Daunorubicin and vincristine binding to plasma membrane vesicles from daunorubicin-resistant and wild type Ehrlich ascites tumor cells

Bridging Clinicopathologic Features and Genetics in Follicular Lymphoma: Towards Enhanced Diagnostic Accuracy and Subtype Differentiation

Follicular lymphoma (FL) is a neoplasm that originates from germinal center B cells and typically forms at least a partial follicular pattern. Approximately 85% of FL cases harbor the t(14;18)(q32;q21)/IGH::BCL2 which leads to the overexpression of BCL2. These cases are referred to as classic FL in the current World Health Organization classification [1]. These neoplasms often exhibit hallmark epigenetic deregulation due to recurrent mutations in genes such as KMT2D, CREBBP, and EZH2, with KMT2D and CREBBP considered founding events in FL lymphomagenesis. In contrast, about 15% of FL cases are negative for the t(14;18), which could present diagnostic challenges. These cases may lack the typical genetic markers and require careful pathological and molecular analysis for accurate diagnosis. This review aims to provide an up-to-date pathology resource on FL, focusing on the pathological and molecular characteristics of these neoplasms. We will detail the diagnostic criteria for FL and emphasize the importance of genetic and mutational analyses in accurately characterizing and distinguishing FL subtypes. Furthermore, we will propose methodologies and best practices for the diagnostic work-up of FL to enhance diagnostic accuracy.

P-glycoprotein in the catfish intestine: inducibility by xenobiotics and functional properties

The p-glycoprotein (pgp)-mediated multixenobiotic resistance (MXR) mechanism of aquatic animals has been associated with protection against pollution. Recent studies in mammals suggest that intestinal pgp may modulate intestinal bioavailability of dietary xenobiotics. In order to further delineate this mechanism in the catfish, these studies: (1) examined the pgp-related distribution in the intestine and liver of catfish, (2) evaluated the MXR response following exposure to various dietary xenobiotics and a prototypic pgp inducer and (3) evaluated pgp functional activity in membrane vesicles, using prototypic substrates and inhibitors. For this purpose, catfish were exposed in vivo to the pgp inducer vincristine (VIN), and the xenobiotics beta-naphthoflavone (BNF), benzo[a]pyrene (BaP), and 3,4,3',4'-tetrachlorobiphenyl (TCB). Membrane vesicles, prepared from liver and intestine (proximal and distal sections) of control and exposed catfish, were subjected to SDS PAGE, Western Blot, and detection with the pgp C219 monoclonal antibody. Transport activity was evaluated in vitro using the pgp substrate [3H]vinblastine (VBL), and the pgp inhibitor verapamil (VP). Immunoblot studies demonstrated a pgp-related protein of approximately 170 kDa in the intestine and liver of catfish. This protein appears to be very susceptible to degradation, and was present in higher levels in the liver, in comparison to the intestine, where regional differences were not observed. Dietary exposure to the pgp substrate VIN, or the xenobiotics BNF, BaP, and TCB, did not appear to affect pgp-related reactivity. Transport studies with VBL indicate that the pgp-related protein of the catfish intestine displays classic pgp-mediated multidrug resistance (MDR) characteristics, such as energy-dependency, and sensitivity to VP. These studies suggest that the pgp-related protein in the catfish intestine and liver is not only immunochemically, but also functionally related to the mammalian MDR. Moreover, the results presented indicate that pgp-related reactivity and transport in intestinal vesicles of catfish may be influenced by factors including method sensitivity, sample collection, sample preparation, and immunoblot conditions.

P-glycoprotein and multidrug resistance-associated protein, but not lung resistance protein, lower the intracellular daunorubicin accumulation in acute myeloid leukaemic cells

The in vitro intracellular daunorubicin accumulation (IDA) of blast cells from 69 patients with newly diagnosed acute myeloid leukaemia (AML) was correlated with the expression and functional activity of the multidrug resistance (MDR) proteins, P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP) and lung-resistance protein (LRP). An inverse and significant association was found between IDA and Pgp-related efflux activity (r = -0.31, P = 0.01) and also MRP (r = -0.25, P = 0.04) but not with LRP (r = -0.13, P = 0.28). Coexpression of the MDR proteins had an additive effect in further lowering of IDA levels, suggesting that the clinical MDR phenotype is dependent on the sum of multiple MDR factors available to the leukaemic cell. Thus, the median IDA of leukaemic cells without any MDR proteins was significantly higher than that of blasts carrying two MDR proteins (0.466 vs. 0.296, P = 0.046). Seven patients with no expression of Pgp, MRP and LRP still had low IDA levels, suggesting the presence of efflux MDR mechanisms other than those studied. The relation of IDA to clinical parameters known to be associated with poor prognosis, such as age, secondary AML, karyotype, peripheral blood blast and CD34 counts, was also studied, but no significance was found on multifactorial analysis. There was a non-significant trend for earlier relapse in patients with low IDA levels (leukaemia-free survival of 16.3 months compared with 21.1 months in patients with high IDA levels). Our data suggest that, while the IDA assay is a quick and relatively easy test for the combined efflux MDR phenotype, it is unable to detect other MDR mechanisms, such as LRP, which may be important to the clinical outcome of patients with AML.

