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.

In vivo recovery and safety of human factor VIII product AAFACT in patients with haemophilia A.

AAFACT, a monoclonal purified, solvent/detergent treated human plasma-derived coagulation factor VIII concentrate obtained from plasma of voluntary, non-remunerated blood donors, is manufactured and marketed in the Netherlands by Sanquin Plasma Products since 1995. In a postmarketing surveillance study, 70 previously treated haemophilia A patients were included (73% severe, 14% moderate and 13% mild haemophilia A). Most of these patients were followed during 4 years for the appearance of adverse events, possible transmissions of blood-borne viruses and the occurrence of antibodies against FVIII. The efficacy of treatment was determined in each patient by the in vivo recovery of FVIII. During this study, only six adverse events, possibly related to the use of AAFACT, were reported. None of these were indicated as serious. Transmissions of HIV, HAV, HBV and HCV in the seronegative patients have not been observed. In none of the patients, inhibitors to FVIII were detected. The in vivo recovery of FVIII during this study was not different from the in vivo recovery observed in eight patients during the preregistration study. There was a correlation of in vivo recovery with age and body weight. From these results, we conclude that the clinical usage of this human plasma-derived FVIII product is efficient and safe.

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.

MDR1 gene-related clonal selection and P-glycoprotein function and expression in relapsed or refractory acute myeloid leukemia.

The expression of P-glycoprotein (P-gp), encoded by the MDR1 gene, is an independent adverse prognostic factor for response and survival in de novo acute myeloid leukemia (AML). Little is known about MDR1 expression during the development of disease. The present study investigated whether MDR1 gene- related clonal selection occurs in the development from diagnosis to relapsed AML, using a genetic polymorphism of the MDR1 gene at position 2677. Expression and function of P-gp were studied using monoclonal antibodies MRK16 and UIC2 and the Rhodamine 123 retention assay with or without PSC 833. No difference was found in the levels of P-gp function and expression between diagnosis and relapse in purified paired blast samples from 30 patients with AML. Thirteen patients were homozygous for the genetic polymorphism of MDR1 (n = 7 for guanine, n = 6 for thymidine), whereas 17 patients were heterozygous (GT). In the heterozygous patients, no selective loss of one allele was observed at relapse. Homozygosity for the MDR1 gene (GG or TT) was associated with shorter relapse-free intervals (P =.002) and poor survival rates (P =.02), compared with heterozygous patients. No difference was found in P-gp expression or function in patients with AML with either of the allelic variants of the MDR1 gene. It was concluded that P-gp function or expression is not upregulated at relapse/refractory disease and expression of one of the allelic variants is not associated with altered P-gp expression or function in AML, consistent with the fact that MDR1 gene-related clonal selection does not occur when AML evolves to recurrent disease. (Blood. 2001;97:3605-3611)

Dose-finding study of valspodar (PSC 833) with daunorubicin and cytarabine to reverse multidrug resistance in elderly patients with previously untreated acute myeloid leukemia.

INTRODUCTION: This trial was designed to determine the maximum tolerated dose of intravenous daunorubicin (DNR) in combination with valspodar and to test the feasibility of P-glycoprotein modulation using valspodar in elderly patients with previously untreated acute myelogenous leukemia receiving standard induction chemotherapy. METHODS: Patients > or =60 years of age with previously untreated AML received valspodar (10 mg/kg/24 h by continuous intravenous infusion [CIV] on days 1-4 with a 2-mg/kg loading dose on day 1) in conjunction with two cycles of induction chemotherapy consisting of cytarabine (200 mg/m(2) CIV on days 1-7), and DNR (35 mg/m(2) [cohort 1] or 45 mg/m(2) [cohort 2] on days 1-3, intravenous bolus). Patients were assessed for dose-limiting toxicities (DLT), response rate, event-free and overall survival, and pharmacokinetics of valspodar and DNR. RESULTS: Valspodar was well tolerated at the lower DNR dose level (ie, 35 mg/m(2)) resulting in a 21% rate of DLT and only three toxic deaths. Treatment-related mortality was unacceptably high at the 45 mg/m(2) DNR dose level. The complete response rate was 49% overall and similar in both cohorts. The median overall survival of patients was 333 days in cohort 1 compared to 98 days in cohort 2. At baseline, 70% of assessable patients were P-glycoprotein positive. CONCLUSION: Substantial inhibition of P-glycoprotein activity can be achieved in this patient population at clinically tolerable doses of valspodar and DNR. The maximum tolerated dose of DNR was established as 35 mg/m(2). This regimen is being further evaluated in phase III trials.

