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Key Role of Human ABC Transporter ABCG2 in Photodynamic Therapy and Photodynamic Diagnosis  [PDF]
Toshihisa Ishikawa,Hiroshi Nakagawa,Yuichiro Hagiya,Naosuke Nonoguchi,Shin-ichi Miyatake,Toshihiko Kuroiwa
Advances in Pharmacological Sciences , 2010, DOI: 10.1155/2010/587306
Abstract: Accumulating evidence indicates that ATP-binding cassette (ABC) transporter ABCG2 plays a key role in regulating the cellular accumulation of porphyrin derivatives in cancer cells and thereby affects the efficacy of photodynamic therapy and photodynamic diagnosis. The activity of porphyrin efflux can be affected by genetic polymorphisms in the ABCG2 gene. On the other hand, Nrf2, an NF-E2-related transcription factor, has been shown to be involved in oxidative stress-mediated induction of the ABCG2 gene. Since patients have demonstrated individual differences in their response to photodynamic therapy, transcriptional activation and/or genetic polymorphisms of the ABCG2 gene in cancer cells may affect patients' responses to photodynamic therapy. Protein kinase inhibitors, including imatinib mesylate and gefitinib, are suggested to potentially enhance the efficacy of photodynamic therapy by blocking ABCG2-mediated porphyrin efflux from cancer cells. This review article provides an overview on the role of human ABC transporter ABCG2 in photodynamic therapy and photodynamic diagnosis. 1. Introduction Photodynamic therapy (PDT) and photodynamic diagnosis are achieved by a photon-induced physicochemical reaction which is induced by excitation of photosensitizer exposed to light. In the 1960s Lipson and Baldes introduced a hematoporphyrin derivative (HpD), a product derived following by treatment of hematoporphyrin with a mixture of acetic and sulfuric acids and sodium hydroxide [1]. Their development of the hematoporphyrin derivative established the basis of today’s PDT and photodynamic diagnosis [2–6]. PDT utilizes porphyrin derivatives to generate singlet oxygen (1O2) and other reactive oxygen species (ROS) that are potent in killing cancer cell in vivo [7]. The modern era of PDT was founded in the 1970s with the pioneering work of Dougherty and his coworkers who purified HpD later called Photofrin. In 1978, Dougherty et al. had carried out the first human trials of Photofrin on women with advanced breast cancer [8]. Photofrin is still the most widely used photosensitizer in clinical PDT. Recent studies of modern PDT began just two decades ago; therefore there are still unsolved problems. Nevertheless, PDT has many applications in a wide range of fields of both preclinical and clinical sciences. In recent years, remarkable advances were made in photodynamic diagnosis technology that makes it easier to reliably achieve complete excision of malignant gliomas [9–11] and meningiomas [12]. The extent of tumor resection that should be undertaken in patients with
Mitochondrial Localization of ABC Transporter ABCG2 and Its Function in 5-Aminolevulinic Acid-Mediated Protoporphyrin IX Accumulation  [PDF]
Hirotsugu Kobuchi, Koko Moriya, Tetsuya Ogino, Hirofumi Fujita, Keiji Inoue, Taro Shuin, Tatsuji Yasuda, Kozo Utsumi, Toshihiko Utsumi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050082
Abstract: Accumulation of protoporphyrin IX (PpIX) in malignant cells is the basis of 5-aminolevulinic acid (ALA)-mediated photodynamic therapy. We studied the expression of proteins that possibly affect ALA-mediated PpIX accumulation, namely oligopeptide transporter-1 and -2, ferrochelatase and ATP-binding cassette transporter G2 (ABCG2), in several tumor cell lines. Among these proteins, only ABCG2 correlated negatively with ALA-mediated PpIX accumulation. Both a subcellular fractionation study and confocal laser microscopic analysis revealed that ABCG2 was distributed not only in the plasma membrane but also intracellular organelles, including mitochondria. In addition, mitochondrial ABCG2 regulated the content of ALA-mediated PpIX in mitochondria, and Ko143, a specific inhibitor of ABCG2, enhanced mitochondrial PpIX accumulation. To clarify the possible roles of mitochondrial ABCG2, we characterized stably transfected-HEK (ST-HEK) cells overexpressing ABCG2. In these ST-HEK cells, functionally active ABCG2 was detected in mitochondria, and treatment with Ko143 increased ALA-mediated mitochondrial PpIX accumulation. Moreover, the mitochondria isolated from ST-HEK cells exported doxorubicin probably through ABCG2, because the export of doxorubicin was inhibited by Ko143. The susceptibility of ABCG2 distributed in mitochondria to proteinase K, endoglycosidase H and peptide-N-glycosidase F suggested that ABCG2 in mitochondrial fraction is modified by N-glycans and trafficked through the endoplasmic reticulum and Golgi apparatus and finally localizes within the mitochondria. Thus, it was found that ABCG2 distributed in mitochondria is a functional transporter and that the mitochondrial ABCG2 regulates ALA-mediated PpIX level through PpIX export from mitochondria to the cytosol.
