprotein: new insights into structure, physiological function, regulation and alterations in disease. Heliyon 2022; 8:e09777. [PMID: 35789865 PMCID: PMC9249865 DOI: 10.1016/j.heliyon.2022.e09777] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 02/04/2022] [Accepted: 06/17/2022] [Indexed: 01/01/2023] Open
Abstract
The multidrug resistance phenomenon presents a major threat to the pharmaceutical industry. This resistance is a common occurrence in several diseases and is mediated by multidrug transporters that actively pump substances out of the cell and away from their target regions. The most well-known multidrug transporter is the P-glycoprotein transporter. The binding sites within P-glycoprotein can accommodate a variety of compounds with diverse structures. Hence, numerous drugs are P-glycoprotein substrates, with new ones being identified every day. For many years, the mechanisms of action of P-glycoprotein have been shrouded in mystery, and scientists have only recently been able to elucidate certain structural and functional aspects of this protein. Although P-glycoprotein is highly implicated in multidrug resistant diseases, this transporter also performs various physiological roles in the human body and is expressed in several tissues, including the brain, kidneys, liver, gastrointestinal tract, testis, and placenta. The expression levels of P-glycoprotein are regulated by different enzymes, inflammatory mediators and transcription factors; alterations in which can result in the generation of a disease phenotype. This review details the discovery, the recently proposed structure and the regulatory functions of P-glycoprotein, as well as the crucial role it plays in health and disease.
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Affiliation(s)
- Iman Imtiyaz Ahmed Juvale
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia Health Campus, Kubang Kerian, Kota Bharu, 16150, Kelantan, Malaysia
| | - Azzmer Azzar Abdul Hamid
- Department of Biotechnology, Kulliyyah of Science, International Islamic University Malaysia, Jalan Sultan Ahmad Shah, Bandar Indera Mahkota, 25200, Kuantan, Pahang, Malaysia
| | - Khairul Bariyyah Abd Halim
- Research Unit for Bioinformatics and Computational Biology (RUBIC), Kulliyyah of Science, International Islamic University Malaysia, Jalan Sultan Ahmad Shah, Bandar Indera Mahkota, 25200, Kuantan, Pahang, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia Health Campus, Kubang Kerian, Kota Bharu, 16150, Kelantan, Malaysia
- Corresponding author.
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Rendic S, Guengerich FP. Update information on drug metabolism systems--2009, part II: summary of information on the effects of diseases and environmental factors on human cytochrome P450 (CYP) enzymes and transporters. Curr Drug Metab 2010; 11:4-84. [PMID: 20302566 PMCID: PMC4167379 DOI: 10.2174/138920010791110917] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Accepted: 02/22/2010] [Indexed: 12/14/2022]
Abstract
The present paper is an update of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 (CYP) enzymes and transporters. The data are presented in tabular form (Tables 1 and 2) and are a continuation of previously published summaries on the effects of drugs and other chemicals on CYP enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29(1-2), 413-580., Rendic, S. Drug Metab. Rev., 2002, 34(1-2), 83-448.). The collected information presented here is as stated by the cited author(s), and in cases when several references are cited the latest published information is included. Inconsistent results and conclusions obtained by different authors are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file, for information about file availability contact the corresponding author.
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Affiliation(s)
- S Rendic
- University of Zagreb, Zagreb, Croatia.
