Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Advanced breast cancer responds to a range of cytotoxic agents, but resistance always develops. Understanding the mechanisms of resistance may provide new therapeutic options. There are several major groups of resistance mechanisms. 1) The multidrug resistant phenotype. This is due to a membrane pump that can extrude a wide range of anticancer drugs--the P-glycoprotein. It is inhibited by a range of clinically used calcium channel blockers such as nifedipine and verapamil. Several other membrane proteins of 180 KD, 170 KD, 300 KD and 85 KD have been reported and are associated with MDR. 2) Glutathione transferences and detoxification mechanisms. These are a multigene family of enzymes that conjugate glutathione to chemically reactive groups. There are 3 major groups of enzymes--acidic, basic and neutral. They have been implicated in resistance to doxorubicin, melphalan cisplatinum chlorambucil and other alkylating agents. Other protecting systems include metallothionein and selenium dependent glutathione peroxidase. HSP27 confers doxorubicin resistance. 3) Topoisomerase II. DNA topoisomerases are involved in several aspects of DNA metabolism in particular genetic recombination, DNA transcription, chromosome segregation. They are a target for doxorubicin, mitoxantrone, VP16. Low levels of expression are associated with resistance. However, it is oestrogen inducible and this may be of therapeutic value. A novel topo IIb which is more drug resistant has been reported. 4) DNA repair. A score or more of genes are involved in the repair of DNA damage by drugs and radiation. Defective DNA repair may predispose to cancer of the breast and be responsible for adverse radiation reactions. Enhanced repair has been shown to be a mechanism of cisplatinum resistance. Several genes are inducible by DNA damage and may confer resistance e.g. A45. 5) Drug activation. Mitomycin C as well as cyclophosphamide and VP16 require activation for their effects. Low levels of cytochrome p450 reductase are associated with MMC resistance.
 ...
PMID:Mechanisms of multidrug resistance in cancer treatment. 135 55

A family of 10 thermoresistant cell lines cloned from Chinese hamster cells transfected with a plasmid containing the structural gene for the small human Mr 27,000 heat shock protein (HSP27) was used to assess the putative role of this heat shock protein in chemoresistance. These cells express varying amounts of human HSP27 in addition to the normal level of endogenous hamster HSP27. As previously observed in the case of thermoresistance, a significant positive linear correlation (P less than 0.05) was found between cell survival in response to doxorubicin and the total amount of HSP27 expressed. Some clones were also examined for resistance to other drugs and chemicals. A statistically significant increased survival relative to the parental cells was observed following treatment with daunorubicin (three clones studied), colchicine, vincristine, actinomycin D, hydrogen peroxide, and sodium arsenite (one clone studied). However, the clone which expressed the highest level of HSP27 was as sensitive as control cells to the cytotoxic action of bis-chloronitrosourea and 5-fluorouracil. The relationship between HSP27 overexpression and increased resistance to cytotoxic agents was also evaluated in three independent pooled cell populations stably transformed with both the human HSP27 and the xanthine-guanine phosphoribosyltransferase gene and selected on the basis of resistance to mycophenolic acid and aminopterin. The results indicated that these cells survived significantly better than the control cells transfected with the marker gene only when exposed to doxorubicin. HSP27-mediated cellular protection was not associated either with decreased drug accumulation or with overexpression of P-glycoprotein. It is suggested that HSP27 might be involved in some form of chemoresistance and could participate in the development of clinical resistance to antineoplastic drugs.
 ...
PMID:Increased survival after treatments with anticancer agents of Chinese hamster cells expressing the human Mr 27,000 heat shock protein. 191 47

Heat-shock proteins seem to play a still undefined role in cancer. One of them particularly, the low molecular weight HSP27, seems to be involved in resistance to chemotherapy. This phenomenon has been reported in breast cancer cell lines, and the aim of this study was to investigate if it also takes place in clinical tumour samples from ovarian cancer patients. We studied ovarian carcinoma samples from 95 patients by means of immunohistochemistry for the overexpression of both the product of the multidrug-resistance gene (P-glycoprotein) and HSP27. The expression of the MDR1 gene in more than 50% of the tumour cells was associated with an almost significantly shorter survival of patients with stage II, III and IV tumours (p = 0.05), although intriguingly not with the response to chemotherapy. Tumours expressing the MDR1 gene, furthermore, also tended to co-express HSP27 (64.9% vs. 42.1%), and this difference was statistically significant (p = 0.026).
 ...
PMID:Co-expression of the MDR1 gene and HSP27 in human ovarian cancer. 971 93

