Biomedical subjects

E A C Wiemer

Publications and source records attributed to E A C Wiemer.

4 recordsLinked to original sources

PubMed2004

Identification of multidrug resistance-associated protein 1 and glutathione as multidrug resistance mechanisms in human prostate cancer cells: chemosensitization with leukotriene D4 antagonists and buthionine sulfoximine.

OBJECTIVE: To assess the involvement of the multidrug resistance-associated protein 1 (MRP1) and the glutathione pathway in the multidrug resistant (MDR) phenotype of prostate cancer in vitro. MATERIALS AND METHODS: Chemoselection of human prostate cancer cell lines PC3 and DU145 with etoposide resulted in the resistant cell lines PC3-R and DU-R. Resistance against etoposide, doxorubicin and vincristine, and its reversal with leukotriene D4 antagonists MK-571 and zafirlukast, and buthionine sulfoximine (BSO), was assessed using tetrazolium-dye viability assays. Western blot analysis of MRP1 expression and glutathione content were measured, and MRP1 function assessed in fluorescence assays. RESULTS: MRP1 was increased in the MDR models; the glutathione content was significantly higher in PC3-R but there was no increase in glutathione in DU-R. Adding non-toxic doses of MK-571, zafirlukast or BSO significantly increased the sensitivity of the MDR models to cytotoxic drugs. MRP1 function was inhibited with MK-571 in the MDR models. CONCLUSION: MRP1 and glutathione mediate MDR in newly developed prostate cancer models.

Blotting, Western↗

PubMed2003

The vault complex.

Vaults are large ribonucleoprotein particles found in eukaryotic cells. They are composed of multiple copies of a Mr 100,000 major vault protein and two minor vault proteins of Mr 193,000 and 240,000, as well as small untranslated RNAs of 86-141 bases. The vault components are arranged into a highly characteristic hollow barrel-like structure of 35 x 65 nm in size. Vaults are predominantly localized in the cytoplasm where they may associate with cytoskeletal elements. A small fraction of vaults are found to be associated with the nucleus. As of yet, the precise cellular function of the vault complex is unknown. However, their distinct morphology and intracellular distribution suggest a role in intracellular transport processes. Here we review the current knowledge on the vault complex, its structure, components and possible functions.

Animals↗

PubMed2002

Selection and characterisation of a phage-displayed human antibody (Fab) reactive to the lung resistance-related major vault protein.

The major vault protein is the main component on multimeric vault particles, that are likely to play an essential role in normal cell physiology and to be associated with multidrug resistance of tumour cells. In order to unravel the function of vaults and their putative contribution to multidrug resistance, specific antibodies are invaluable tools. Until now, only conventional major vault protein-reactive murine monoclonal antibodies have been generated, that are most suitable for immunohistochemical analyses. The phage display method allows for selection of human antibody fragments with potential use in clinical applications. Furthermore, cDNA sequences encoding selected antibody fragments are readily identified, facilitating various molecular targeting approaches. In order to obtain such human Fab fragments recognising major vault protein we used a large non-immunized human Fab fragment phage library. Phages displaying major vault protein-reactive Fabs were obtained through several rounds of selection on major vault protein-coated immunotubes and subsequent amplification in TG1 E coli bacteria. Eventually, one major vault protein-reactive clone was selected and further examined. The anti-major vault protein Fab was found suitable for immunohistochemical and Western blot analysis of tumour cell lines and human tissues. BIAcore analysis showed that the binding affinity of the major vault protein-reactive clone almost equalled that of the murine anti-major vault protein Mabs. The cDNA sequence of this human Fab may be exploited to generate an intrabody for major vault protein-knock out studies. Thus, this human Fab fragment should provide a valuable tool in elucidating the contribution(s) of major vault protein/vaults to normal physiology and cellular drug resistance mechanisms.

ATP-Binding Cassette Transporters↗

PubMed2002

Increased expression of the breast cancer resistance protein (BCRP) in relapsed or refractory acute myeloid leukemia (AML).

Expression of the multidrug resistance proteins P-glycoprotein, encoded by the MDR1 gene, multidrug resistance-associated protein (MRP1) and the lung resistance-related protein or major vault protein (LRP/MVP) is associated with clinical resistance to chemotherapy in acute myeloid leukemia (AML). Recently, the breast cancer-resistant protein (BCRP), the equivalent of mitoxantrone-resistant protein (MXR) or placental ABC transporter (ABCP), was described in AML. We investigated MDR1, MRP1, LRP/MVP and BCRP mRNA expression simultaneously in 20 paired clinical AML samples from diagnosis and relapse or refractory disease, using quantitative Taqman analysis. In addition, standard assays for P-glycoprotein expression and function were performed. BCRP was the only resistance protein that was expressed at a significantly higher RNA level (median 1.7-fold, P = 0.04) at relapsed/refractory state as compared to diagnosis. In contrast, LRP/MVP mRNA expression decreased as disease evolved (P = 0.02), whereas MDR1 and MRP1 mRNA levels were not different at relapse as compared to diagnosis. Also, at the protein level no difference of MDR1 between diagnosis and relapse was found. A significant co-expression of BCRP and MDR1 was found at diagnosis (r = 0.47, P = 0.04). The present results suggest that BCRP, but not MDR1, MRP1 or LRP/MVP is associated with clinical resistant disease in AML.

ATP Binding Cassette Transporter, Subfamily B, Mem↗