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Guo X, Ma N, Wang J, Song J, Bu X, Cheng Y, Sun K, Xiong H, Jiang G, Zhang B, Wu M, Wei L. Increased p38-MAPK is responsible for chemotherapy resistance in human gastric cancer cells. BMC Cancer 2008; 8:375. [PMID: 19091131 PMCID: PMC2628930 DOI: 10.1186/1471-2407-8-375] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 12/18/2008] [Indexed: 12/12/2022] Open
Abstract
Background Chemoresistance is one of the main obstacles to successful cancer therapy and is frequently associated with Multidrug resistance (MDR). Many different mechanisms have been suggested to explain the development of an MDR phenotype in cancer cells. One of the most studied mechanisms is the overexpression of P-glycoprotein (P-gp), which is a product of the MDR1 gene. Tumor cells often acquire the drug-resistance phenotype due to upregulation of the MDR1 gene. Overexpression of MDR1 gene has often been reported in primary gastric adenocarcinoma. Methods This study investigated the role of p38-MAPK signal pathway in vincristine-resistant SGC7901/VCR cells. P-gp and MDR1 RNA were detected by Western blot analysis and RT-PCR amplification. Mitgen-activated protein kinases and function of P-gp were demonstrated by Western blot and FACS Aria cytometer analysis. Ap-1 activity and cell apoptosis were detected by Dual-Luciferase Reporter Assay and annexin V-PI dual staining. Results The vincristine-resistant SGC7901/VCR cells with increased expression of the multidrug-resistance 1 (MDR1) gene were resistant to P-gp-related drug and P-gp-unrelated drugs. Constitutive increases of phosphorylated p38-MAPK and AP-1 activities were also found in the drug-resistant cells. Inhibition of p38-MAPK by SB202190 reduced activator protein-1 (AP-1) activity and MDR1 expression levels and increased the sensitivity of SGC7901/VCR cells to chemotherapy. Conclusion Activation of the p38-MAPK pathway might be responsible for the modulation of P-glycoprotein-mediated and P-glycoprotein-unmediated multidrug resistance in the SGC7901/VCR cell line.
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Affiliation(s)
- Xianling Guo
- Tumor Immunology and Gene Therapy Center, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, PR China.
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Gan Y, Wientjes MG, Au JLS. Expression of basic fibroblast growth factor correlates with resistance to paclitaxel in human patient tumors. Pharm Res 2006; 23:1324-31. [PMID: 16741658 DOI: 10.1007/s11095-006-0136-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Accepted: 01/26/2006] [Indexed: 11/25/2022]
Abstract
BACKGROUND Preclinical results indicate acidic fibroblast growth factor (aFGF) and basic FGF (bFGF) present in solid tumors as a cause of broad-spectrum chemoresistance, whereas earlier clinical studies suggest that bFGF expression is associated with opposing outcomes in patients. We investigated the relationship between FGF expression and paclitaxel activity in tumors from bladder, breast, head and neck, ovarian, and prostate cancer patients. MATERIALS AND METHODS Tumors (n = 96) were maintained in three-dimensional histocultures, retaining tumor-stromal interaction. Bladder tumors were treated with paclitaxel for 2 h, and the other tumors for 24 h. Antiproliferative and proapoptotic effects of paclitaxel were quantified and correlated with expression of aFGF, bFGF, P-glycoprotein (Pgp), p53, and bcl-2. RESULTS Fifty-one percent (49/96) and 63% (61/96) of tumors showed aFGF and bFGF staining, respectively. aFGF expression was positively correlated with tumor stage (p < 0.01), and bFGF expression with tumor grade and Pgp expression (p < 0.05). Paclitaxel inhibited antiproliferation in 86% of tumors (83/96), with an average inhibition of 46 +/- 19% (mean +/- SD) in the responding tumors. Paclitaxel also induced apoptosis in 96% of tumors (92/96), with an average apoptotic index of 12 +/- 7% in the responding tumors. aFGF expression did not correlate with tumor sensitivity to paclitaxel, whereas bFGF expression showed an inverse correlation (p < 0.01). bFGF expression was a stronger predictor of paclitaxel resistance compared to Pgp, p53, or Bcl-2. CONCLUSION These results support a role of bFGF in paclitaxel resistance in human patient tumors.
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Affiliation(s)
- Yuebo Gan
- College of Pharmacy, The Ohio State University, 500 West 12th Avenue, Columbus, OH 43210, USA
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Liem AA, Chamberlain MP, Wolf CR, Thompson AM. The role of signal transduction in cancer treatment and drug resistance. EUROPEAN JOURNAL OF SURGICAL ONCOLOGY 2002; 28:679-84. [PMID: 12359208 DOI: 10.1053/ejso.2002.1303] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Drug resistance in the treatment of cancer still remains a major clinical challenge, in part due to an insufficient understanding of the pathways by which these drugs interact with the mechanisms underlying cellular behaviour and cancer pathogenesis. Signal transduction involves cell differentiation, proliferation and cell death with alterations in these mechanisms being involved in the pathogenesis of cancer. It has been postulated that such pathways could be linked to anti-cancer drug resistance. Recently, novel approaches to overcome anti-cancer drug resistance through manipulation of signal transduction pathways, have been introduced in clinical trials. In this article we present a review of the current understanding in the field of signal transduction and the existing evidence for its role in drug resistance. We also discuss its clinical relevance with regard to overcoming drug resistance.
