Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

P-glycoprotein, the human multidrug resistance (MDR1) gene product, is an integral membrane protein expressed on the plasma membrane of MDR tumor cells and is the best characterized of a family of efflux transporters that confer chemotherapeutic resistance. The use of gamma-emitting 99mTc-agents to image P-glycoprotein function in human tumors in vivo has been proposed. Net tumor cell content of 99mTc-Sestamibi, 99mTc-Tetrofosmin and several 99mTc-Q-complexes 99mTc-Q58 and 99mTc-Q63) are a function of passive potential-dependent influx and MDR1 P-glycoprotein-mediated active extrusion. To better understand the overall fidelity of these P-glycoprotein substrates to report MDR activity in vivo in relation to tissue perfusion, a compartmental model of tracer pharmacokinetics was developed. Modeling indicates that tissue perfusion will impact pharmacokinetics in vivo in a manner that will tend to diminish P-glycoprotein-mediated phenotypic differences between tissues when they are perfusion-limited. However, dynamic imaging to extract efflux rate constants is independent of perfusion and may represent the highest quality methodology for collecting the desired information regarding activity of the efflux transposter. Much work remains to translate these concepts and biological targeting properties into clinical practice.
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PMID:Pharmacokinetic modeling of multidrug resistance P-glycoprotein transport of gamma-emitting substrates. 920 49

Suramin is a multi-targeted antiproliferative drug developed for the treatment of African trypanosomiasis but with potential efficacy for the treatment of human cancer. Cell growth inhibition was determined in vitro for three human colonic tumor cell lines using three different doses of suramin (50, 100 and 200 microM). At the lower suramin concentration cell growth was stimulated relative to control cultures in all three cell lines. At the higher dose which is at the upper end of the tolerable dose in humans suramin reduced cell numbers by greater than 50%. Inhibition of cellular proliferation was reduced relative to increases in cell plating density. Addition of vinblastine six and to a lesser extent 72 hours post suramin (200 microM) resulted in an inhibition of cell growth and/or toxicity that exceeded that which occurred as a result of exposure to either suramin or vinblastine alone. To investigate the possible mechanism by which suramin sensitizes cells to vinblastine we determined the effect of suramin on expression of the multidrug resistance (mdr1) gene. A decrease in mdr1 mRNA was evident in one colon tumor cell line and a slight decrease detected in a second line. The results establish that suramin is effective in controlling growth in colonic tumor cells and confirms that suramin activity is synergistic with other chemotherapeutics. The effect of suramin on MDR is of potential value that needs to be more thoroughly investigated particularly in cancers such as the those of the colon that are often drug refractory.
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PMID:Suramin is synergistic with vinblastine in human colonic tumor cell lines: effect of cell density and timing of drug delivery. 921 65

P-glycoprotein expression on tumor cells is a frequent cause of pleiotropic drug resistance in cell lines and tumor specimens. Besides the multidrug resistance gene (MDR1), other mechanisms of increased drug extrusion have been described, such as the MDR-related protein and the lung resistance protein. In addition, other gene-regulated processes may lead to cell survival after exposure to cytostatic agents. It has been shown that p-glycoprotein can be circumvented in vitro by noncytotoxic agents such as verapamil and cyclosporin A, which interact pharmacologically with p-glycoprotein-mediated efflux. More recently, molecular approaches to downregulate p-glycoprotein expression or function have been studied. These approaches and the clinical results obtained so far will be discussed.
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PMID:Inhibitors of multidrug resistance. 937 75

CI-980 is a synthetic mitotic inhibitor that binds to the colchicine binding site of tubulin. It demonstrates broad activity against human and murine tumor models and shows no cross resistance with tumor models whose mechanism of resistance is mediated by P-glycoprotein (MDR-1). A phase I study was completed in 25 patients with solid tumors using a 24-hour infusion schedule, with courses repeated every 3 weeks. Eight dose levels were tested between 1.2 and 15.6 mg/m2. The maximum tolerated dose was 14.4 mg/m2. Neutropenia was dose-related but not dose-limiting; thrombocytopenia was infrequent. CNS toxicities were dose-limiting and consisted of dizziness, headache, loss of coordination, loss of consciousness, nervousness, and other symptoms. These events occurred near the end of the infusion and were reversible, usually within 24 hours. One patient who was to be treated at dose level 8 (intended dose was 19.2 mg/m2; actual dose was 15.6 mg/m2) became encephalopathic prior to completion of the infusion. Other adverse events included gastrointestinal toxicities (nausea, vomiting, anorexia, constipation, stomatitis, dyspepsia, bleeding, cheilitis), IV site erythema, fever, and fatigue. A partial response was observed in one patient with colon cancer and reductions in CA-125 levels were observed in 2 patients with ovarian cancer. Pharmacokinetics were linear and dose-proportional. Results indicate high systemic clearance and wide tissue distribution. Mean pharmacokinetic parameter values: T1/2 = 5.52 hours, plasma clearance 1163 mL/min/m2, and Vdss 376 L/m2.
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PMID:A phase I trial and pharmacokinetic evaluation of CI-980 in patients with advanced solid tumors. 938 46