To identify prognostic factors alternative or additional to P-glycoprotein (Pgp), we studied the impact of the multidrug resistance-related protein (MRP), bcl-2 (flow cytometry), mutant p53 (single-strand conformation polymorphism), and heat-shock protein 27 (HSP27, Western blotting) in myeloid blasts obtained at the time of diagnosis in patients with de novo acute myeloid leukemia (AML). We collected bone marrow samples from untreated AML patients, prepared the cells as well as the cellular protein, and froze all the material. We then analyzed 20 patients who responded with complete remission (CR) and 20 patients who had blast persistence (BP). The purpose of the study was to determine whether leukemic blasts from patients with BP were more resistant to chemotherapy than those from patients with CR. There was no significant correlation between the expression of any of these proteins alone and treatment outcome in both groups studied. In contrast, there was a significant correlation between the coexpression of at least two of these proteins and response (p = 0.0298), which turned out to be a significant independent prognostic factor for treatment failure (p = 0.0329, relative risk = 1.5) according to multivariate analysis. We conclude that drug resistance in AML is multifactorial. Thus, coexpression of different resistance mechanisms may be responsible for the primary drug resistance in de novo AML.
 ...
PMID:In acute myeloid leukemia, coexpression of at least two proteins, including P-glycoprotein, the multidrug resistance-related protein, bcl-2, mutant p53, and heat-shock protein 27, is predictive of the response to induction chemotherapy. 980 49

Infection of HeLa cells with adenovirus-carrying HSF1(+) cDNA, which encodes a mutated form of HSF1 with constitutive transactivation capacity, increased multidrug resistance 1 (MDR1) mRNA level and P-glycoprotein (P-gp) cell surface content and stimulated rhodamine 123 accumulation and vinblastine efflux activity. On the other hand, infection with adenovirus-carrying HSP70 and HSP27 cDNAs did not increase MDR1/P-gp expression. HSF1 regulates MDR1/P-gp expression at the transcriptional level, since HSF1(+) bound the heat-shock consensus elements (HSEs) in the MDR1 gene promoter and also activated the expression of an MDR1 promoter-driven reporter plasmid (pMDR1(-1202)). In addition, heat-shock increased pMDR1(-1202) promoter activity but not the activity of a similar reporter plasmid with point mutations at specific HSEs, and the heat-induced increase was totally inhibited by co-transfection with an expression plasmid carrying HSF1(-), a dominant negative mutant of HSF1. The stress inducers arsenite, butyrate, and etoposide also increased pMDR1(-1202) promoter activity, but the increase was not inhibited (in the case of butyrate) or was only partially inhibited (in the case of arsenite and etoposide) by HSF1(-). These results demonstrate that HSF1 regulates MDR1 expression, and that the HSEs present in the -315 to -285 region mediate the heat-induced activation of the MDR1 promoter. However, other factors may also participate in MDR1 induction by stressing agents.
 ...
PMID:Regulation of multidrug resistance 1 (MDR1)/P-glycoprotein gene expression and activity by heat-shock transcription factor 1 (HSF1). 1081 97

Although the heat shock protein 90 (HSP90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) shows clinical promise, potential limitations encourage development of alternative chemotypes. We discovered the 3,4-diarylpyrazole resorcinol CCT018159 by high-throughput screening and used structure-based design to generate more potent pyrazole amide analogues, exemplified by VER-49009. Here, we describe the detailed biological properties of VER-49009 and the corresponding isoxazole VER-50589. X-ray crystallography showed a virtually identical HSP90 binding mode. However, the dissociation constant (K(d)) of VER-50589 was 4.5 +/- 2.2 nmol/L compared with 78.0 +/- 10.4 nmol/L for VER-49009, attributable to higher enthalpy for VER-50589 binding. A competitive binding assay gave a lower IC(50) of 21 +/- 4 nmol/L for VER-50589 compared with 47 +/- 9 nmol/L for VER-49009. Cellular uptake of VER-50589 was 4-fold greater than for VER-49009. Mean cellular antiproliferative GI(50) values for VER-50589 and VER-49009 for a human cancer cell line panel were 78 +/- 15 and 685 +/- 119 nmol/L, respectively, showing a 9-fold potency gain for the isoxazole. Unlike 17-AAG, but as with CCT018159, cellular potency of these analogues was independent of NAD(P)H:quinone oxidoreductase 1/DT-diaphorase and P-glycoprotein expression. Consistent with HSP90 inhibition, VER-50589 and VER-49009 caused induction of HSP72 and HSP27 alongside depletion of client proteins, including C-RAF, B-RAF, and survivin, and the protein arginine methyltransferase PRMT5. Both caused cell cycle arrest and apoptosis. Extent and duration of pharmacodynamic changes in an orthotopic human ovarian carcinoma model confirmed the superiority of VER-50589 over VER-49009. VER-50589 accumulated in HCT116 human colon cancer xenografts at levels above the cellular GI(50) for 24 h, resulting in 30% growth inhibition. The results indicate the therapeutic potential of the resorcinylic pyrazole/isoxazole amide analogues as HSP90 inhibitors.
 ...
PMID:Inhibition of the heat shock protein 90 molecular chaperone in vitro and in vivo by novel, synthetic, potent resorcinylic pyrazole/isoxazole amide analogues. 1743 Nov 2