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Affiliation(s)
- A A Liem
- Department of Surgery and Molecular Oncology, University of Dundee, UK
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Abstract
Queuosine is a hypermodified nucleoside found in position 34, the anticodon wobble position, of four tRNA species. This modification is distributed with near uniformity across all life forms found on this planet. Yet the molecular mechanisms involved with accomplishing this ubiquitous posttranscriptional modification of tRNA are dramatically different between prokaryotic and eukaryotic organisms, which suggests that these were formed by convergent evolution of a fundamental life process essential to nearly all life forms. This minireview describes the differences between these modification systems and points to a new direction for developing research on the molecular function queuosine-modified tRNA in diverse species.
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Affiliation(s)
- R C Morris
- The Center for Pediatric Research, Eastern Virginia Medical School, 855 West Brambleton Avenue, Norfolk, Virginia 23510, USA.
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Matheny CJ, Lamb MW, Brouwer KR, Pollack GM. Pharmacokinetic and pharmacodynamic implications of P-glycoprotein modulation. Pharmacotherapy 2001; 21:778-96. [PMID: 11444575 DOI: 10.1592/phco.21.9.778.34558] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
P-glycoprotein (P-gp) is a cell membrane-associated protein that transports a variety of drug substrates. Although P-gp has been studied extensively as a mediator of multidrug resistance in cancer, only recently has the role of P-gp expressed in normal tissues as a determinant of drug pharmacokinetics and pharmacodynamics been examined. P-glycoprotein is present in organ systems that influence drug absorption (intestine), distribution to site of action (central nervous system and leukocytes), and elimination (liver and kidney), as well as several other tissues. Many marketed drugs inhibit P-gp function, and several compounds are under development as P-gp inhibitors. Similarly, numerous drugs can induce P-gp expression. While P-gp induction does not have a therapeutic role, P-gp inhibition is an attractive therapeutic approach to reverse multidrug resistance. Clinicians should recognize that P-gp induction or inhibition may have a substantial effect on the pharmacokinetics and pharmacodynamics of concomitantly administered drugs that are substrates for this transporter.
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Affiliation(s)
- C J Matheny
- Division of Drug Delivery and Disposition, School of Pharmacy, University of North Carolina at Chapel Hill, 27599-7360, USA
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Kantharidis P, El-Osta S, Silva MD, Lee G, Hu XF, Zalcberg J. Regulation of MDR1 gene expression: emerging concepts. Drug Resist Updat 2000; 3:99-108. [PMID: 11498374 DOI: 10.1054/drup.2000.0121] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Drug resistance genes, such as MDR1, involved in drug efflux, and their regulation have been the subject of intense research efforts in the past 10 years. Many factors and cellular signalling pathways play a role in the regulation of MDR1 gene expression. Commonly used chemotherapeutic agents activate in vitro and in vivo general stress response pathways, potential targets of which include MDR1 and other drug resistance genes. The contribution of these agents to the emergence of drug-resistant tumour cells is of concern. Recent evidence points to a role for the epigenetic regulation of MDR1 gene expression. The identification of key components in the DNA methylation/chromatin system of gene regulation may in time lead to more informed and targeted approaches to treating drug-resistant tumours. Copyright 2000 Harcourt Publishers Ltd.