Drug resistance in multiple myeloma.

The development of multidrug resistance (MDR) is a major obstacle to improving treatment outcomes in multiple myeloma. Recent studies have indicated that several specific mechanisms of MDR may be involved in clinically refractory multiple myeloma patients, such as expression of P-glycoprotein (P-gp), expression of the lung-resistance protein (LRP) and suppression of apoptosis via expression of Bcl-2. The emergence of these mechanisms of MDR in multiple myeloma is enhanced by exposure to chemotherapeutic agents. Recently, clinical reversal of MDR by noncytotoxic P-gp modulators such as verapamil, cyclosporin A (CsA), and PSC 833 was explored in acute leukemia and multiple myeloma. Preliminary results from clinical phase I/II trials indicate that reversal of MDR via modulation of P-gp is possible and that coadministration of these MDR modulators with chemotherapeutic agents alters the plasma pharmacokinetics of chemotherapeutic agents. Phase II and III clinical trials investigating the efficacy of these and other agents in the reversal of MDR in hematologic malignancies are ongoing.

Influence of tyrosine phosphorylation on protein interaction with FcgammaRIIa.

The cytoplasmic tail of Fc(gamma)RIIa present on human neutrophils shares with other antigen receptors a common amino acid sequence called ITAM (Immunoreceptor Tyrosine-based Activation Motif). After receptor ligation, the tyrosine residues within this motif become phosphorylated. We prepared a recombinant fusion protein of the cytoplasmic tail of Fc(gamma)RIIa (containing the ITAM) with glutathione-S-Transferase (GST-CT) to characterize the phosphorylation of Fc(gamma)RIIa and its ability to interact with other proteins involved in signal transduction. The GST-CT became phosphorylated in the presence of Lyn, Hck and Syk (immunoprecipitated from human neutrophils), but not in the presence of Fgr. Of the active kinases, only Lyn (mainly present in the membrane fraction) was found to associate with the GST-CT in the absence of ATP. This association was also observed in immunoprecipitates of Fc(gamma)RIIa from resting neutrophils, suggesting that Lyn might be the kinase responsible for the initial Fc(gamma)RIIa phosphorylation. Moreover, we observed specific association of Syk and the p85 subunit of PI 3-kinase after incubation of the GST-CT with neutrophil cytosol. This interaction was dependent on tyrosine phosphorylation of the GST-CT. Substitution of 269Tyr by Phe almost completely abolished tyrosine phosphorylation of the fusion protein. Substitution of either 253Tyr or 269Tyr eliminated Syk binding, but only 253Tyr appeared to be essential for p85 binding. We hypothesize that, upon activation, the membrane-associated Lyn is responsible for the initial tyrosine phosphorylation of Fc(gamma)RIIa, thus creating a docking site for Syk and PI 3-kinase.

Tyrosine phosphorylation-dependent activation of phosphatidylinositide 3-kinase occurs upstream of Ca2+-signalling induced by Fcgamma receptor cross-linking in human neutrophils.

The effect of wortmannin on IgG-receptor (FcgammaR)-mediated stimulation of human neutrophils was investigated. The Ca2+ influx induced by clustering of both Fcgamma receptors was inhibited by wortmannin, as was the release of Ca2+ from intracellular stores. Wortmannin also inhibited, with the same efficacy, the accumulation of Ins(1,4,5)P3 observed after FcgammaR stimulation, but did not affect the increase in Ins(1,4,5)P3 induced by the chemotactic peptide, formyl-methionine-leucine-phenylalanine. Because wortmannin is, in the concentrations used here, an inhibitor of PtdIns 3-kinase, these results suggested a role for PtdIns 3-kinase upstream of Ca2+ signalling, induced by FcgammaR cross-linking. Support for this notion was obtained by investigating the effect of another inhibitor of PtdIns 3-kinase, LY 294002, and by studying the kinetics of PtdIns 3-kinase activation. We found translocation of PtdIns 3-kinase to the plasma membrane and increased PtdIns 3-kinase activity in the membrane as soon as 5 s after FcgammaR cross-linking, even before the onset of the Ca2+ response. Moreover, the translocation of PtdIns 3-kinase to the plasma membrane was inhibited by co-cross-linking of either FcgammaRIIa and FcgammaRIIIb with the tyrosine phosphatase, CD45, indicating a requirement for protein tyrosine phosphorylation in the recruitment of PtdIns 3-kinase to the plasma membrane. Taken together, our results suggest a role for PtdIns 3-kinase in early signal transduction events after FcgammaR cross-linking in human neutrophils.