Characterization of the ATPase activity of P-glycoprotein from multidrug-resistant Chinese hamster ovary cells

P-Glycoprotein (Pgp) was isolated from CHRC5 membranes by selective detergent extraction and further purified by lentil lectin affinity chromatography. The purified product displayed a very high basal ATPase activity (1.65 mumol/min per mg protein in the absence of added drugs or lipids) with an apparent Km for ATP of 0.4 mM. There was no evidence of cooperativity, suggesting that the two ATP sites operate independently of each other. Pgp ATPase activity was stimulated by verapamil, trifluoperazine and colchicine, and inhibited by daunomycin and vinblastine. All drugs and chemosensitizers acted as mixed activators or inhibitors, producing changes in both the Vmax of the ATPase and the Km for ATP. ADP competitively inhibited Pgp ATPase, with a Ki of 0.2 mM. The macrolide antibiotics bafilomycin A1, concanamycin A and concanamycin B, inhibited Pgp ATPase at concentrations of 0.1-10 microM, and at an inhibitor:protein stoichiometry of 0.65-1.0 mumol/mg protein, which is at the low end of the range characteristic of P-type ATPases. Pgp ATPase was relatively selective for adenine nucleotides. Several phospholipids stimulated Pgp ATPase activity in a dose-dependent manner, whereas others produced inhibition. Metabolic labelling showed that the endogenous phospholipids associated with purified Pgp consisted largely of phosphatidylethanolamine and phosphatidylserine, with only a small amount of phosphatidylcholine. 32P-Labelling studies indicated that purified Pgp was partially phosphorylated. It can be concluded that Pgp is a constitutively active, adenine nucleotide-specific ATPase whose catalytic activity can be modulated by both drugs and phospholipids.

Kinetics of daunorubicin transport in Ehrlich ascites tumor cells with different expression of P-glycoprotein

The classical multidrug resistance (MDR) phenotype is characterized by a decrease in the intracellular drug concentration in resistant cells as compared to sensitive cells. P-glycoprotein (P-gp) is thought to be responsible for an active efflux of lipophilic drugs. Four Ehrlich ascites tumor cell lines selected in vivo for resistance to daunorubicin (DNR) and their sensitive counterpart were investigated. The resistant sublines EHR2/0.1, EHR2/0.2, EHR2/0.4, and EHR2/0.8 were developed by treatment of tumor bearing mice with DNR 0.1, 0.2, 0.4, and 0.8 mg/kg x 4 weekly, respectively. One passage from EHR2/0.1, EHR2/0.2, and EHR2/0.4 and two passages from EHR2/0.8 were investigated. Western blot analysis showed significantly different amounts of P-gp (a 6-fold variation). Efflux of DNR in a drug free medium was investigated with and without presence of verapamil (VER). Efflux from sensitive and resistant cells was described by mono- and bi-exponential kinetics, respectively. In all cases but one, a correlation between resistance, expression of P-gp, P-gp mediated efflux capacity and effect of VER was established. In passage No. 12 of EHR2/0.8, however, a high expression of P-gp was found in spite of a low degree of resistance and a low efflux capacity. In this subline the effect of VER did not correlate to the expression of P-gp. Active efflux seemed to be saturable and was suggested to constitute the major route of efflux in MDR cells. A dose-response relationship was established for the effect of VER on efflux. In conclusion, the results support that P-gp acts as a drug efflux pump. No simple correlation, however, could be established between P-gp and drug transport in all the investigated cell lines. Other factors which might influence transmembranous transportation of DNR are suggested. The active efflux capacity of the cell lines seemed to determine the degree of resistance and the sensitivity to circumvention by VER.

