Biomedical subjects

M Kuwano

Publications and source records attributed to M Kuwano.

At least 55 records · Page 3Linked to original sources

PubMed1999

Structural characterization of the human interleukin-13 receptor alpha1 gene promoter.

Human cancer cells have been found to express a large number of IL-13 receptors. We have previously shown that mRNA encoding one of these receptors, IL-13Ralpha1, is increased in cisplatin-resistant cells and is upregulated in tumor cells cultured with cisplatin. To understand the molecular mechanism of IL-13Ralpha1 gene expression, we cloned approximately 52 kbp of the IL-13Ralpha1 gene and sequenced the first exon and about 1 kbp of the upstream DNA. The first exon is 211 bp and contains 88 bp of coding sequence, while the first intron is about 13 kbp in length. The promoter region, which is GC rich, was found to lack both TATA and CCAAT boxes. Transient expression assays revealed that transcription of the IL-13Ralpha1 gene was significantly higher in cisplatin-resistant cells than in parental, cisplatin-sensitive cells. Deletion analysis of the IL-13Ralpha1 promoter identified a 70-bp core promoter region upstream of the transcription initiation site. Electrophoretic gel mobility shift assays showed that a synthetic IL-13Ralpha1 oligonucleotide (nt -40 to nt -15) bound a nuclear factor from cisplatin-resistant cells to a significantly greater degree than the equivalent factor from parental cells. This oligonucleotide was found to contain a palindromic sequence with a BstEII recognition site at its center. This palindromic sequence functions to mediate upregulation of IL-13Ralpha1 promoter in cisplatin-resistant cells and deletion or disruption of this sequence also resulted in severe reduction of the promoter activity. These findings suggest that IL-13Ralpha1 expression is upregulated at the transcriptional level in cisplatin-resistant cells. The characterization of both the IL-13Ralpha1 promoter and the transcription factors binding to it may contribute to our understanding of IL-13Ralpha1 regulation in cancer cells.

Antineoplastic Agents↗

PubMed1999

Enhanced transport of anticancer agents and leukotriene C4 by the human canalicular multispecific organic anion transporter (cMOAT/MRP2).

We established stable human canalicular multispecific organic anion transporter (cMOAT/MRP2) cDNA transfectants, CHO/cMOAT from non-polarized Chinese hamster ovary (CHO)-K1 and LLC/cMOAT from polarized pig kidney epithelial LLC-PK1. Human cMOAT was mainly localized in the plasma membrane of CHO/cMOAT and in the apical membrane of LLC/cMOAT. The ATP-dependent uptake of leukotriene C4 (LTC4) into CHO/cMOAT membrane vesicles was enhanced compared with empty vector transfectants. Km values in CHO/cMOAT membrane vesicles were 0.24 microM for LTC4 and 175 microM for ATP. Drug sensitivity to vincristine and cisplatin in human cMOAT cDNA transfectants decreased, but not to etoposide. Cellular accumulation of vincristine and cisplatin in human cMOAT cDNA transfectants decreased, but not of etoposide. The uptake of LTC4 into CHO/cMOAT membrane vesicles was inhibited by exogenous administration of vincristine or cisplatin, but not that of etoposide. Moreover, this inhibition was more enhanced in the presence of glutathione. These consequences indicate that drug resistance to vincristine or cisplatin appears to be modulated by human cMOAT through transport of the agents, possibly in direct or indirect association with glutathione.

Adenosine Triphosphate↗

PubMed1999

Is nuclear expression of Y box-binding protein-1 a new prognostic factor in ovarian serous adenocarcinoma?