The anti-Fc gamma RIII mAb 3G8 induces neutrophil activation via a cooperative actin of Fc gamma RIIIb and Fc gamma RIIa.

Human neutrophils express two types of Fc gamma receptors, the transmembrane Fc gamma RIIa and the glycan-phosphatidylinositol-anchored Fc gamma RIIIb, that show synergism in provoking a cellular response. To analyse further the requirements for this synergism to occur we used the monoclonal antibody 3G8, directed against Fc gamma RIII. This antibody is able to induce neutrophil activation, as measured by an increase in the intracellular free Ca2+ concentration and homotypic neutrophil aggregation, but only when the Fc part of the antibody is able to interact with Fc gamma RIIa. We observed that binding of the Fab parts of 3G8 mAb to two Fc gamma RIIIb molecules and binding of the Fc part to one Fc gamma RIIa molecule is required, because a bispecific antibody, 2B1, in which only one 3G8 Fab is present, did not induce neutrophil activation. Moreover, engagement of one Fc gamma RIIa molecule and two Fc gamma RIIb molecules on the same cell is instrumental to achieve activation of the mAb 3G8. The activation of neutrophils by the 3G8 antibody represents a further example of synergistic activation of neutrophils via Fc gamma receptors.

Functional association between the human myeloid immunoglobulin A Fc receptor (CD89) and FcR gamma chain. Molecular basis for CD89/FcR gamma chain association.

FcR gamma chain has previously been shown to interact with the TCR-CD3 complex, the IgE Fc receptor I (Fc epsilon RI), and the class I and IIIA IgG receptors (Fc gamma RI and Fc gamma RIIIa). Here, we demonstrate that the Fc receptor gamma chain associates with Fc alpha R in transfected IIA1.6 B lymphocytes. Fc alpha R could be expressed at the surface of IIA1.6 B cells by itself, but was devoid of signaling capacity. Upon co-expression of FcR gamma chain, a physical interaction with Fc alpha R could be demonstrated. This association proved crucial for the triggering of both proximal (intracellular calcium increase and tyrosine phosphorylation), as well as distal (IL-2 release), signal transduction responses. We next tested the hypothesis that a positively charged arginine residue (Arg209) within the transmembrane domain of Fc alpha R promotes association with FcR gamma chain. We therefore constructed Fc alpha R molecules where Arg209 was mutated to either a positively charged histidine, a negatively charged aspartic acid, or an uncharged leucine. A functional association between Fc alpha R and FcR gamma chain was observed only with a positively charged residue (Arg209 or His209) present within the Fc alpha R transmembrane domain. These data show that transmembrane signal transduction by the Fc alpha R is mediated via FcR gamma chain, and that Fc alpha R requires a positively charged residue within the transmembrane domain to promote functional association.

Effect of tumor necrosis factor-induced integrin activation on Fc gamma receptor II-mediated signal transduction: relevance for activation of neutrophils by anti-proteinase 3 or anti-myeloperoxidase antibodies.

Antineutrophil cytoplasmic autoantibodies (ANCA) have been described in sera of patients with several forms of systemic vasculitis, including Wegener's granulomatosis and microscopic polyarteritis. The two main targets of ANCA in vasculitis are proteinase 3 (PR3) and myeloperoxidase (MPO). ANCA are capable of activating neutrophils primed by tumor necrosis factor-alpha (TNF-alpha) in vitro, which may be relevant for the induction of the vascular inflammation observed in vivo. Recently, it has been suggested that engagement of Fc gamma receptor IIa (Fc gamma RIIa) on the neutrophils is involved in the activation by ANCA. In the present study, we show that activation of the neutrophil respiratory burst by anti-PR3 and anti-MPO is strongly enhanced after TNF priming and lost on removal of the Fc parts of the antibodies. Similar results were obtained when the neutrophils were activated with antibodies against known membrane antigens without major changes in the expression of the target antigens. The TNF-induced enhancement of the neutrophil activation was not observed when adherence of the cells was prevented by continuous stirring of the suspension or by the addition of CD18 antibodies before TNF exposure. Hence, our results indicate that engagement of both Fc gamma RIIa and beta 2 integrins is instrumental in neutrophil activation induced by ANCA.

Heterotypic Fc gamma R clusters evoke a synergistic Ca2+ response in human neutrophils.

