PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Genes, MDR”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1996

Retroviral transfer and expression of the human multiple drug resistance (MDR) gene in peripheral blood progenitor cells.

The multiple drug resistance (MDR) gene P-glycoprotein product is a transmembrane efflux pump that prevents toxicity of a variety of chemotherapeutic agents, including the anthracyclines, Vinca alkaloids, podophyllins, and taxol. The bone marrow toxicity of these drugs is due to the low or absent expression of MDR in marrow cells. Transfer and expression of the human MDR gene into bone marrow progenitors should prevent this toxicity. We report here the efficient transfer and expression of the MDR gene by retroviral-mediated gene transfer into CD34(+) cells isolated from peripheral blood progenitor cells (PBPCs), comparable to that obtained using bone marrow-derived progenitors. Optimal MDR transduction of these PBPC-derived cells requires exposure to growth factors and a period of preincubation. In addition, we demonstrate that we can transduce up to 100% of progenitor cells derived from PBPCs and can protect up to 25% of these progenitors from a dose of taxol toxic to untransduced controls.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Expression of multidrug resistance gene (mdr-1) mRNA in gastric and colorectal cancers.

Fresh surgical specimens of 52 gastric cancers and 25 colorectal cancers were analyzed for the expression of multidrug resistance (mdr-1) gene mRNA with non-isotopic in situ hybridization (ISH) using a biotin-labeled oligonucleotide probe. The mdr-1 mRNA was expressed in 15.4% in cancerous portions and 1.9% in non-cancerous portions of gastric cancers (p < 0.02). In colorectal cancers, the mdr-1 mRNA was positive in 36% in cancerous portions and 28% in non-cancerous portions. In gastric cancers, the well-differentiated type showed a significantly higher positive rate than the poorly differentiated type (p < 0.01). These results suggest that the mdr-1 mRNA expression in gastric and colorectal cancers is related to the degree of cellular differentiation.

Adenocarcinoma↗
PubMed1996

[The karyotypic variability of Chinese hamster CHLV-79 RJK cells characterized by multiple drug resistance resulting from the amplification of the mdr gene family].

Variability in karyotype structure of Chinese hamster lung V-79 RJK cells and of their six cell sublines, selected for increasing concentrations of ethidium bromide (EB), was investigated in addition to the number of mdr gene copies in cells, both EB sensitive and resistant. It is shown that EB resistant cells exhibit cross-resistance to different drugs resulting from mdr genes amplification. Southern DNA blot hybridization has shown that in Vebr-2 cells (the 1st step of selection) the number of mdr gene copies increased by 10 times, whereas in Vebr-30 cells (the 6th step of selection) the number of mdr gene copies remained the same as in Vebr-2 cells. The level of mdr genes expression in Vebr-30 cells being higher than in Vebr-2 cells. In Vebr-2 cells, homogeneously and differentially stained regions (HSRs) were detected in loci 1p31 and 1q26 of chromosome 1 material (markers Z1 and Z6, respectively). On the following selection steps (prolonged cultivation or increased drug concentration) additional HSRs appeared in chromosome 2 (locus 2qter), in derivatives of chromosome 5 (marker Z7, locus Z7pter) and chromosome X (marker Z2, locus Z2qter). In the course of prolonged cultivation, chromosome 2 and derivatives of chromosomes 1, 2, 5 and X, in which HSRs were found, participated in the formation of new markers resulting from deletions, inversions, insertions and translocations of the chromosomal material. It is supposed that mdr genes amplification in V-79 RJK cells resistant to EB may be regarded as a factor inducing subsequent genome destabilization and eventual progressive changes in the karyotype structure.

Animals↗
PubMed1997

Differential changes in genome structure and expression of the mdr gene family in multidrug-resistant murine erythroleukemia cell lines.