MEN 10710 is a new synthetic distamycin derivative possessing four pyrrole rings and a bis-(2-chloroethyl)aminophenyl moiety linked to the oligopyrrole backbone by a flexible butanamido chain. Its biological properties have been investigated in comparison with the structurally related compound, tallimustine (FCE24517), and the classical alkylating agent, melphalan (L-PAM). Cytotoxic potency of MEN 10710 was increased from 10- to 100-fold, as compared to tallimustine or L-PAM in murine L1210, human LoVo and MCF7 tumor cell lines. MEN 10710 was still active against L1210/L-PAM leukemic cells, while a partial cross-resistance was observed in LoVo/DX and in MCF7/DX cells selected for resistance to doxorubicin and expressing a MDR phenotype. Treatment with verapamil (VRP) reduced the resistance to tallimustine, but not to MEN 10710, in MCF7/DX cells. The cytotoxic effects reflect in vivo antitumor potency and toxicity in the treatment of human tumor xenografts. MEN 10710 was more effective in A2780/DDP, an ovarian carcinoma selected for resistance to cisplatin. On the other hand, the IC30 for inhibiting murine granulocyte/macrophage colony formation was 50 times higher for MEN 10710 than for tallimustine, suggesting a lower myelotoxic potential. In conclusion, the particular biological profile of MEN 10710 characterized by a marked cytotoxic potency, an interesting antitumor efficacy and a reduced in vitro myelosuppressive action may represent a further improvement in the rational design of a novel distamycin-related alkylating compound.
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PMID:Cytotoxic and antitumor activity of MEN 10710, a novel alkylating derivative of distamycin. 940 11

Idarubicin (4-demethoxydaunorubicin) (IDA) is a daunorubicin analogue with substantial activity in hematologic malignancies and solid tumors. Among several reasons, IDA is of interest because of its main metabolite derivative, the C-13 alcohol analogue, idarubicinol (IDOL). Previous studies have suggested that IDOL, unlike other anthracycline metabolic derivatives, possesses a striking growth-inhibitory activity in tumor cell lines. This suggests that IDOL, like IDA could be useful in circumventing MDR. IDA is bioavailable in an oral dosage form. After oral administration of IDA to the patients, the concentration of IDOL quickly exceeds that of IDA and is retained in the plasma for a longer period. Hence, administration of IDA to cancer patients results ina much greater overall exposure of the tumor to IDOL than to the parent compound. At the Oncology Center (CRO) in Aviano we performed a dose-finding and pharmacokinetic (PK) study of chronic daily oral IDA with intrapatient escalation in patients with metastatic breast cancer (MBC). All the patients were pretreated with anthracyclines (the cumulative dose was 530 mg and 264 mg, respectively, for epirubicin and (DOX) and had at admittance a PS < or = 2 and a left ventricular ejection fraction > 50%. IDA (1 mg capsules) was administered orally twice a day for 21 days every two weeks. Treatment was continued at escalating doses until progression or intolerance. Twenty-five patients were enrolled. MTD has not yet been reached and clinical results are reported in Table 1. Treatment was well-tolerated in all but one patient (300 ANC at day 28). Three patients had tox G3 ANC for more than three weeks after 3, 6, and 7 mg doses, respectively. Two of them stopped chemotherapy after 1 cycle and 1 patient stopped after 2 cycles (6 mg doses). Despite previous treatments with anthracyclines (the mean cumulative dose before entering the study was 530 and 264 mg, respectively, for epirubicin and DOX) no cardiotoxicity due to IDA treatment was observed. This trial demonstrates the feasibility of chronic daily IDA administration. At the dosage reported, treatment was generally well tolerated. The PK findings (high IDOL concentrations) and the unexpected G4 myelotoxicity in patients with the highest IDOL plasma concentrations suggest that IDOL is clinically relevant.
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PMID:Pharmacology of chronic oral daily administration of idarubicin. 940 45