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Affiliation(s)
- Phillip Kantharidis
- Sir Donald and Lady Trescowthick Research Laboratories, Peter MacCallum Cancer Institute, St Andrews Place, East Melbourne, Victoria, 3002, Australia
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Yin Y, Allen PD, Jia L, MacEy MG, Kelsey SM, Newland AC. Constitutive levels of cAMP-dependent protein kinase activity determine sensitivity of human multidrug-resistant leukaemic cell lines to growth inhibition and apoptosis by forskolin and tumour necrosis factor alpha. Br J Haematol 2000; 108:565-73. [PMID: 10759715 DOI: 10.1046/j.1365-2141.2000.01903.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) signal pathway regulates cell proliferation, differentiation and cell death. It may also regulate the multidrug resistance (MDR) phenotype in leukaemic cells. These data showed that MDR1+ K/Dau600 cells exhibited a higher basal level of PKA activity than MDR- parental cells. The significance of this on tumour necrosis factor alpha (TNFalpha)-induced apoptosis and cytostasis was investigated further. In comparison with MDR1- parental cells, K/Dau600 cells had a higher expression of PKA regulatory subunit RIalpha and nuclear catalytic subunit PKAcalpha. They were also more susceptible to inhibition of proliferation and induction of apoptosis by TNFalpha and/or forskolin, but this could be attenuated by H89. An increase in cAMP was associated with the apoptosis in the K/Dau600 cell line. Forskolin inactivated NF-kappaB in K/Dau600 cells but not in K562 cl. 6 cells, whereas TNF activated NF-kappaB in K562 cl.6 cells but not in K/Dau600 cells. 8-Cl-cAMP exhibited similar inhibitory effects on the proliferation of all of the cell lines used via its metabolite 8-Cl-adenosine, which indicates that these effects were independent of residual PKA or cAMP. Therefore, the differential sensitivity to apoptosis and/or growth inhibition could be mediated via cAMP, partly through PKA via NF-kappaB and partly by PKA-independent pathways.
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Affiliation(s)
- Y Yin
- Department of Haematology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Turner Street, London E1 2AD, UK
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Wang H, Cai Q, Zeng X, Yu D, Agrawal S, Zhang R. Antitumor activity and pharmacokinetics of a mixed-backbone antisense oligonucleotide targeted to the RIalpha subunit of protein kinase A after oral administration. Proc Natl Acad Sci U S A 1999; 96:13989-94. [PMID: 10570186 PMCID: PMC24178 DOI: 10.1073/pnas.96.24.13989] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Overexpression of the RIalpha subunit of cAMP-dependent protein kinase (PKA) has been demonstrated in various human cancers. PKA has been suggested as a potential target for cancer therapy. The goal of the present study was to evaluate an anti-PKA antisense oligonucleotide (mixed-backbone oligonucleotide) as a therapeutic approach to human cancer treatment. The identified oligonucleotide inhibited the growth of cell lines of human colon cancer (LS174T, DLD-1), leukemia (HL-60), breast cancer (MCF-7, MDA-MB-468), and lung cancer (A549) in a time-, concentration-, and sequence-dependent manner. In a dose-dependent manner, the oligonucleotide displayed in vivo antitumor activity in severe combined immunodeficient and nude mice bearing xenografts of human cancers of the colon (LS174T), breast (MDA-MB-468), and lung (A549). The routes of drug administration were intraperitoneal and oral. Synergistic effects were found when the antisense oligonucleotide was used in combination with the cancer chemotherapeutic agent cisplatin. The pharmacokinetics of the oligonucleotide after oral administration of (35)S-labeled oligonucleotide into tumor-bearing mice indicated an accumulation and retention of the oligonucleotide in tumor tissue. This study further provides a basis for clinical studies of the antisense oligonucleotide targeted to the RIalpha subunit of PKA (GEM 231) as a cancer therapeutic agent used alone or in combination with conventional chemotherapy.