The genome structure and expression of mdr genes were examined in multidrug-resistant sublines of two different murine (DBA/2J) Friend erythroleukemia cell lines, PC4 and C7D, derived by stepwise exposure to increasing concentrations of adriamycin beginning with 5 ng/ml. The PC4 cell lines selected in higher drug concentrations (80-1280 ng/ml) demonstrated amplification of all three mdr genes with preferential amplification of mdr3. Overexpression of the mdr2 and mdr3 genes accompanied their genomic amplification; however, expression of mdr1 was not seen despite amplification. In the C7D cell lines selected with higher drug concentrations (40-160 ng/ ml), amplification and overexpression of mdr1 and mdr2 without mdr3 was observed. Increased expression of mdr1 occurred prior to gene amplification. The distribution of mdr-specific genes in micrococcal nuclease-generated chromatin fractions differing in transcriptionally active sequences and proteins was different between the parent and drug-resistant sublines. An enrichment (two- to threefold) of mdr3 genes in the H1-depleted mononucleosome fraction enriched for actively transcribed genes (e.g., globin) was detected by Southern analysis of chromatin fractions in PC4-80 cells (selected in 80 ng/ml of adriamycin and overexpressing mdr3), compared to the parental cells. mdr3 enrichment was also detected using a new PCR-based method, which examined mdr3 genes and repetitive sequences. Of note, the H1-depleted chromatin fraction from PC4-20 showed enrichment of the mdr3 gene, although mdr3 expression was not detected in the cell line. These studies showed a different pattern of gene amplification and overexpression in genetically related erythroleukemia cell lines selected for resistance to the same chemotherapeutic agent. A change in chromatin organization of mdr genes preceded overexpression and amplification of the mdr3 gene.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Time course of MDR gene amplification during in vivo selection for doxorubicin-resistance and during reversal in murine leukemia L 1210.

MDR gene expression in murine leukemia L 1210 cells was investigated during treatment in vivo with 0.5 mg doxorubicin/kg body weight (BW). Drug resistance (measured by an in vitro short-term test and immunohistochemistry) increased with the number of treatments and the maximum resistance reached after 8 treatments was similar with that of an established multidrug- resistant cell line (20 treatments, 2 mg/kg BW). Southern-blot and DNA dot-blot analyses show that development of MDR is associated with MDR-gene amplification and correlates with the degree of drug resistance and P-glycoprotein-expression. After cessation of doxorubicin treatment, resistance decreased continuously and disappeared after 20 passages. This decrease in resistance is accompanied by a loss of MDR gene amplification and P-glycoprotein expression. Furthermore, P-glycoprotein expression was analyzed in the first hours after treatment with doxorubicin in vivo (0.5 mg/kg BW). Expression was markedly increased and peaked at about 24 hours after treatment. In contrast, only slightly increased resistance and no MDR gene amplification could be detected.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Down-regulation of the mdr gene by thyroid hormone during Xenopus laevis development.

The developmental regulation of mdr in Xenopus laevis has been investigated. Xe-mdr expression was first detected in the early tadpole stage just prior to the onset of feeding and increased during intestinal development, with a sharp decline at metamorphosis. Xe-mdr expression was found to be localized specifically to the epithelial cells lining the intestinal tract. When premetamorphic tadpoles were treated with 5 nM triiodothyronine to induce metamorphosis, a significant decrease in mdr message and protein was observed after 3 days, a time at which the primary epithelium remained intact. Furthermore, in thyroid-hormone treated primary cultures of brush border epithelial cells, a reduction in mdr message also was observed. These results demonstrate that the Xe-mdr gene is developmentally regulated and suggest a role for thyroid hormone in this process. This is the first report of a naturally occurring substance that can down-regulate mdr gene expression in vivo.

Animals↗
PubMedDate not supplied

Expression of multidrug resistance gene (MDR-1) in human normal leukocytes.

BACKGROUND: The mdr-1 gene, which codes for a 170-kd transmembrane glycoprotein (P170), is frequently overexpressed in multidrug resistant (MDR) tumor cell lines and in spontaneous tumors, including leukemia and lymphoma. However, it is also constitutively expressed as a normal gene in normal tissues. METHODS: We used human mdr-1 cDNA and three anti-P170 monoclonal antibodies (MoAbs: MRK-16, C-219 and JSB-1) to investigate the normal peripheral blood leukocyte content of mdr-1 specific mRNA and of P170 through immunocytochemistry and flow cytometry. RESULTS: We did not find any increase in mdr-1-specific mRNA, while small amounts of P170 were easily detectable in about two thirds of the lymphocytes and monocytes and in about one third of the granulocytes. The level of P170 expression in leukocytes was similar to that found in non-MDR tumor cell lines. CONCLUSIONS: mdr-1 is constitutively expressed in human normal leukocytes at levels that cannot significantly affect drug resistance. Accordingly, low-level mdr-1 expression in leukemic cells should not be considered a label of pleiotropic drug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Mitotane enhances cytotoxicity of chemotherapy in cell lines expressing a multidrug resistance gene (mdr-1/P-glycoprotein) which is also expressed by adrenocortical carcinomas.