Chemomodulation of drugs involved in multidrug resistance in chronic lymphatic leukemia of the B-cell type

Reduced drug accumulation may be one reason for intrinsic drug resistance in chronic lymphatic leukemia of the B-cell type (B-CLL). Immunophenotyped leukemic human B-cells from 38 cases of B-CLL were characterized for P-glycoprotein (PGP) content. In all, 30 cases of B-CLL were additionally analyzed for further parameters: accumulation of daunorubicin (DNR, n = 20) and rhodamine 123 (Rh123, n = 30) in both the presence and the absence of verapamil (VRP). Also, 16 cases of B-CLL were analyzed for vincristine (VCR) accumulation with or without VRP. Concerning the relative expression of PGP, these 16 cases of B-CLL were representative for the whole group of 30 cases. Spontaneous accumulation of Rh123 and VCR varied over a wide range: accumulation of Rh123, by a factor of 11.8; accumulation of VCR, by a factor of 9.7; and accumulation of DNR, by a factor of 3.6. VRP modulated the accumulation of RH123 in 16/30 cases (53%), that of VCR in 69% of cases, and that of DNR in 11% of cases. The maximal VRP-mediated increases in accumulation amounted to factors of 1.3 for DNR, 2.3 for Rh123, and 7.8 for VCR. Spontaneous drug accumulation did not correlate with the extent of chemomodulation. The amount of PGP in B-CLL cells (all cases studied were PGP-positive) did not correlate with drug accumulation or with the extent of VRP-mediated chemomodulation. Thus, high expression of PGP is only partially responsible for defective drug accumulation in B-CLL. Only the degree of chemomodulation by VRP is predictive for the extent of the PGP-related functional drug accumulation defect. Thus, in B-CLL, PGP-independent drug accumulation defects seem to be as important as those mediated by PGP. The extent of this drug accumulation defect varies for the different drugs in the following order VCR > Rh123 > DNR. The relevance of PGP-mediated and -independent drug accumulation defects in vivo may depend to a large extent on the drug being used and on the individual cell type. Both types of defect in drug accumulation are of high importance when regimens include VCR a drug commonly used in second-line chemotherapy of B-CLL. Both defects in drug accumulation may be responsible for intrinsic VCR resistance in B-CLL.

Pharmacologic circumvention of multidrug resistance

The ability of malignant cells to develop resistance to chemotherapeutic drugs is a major obstacle to the successful treatment of clinical tumors. The phenomenon multidrug resistance (MDR) in cancer cells results in cross-resistance to a broad range of structurally diverse antineoplastic agents, due to outward efflux of cytotoxic substrates by the mdr1 gene product, P-glycoprotein (P-gp). Numerous pharmacologic agents have been identified which inhibit the efflux pump and modulate MDR. The biochemical, cellular and clinical pharmacology of agents used to circumvent MDR is analyzed in terms of their mechanism of action and potential clinical utility. MDR antagonists, termed chemosensitizers, may be grouped into several classes, and include calcium channel blockers, calmodulin antagonists, anthracycline and Vinca alkaloid analogs, cyclosporines, dipyridamole, and other hydrophobic, cationic compounds. Structural features important for chemosensitizer activity have been identified, and a model for the interaction of these drugs with P-gp is proposed. Other possible cellular targets for the reversal of MDR are also discussed, such as protein kinase C. Strategies for the clinical modulation of MDR and trials combining chemosensitizers with chemotherapeutic drugs in humans are reviewed. Several novel approaches for the modulation of MDR are examined.

A comparison of membrane properties and composition between cell lines selected and transfected for multi-drug resistance

Cell lines selected (CHRC5) and transfected (LR-73-1A) for multi-drug resistance have total lipid compositions which are indistinguishable between resistant and parental cells. Lipid composition was evaluated by 1H NMR and the total fatty acid content by GLC. No change in surface hydrophobicity, as measured with the fluorescent probe dansyl-PE, was observed as a result of transfection of CHO cells with the mdr1 gene. However, the selected cell line, CHRC5, showed a decreased surface hydrophobicity. This decreased surface hydrophobicity was indicated by an 8 nm increase in the fluorescence emission of dansyl-PE in the CHRC5 cell line compared with the AB1. Both resistant cell lines showed an increase in the polarisation of the fluorescent probe, TMA-DPH in the plasma membranes corresponding to a 14% and a 24% change in fluorescence polarisation for the selected and transfected cell lines, respectively. This is indicative of reduced mobility of the acyl chains in the resistant cell lines. Both the CHRC5 and the transfected cell lines showed almost a 2-fold increase in the initial rate of membrane cycling. The membrane cycling could be inhibited by a known bilayer stabiliser, the N-carbobenzoxy-D-Phe-L-Phe-Gly. These results indicate that the properties of the plasma membrane from resistant cells are altered compared with their parental cell line.