BACKGROUND: Nuclear expression of Y box-binding protein (YB-1), a member of the DNA binding protein family, has been reported to be much more highly concentrated in cisplatin-resistant cell lines than in their parental counterparts, suggesting an ability to limit cisplatin sensitivity. Moreover, YB-1 plays a key role in P-glycoprotein expression. Because ovarian carcinoma traditionally has been treated with cisplatin-based chemotherapy, the sensitivity of the tumors to chemotherapy could reflect a particular prognosis in patients with ovarian carcinoma. The aim of the current study was to determine whether YB-1 expression correlated with prognosis in ovarian serous adenocarcinoma patients. METHODS: The expression of YB-1 in the nucleus was examined immunohistochemically in 42 paraffin embedded primary Stage III (International Federation of Gynecology and Obstetrics) serous ovarian carcinoma tumors extirpated by primary surgery at Kyushu University Hospital between 1985-1995. RESULTS: Of the 40 primary ovarian tumors examined, 12 (30%) were positive for YB-1 expression in the nucleus. There was no significant difference in intraperitoneal stage, histologic grade, or residual tumor size after primary surgery between patients with tumors with positive and those with negative nuclear expression of YB-1 protein. The disease free survival curve for patients whose tumors were positive for nuclear expression of YB-1 protein was significantly worse than that for patients whose tumors were negative (P = 0.0025). P-glycoprotein was overexpressed in 4 of 12 tumors with nuclear YB-1 expression (33%) but there was no statistical significance between the expression of nuclear YB-1 and P-glycoprotein. CONCLUSIONS: The expression of YB- 1 protein in the nucleus may be considered a useful prognostic marker and also may reflect the sensitivity of ovarian serous adenocarcinoma to chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Cellular balance of glutathione levels through the expression of gamma-glutamylcysteine synthetase and glutathione thiol transferase genes in human hepatic cells resistant to a glutathione poison.

Buthionine sulfoximine (BSO) is a synthetic amino acid that irreversibly inhibits glutathione biosynthesis and deranges reduced glutathione (GSH) metabolism in liver cells. We isolated two BSO-resistant lines, HLE/BSO2-1 and HLE/BSO2-2, from human hepatic HLE/WT cells. Cellular levels of the Pi class glutathione thiol transferase (GSTP1) were 3-fold lower in BSO-resistant lines than in HLE/WT cells. By contrast, gamma-glutamylcysteine synthetase (GCS) heavy subunit (GCSh) mRNA levels were markedly decreased in HLE/BSO2-1 and HLE/BSO2-2 as compared with HLE/WT. The expression of a dominant-negative mutant of c-Jun inhibited the GCSh promoter activity in HLE/WT, but not in HLE/BSO2-1. Cellular levels of AP-1, however, were not decreased in either BSO-resistant cell line. Transfection of GCSh promoter of various lengths driven reporter constructs showed no sequence-specific increase in the promoter activities in HLE/BSO2-1. However, transfection of GSTP1 cDNA into HLE/BSO2-1 and HLE/BSO2-2 restored the levels of GCSh mRNA and the GCSh promoter activity to those of HLE/WT. Sequences between -315 and -241 bp of the 5' region contained an AP-1 site responsible for the enhanced GCSh promoter activity in GSTP1 transfectants of HLE/BSO2-1. In vivo footprint analysis showed a specific protection of the AP-1 site on GCSh promoter in GSTP1 transfected HLE/BSO2-1. GSH homeostasis thus appears to be maintained by an interaction between GSTP1 and GCS in human hepatic cells resistant to the GSH poison.

Buthionine Sulfoximine↗

PubMed1999

Metabolic fate of oxidized guanine ribonucleotides in mammalian cells.

8-Oxo-7,8-dihydroguanine- (8-oxoguanine-) containing nucleotides are generated in the cellular nucleotide pool by the action of oxygen radicals produced during normal cellular metabolism. We examined the interconversion and metabolic fate of 8-oxoguanine-containing ribonucleotides in mammalian cells. (1) 8-OxoGTP can be generated not only by direct oxidation of GTP but also by phosphorylation of 8-oxoGDP by nucleotide diphosphate kinase, and the 8-oxoGTP thus formed can serve as a substrate for RNA polymerase II to induce transcription errors. (2) MTH1 protein carrying intrinsic 8-oxo-dGTPase activity has the potential to hydrolyze 8-oxoGTP to 8-oxoGMP, thus preventing misincorporation of 8-oxoguanine into RNA. 8-OxoGMP, the degradation product, cannot be reutilized, since guanylate kinase, which has the potential to phosphorylate both GMP and dGMP, is inactive on 8-oxoGMP. (3) Ribonucleotide reductase, which catalyzes reduction of four naturally occurring ribonucleoside diphosphates, cannot convert 8-oxoguanine-containing ribonucleotide to the deoxyribonucleotide. This step appears to serve as a gatekeeper to prevent formation of mutagenic substrates for DNA synthesis from oxidized ribonucleotides.