Olomoucine II, but Not Purvalanol A, Is Transported by Breast Cancer Resistance Protein (ABCG2) and P-Glycoprotein (ABCB1)  [PDF]
Jakub Hofman, Radim Ku?era, Daniela Cihalova, Jiri Klimes, Martina Ceckova, Frantisek Staud
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075520
Abstract: Purine cyclin-dependent kinase inhibitors have been recognized as promising candidates for the treatment of various cancers; nevertheless, data regarding interaction of these substances with drug efflux transporters is still lacking. Recently, we have demonstrated inhibition of breast cancer resistance protein (ABCG2) by olomoucine II and purvalanol A and shown that these compounds are able to synergistically potentiate the antiproliferative effect of mitoxantrone, an ABCG2 substrate. In this follow up study, we investigated whether olomoucine II and purvalanol A are transported by ABCG2 and ABCB1 (P-glycoprotein). Using monolayers of MDCKII cells stably expressing human ABCB1 or ABCG2, we demonstrated that olomoucine II, but not purvalanol A, is a dual substrate of both ABCG2 and ABCB1. We, therefore, assume that pharmacokinetics of olomoucine II will be affected by both ABCB1 and ABCG2 transport proteins, which might potentially result in limited accumulation of the compound in tumor tissues or lead to drug-drug interactions. Pharmacokinetic behavior of purvalanol A, on the other hand, does not seem to be affected by either ABCG2 or ABCB1, theoretically favoring this drug in the potential treatment of efflux transporter-based multidrug resistant tumors. In addition, we observed intensive sulfatation of olomoucine II in MDCKII cell lines with subsequent active efflux of the metabolite out of the cells. Therefore, care should be taken when performing pharmacokinetic studies in MDCKII cells, especially if radiolabeled substrates are used; the generated sulfated conjugate may largely contaminate pharmacokinetic analysis and result in misleading interpretation. With regard to chemical structures of olomoucine II and purvalanol A, our data emphasize that even drugs with remarkable structure similarity may show different pharmacokinetic behavior such as interactions with ABC transporters or biotransformation enzymes.
Gene and functional up-regulation of the BCRP/ABCG2 transporter in hepatocellular carcinoma  [cached]
Sukowati Caecilia HC,Rosso Natalia,Pascut Devis,Anfuso Beatrice
BMC Gastroenterology , 2012, DOI: 10.1186/1471-230x-12-160
Abstract: Background The Breast Cancer Resistance Protein (BCRP/ABCG2) is one member of ABC transporters proteins super family responsible of drug resistance. Since data on ABCG2 expression in liver malignances are scanty, here we report the expression of ABCG2 in adult human hepatocellular carcinoma (HCC) in both in vivo and in vitro models with different degree of malignancy. Methods In cell lines derived from human hepatocellular carcinoma, ABCG2 gene expression was assessed by reverse transcription quantitative real time PCR and function by Hoechst 33342 efflux assay; protein content was assessed by SDS-PAGE Western blot. Results ABCG2 expression was found to be highest in the most undifferentiated cell lines, and this was related with a higher functional activity. ABCG2 expression was sensitive to antineoplastic drugs since exposure to 5 μM doxorubicin for 24 hours resulted in significant up-regulations of ABCG2 in all cell lines, particularly in those lines with low basal ABCG2 expression (p<0.01). The gene expression was also investigated in 51 adult liver tissues with HCC and related cirrhosis; normal liver tissue was used as control. ABCG2 gene expression was higher in HCC than both cirrhotic paired tissue and normal tissue. This up-regulation was greater (p<0.05) in pathological poorly differentiated grade G3/G4 than in well-differentiated G1/G2 HCC. Conclusions Our results suggest a correlation of ABCG2 gene expression and differentiation stage both in human and HCC derived cell lines. The rapid up-regulation of ABCG2 to exposure to doxorubicin emphasizes the importance of this transporter in accounting for drug resistance in liver tumors.
