Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.44 (P-glycoprotein)
13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anti-B4-blocked ricin (anti-B4-bR) is an immunotoxin directed against CD19-positive cells that is currently being tested in several B-cell leukemia/lymphoma clinical trials. To explore the possibility of using anti-B4-bR in combination with chemotherapy protocols, we investigated the in vitro and in vivo cytotoxic effects of combining it with doxorubicin or etoposide using the lymphoma cell line Namalwa and a P-glycoprotein-expressing cell line, Namalwa/mdr-1, obtained by retroviral infection of Namalwa cells with the mdr-1 gene. Namalwa/mdr-1 cells were slightly more sensitive to anti-B4-bR than Namalwa cells; IC37 values were approximately 4 pmol/L and 8 pmol/L, respectively. When anti-B4-bR was combined simultaneously with doxorubicin or etoposide, additive to supra-additive killing of Namalwa and Namalwa/mdr-1 cells was observed. In xenografts of Namalwa/mdr-1 cells in severe combined immunodeficiency (SCID) mice, doxorubicin and etoposide at their maximum tolerated doses (3 mg/kg x 3 or 15 mg/kg x 3) showed no therapeutic effect. However, treatment with 5 daily bolus injections of anti-B4-bR (50 micrograms/kg) followed by treatment with doxorubicin or etoposide significantly increased the life span of the mice by 129% and 115%, respectively. After treatment with anti-B4-bR, the Namalwa/mdr-1 population expressed lower levels of P-glycoprotein, and this decrease may account for the synergistic action of the drug combinations. These results suggest that anti-B4-bR could be used to good effect in combination with current treatment regimens and further hint at a promising role for this immunotoxin in treatment of disease at the minimal residual disease stage, where cells may be resistant to chemotherapy.
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PMID:Anti-B4-blocked ricin synergizes with doxorubicin and etoposide on multidrug-resistant and drug-sensitive tumors. 749 89

A procedure for efficient transfer of the human MDR1 (multi-drug resistance) gene into murine hematopoietic stem cells was developed. Cells expressing Sca-1 but no lineage-specific or major histocompatibility complex (MHC) class II antigens (Lin-MHC II-Sca-1+) were enriched from 5-fluorouracil-pretreated bone marrow by Ficoll density-gradient and immunomagnetic sorting. Purified cells were cocultured with growth factors and fibroblasts producing replication-deficient retroviruses containing human MDR1 cDNA. Fluorescence-activated cell sorter analysis and rhodamine-123 efflux experiments showed that greater than 60% of cocultured hematopoietic cells expressed functional human P-glycoprotein. After 6 to 8 days, hematopoietic cells were injected intravenously into sublethally irradiated SCID mice. Stem cell properties of the isolated population were confirmed by sustained expression of MDR1 marker cDNA for greater than 4 to 6 months after transplantation, multilineage engraftment, and presence of MDR1 cDNA in bone marrow of secondary recipient mice after retransplantation. Reconstitution of H-2K-mismatched SCID mice showed high engraftment capacity of Lin-MHC II-Sca-1+ cells. MDR1 cDNA was detected in blood of 78% of recipients. P-glycoprotein was expressed in bone marrow of 71% of mice, in both lymphocytes and myelomonocytoid progenitors. P-glycoprotein function in host marrow was confirmed by rhodamine-123 efflux. Transduction of P-glycoprotein may be useful for gene therapy in two ways: to protect bone marrow from myelosuppression after chemotherapy and as a selectable marker in vivo for the introduction of otherwise nonselectable genes.
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PMID:Efficient expression of functional human MDR1 gene in murine bone marrow after retroviral transduction of purified hematopoietic stem cells. 779 16