Animals↗

PubMed1999

Transcription factor Y-box binding protein 1 binds preferentially to cisplatin-modified DNA and interacts with proliferating cell nuclear antigen.

The Y-box binding protein (YB-1) binds to inverted CCAAT box sequences that are present in the promoter region of many genes. We previously showed that YB-1 is overexpressed in human cancer cell lines that are resistant to cisplatin and that the depletion of YB-1 by transfection of a vector expressing YB-1 antisense RNA increases the sensitivity of human cancer cells to cisplatin. To determine whether YB-1 can bind to cisplatin-modified DNA, we fused YB-1 cDNA to glutathione S-transferase (GST) cDNA and purified the resulting GST fusion protein. When we tested the fusion protein with unmodified or cisplatin-modified oligonucleotides, we found that GST-YB-1 bound more strongly to cisplatin-modified oligonucleotides, as did GST fusion proteins of high mobility group 1 (HMG1), HMG2, and xeroderma pigmentosum group A protein. When we assayed the ability of proliferating cell nuclear antigen (PCNA) to interact with the GST fusion proteins, we observed binding to YB-1 but not to HMG1, HMG2, or xeroderma pigmentosum group A. Subsequent experiments demonstrated that YB-1 and PCNA interact directly via the COOH-terminal region of YB-1. Using immunochemical coprecipitation methods, we observed binding of YB-1 and PCNA in vivo. These results suggest that YB-1 can function as a recognition protein for cisplatin-damaged DNA and that it may be important in DNA repair or in directing the cellular response to DNA damage.

CCAAT-Enhancer-Binding Proteins↗

PubMed1999

Contribution of P-glycoprotein to bunitrolol efflux across blood-brain barrier.

In this study, we investigated the mechanism of the blood-brain barrier (BBB) transport of bunitrolol (BTL), as a model of beta-blocker, in vivo and in vitro. In order to define the contribution of P-glycoprotein (P-gp) to the active efflux of BTL from brain to blood, we examined the in vivo brain distribution of BTL in mdr1a(-/-) mice with a disrupted mdr1a gene. After intravenous administration of BTL to mdr1a(-/-) mice, the brain concentration and Kp value of BTL were significantly increased as compared with those in mdr1a(+/+) mice. Next, the contribution of the mdr1a P-gp to in vitro uptake of BTL was compared in LV500 cells and L cells (mouse mdr1a-expressing cells and host cells, respectively). The intracellular accumulations of [3H]vinblastine and BTL by LV500 cells were lower than those by L cells, but were significantly increased by verapamil, a P-gp inhibitor. Furthermore, the BTL uptake by KB-VJ300 cells, which express human P-gp, was also significantly lower than that by KB host cells, and was increased by verapamil. The steady-state uptake of BTL by LLC-GA5-COL300 cells, expressing human P-gp, was significantly increased in the presence of 20 microM cyclosporin A (another P-gp inhibitor), which had no effect in the LLC-PK1 host cells. On the other hand, the steady-state intracellular accumulation of BTL by MBEC4 cells, which express mdr1b P-gp instead of mdr1a P-gp, was not significantly changed in the presence of verapamil. This finding suggested that BTL is not a good substrate for mdr1b P-gp. In conclusion, our results suggest that BTL is transported from brain to blood by mdr1a P-gp in mice and by MDR1 in humans, and this presumably accounts for the low brain distribution of BTL.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

The human multidrug resistance protein 2 gene: functional characterization of the 5'-flanking region and expression in hepatic cells.