P-Glycoprotein (Pgp), product of the mdr-1 gene, is a 130- to 180-kDa plasma membrane phosphoglycoprotein which mediates multidrug resistance in cell culture by increasing efflux of the natural product chemotherapeutic agents. High levels of expression of mdr-1/Pgp are found in both the normal adrenal and adrenocortical cancers. By RNA in situ hybridization the expression in adrenocortical cancer is shown to be widely distributed. The present study demonstrates that decreased drug accumulation mediated by mdr-1/Pgp can be overcome by clinically achievable concentrations of mitotane (o,p'-DDD). The increase in drug accumulation with the addition of mitotane is due at least in part to a decrease in drug efflux and results in an increase in cytotoxicity when agents of the natural product class are used. This effect is observed in cells with a broad range of mdr-1/Pgp expression, including levels comparable to those found in most adrenocortical cancers. Similar increases in drug accumulation can be demonstrated in an unselected adrenocortical cancer cell line that expresses mdr-1/Pgp. The finding that multidrug resistance mediated by mdr-1/Pgp can be reversed by mitotane provides a rational basis for exploring the use of mitotane in combination with natural product chemotherapeutic agents in adrenocortical cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

[Use of thermostable DNA polymerase from Thermus thermophilus KTP in a combined reverse transcription and amplification reaction of detecting interleukin 2alpha RNA and determining expression of the multidrug resistance gene (MDR-1)].

According to our data native Tth DNA polymerase displays higher reverse transcription activity than Taq DNA polymerase. This allows one to use Tth DNA polymerase in the complete reaction of reverse transcription and amplification (RT/PCR). We used this enzyme to synthesize the interleukine (IL-2 alpha) RNA template synthesized by the RT/PCR method in vitro. The conditions for RNA IL-2 alpha detection were optimized. The maximum yield of the specific product was obtained at pH 8.5-9.0. The influence of bivalent cations on the efficiency of RT reaction of coupled RT/PCR can be expressed as: Mn2+ > or = Cu2+ > Mg2+ > Cd2+ >> Co2+. The optimal ratio is 1.25-1.88 for Mn2+/dNTPs and 1.88-2.5 for Cu2+/dNTPs and Cd2+/dNTPs. The maximum yield of the RT/PCR product is found at Mg2+/dNTPs = 3.75. When Mn2+ is used instead of Mg2+ in the PCR reaction the efficiency of RT/PCR decreases. The RT/PCR method embracing thermostable Tth DNA-polymerase provides detection of 10(3) copies of RNA IL-2 alpha. An efficient method of the express-diagnostics of MDR-1 gene expression by coupled RT/PCR using Tth DNA polymerase is described.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Two members of the mouse mdr gene family confer multidrug resistance with overlapping but distinct drug specificities.

We report the cloning and functional analysis of a complete clone for the third member of the mouse mdr gene family, mdr3. Nucleotide and predicted amino acid sequence analyses showed that the three mouse mdr genes encode highly homologous membrane glycoproteins, which share the same length (1,276 residues), the same predicted functional domains, and overall structural arrangement. Regions of divergence among the three proteins are concentrated in discrete segments of the predicted polypeptides. Sequence comparison indicated that the three mouse mdr genes were created from a common ancestor by two independent gene duplication events, the most recent one producing mdr1 and mdr3. When transfected and overexpressed in otherwise drug-sensitive cells, the mdr3 gene, like mdr1 and unlike mdr2, conferred multidrug resistance to these cells. In independently derived transfected cell clones expressing similar amounts of either MDR1 or MDR3 protein, the drug resistance profile conferred by mdr3 was distinct from that conferred by mdr1. Cells transfected with and expressing MDR1 showed a marked 7- to 10-fold preferential resistance to colchicine and Adriamycin compared with cells expressing equivalent amounts of MDR3. Conversely, cells transfected with and expressing MDR3 showed a two- to threefold preferential resistance to actinomycin D over their cellular counterpart expressing MDR1. These results suggest that MDR1 and MDR3 are membrane-associated efflux pumps which, in multidrug-resistant cells and perhaps normal tissues, have overlapping but distinct substrate specificities.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Differential regulation of mdr genes in response to 2-acetylaminofluorene treatment in cultured rat and human hepatocytes.