Human bone marrow (BM) CD34+ cells were stained with the vital dye, rhodamine 123 (Rh123), and analyzed for their biological properties based on the level of dye retention. Heterogeneous rhodamine staining is seen within the CD34+ population, and the staining patterns differ dramatically between fetal BM (FBM), adult BM (ABM) and mobilized peripheral blood (MPB). Kinetic analysis of the efflux of Rh123 from ABM CD34+ cells showed that efflux of Rh123 was most rapid from the most primitive Thy-1+ subset. The efflux of Rh123 could be inhibited by verapamil, suggesting that rhodamine efflux from primitive hematopoietic cells is primarily due to the P-glycoprotein (P-gp) pump or another intracellular transport system affected by verapamil. When four CD34+ subpopulations were plated onto SyS1 BM stromal cell cocultures after 1 to 2 weeks, only wells plated with CD34+ Thy-1+Rh123lo (low-level Rh123 retention) or CD34+Thy-1+Rh123mid (mid-level Rh123 retention) cells maintained greater than 50% of cells in an uncommitted CD34+33- stage. CD34+Lin- (lineage-negative) cells were fractionated based on Rh123 dye staining into Rh123hi (high-level Rh123 retention), Rh123mid, and Rh123lo and deposited as single cells into long-term SyS1 BM stromal cell cultures. The Rh123mid fraction had immense early proliferative activity in vitro, but lost the ability to form cobblestone areas after 5 to 6 weeks in culture. In contrast, the Rh123lo fraction proliferated more slowly but sustained long-term in vitro hematopoiesis as evidenced by continued cobblestone area-forming cells (CAFC) activity for at least 6 weeks. The Rh123hi fraction showed a plating efficiency similar to that of the Rh123lo or Rh1123mid fractions but did not extensively proliferative in vitro and did not show evidence of CAFC activity. We predicted from these in vitro results that the Rh123lo subsets possesses long-term engrafting potential. Indeed, on transplantation into the SCID-hu bone assay, all long-term engrafting potential and multilineage differentiation potential resided within the Rh123lo-mid but not Rh123hi subset. Furthermore, human marrow subpopulations derived from chimeric sheep after in utero transplantation with CD34+Thy-1+Lin- cells were reisolated based on Rh123 staining. Again, CD34+Lin- subsets showing Rh123lo-mid had long-term growth in culture, whereas Rh123hiCD34+Lin- cells did not. These results show that, after injection of CD34+Thy-1+Lin- cells into an in utero microenvironment, primitive CD34+ cells maintain a Rh123 phenotype that correlates with their in vitro CAFC activity. Thus, Rh123 staining is an effective way to define functional subsets of primitive hematopoietic cell populations.
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PMID:Primitive human hematopoietic cells displaying differential efflux of the rhodamine 123 dye have distinct biological activities. 869 47

A certain percentage of cancers are primarily or subsequently resistant to chemetherapeutic agents. Several biological mechanisms are implicated in this phenomenon, including multidrug resistance/P-glycoprotein (mdr1/P-gp), resistance related proteins (P-95 and P-110), multidrug resistance associated protein (P-190), iso-enzymes of gluthatione S-transferase, topo-isomerases, glutathione peroxidase and others. mdr1/P-gp overexpression has been studied in many types of cancer. It represents an inducible, transferable and phylogenetically ancestral biological system. It is expressed at the surface of the cell, and in that way, it participates to several normal functions. The recent introduction of modulators/revertants of mdr1/P-gp may change some concepts in using chemotherapy for cancers. The first step is represented by a better knowledge of the cancers which overexpressed mdr1/P-gp, with determination of the best biological technique, including the gold standards. This allows the clinician to clarify the best impact of such a therapeutic way and to define the criteria of modulator selection. Such criteria includes in vitro selection using a panel of sensitive/resistant cell lines, in vivo tests including transgenic mice, nude or SCID mice, and toxicological studies. Choice of modulated drug is easier and depends on the biological target. For mdr1/P-gp, major drugs included doxorubicin and vinca-alkaloids. Due to the fact that some modulators have an influence on the pharmacokinetic parameters of chemotherapeutic drugs, it is important to verify such parameters. The last choice concerns the strategy of drug development with three levels of action: 1) modulation of clinical chemoresistance, intrinsic or acquired one; 2) modulation of biological resistance; 3) leading to the prevention of the amplification of low levels of chemoresistance. A new therapeutic way is born, which takes care of a dynamic aspect of the tumor, and necessitates a new use of chemotherapy.
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PMID:[Modulation of chemoresistance: methodology of therapeutic trials]. 873 92