The human multidrug resistance protein 2 (MRP2), also termed as the canalicular multispecific organic anion transporter (cMOAT), is a member of the adenosine triphosphate-binding cassette transporter superfamily. In the liver, MRP2 mediates the multispecific efflux of various types of organic anions, including glucuronate, sulfate, and glutathione conjugates, across the canalicular hepatocyte membrane to the bile. To investigate how the MRP2 gene is expressed in liver cells, the 5'-flanking region of the human MRP2 gene was isolated from a human placental genomic library. Sequence analysis of the MRP2 promoter showed a number of consensus binding sites for both ubiquitous and liver-enriched transcription factors. Transfection of human hepatic HepG2 cells with a series of 5'-deleted promoter luciferase constructs identified a putative silencer element localized in the -1,659/-491 region and a liver-specific positive regulatory element localized in the -491/-258 region. This latter region contained the liver-abundant transcription factor CCAAT-enhancer binding protein beta (C/EBPbeta). The transcriptional activity of the promoter construct containing a mutation in the C/EBPbeta binding site was significantly decreased in HepG2 cells. This study suggests that C/EBPbeta (-356 to -343) may regulate the liver expression of the MRP2 gene.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed1999

Biological implications of macrophage infiltration in human tumor angiogenesis.

Tumor angiogenesis is believed to be induced by increased production of angiogenic factors and decreased production of angiogenic inhibitors by cancer cells, vascular endothelial cells, and other stromal cell types. Most solid tumor cells are surrounded by stroma comprising interstitial connective tissue, blood vessels, fibroblastic cells, etc. Interaction between the stroma and malignant cells appears to have a critical role in the development of tumor neovasculature. We focused on macrophages, which demonstrate wide heterogeneity in biological function and have an essential role in tumor angiogenesis. Macrophages are terminally differentiated cells which produce a number of potent angiogenic cytokines and growth factors such as vascular endothelial growth factor, tumor necrosis factor-alpha, interleukin-8, and basic fibroblast growth factor. They also modulate events in the extracellular matrix through the secretion of extracellular matrix-degrading enzymes and -modulating enzymes. Thus macrophages could influence various stages of angiogenesis either positively or negatively. We found a close correlation between increased macrophage index, malignancy, and high vascular grade in malignant melanoma, and present a model for the possible involvement of activated macrophages in neovascularization in human malignant melanoma.

Animals↗

PubMed1999

Induction of macrophage inflammatory protein-1alpha and vascular endothelial growth factor during inflammatory neovascularization in the mouse cornea.

We predicted that the appearance of macrophages in inflammatory areas is necessary for angiogenic responses in various inflammatory diseases. Using a mouse inflammatory corneal model in which model mouse corneas were cauterized with silver nitrate, we examined the infiltration of macrophages immunohistochemically and the total area of neovascularization quantitively. The expression of macrophage inflammatory protein-1alpha (MIP-1alpha) and vascular endothelial growth factor (VEGF) levels were also examined. A day after cauterization, short capillaries began to develop into the corneal stroma, and after 4 or 5 days the neovascularization became maximal and then began to regress. The number of macrophages within the cauterized cornea increased to a maximum at day 3 and began to decrease at day 5. The number of infiltrated macrophages reached maximum at day 3. Both MIP-1alpha and VEGF protein levels increased markedly immediately after the chemical cauterization, and production of MIP-1alpha (85.8 pg/4 corneas) and VEGF (206.5 pg/4 corneas) was maximal at 1 day and 0.5 day after cauterization, respectively. MIP-1alpha and VEGF mRNA levels also increased at 0.5 day after cauterization. In situ hybridization showed that MIP-1alpha was localized in corneal epithelial cells, and VEGF was localized in corneal epithelial cells and infiltrating inflammatory cells. MIP-1alpha and VEGF may have an important role in recruiting macrophages and neovascularization.

Journal Article↗

PubMed1999

Association of 5' CpG demethylation and altered chromatin structure in the promoter region with transcriptional activation of the multidrug resistance 1 gene in human cancer cells.