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Affiliation(s)
- H Wang
- Division of Clinical Pharmacology, Department of Pharmacology, Comprehensive Cancer Center, University of Alabama, Birmingham, AL 35294-0019, USA
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Osborn MT, Berry A, Ruberu MS, Ning B, Bell LM, Chambers TC. Phorbol ester induced MDR1 expression in K562 cells occurs independently of mitogen-activated protein kinase signaling pathways. Oncogene 1999; 18:5756-64. [PMID: 10523856 DOI: 10.1038/sj.onc.1202943] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The MDR1 gene encoding the multidrug pump P-glycoprotein is transcriptionally activated in response to diverse extracellular stimuli, including the tumor promoting phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA). However, the signal transduction pathway responsible is unknown. Downstream of protein kinase C (PKC), the effects of TPA are often mediated by the Raf-1/MEK/ERK mitogen-activated protein kinase (MAPK) cascade, and Raf-1 has been implicated in MDR1 induction by serum and mitogens. Therefore, we examined the potential role of MAPK activation in TPA-mediated MDR1 induction in human leukemia K562 cells. MDR1 mRNA expression was significantly increased by TPA in the concentration range of 4 - 100 nM, with a maximal response 5 - 10 h after TPA addition. TPA-mediated MDR1 induction was inhibited by several PKC inhibitors including staurosporine, H7 and calphostin C. TPA stimulated the subcellular translocation of PKCalpha from the cytosol to the membrane and nucleus but did not affect other PKC isozymes. TPA also activated the Raf1/MEK/ERK cascade and activated another MAPK member, p38, but not JNK. In order to determine the potential role of MAPKs in MDR1 induction by TPA, specific inhibitors were utilized. The MEK inhibitor PD 098059, as well as the PKC inhibitors, completely blocked TPA-mediated ERK activation. However, under identical conditions, MDR1 induction by TPA was completely unaffected by PD 098059. Furthermore, SB 202190, which effectively inhibited TPA-mediated p38 activation, failed to inhibit TPA-induced MDR1 mRNA expression. These data demonstrate that MDR1 induction by TPA occurs via a PKC-dependent mechanism that operates independently of ERK, p38 or JNK pathways, and thus have important implications for understanding the mechanisms of MDR1 induction by extracellular stimuli.
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Affiliation(s)
- M T Osborn
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
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Daschner PJ, Ciolino HP, Plouzek CA, Yeh GC. Increased AP-1 activity in drug resistant human breast cancer MCF-7 cells. Breast Cancer Res Treat 1999; 53:229-40. [PMID: 10369069 DOI: 10.1023/a:1006138803392] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The expression, DNA binding, and transactivating activity of activator protein 1 (AP-1) was examined in a series of multidrug resistant (MDR) MCF-7 human breast cancer cells that have increasing levels of MDR1 gene expression. We observed an increase in the amount of both c-jun and c-fos mRNA in cells with 12-, 65-, or 200-fold higher resistance to adriamycin when compared to drug-sensitive MCF-7 wild type (WT) cells. Electrophoretic mobility shift assays (EMSA) demonstrated an increase in the DNA binding activity of an AP-1 complex in nuclear extracts from MDR MCF-7 cells when compared to extracts from WT cells. We observed a proportional increase in luciferase expression from a reporter vector containing consensus AP-1 binding sites in transiently transfected MDR cells when compared to WT cells, indicating that AP-1 mediated gene expression is increased in drug-resistant MCF-7 cells. Since the MDR1 promoter contains a putative AP-1 binding site, we used EMSA to examine AP-1 binding activity to an oligonucleotide probe that contained the relevant MDR1 promoter sequences (-123 to -108). Nuclear extracts from resistant MCF-7 cells displayed an increased level of DNA binding of Jun/Jun dimers to the probe, indicating that AP-1 was capable of binding to this promoter site. A luciferase reporter construct containing triplicate copies of the MDR1 promoter sequence was expressed at higher levels in transiently transfected MDR cells when compared to expression in WT cells. Co-transfection of WT cells with a c-jun expression vector and either of the AP-1 luciferase constructs demonstrated that c-jun could activate gene expression from both the consensus and the MDR1 AP-1 sites in a dose dependent manner. In addition, RT-PCR and western blot analysis showed that levels of MDR1 mRNA and Pgp were increased in c-jun transfected WT cells. Taken together, these data indicate that increased AP-1 activity may be an important mediator of MDR by regulating the expression of MDR1.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Blotting, Western
- Breast Neoplasms/metabolism
- Cell Nucleus/metabolism
- DNA/metabolism
- Doxorubicin/pharmacology
- Drug Resistance, Neoplasm