Multiple myeloma is a plasma cell malignancy which is generally incurable in spite of a high initial response to chemotherapy. Relapsing disease commonly heralds an increase in the incidence of drug resistance which is often mediated by the product of the MDR-1 gene, P-glycoprotein (Pgp). One approach to modulating drug resistance due to Pgp overexpression has involved the use of agents known as chemomodulators which inhibit its function. We have developed a human xenograft model of multiple myeloma using the SCID mouse to evaluate the efficacy and toxicities of new MDR-1 chemomodulators. Cyclosporin A (CsA) is a widely used immunosuppressant which has been demonstrated to be a potent inhibitor of Pgp in vitro at concentrations which are clinically achievable. Preliminary studies revealed an acute toxicity in our SCID model which was associated with the combination of CsA and doxorubicin, and which was not observed with either drug alone, nor with cremaphor, the vehicle for CsA. In the current study, non-tumor bearing SCID mice were dosed with doxorubicin or the combination of doxorubicin with cremaphor, verapamil or CsA. Animals were sacrificed and tissues harvested for morphologic examination and for HPLC analysis of doxorubicin levels. In all tissues examined, there was a marked increase in tissue levels of doxorubicin when combined with CsA. Results also revealed a higher incidence and severity of myocardial damage in those animals receiving the combination of doxorubicin and CsA than in those receiving other combinations. The elevations in tissue levels observed with doxorubicin and CsA may contribute to the acute toxicities observed in the SCID mouse model.
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PMID:Cardiotoxicity in the SCID mouse following administration of doxorubicin and cyclosporin A. 884 85

Rhizoxin is an antineoplastic drug that inhibits tubulin polymerization. In this study, we demonstrated that rhizoxin was approximately twice as active in vitro against a human small-cell lung cancer cell line with non-P-glycoprotein-mediated resistance to vindesine, H69/VDS, as against its parental line, H69. Tubulin polymerization in H69/VDS, demonstrated by Western blot analysis, was inhibited markedly by rhizoxin compared with that in H69, in a concentration-dependent manner. A drug-accumulation study showed that the intracellular rhizoxin level in H69/VDS was 15% lower than that in H69, whereas efflux from H69/VDS was enhanced slightly. These results indicate that enhanced inhibition of tubulin polymerization rather than increased intracellular drug concentration accounted for the higher sensitivity of H69/VDS to rhizoxin. In an experiment using mice with severe combined immunodeficiency and inoculated subcutaneously with H69/VDS, in vivo tumor growth was reduced markedly by three intermittent intraperitoneal doses of rhizoxin compared with that in mice inoculated with H69. Three weeks after the last rhizoxin dose, the relative treated/untreated tumor volumes were 0.29 for H69, but only 0.06 for H69/VDS, indicating that H69/VDS regrowth was minimal even after a 3-week treatment-free period. In conclusion, rhizoxin conquers vindesine resistance of a human small-cell lung cancer cell line in vitro and in vivo.
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PMID:In vitro and in vivo modulation by rhizoxin of non-P-glycoprotein-mediated vindesine resistance. 917 91