Selection of human cells for resistance to vincristine or doxorubicin often induces overexpression of the multidrug resistance 1 gene (MDR1), which encodes the cell surface P-glycoprotein, as a result of gene amplification or transcriptional activation. However, the precise mechanism underlying such transcriptional activation of MDR1 remains unclear. The relation between methylation status of CpG sites in the MDR1 promoter region and transcriptional activation of MDR1 has now been investigated. The P-glycoprotein-overexpressing, multidrug-resistant KB/VJ300 and KB-C1 cells, which were established from human cancer KB3-1 cells, were examined; MDR1 is transcriptionally activated but not amplified in KB/VJ300 cells, whereas it is amplified in KB-C1 cells. Determination of the methylation status revealed that the MDR1 promoter region was hypomethylated in KB/VJ300 and KB-C1 cells, but hypermethylated in KB3-1 cells. Prior treatment of KB3-1 cells with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine resulted in a 90-fold increase in the frequency of vincristine-resistance. Of three lines, KB/CdR-1, KB/CdR-2, and KB/CdR-3, established from KB3-1 cells after exposure to 5-aza-2'-deoxycytidine, MspI/HpaII sites in the MDR1 promoter region were hypomethylated in KB/CdR-1 and KB/CdR-2 cells, but not in KB/CdR-3 cells. MDR1 mRNA expression was detected in KB/CdR-1 and KB/CdR-2 cells, but not in KB/CdR-3 cells. The binding of YB-1 and Sp1, transcription factors implicated in MDR1 expression, in the MDR1 promoter was not affected by the methylation status of a neighboring CpG sites. The MDR1 promoter region in KB/VJ300 cells showed an increased sensitivity to DNase I compared with that in KB3-1 cells, suggesting an altered chromatin structure. The methylation status of the promoter region may plays an important role in MDR1 overexpression and in acquisition of the P-glycoprotein-mediated multidrug resistance phenotype.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Genomic structure of the canalicular multispecific organic anion-transporter gene (MRP2/cMOAT) and mutations in the ATP-binding-cassette region in Dubin-Johnson syndrome.

Dubin-Johnson syndrome (DJS) is an autosomal recessive disease characterized by conjugated hyperbilirubinemia. Previous studies of the defects in the human canalicular multispecific organic anion transporter gene (MRP2/cMOAT) in patients with DJS have suggested that the gene defects are responsible for DJS. In this study, we determined the exon/intron structure of the human MRP2/cMOAT gene and further characterized mutations in patients with DJS. The human MRP2/cMOAT gene contains 32 exons, and it has a structure that is highly conserved with that of another ATP-binding-cassette gene, that for a multidrug resistance-associated protein. We then identified three mutations, including two novel ones. All mutations identified to date are in the cytoplasmic domain, which includes the two ATP-binding cassettes and the linker region, or adjacent putative transmembrane domain. Our results confirm that MRP2/cMOAT is the gene responsible for DJS. The finding that mutations are concentrated in the first ATP-binding-cassette domain strongly suggests that a disruption of this region is a critical route to loss of function.

ATP-Binding Cassette Transporters↗

PubMed1999

Effect of multidrug resistance-reversing agents on transporting activity of human canalicular multispecific organic anion transporter.