Expression of P-glycoprotein (P-gp), the mdr gene product, was investigated in primary cultures of rat and human hepatocytes exposed to 2-acetylaminofluorene (2-AAF). Increased levels of mdr1 mRNAs were evident in 2-AAF-treated rat hepatocytes by Northern blot analysis using rat mdr gene-specific probes, while transcripts of the mdr2 and mdr3 genes were decreased and unaffected respectively. Rat hepatocytes exposed to 2-AAF were also found to accumulate doxorubicin, an anticancer drug known to be transported by P-gp, poorly, thereby demonstrating that 2-AAF-mediated mdr1 induction resulted in increased P-gp activity. In contrast to their rat counterparts, human hepatocytes obtained from 10 individuals exhibited no change in both MDR1 and MDR2 mRNA levels, as well as in doxorubicin intracellular retention, in response to 2-AAF treatment, while cytochromes P-450 CYP1A1 and CYP1A2 were induced in both human and rat hepatocyte cultures. These data provide strong evidence that regulation of expression of mdr genes in liver cells in response to carcinogens such as 2-AAF is gene- and species-specific.

2-Acetylaminofluorene↗
PubMed2002

[Correlation of the uptake of technetium-99m methoxyisobutyl isonitrile with expression of multidrug resistance genes mdr-1 and MRP in human lung cancer].

OBJECTIVE: To investigate the relationship between the uptake of technetium-99m methoxyisobutyl isonitrile ((99m)Tc-MIBI) and the expression of multidrug resistance genes mdr-1 and MRP in lung cancer so as to guide chemotherapy. METHODS: Eighteen lung cancer patients were given 1 110 MBq(99m)Tc-MIBI intravenously. Chest single-photon emission-computed tomography was performed 60 and 120 min after the injection. The early and delay uptake rates and retain index of (99m)Tc-MIBI were calculated by the count ratio of the lung lesion to contralateral normal lung tissue. The expressions of mdr-1 and MRP genes in specimens of lung cancer and normal lung tissues near the cancers resected during operation among the 27 patients were detected with RT-PCR method. RESULTS: The positive rate of (99m)Tc-MIBI in the chest of lung cancer patients was 83.3% (15/18). The early uptake ratio of imaging in lung cancer patients was 1.99 +/- 0.64. After time decay correction, the rate of target to background and the retain index in 13 delay imagings were 2.06 +/- 0.69 and -45% approximately 33% respectively. In specimens of lung cancer, the positive expression rates of mdr-1 and MRP were 22.2%(6/27) and 63%(17/27) with the expression amount of 0.39 +/- 0.1 and 0.23 +/- 0.17 respectively. In specimens of normal lung tissues near lung cancer, the positive expression rates of mdr-1 and MRP genes were 35%(7/20) and 45.0%(9/20) with the expression amount of 0.44 +/- 0.14 and 0.17 +/- 0.18 respectively. In lung cancer tissues, the positive rate of MRP was higher than that of mdr-1 (P < 0.05), however, in the tissues near lung cancer, no significant difference was found between the positive rate of MRP and that of mdr-1 (P >< 0.05). There was no marked correlation (P >< 0.05) among the co-expression or expression of mdr-1 and/or MRP and the early uptake or retain index in lung cancer. CONCLUSION: The primary chemoresistance of lung cancer has not significant correlation to the expression of multidrug resistance genes mdr-1 and MRP. Other resistance mechanism may exist. (99m)Tc-MIBI imaging has not much clinical value in predicting the expression of mdr-1 and MRP genes.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Targeted disruption of the mouse mdr1b gene reveals that steroid hormones enhance mdr gene expression.

To evaluate the role of P-glycoprotein in steroid secretion in adrenal cells, we have used gene targeting to introduce a null mutation into one allele of the mdr1b gene in mouse Y1 adrenal cells. Characterization of both the wild-type and the mutant cell lines revealed the following. 1) The expression of mdr1b is enhanced by steroid hormones, in a feedback regulatory mechanism. Inhibition of steroid biosynthesis by 2-aminoglutethimide blocks the adrenocorticotropin (ACTH)-induced increase in mdr1b mRNA levels. 2) ACTH-stimulated steroid secretion is markedly decreased in the mutant cell line. This decreased steroid secretion in the mutant cells occurs despite an increase in the levels of mdr1b mRNA and P-glycoprotein. Kinetic analyses of vinblastine and daunomycin accumulation in both the wild-type and the mutant cell lines during ACTH-stimulated steroidogenesis show that in the mutant cells both drugs accumulated to higher levels than in Y1 cells, suggesting that the remaining mdr1b allele in the mutant cells is relatively inactive as an exporter of steroids, or that the targeted disruption of the mdr1b allele is associated with other changes in the mutant cells which block ACTH-stimulated steroid secretion.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

Organ-specific modulation of steady-state mdr gene expression and drug resistance in murine colon cancer cells.