- Electrophoresis, Polyacrylamide Gel
- Female
- Gene Expression/drug effects
- Humans
- Paclitaxel/pharmacology
- Promoter Regions, Genetic/drug effects
- Proto-Oncogene Proteins c-fos/biosynthesis
- Proto-Oncogene Proteins c-jun/biosynthesis
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Transcription Factor AP-1/metabolism
- Tumor Cells, Cultured
- Up-Regulation/drug effects
- Vinblastine/pharmacology
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Affiliation(s)
- P J Daschner
- Intramural Research Support Program, SAIC, NCI-FCRDC, Frederick, MD 21702, USA
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Wang S, Ghosh RN, Chellappan SP. Raf-1 physically interacts with Rb and regulates its function: a link between mitogenic signaling and cell cycle regulation. Mol Cell Biol 1998; 18:7487-98. [PMID: 9819434 PMCID: PMC109329 DOI: 10.1128/mcb.18.12.7487] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/1998] [Accepted: 08/26/1998] [Indexed: 01/02/2023] Open
Abstract
Cells initiate proliferation in response to growth factor stimulation, but the biochemical mechanisms linking signals received at the cell surface receptors to the cell cycle regulatory molecules are not yet clear. In this study, we show that the signaling molecule Raf-1 can physically interact with Rb and p130 proteins in vitro and in vivo and that this interaction can be detected in mammalian cells without overexpressing any component. The binding of Raf-1 to Rb occurs subsequent to mitogen stimulation, and this interaction can be detected only in proliferating cells. Raf-1 can inactivate Rb function and can reverse Rb-mediated repression of E2F1 transcription and cell proliferation efficiently. The region of Raf-1 involved in Rb binding spanned residues 1 to 28 at the N terminus, and functional inactivation of Rb required a direct interaction. Serum stimulation of quiescent human fibroblast HSF8 cells led to a partial translocation of Raf-1 into the nucleus, where it colocalized with Rb. Further, Raf-1 was able to phosphorylate Rb in vitro quite efficiently. We believe that the physical interaction of Raf-1 with Rb is a vital step in the growth factor-mediated induction of cell proliferation and that Raf-1 acts as a direct link between cell surface signaling cascades and the cell cycle machinery.
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Affiliation(s)
- S Wang
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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Sur M, Taylor L, Cooper K, Sur RK. Lack of correlation of P-glycoprotein expression with response to MIC chemotherapy in oesophageal cancer. J Clin Pathol 1997; 50:534. [PMID: 9378827 PMCID: PMC500009 DOI: 10.1136/jcp.50.6.534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Bosanquet AG, Burlton AR, Bell PB, Harris AL. Ex vivo cytotoxic drug evaluation by DiSC assay to expedite identification of clinical targets: results with 8-chloro-cAMP. Br J Cancer 1997; 76:511-8. [PMID: 9275029 PMCID: PMC2227987 DOI: 10.1038/bjc.1997.417] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
There is a pressing need to reduce the time and cost of developing new cytotoxic agents and to accurately identify clinically active agents at an early stage. In this study, the differential staining cytotoxicity (DiSC) assay was used to assess the efficacy of the novel antitumour cAMP analogue, 8-chloro-cAMP (8-Cl-cAMP) (and its metabolite 8-Cl-adenosine) against 107 fresh specimens of human neoplastic and normal cells. Diagnoses included chronic and acute leukaemias, myeloma, non-Hodgkin's lymphoma (NHL) and miscellaneous solid tumours. The aim was to identify targets for subsequent phase I, II and III trials. 8-Cl-cAMP was tested at 4-985 microM, along with standard chemotherapeutic drugs. 8-Cl-cAMP and its metabolite caused no morphologically observable cell differentiation but induced dose-dependent cytotoxicity. Compared with untreated patients, previously treated chronic lymphocytic leukaemia (CLL) patients showed no increase in ex vivo resistance to 8-Cl-cAMP (P = 0.878); minimal cross-resistance with other cytotoxic drugs was detected. Compared with normal cells (mean LC90 = 1803 microM), 8-Cl-cAMP showed significant ex vivo activity against CLL (117.0 microM; P < 0.0001) and NHL (140.0 microM; P < 0.0001), of which eight were mantle cell NHL (84.7 microM), and greatest activity against cells from patients with acute myeloid leukaemia (AML; mean LC90 = 24.3 microM; in vitro therapeutic index 74-fold, P < 0.0001). Solid tumour specimens were comparatively resistant to 8-Cl-cAMP. The results highlight the clinical potential of 8-Cl-cAMP, point to several new phase I, II and III trial possibilities and provide a rationale for the inclusion of ex vivo cytotoxic drug evaluation in the drug development process.
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Affiliation(s)
- A G Bosanquet
- Bath Cancer Research Unit, School of Postgraduate Medicine, University of Bath, Royal United Hospital, UK
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