Transporter-Mediated Drug Interaction Strategy for 5-Aminolevulinic Acid (ALA)-Based Photodynamic Diagnosis of Malignant Brain Tumor: Molecular Design of ABCG2 Inhibitors  [PDF]
Toshihisa Ishikawa,Kenkichi Takahashi,Naokado Ikeda,Yoshinaga Kajimoto,Yuichiro Hagiya,Shun-ichiro Ogura,Shin-ichi Miyatake,Toshihiko Kuroiwa
Pharmaceutics , 2011, DOI: 10.3390/pharmaceutics3030615
Abstract: Photodynamic diagnosis (PDD) is a practical tool currently used in surgical operation of aggressive brain tumors, such as glioblastoma. PDD is achieved by a photon-induced physicochemical reaction which is induced by excitation of protoporphyrin IX (PpIX) exposed to light. Fluorescence-guided gross-total resection has recently been developed in PDD, where 5-aminolevulinic acid (ALA) or its ester is administered as the precursor of PpIX. ALA induces the accumulation of PpIX, a natural photo-sensitizer, in cancer cells. Recent studies provide evidence that adenosine triphosphate (ATP)-binding cassette (ABC) transporter ABCG2 plays a pivotal role in regulating the cellular accumulation of porphyrins in cancer cells and thereby affects the efficacy of PDD. Protein kinase inhibitors are suggested to potentially enhance the PDD efficacy by blocking ABCG2-mediated porphyrin efflux from cancer cells. It is of great interest to develop potent ABCG2-inhibitors that can be applied to PDD for brain tumor therapy. This review article addresses a pivotal role of human ABC transporter ABCG2 in PDD as well as a new?approach of quantitative structure-activity relationship (QSAR) analysis to design potent ABCG2-inhibitors.
Reversing multidrug resistance in breast cancer cells by silencing ABC transporter genes with nanoparticle-facilitated delivery of target siRNAs
Li YT, Chua MJ, Kunnath AP, Chowdhury EH
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S30500
Abstract: sing multidrug resistance in breast cancer cells by silencing ABC transporter genes with nanoparticle-facilitated delivery of target siRNAs Original Research (3642) Total Article Views Authors: Li YT, Chua MJ, Kunnath AP, Chowdhury EH Published Date June 2012 Volume 2012:7 Pages 2473 - 2481 DOI: http://dx.doi.org/10.2147/IJN.S30500 Received: 02 February 2012 Accepted: 17 March 2012 Published: 05 June 2012 Yong Tsuey Li,1 Ming Jang Chua,1 Anil Philip Kunnath,1 Ezharul Hoque Chowdhury,1,2 1Faculty of Medicine and Health Science, International Medical University (IMU), No 126, Jalan 19/155B, Bukit Jalil, 57000 Kuala Lumpur, Malaysia; 2Jeffrey Cheah School of Medicine and Health Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University Kuala Lumpur, Malaysia Background: Multidrug resistance, a major impediment to successful cancer chemotherapy, is the result of overexpression of ATP-binding cassette (ABC) transporters extruding internalized drugs. Silencing of ABC transporter gene expression with small interfering RNA (siRNA) could be an attractive approach to overcome multidrug resistance of cancer, although delivery of siRNA remains a major hurdle to fully exploit the potential of siRNA-based therapeutics. Recently, we have developed pH-sensitive carbonate apatite nanoparticles to efficiently carry and transport siRNA across the cell membrane, enabling knockdown of the cyclin B1 gene and consequential induction of apoptosis in synergy with anti-cancer drugs. Methods and results: We report that carbonate apatite-mediated delivery of the siRNAs targeting ABCG2 and ABCB1 gene transcripts in human breast cancer cells which constitutively express both of the transporter genes dose-dependently enhanced chemosensitivity to doxorubicin, paclitaxel and cisplatin, the traditionally used chemotherapeutic agents. Moreover, codelivery of two specific siRNAs targeting ABCB1 and ABCG2 transcripts resulted in a more robust increase of chemosensitivity in the cancer cells, indicating the reversal of ABC transporter-mediated multidrug resistance. Conclusion: The delivery concept of multiple siRNAs against ABC transporter genes is highly promising for preclinical and clinical investigation in reversing the multidrug resistance phenotype of breast cancer.
Extra-Renal Elimination of Uric Acid via Intestinal Efflux Transporter BCRP/ABCG2  [PDF]
Atsushi Hosomi, Takeo Nakanishi, Takuya Fujita, Ikumi Tamai
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030456
Abstract: Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats.
Genome-Wide Identification, Characterization and Phylogenetic Analysis of 50 Catfish ATP-Binding Cassette (ABC) Transporter Genes  [PDF]
Shikai Liu, Qi Li, Zhanjiang Liu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063895
Abstract: Background Although a large set of full-length transcripts was recently assembled in catfish, annotation of large gene families, especially those with duplications, is still a great challenge. Most often, complexities in annotation cause mis-identification and thereby much confusion in the scientific literature. As such, detailed phylogenetic analysis and/or orthology analysis are required for annotation of genes involved in gene families. The ATP-binding cassette (ABC) transporter gene superfamily is a large gene family that encodes membrane proteins that transport a diverse set of substrates across membranes, playing important roles in protecting organisms from diverse environment. Methodology/Principal Findings In this work, we identified a set of 50 ABC transporters in catfish genome. Phylogenetic analysis allowed their identification and annotation into seven subfamilies, including 9 ABCA genes, 12 ABCB genes, 12 ABCC genes, 5 ABCD genes, 2 ABCE genes, 4 ABCF genes and 6 ABCG genes. Most ABC transporters are conserved among vertebrates, though cases of recent gene duplications and gene losses do exist. Gene duplications in catfish were found for ABCA1, ABCB3, ABCB6, ABCC5, ABCD3, ABCE1, ABCF2 and ABCG2. Conclusion/Significance The whole set of catfish ABC transporters provide the essential genomic resources for future biochemical, toxicological and physiological studies of ABC drug efflux transporters. The establishment of orthologies should allow functional inferences with the information from model species, though the function of lineage-specific genes can be distinct because of specific living environment with different selection pressure.