The multidrug resistance phenotype is found to be frequently associated with the overexpression of proteins which lead to a decrease of drug accumulation within human tumor cells. A 170 kDa membrane glycoprotein which is related to the overexpression of the mdr1 gene is inserted in the plasma membrane and pumps the cytotoxic drugs out of the cells. The aim of this work was to study the morphological modifications of resistant CEM/VLB 100 cells relative to their parental drug-sensitive ones and the detection of the ultrastructural localization of P-glycoprotein at the cytoplasmic level. Using a scanning electron microscope, CEM resistant cells showed wide smooth protrusions while CEM sensitive cells showed microvilli and fine folds. With transmission electron microscopy, an enhanced secretory system was observed in CEM resistant cells: both electron transparent and electron opaque vesicles were associated with the Golgi system, revealed by wheat germ agglutinin-colloidal gold labelling. These vesicles were the binding site of C 219 and MRK 16 antimembrane glycoprotein antibodies, and some of them were determined to belong to the lysosomal system after PTA staining. These vesicles may be an additional way to decrease the cellular uptake of drugs in multidrug resistant cells. Moreover, some nuclear and nucleolar modifications were also observed. These observations show that MDR has wide morphological features which concern several organelles.
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PMID:Ultrastructural changes related to multidrug resistance in CEM cells: role of cytoplasmic vesicles in drug exclusion. 941 88

The question of whether metastatic potential and drug resistance are related phenotypes was addressed by comparing the biological behavior of the parental B16 melanoma and a multidrug resistant variant derived from it, the B16/Col/R. A more pronounced metastatic spread to lungs was observed in mice inoculated i.v. with the B16/Col/R variant than in those bearing the parental line. In addition, in the mice injected with the drug resistant melanoma, unusual tumor masses were observed. Large abdominal and spinal cord growths were seen with the MDR variant but not encountered in mice inoculated with the original B16 melanoma. We further attempted to test the capacity of the two cell types to perform several cellular functions relevant to the metastatic process. The B16/Col/R cells displayed a higher aggregability and cell motility than did the B16 cells. Adherence to endothelial cells was higher in the parental line than in the B16/Col/R, possibly supporting a more efficient extravasation of the variant cells. The drug resistant variant displayed a higher capacity to grow locally in kidney, spleen, cecum and peritoneum, as compared to the parental melanoma, indicating a higher ability of homing and growth in these potential target organs for metastasis. A correlation between metastatic potential and multidrug resistance appears therefore to exist in the system examined.
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PMID:Metastatic potential and multidrug resistance correlation in the B16 melanoma system. 941 12

We have established an in vivo etoposide-resistant glioma cell line (C6/VP) from C6 rat glioma cells by stepwise exposure to increasing doses of etoposide. The C6/VP cells were 10 times more resistant to etoposide than the parental C6 cells. In addition C6/VP cells demonstrated cross-resistance to vincristine and vinblastine, but not to ADM or m-AMSA. Interestingly, the cells had collateral sensitivity to ACNU, cisDDP and Ara-C. The C6/VP cells did not express the MDR gene or p-glycoprotein, while they showed 16 times less topoisomerase II catalytic activity compared to the C6 cells. Although there was no significant difference between C6 and C6/VP cells in amounts of topoisomerase II in nuclear extracts, the C6/VP cells had 2.9 times higher amounts of the enzyme than C6 cells in nuclear scaffold prepared from a relatively low-salt buffer (0.5 M NaCl). Northern blot analysis demonstrated that mRNAs of topoisomerase IIalpha isoforms were expressed both in C6 and C6/VP cells, and that the amounts of topoisomerase IIalpha in C6/VP cells were 14 times greater than in C6 cells. The total uptake of etoposide in tumor tissues derived from C6/VP cells was 3 times less than those derived from parental C6 cells. These results indicate that the C6/VP acquired a multi-drug resistance phenotype by a reduction of the catalytic activity of topoisomerase II and/or diminished accumulation of drugs. This phenotype did not involve the p-glycoprotein. Alterations of topoisomerase II in the C6/VP cells also were accompanied by an increased amount of the topoisomerase IIalpha isoform, most of which was localized in the nuclear scaffold (matrix). This suggests that altered binding of topoisomerase II to topologically organized DNAs in the nuclear scaffold may be the molecular basis of this multi-drug resistance phenotype.
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PMID:In vivo etoposide-resistant C6 glioma cell line: significance of altered DNA topoisomerase II activity in multi-drug resistance. 952 24

A set of 40 phenothiazines, thioxanthenes, and structurally related drugs with multidrug resistance modulating activity in tumor cells in vitro were selected from literature data and subjected to three-dimensional quantitative structure-activity relationship study using comparative molecular field analysis (CoMFA). More than 350 CoMFA models were derived and evaluated using steric, electrostatic, and hydrophobic fields alone and in combination. Four alignment strategies based on selected atom pairs or field fit alignment were compared. Several training and test sets were analyzed for both neutral and protonated drug forms separately. Each chemical class was trained and tested individually, and finally the classes were combined together into integrated models. All models obtained were statistically significant and most of them highly predictive. All fields contributed to MDR reversing activity, and hydrophobic fields improved the correlative and predictive power of the models in all cases. The results point to the role of hydrophobicity as a space-directed molecular property to explain differences in anti-MDR activity of the drugs studied.
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PMID:Molecular modeling of phenothiazines and related drugs as multidrug resistance modifiers: a comparative molecular field analysis study. 959 32


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