We studied the expression of inducible heat shock protein (HSP27, HSP72) and multidrug-resistance protein (MRP) in co-cultures of human colon carcinoma cell spheroids obtained from different grades of tumour with normal human colon epithelium, myofibroblast and endothelial cell monolayers. We also measured the influence of recombinant human transforming growth factor beta1 (rhTGF-beta1) and camptothecin (CPT-11), added as single agents or in combination, on the levels of the HSPs, MRP, interleukin (IL)-6 and nitric oxide (NO). An immunoblotting analysis with densitometry showed that rhTGF-beta1 and/or CPT-11 increased HSP27, HSP72 and MRP expression in tumour cells and myofibroblasts, as well as in co-cultures compared with appropriate controls. By contrast, in colonic epithelium, inhibition of HSPs and MRP was comparable with that of the control. In endothelial cells, HSP72 was undetectable. Direct interaction of colon tumour spheroids with normal myofibroblasts caused a significant, tumour-grade dependent increase in IL-6 production. Production of IL-6 was significantly lowered by rhTGF-beta1 and/or CPT-11. Tumour cell spheroids cultivated alone produced larger amounts of NO than normal cells. In co-culture, the level of the radical decreased compared with the sum of NO produced by the monocultures of the two types of cells. rhTGF-beta1 and/or CPT-11 decreased NO production both in tumour and normal cell monocultures and their co-cultures. In conclusion, direct interactions between tumour and normal cells influence the expression of HSP27, HSP72 and MRP, and alter IL-6 and NO production. rhTGF-beta1 and/or CPT-11 may potentate resistance to chemotherapy by increasing HSP and MRP expression but, on the other hand, they may limit tumour cell spread by decreasing the level of some soluble mediators of inflammation (IL-6 and NO).
 ...
PMID:Expression of HSP27, HSP72 and MRP proteins in in vitro co-culture of colon tumour cell spheroids with normal cells after incubation with rhTGF- beta1 and/or CPT-11. 2009 46

Drug resistance related proteins P-glycoprotein (P170), multidrug resistance associated protein (MRP), glutathione S-transferase-pi (GST-pi), glutathione peroxidase (GPX), topoisomerase II (Topo II), thymidylate synthase (TS), O-6-methylguanine-DNA-methyltransferase (MGMT), the heat shock proteins HSP27 and HSP70 and the protooncogenes Fos, Jun and EGFR were investigated in human lung carcinomas and matched normal tissues. We found that the mRNA expression of Topo II and TS were elevated in tumor tissue versus corresponding normal tissue. Additionally Topo II and TS correlated with the proliferating activity determined by expression of histone 3. P170, MRP, HSP70 and also EGFR mRNA were elevated in some tumor probes, but not GST-pi, GPX, MGMT and HSP27 mRNA. Additionally, we determined various values of Fos and Jun mRNA expression but there was no uniform pattern. The finding that some proteins were abnormally expressed in lung tumors compared to the adjacent normal tissue is an important finding for further investigations on the development of individualized chemotherapy but more samples should be examined to extend these observations.
 ...
PMID:Comparison of the mRNA expression of factors related to drug resistance in lung tumors and adjacent normal tissue. 2154 93

Heat shock proteins (HSPs) are involved in tumour immunity, and are correlated with survival and drug resistance in numerous types of cancer. The present study investigated the expression of HSPs and multiple drug resistance (MDR) in human chondrosarcoma. HSP and P-glycoprotein (the MDR1 gene product) expression was evaluated by immunohistochemical analysis of paraffin-embedded sections obtained from 37 patients with chondrosarcoma (19 male and 18 female; aged 33-85 years; mean age, 48.5 years). HSP73 and 90 were significantly overexpressed in patients with local recurrence: HSP73 was expressed in 7/7 patients (100%) with local recurrence and 9/18 patients (50%) without recurrence (P<0.02), while HSP90 was expressed in all patients with recurrence but only 8/18 (44%) without recurrence (P<0.02). A marked association was also identified between HSP expression and survival. HSP72 and 73 were significantly overexpressed in tumours from patients who succumbed to the disease (all positive for HSP72 and 73; P<0.05). No differences were observed between HSP27, 73 or 90-positive or -negative tumours according to age or gender. In addition, HSP72 expression was correlated with differentiation of the tumours (P<0.02). These results indicate that HSP72, 73 and 90 may function as novel prognostic markers for chondrosarcoma, and initiate further studies regarding the use of such markers for the identification of patients with poor prognosis.
 ...
PMID:Recurrence rate and progression of chondrosarcoma is correlated with heat shock protein expression. 2687 Feb 41