BACKGROUND: The major cause of death from cancer is metastases that are resistant to conventional therapies. The resistance of metastatic tumor cells to chemotherapy can be caused by their intrinsic properties, such as increased expression of the mdr genes. PURPOSE: The purpose of our present study was to determine some of the mechanisms by which the organ microenvironment influences the response of tumor cells to chemotherapy. METHODS: Murine CT-26 colon cancer cells growing in continuous culture (parental cells) were harvested and injected subcutaneously into the lateral flank (to produce subcutaneous tumors) or the lateral tail vein (to produce experimental lung metastases) of 10 8-week-old syngeneic male BALB/c mice. Seven days after tumor-cell injection, the mice were given intravenous injections of either doxorubicin (10 mg/kg) or 0.9% NaCl (controls). This in vivo injection was repeated 7 days later. Mice with subcutaneous tumors and lung metastases were killed by cervical dislocation on day 21, and tumor samples from control mice were harvested and adapted to culture. The sensitivity of the cultured cells to doxorubicin and fluorouracil (5-FU) was determined at multiple time points. Levels of mdr-1 DNA were measured by slot-blot and Southern-blot analyses. mdr mRNA expression levels were measured by Northern-blot analysis using mdr-1- and mdr-3-specific hybridization probes, and P-glycoprotein level was determined by fluorescence-activated cell sorting using different monoclonal antibodies. RESULTS: Treatment with doxorubicin produced 80% growth inhibition of CT-26 subcutaneous tumors but had little effect on the number (and size) of experimental lung metastases. Collectively, the results suggest that the multidrug-resistant phenotype developed in CT-26 cells growing in the lung environment. Cultures established from lung metastases were initially resistant to doxorubicin (but not to 5-FU) and showed elevated expression of mdr-1 mRNA transcripts and P-glycoprotein. This resistance could be overcome by verapamil and disappeared after 21 days in culture. No mdr gene amplification was detected. The expression level of mdr-specific mRNA (predominance of mdr-1) and P-glycoprotein was directly associated with resistance to doxorubicin. CONCLUSIONS: Results of this study have demonstrated that the in vivo sensitivity of murine CT-26 colon carcinoma cells to doxorubicin depends on the organ environment. The organ environment can influence the P-glycoprotein-mediated multidrug-resistant phenotype in tumor cells, and the increased expression of P-glycoprotein is transient; once removed from the environment (lung), the cell's resistance reverts to that of the sensitive parent cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

A bacterial analog of the mdr gene of mammalian tumor cells is present in Streptomyces peucetius, the producer of daunorubicin and doxorubicin.

Sequence analysis of the drrAB locus from Streptomyces peucetius (American Type Culture Collection 29050) reveals the presence of two genes, drrA and drrB, both of which are required for daunorubicin and doxorubicin (Adriamycin) resistance in the heterologous host Streptomyces lividans. The DrrA protein is similar to a large family of ATP-binding transport proteins, including the proteins encoded by the mdr genes from mammalian tumor cells, which confer resistance to daunorubicin, doxorubicin, and some other structurally unrelated chemotherapeutic agents. The DrrB protein shows no significant similarity to other known proteins but is probably very hydrophobic, suggesting that it is located in the bacterial membrane. These two proteins may act jointly to confer daunorubicin and doxorubicin resistance by an analog of the antiport mechanism established for mammalian tumor cells that contain amplified or overexpressed mdr genes. Transcriptional analysis of the drrAB region supports the presence of one transcript containing drrA and drrB and indicates that these genes are expressed only during antibiotic production.

Base Sequence↗
PubMed1993

[The amplification and overexpression of the mdr genes in Chinese hamster CHLV-79 RJK cells resistant to ethidium bromide correlate with the presence of karyotypic markers of the amplification].

Evidence is provided that selection of the Chinese hamster cells CHLV-79 RJK with ethidium bromide results in amplification and overexpression of mdr family genes, one of which is encoding a transmembrane P-glycoprotein reducing the intracellular drug concentration. It is likely that the amplified copies are located at or near the sites of resident mdr gene localization to look as an abnormal chromosomal banding pattern in chromosome 1q26. In the following selection steps to higher drug concentration, the cells are keeping the degree of amplification, but mdr gene expression increases by many times. The data suggest that the resistance of the Chinese hamster cells CHLV-79 RJK to higher concentrations of ethidium bromide may be achieved via a variety of mechanisms, including as well mdr gene amplification as transcriptional regulation of these genes.

ATP Binding Cassette Transporter, Subfamily B, Mem↗