Drug resistance is one of the problems severely limiting chemotherapy in cancer patients. Thus, it is very important to develop new drugs that are effective against drug-resistant tumour cells. The novel anti-tumour agent NK109 has been developed from benzo[c]phenanthridine derivatives by Nippon Kayaku (Tokyo, Japan). We have confirmed that NK109 shows anti-tumour effects against a number of human tumour cell lines by inhibiting DNA topoisomerase II activity through the stabilization of the cleavable complex. Further, its efficacy against several drug-resistant tumour cell lines was also shown. NK109 showed potent anti-tumour activity against doxorubicin-resistant human tumour cell lines that have a typical multidrug resistance phenotype caused by P-glycoprotein. NK109 was not pumped extracellularly by P-glycoprotein and, consequently, NK109 accumulated in resistant cells. Cisplatin-resistant human tumour cell lines, which demonstrated decreased cisplatin accumulation, were sensitive to NK109. NK109 non-cross-resistance was confirmed using xenografts of tumour cells that were resistant to cisplatin in SCID mice. Furthermore, etoposide-resistant cells, with decreased topoisomerase II activity, were markedly sensitive to NK109 when compared with their parent cells, suggesting the possibility that the cytotoxic mechanism of NK109 differs from that of etoposide. In conclusion, NK109 is a very promising new anti-tumour drug for clinical use, because the efficacy of NK109 is not susceptible to several known molecular alterations that are associated with drug resistance. A clinical study of this compound is now in progress in Japan.
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PMID:Anti-tumour activities of a new benzo[c]phenanthridine agent, 2,3-(methylenedioxy)-5-methyl-7-hydroxy-8-methoxybenzo[c]phena nthridini um hydrogensulphate dihydrate (NK109), against several drug-resistant human tumour cell lines. 930 54

We have established a reproducible in vivo model of human multiple myeloma in the severe combined immunodeficiency (SCID) mouse using both the drug-sensitive 8226/S human myeloma cell line and the P-glycoprotein-expressing multidrug-resistant 8226/C1N subline. As demonstrated previously, the SCID mouse is well suited as a model for myeloma because: (a) human SCID xenografts are readily attained; (b) human myeloma xenografts are readily detected by their immunoglobulin secretion; and (c) differential therapy effects in drug-sensitive versus drug-resistant cell lines are readily demonstrable by monitoring mouse urinary human immunoglobulin output. In the current study, we have utilized this model to evaluate the in vivo efficacy of chemomodulators of P-glycoprotein-related multidrug resistance. In our initial experiments, doxorubicin alone was effective in treating the 8226/S human myeloma xenografts but had no effect on the drug-resistant 8226/C1N xenografts, in the absence of the chemosensitizing agent verapamil. In subsequent experiments, the combination of verapamil and doxorubicin resulted in both a decrease in human lambda light chain urinary excretion and an increase in survival of those animals bearing the 8226/C1N tumor. The median survival time of animals injected with 8226/C1N cells and subsequently treated with doxorubicin was 48.6 +/- 7 days, which compared to a survival of 89.6 +/- 18 days in animals receiving the 8226/S cell line and treated with doxorubicin alone (P < 0.001). When verapamil was added to the treatment regimen of those animals bearing the 8226/C1N xenografts, there was a 179% increase in their life span (P < 0.001), which corresponded with the observed decreased light chain in the urine. In animals receiving multiple courses of chemotherapy, an attenuated response to verapamil and doxorubicin was observed, in a manner analogous to the clinical setting of human drug-resistant myeloma escape from chemosensitivity. The SCID human myeloma xenograft model thus offers a means of evaluating the in vivo efficacy and potential toxicities of new therapeutic approaches directed against P-glycoprotein in multidrug-resistant human myeloma.
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PMID:Severe combined immunodeficiency (SCID) mouse modeling of P-glycoprotein chemosensitization in multidrug-resistant human myeloma xenografts. 981 57