The canalicular multispecific organic anion transporter (cMOAT), also termed MRP2, is a recently identified ATP-binding cassette transporter. We previously established stable human cMOAT cDNA-transfected cells, LLC/cMOAT-1 from LLC-PK1 cells, and LLC/CMV cells that were transfected with an empty vector. We found that LLC/cMOAT-1 cells have increased resistance to vincristine (VCR), 7-ethyl-10-hydroxy-camptothecin, and cisplatin but not to etoposide. The multidrug resistance-reversing agents cyclosporin A (CsA) and 2-[4-(diphenylmethyl)-1-piperazinyl]-5-(trans-4,6-dimethyl-1,3, 2-dioxaphosphorinan-2-yl)-2, 6-dimethyl-4-(3-nitrophenyl)-3-pyridinecarboxylate P-oxide (PAK-104P) almost completely reversed the resistance to VCR, 7-ethyl-10-hydroxy-camptothecin, and cisplatin of LLC/cMOAT-1 cells; and DL-buthionine-(S,R)-sulfoximine, (3'-oxo-4-butenyl-4-methyl-threonine(1), (valine(2)) cyclosporin (PSC833), and 3-([(3-(2-[7-chloro-2-quinolinyl]ethenyl)phenyl)-((3-dimethylamino-3- oxopropyl)-thio)-methyl]thio)propanoic acid (MK571) partially reversed the resistance to these drugs. CsA and PAK-104P at 10 microM enhanced the accumulation of VCR in LLC/cMOAT-1 cells almost to the level in LLC/CMV cells without the agents. The efflux of VCR from LLC/cMOAT-1 cells was enhanced compared with LLC/CMV cells and inhibited by CsA and PAK-104P. Transport of leukotriene C(4) (LTC(4)) and S-(2, 4-dinitrophenyl)glutathione also was studied with membrane vesicles prepared from these cells. LTC(4) and S-(2, 4-dinitrophenyl)glutathione were actively transported into membrane vesicles prepared from LLC/cMOAT-1 cells. The K(m) and V(max) values for the uptake of LTC(4) by the LLC/cMOAT-1 membrane vesicles were 0. 26 +/- 0.05 microM and 7.48 +/- 0.67 pmol/min/mg protein, respectively. LTC(4) transport was competitively inhibited by PAK-104P, CsA, MK571, and PSC833, with K(i) values of 3.7, 4.7, 13.1, and 28.9 microM, respectively. These findings demonstrate that cMOAT confers a novel drug-resistance phenotype. CsA and PAK-104P may be useful for reversing cMOAT-mediated drug resistance in tumors.

Adenosine Triphosphate↗

PubMed1999

Macrophage infiltration and heme oxygenase-1 expression correlate with angiogenesis in human gliomas.

Macrophages are key participants in angiogenesis. In this study on human brain tumors, we first investigated whether macrophage infiltration is associated with angiogenesis and malignant histological appearance. Immunostaining of macrophages and small vessels in resected glioma specimens indicated that numbers of infiltrating macrophages and small vessel density were higher in glioblastomas than in astrocytomas or anaplastic astrocytomas. Macrophage infiltration was closely correlated with vascular density in human gliomas. Heme oxygenase-1 (HO-1), which is the rate-limiting enzyme in heme catabolism, was also associated with activated macrophages. Expression of mRNA encoding HO-1 was correlated with macrophage infiltration and vascular density in human glioma samples. Infiltrating macrophages were positively stained with anti-HO-1 antibody by immunohistochemical analysis, and in situ hybridization for HO-1 indicated that HO-1 was expressed in infiltrating macrophages in gliomas. HO-1 gene may be a useful marker for macrophage infiltration as well as neovascularization in human gliomas.

Adolescent↗

PubMed1999

Suppression of retinal neovascularization by the NF-kappaB inhibitor pyrrolidine dithiocarbamate in mice.

PURPOSE: To evaluate the effect of pyrrolidine dithiocarbamate (PDTC), an inhibitor of nuclear factor kappaB (NF-kappaB), on retinal neovascularization in a murine model of ischemic retinopathy. METHODS: One-week-old C57BL/6N mice were exposed to 75%+/-2% oxygen for 5 days and then were returned to room air to induce retinal neovascularization. After the return to room air, the left and right eyes were injected intravitreally with PDTC or a vehicle, respectively. Retinal neovascularization was examined by injecting fluorescein dextran and angiography after 5 days in room air and was quantitated histologically with a masked protocol. The effects of PDTC on NF-kappaB activation were evaluated by immunohistochemistry. To examine the toxicity of PDTC, the histologic change in the retina was examined by light and electron microscopy. RESULTS: Retinal neovascularization in the eye injected with PDTC by intravitreal methods was reduced in 100% of animals compared with that apparent in the vehicle-treated eye. The inhibitory effect was dose-dependent, with a maximal inhibition of 39% (P < 0.01) at a dose of 1 nmole. The immunostaining intensity for NF-KB in the retina was reduced by PDTC injections. No side effects by PDTC in the retina were observed by light and electron microscopy. CONCLUSIONS: NF-kappaB activation appears to be required for retinal angiogenesis, given that the administration of PDTC suppressed retinal neovascularization. PDTC may prove beneficial in the treatment of ischemic neovascular diseases such as diabetic retinopathy and retinal vein occlusion.