The ABC transporter gene family of Daphnia pulex
Armin Sturm, Phil Cunningham, Michael Dean
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-170
Abstract: We identified 64 ABC proteins in the Daphnia genome, which possesses members of all current ABC subfamilies A to H. To unravel phylogenetic relationships, ABC proteins of Daphnia were compared to those from yeast, worm, fruit fly and human. A high conservation of Daphnia of ABC transporters was observed for proteins involved in fundamental cellular processes, including the mitochondrial half transporters of the ABCB subfamily, which function in iron metabolism and transport of Fe/S protein precursors, and the members of subfamilies ABCD, ABCE and ABCF, which have roles in very long chain fatty acid transport, initiation of gene transcription and protein translation, respectively. A number of Daphnia proteins showed one-to-one orthologous relationships to Drosophila ABC proteins including the sulfonyl urea receptor (SUR), the ecdysone transporter ET23, and the eye pigment precursor transporter scarlet. As the fruit fly, Daphnia lacked homologues to the TAP protein, which plays a role in antigene processing, and the cystic fibrosis transmembrane conductance regulator (CFTR), which functions as a chloride channel. Daphnia showed two proteins homologous to MDR (multidrug resistance) P-glycoproteins (ABCB subfamily) and six proteins homologous to MRPs (multidrug resistance-associated proteins) (ABCC subfamily). However, lineage specific gene duplications in the ABCB and ABCC subfamilies complicated the inference of function. A particularly high number of gene duplications were observed in the ABCG and ABCH subfamilies, which have 23 and 15 members, respectively.The in silico characterisation of ABC transporters in the Daphnia pulex genome revealed that the complement of ABC transporters is as complex in crustaceans as that other metazoans. Not surprisingly, among currently available genomes, Daphnia ABC transporters most closely resemble those of the fruit fly, another arthropod.ATP-binding cassette (ABC) proteins constitute one of the largest protein superfamilies and a
Export of recombinant proteins in Escherichia coli using ABC transporter with an attached lipase ABC transporter recognition domain (LARD)
Chan Chung, Jinsun You, Kyeongyeon Kim, Yuseok Moon, Hoeon Kim, Jung Ahn
Microbial Cell Factories , 2009, DOI: 10.1186/1475-2859-8-11
Abstract: The LARDs included four glycine-rich repeats comprising a β-roll structure, and were added to the C-terminus of test proteins. Either Pro-Gly linker or Factor Xa site was added between fusion proteins and LARDs. We attached different length of LARDs such as LARD0, LARD1 or whole TliA (the longest LARD) to three types of proteins; green fluorescent protein (GFP), epidermal growth factor (EGF) and cytoplasmic transduction peptide (CTP). These fusion proteins were expressed in Escherichia coli together with ABC transporter of either P. fluorescens or Erwinia chrysanthemi. Export of fusion proteins with the whole TliA through the ABC transporter was evident on the basis of lipase enzymatic activity. Upon supplementation of E. coli with ABC transporter, GFP-LARDs and EGF-LARDs were excreted into the culture supernatant.The LARDs or whole TliA were attached to C-termini of model proteins and enabled the export of the model proteins such as GFP and EGF in E. coli supplemented with ABC transporter. These results open the possibility for the extracellular production of recombinant proteins in Pseudomonas using LARDs or TliA as a C-terminal signal sequence.Type I secretion system (T1SS) works in a continuous secretion process across both the inner and the outer membrane of Gram-negative bacteria [1,2]. The proteins involved in Type I secretion form a channel that exports proteins from the cytoplasm to the extracellular environment. An ATP binding cassette (ABC) protein recognizes the C-terminal signal sequence of the target protein, which is not cleaved during secretion and which hydrolyzes ATP for protein translocation [3,4]. Hence T1SSs are also known as ABC transporters. Membrane fusion protein (MFP) is exposed mainly to the periplasm and has one transmembrane segment anchored in the inner membrane [5]. MFP connects the ABC protein and outer membrane protein (OMP) during formation of the transport complex [6,7]. OMP is an outer membrane porin protein that forms a tunnel ac
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