A murine model in which to study multiple drug resistance in human hepatocellular carcinoma was developed. PRF/PLC/5 hepatoma cells (Alex 0) and an induced multidrug resistant clone (Alex 0.5) were injected intrasplenically into severe combined immunodeficiency mice. In 70% of injected mice, hepatoma cells engrafted in the liver and grew as intrahepatic metastasis. Since Alex cells contain an integrated hepatitis B virus genome and secrete hepatitis B surface antigen (HBsAg), the serum HBsAg concentration in tumor-bearing mice was used to quantitate tumor burden. Tumor wet weight determined at necropsy was directly proportional to the serum HBsAg concentration. In Alex 0 cells, IC50s for doxorubicin, vinblastine, and cis-platinum were 0.35 microM, 0.029 microM, and 3.70 microM, respectively. Alex 0.5 cells were 25-, 14-, and 1.4-fold more resistant to doxorubicin, vinblastine, and cis-platinum, respectively. Immunoblotting of Alex 0 cell membranes with an anti-P-glycoprotein antibody (C219) revealed small amounts of P-glycoprotein, whereas Alex 0.5 membranes overexpressed the protein. Concurrent exposure to verapamil (10 microM) sensitized both cell lines to the cytotoxic action of vinblastine and doxorubicin but had no effect on the cytotoxicity of cis-platinum. Mice bearing intrahepatic xenografts derived from Alex 0 and 0.5 cells had no response to treatment with i.v. vinblastine or doxorubicin, as was anticipated from in vitro drug testing. Addition of verapamil to vinblastine treatment did not improve the success of in vivo chemotherapy. Immunotherapy with a human anti-P-glycoprotein antibody (MRK16) suppressed the in vivo growth of tumors derived from both cell lines. The effect was most pronounced in mice bearing Alex 0.5 tumors. Immunoblotting of tumors which initially responded to MRK16 therapy, but subsequently relapsed, revealed a marked decrease in P-glycoprotein expression when compared to results in tumors that were untreated or treated with vinblastine or control antibody. In summary, we have developed an intrahepatic tumor xenograft model of human hepatocellular carcinoma in mice that permits noninvasive serial quantification of tumor burden by determination of serum HBsAg levels and demonstrated a positive response to immunotherapy with anti-P-glycoprotein antibodies.
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PMID:Establishment and serial quantification of intrahepatic xenografts of human hepatocellular carcinoma in severe combined immunodeficiency mice, and development of therapeutic strategies to overcome multidrug resistance. 981 20

Distant metastases and multidrug resistance are critical problems in the therapy of human small cell lung cancer (SCLC). In this study, we investigated whether transduction of the monocyte chemoattractant protein-1 (MCP-1) gene into multidrug-resistant (MDR) human lung cancer cells affected the formation of metastases or their inhibition by the anti-P-glycoprotein (P-gp) monoclonal antibody (MAb) MRK16. MDR human SCLC (H69/VP) cells were transduced with the human MCP-1 gene inserted into the expression vector BCMGSNeo. MCP-1 gene transduction had no effect on drug sensitivity, the expression of surface antigens or the in vitro proliferation of H69/VP cells. Using the metastatic model of NK cell-depleted SCID mice, H69/VP cells transduced with the MCP-1 gene were inoculated intravenously (i.v.) and formed metastatic colonies in the liver, kidneys and lymph nodes, similar to those formed by parent or mock-transduced cells. However, systemic treatment of the mice with MRK16 reduced the metastases of H69/VP cells in the liver, kidneys and lymph nodes, and was significantly more effective in inhibiting the metastases of MCP-1 producing H69/VP than those of mock-transduced cells. MCP-1 gene transduction significantly prolonged the survival of tumor-bearing mice treated with MRK16. Our findings suggest that local production of MCP-1 in the tumor site increases the anti-P-gp antibody-dependent cell-mediated cytotoxicity, and the MCP-1 gene-induced modification of MDR human SCLC cells thereby enhances the antimetastatic effect of therapy with anti-P-gp antibody. Thus, the accumulation of effector cells in the tumor site is a very important factor in the therapy using the anti-P-gp antibody.
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PMID:Monocyte chemoattractant protein-1 gene modification of multidrug-resistant human lung cancer enhances antimetastatic effect of therapy with anti-P-glycoprotein antibody in SCID mice. 1004 81


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