Animals↗

PubMed1999

Structural and functional analysis of the control region of the human DNA topoisomerase II alpha gene in drug-resistant cells.

We have previously shown that the DNA topoisomerase II alpha (topo II alpha) gene is down-regulated in VP16/VM26-resistant cells at the transcriptional level. To determine the DNA elements responsible for down-regulation, the transcriptional activities of luciferase reporter constructs containing various lengths of the promoter sequences were investigated by transient transfection of two resistant cell lines, KB/VP2 and KB/VM4. The transcriptional activities of the full-length promoter (-295 to +85) and of three deletion constructs (-197, -154 and -74 to +85) were significantly down-regulated in resistant cells. In contrast, the transcriptional activity of the minimal promoter (-20 to +85) in resistant cells was similar to that in parental KB cells. Furthermore, introduction of a mutation in ICE1 abolished the down-regulation of the topo II alpha promoter activity in drug-resistant cells. In vivo footprinting analysis of topo II alpha gene promoter revealed several specific protein-binding sites, a GC box, ICE1, ICE2 and ICE3. In vivo footprinting analysis also identified a cluster of hypersensitive sites. However, there was no marked difference in protein-binding sites between parental and resistant cells. To confirm our previous results, we have established the VP16-resistant cell lines T12-VP1 and T12-VP2 from T12 cells derived from human bladder cancer T24 cells stably transfected with the chloramphenicol acetyltransferase reporter gene driven by the topo II alpha gene promoter. The expression to topo II alpha was down-regulated in both cell lines. We also found that CAT gene expression was significantly decreased to one-fifth of that in T12 parental cells. These results suggest that the expression of the topo II alpha gene requires the binding of multiple factors to the core promoter and is down-regulated at the transcriptional level, probably through binding of a negative factor to ICE1 in drug-resistant cells.

Antigens, Neoplasm↗

PubMed1999

Multidrug resistance-associated protein subfamily transporters and drug resistance.

Multidrug resistance-associated protein gene MRP/MRP1, and its family genes, including MRP2/cMOAT, have been isolated and characterized. These ATP-binding cassette (ABC) superfamily transporter genes are differentially expressed in various normal tissues and multidrug-resistant cell lines. Transfection of MRP/MRP1 and MRP2/cMOAT cDNA confers drug resistance on different spectra of anticancer agents from that of MDR1 coding P-glycoprotein. Although it remains unclear how MRP/MRP1 and related family genes are specifically involved in drug resistance in clinical cancers, current knowledge of the MRP subfamily suggests the importance of this class of transporters as a molecular target for drug sensitivity to anticancer agents.

ATP-Binding Cassette Transporters↗

PubMed1999

[Anti-tumor effects of carmofur on human 5-FU resistant cells].

As a part of studies to clarify the efficacy mechanism of carmofur (HCFU), a 5-FU analog, the degree of cross-resistance to HCFU of cell lines of cultured human colon cancer DLD-1 and a stomach cancer NUGC-3, both of which had acquired resistance to 5-FU, was studied in vitro and in vivo. In vitro, both resistant cell lines showed no or little cross-resistance to HCFU under a short-term drug exposure, and very low cross-resistance to HCFU, as compared to resistance to 5-FU, under a long-term drug exposure. In therapeutic experiments using nude mice bearing parent or subcutaneously transplanted 5-FU-resistant DLD-1 cells, HCFU exerted almost the same growth-inhibitory effects on both tumors. These results suggest that HCFU itself may have its own anti-tumor mechanism, different from that of 5-FU.

Animals↗