Both Fc gamma receptors on human neutrophils (Fc gamma RIIa and Fc gamma RIIIb) are capable of initiating signal transduction after multivalent cross-linking. However, immune complexes most likely activate neutrophils by a combined homotypic and heterotypic cross-linking of Fc gamma Rs. We have investigated the effect of homotypic and heterotypic Fc gamma R cluster formation on changes in the intracellular free Ca2+ concentration. Combined heterotypic and homotypic cluster formation resulted in a Ca2+ response that was strongly enhanced as compared to the sum of both individual Fc gamma R responses. This synergistic response was caused by the formation of heterotypic clusters of Fc gamma Rs and not by the simultaneous formation of homotypic clusters. This conclusion was supported by experiments with a bispecific antibody binding to both Fc gamma RIIa and Fc gamma RIIIb. The heterotypic Fc gamma R cross-linking results in efficient activation of Ca2+ influx, probably caused by a more pronounced depletion of intracellular Ca2+ stores. Stimulation with immune complexes also induced Ca2+ influx in normal neutrophils, but not in Fc gamma RIIIb-deficient neutrophils. The synergism between both Fc gamma Rs was also apparent in other responses of neutrophils, such as the activation of the respiratory burst. This study shows that the two different Fc gamma Rs on neutrophils complement each other in mediating an important cellular response.

Functional characteristics of the rat liver macrophage population after a single intravenous injection of liposome-encapsulated muramyl peptides.

In this study, we investigated different functional characteristics of the rat liver macrophage population after a single i.v. injection of liposome-encapsulated muramyl dipeptide (MDP) or its lipophilic derivative muramyl tripeptide-phosphatidylethanolamine (MTP-PE). The in situ induced tumoricidal activity of the liver macrophage population was determined in vitro against C26 colon adenocarcinoma cells. For investigating which cells are responsible for the observed cytotoxic effects, subfractions of the liver macrophage population, differing in cell size, were isolated at different intervals after injection of the liposomal muramyl peptides. From these subfractions, the number of cells, degree of cytotoxicity, and the response to an additional activation with free MDP in vitro were determined. Maximal induction of tumoricidal activity of the liver macrophage population was reached between 12 and 24 hours after injection of liposomal MDP, while no significant differences between the subfractions were observed. Heterogeneity of tumor cytolytic capacity was observed in subfractions of macrophages isolated at 2 and 48 hours after injection. At these time points, highest cytolytic activity was observed for the small to intermediate-size macrophages. No significant cytotoxicity was detectable in any subfraction 72 hours after injection of liposomal MDP. An identical pattern of macrophage tumoricidal activity was observed after injection of liposomal MTP-PE, although slightly lower cytotoxicity levels were found. When isolated during the first 12 hours after injection of liposomal MDP, the macrophage population was unable to respond to a subsequent in vitro exposure to MDP, with respect to tumor cytotoxicity. Twenty-four and 48 hours after injection, the smallest cells could be slightly reactivated, whereas the larger cells still remained unresponsive.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of protein kinase C accelerates internalization of transferrin receptor but not of major histocompatibility complex class I, independent of their phosphorylation status.

Phosphorylation of membrane glycoproteins has often been invoked as a determinant of receptor internalization and receptor trafficking in a more general sense. Here we have studied the trafficking of major histocompatibility complex (MHC) Class I molecules and transferrin receptor (Tfr) related to their phosphorylation status in the human lymphoblastoid cell line JY. High resolution isoelectric focusing (IEF) allows the visualization of phosphorylated and non-phosphorylated protein species simultaneously, using protein backbone-labeling. Analysis on IEF was combined with a neuraminidase protection assay, in which sialic acid modification of the N-linked glycans present on Tfr and Class I molecules is used as a reporter group for cell surface expression. Phosphorylation of Class I heavy chains and Tfr was induced by exposure of cells to the phorbol ester tetradecanoyl phorbol acetate. We show that 1) phosphorylation of MHC Class I molecules is restricted to the cell surface fraction, 2) phosphorylation of MHC Class I molecules by protein kinase C (PKC) is not correlated with their internalization, as no internalization of Class I molecules, phosphorylated or non-phosphorylated, could be detected, 3) the initial rate, but not the final extent of the internalization of Tfr is affected by activation of PKC, and 4) phosphorylated Tfr behaves in a manner identical to non-phosphorylated Tfr in terms of internalization. The effect of activation of PKC on internalization of Tfr therefore most likely takes place at the level of the internalization machinery. Our data concerning the internalization of MHC Class I molecules contrast with earlier studies describing constitutive internalization in the B lymphoblastoid cell line A 46 and in HPB-ALL cells.