Second messengers and ion channels in acetylcholine-induced chloride secretion in hen trachea

1. Hen tracheal epithelium can be stimulated by serosal application of acetylcholine (ACh) to secrete Cl- equal to approximately 60-90 microA/cm2. 2. Radio-ligand-displacement for IP3, cAMP and cGMP and ion channel selective drugs in voltage clamp set-ups were employed to characterize second messengers and Cl-, K+ and Ca2+ channels involved in the ACh response. 3. ACh induced a significant rise in IP3 in isolated tracheocytes, while ACh did not influence the production of cAMP in whole tissue, isolated tracheocytes or basolateral cell membrane vesicles. Further ACh desensitization did not effect cAMP level in tracheocytes. In addition neither ACh stimulation nor desensitization interfered with cAMP production in presence of 4.5 microM forskolin in tracheocytes, a level of forskolin rising base level cAMP by around five fold. 4. Around 35% of ACh Cl- secretion depends on Ca2+ mobilization from internal stores and about 65% on Ca2+ influx over basolateral membrane. The activated Ca2+ channel is insensitive to class I, II, III and IV Ca2+ antagonists. 5. A 23187 can mimic the ACh effect although 30% is indomethacin-sensitive demonstrating a prostaglandin activated adenylyl cyclase. 6. Two K+ channels are involved in ACh secretion, one sensitive to Ba2+ and quinine and both insensitive to 4-aminopyridine, apamin, charybdotoxin and TEA. 7. Flufenamate and triaminopyrimidine block a non-selective ion channel likely involved in the ACh response. An ACh activated apical Cl- channel is NPPB-sensitive.

P-glycoprotein as multidrug transporter: a critical review of current multidrug resistant cell lines

MDR has been studied extensively in mammalian cell lines. According to usual practice, the MDR phenotype is characterized by the following features: cross resistance to multiple chemotherapeutic agents (lipophilic cations), defective intracellular drug accumulation and retention, overexpression of P-gp (often accompanied by gene amplification), and reversal of the phenotype by addition of calcium channel blockers. An hypothesis for the function of P-gp has been proposed in which P-gp acts as a carrier protein that actively extrudes MDR compounds out of the cells. However, basic questions, such as what defines the specificity of the pump and how is energy for active efflux transduced, remain to be answered. Furthermore, assuming that P-gp acts as a drug transporter, one will expect a relationship between P-gp expression and accumulation defects in MDR cell lines. A review of papers reporting 97 cell lines selected for resistance to the classical MDR compounds has revealed that a connection exists in most of the reported cell lines. However, several exceptions can be pointed out. Furthermore, only a limited number of well characterized series of sublines with different degrees of resistance to a single agent have been reported. In many of these, a correlation between P-gp expression and transport properties can not be established. Co-amplification of genes adjacent to the mdr1 gene, mutations [122], splicing of mdr1 RNA [123], modulation of P-gp by phosphorylation [124] or glycosylation [127], or experimental conditions [26,78] could account for some of the complexity of the phenotype and the absence of correlation in some of the cell lines. However, both cell lines with overexpression of P-gp without increased efflux [i.e., 67,75] and cell lines without P-gp expression and accumulation defects/increased efflux [i.e., 25,107] have been reported. Thus, current results from MDR cell lines contradict--but do not exclude--that P-gp acts as multidrug transporter. Other models for the mechanism of resistance have been proposed: (1) An energy-dependent permeability barrier working with greater efficacy in resistant cells. This hypothesis is supported by studies of influx which, although few, all except one demonstrate decreased influx in resistant cells; (2) Resistant cells have a greater endosomal volume, and a greater exocytotic activity accounts for the efflux.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of the cooperative cross-linking of doxorubicin N-hydroxysuccinimide ester derivatives to water soluble proteins

Protein-anthracycline interactions have been examined by using reactive N-hydroxysuccinimide ester derivatives of doxorubicin. These compounds cross-link to lysine epsilon-amino groups with high efficiency and offer the possibility for structural studies of protein-anthracycline complex formation by using gel filtration, ultracentrifugation and spectrophotometric methods. The results are in accordance with association of anthracycline to the hydrophobic ligand binding cavities of serum albumin. The results for proteins not having hydrophobic domains (IgG, serum transferrin, lactotransferrin, ovotransferrin) suggest that complex formation is cooperative and involves two steps: initial self-association of anthracycline into aggregated structures and subsequent binding of protein at the aggregate surface. With serum transferrin, anthracycline self-association makes possible the assembly of stable nanometer-sized protein-anthracycline particles held together by non-covalent bonds. This reaction, which is highly reproducible and efficient, may have applications in the field of development of anthracycline carrier systems.

Transport of the multidrug resistance modulators verapamil and azidopine in wild type and daunorubicin resistant Ehrlich ascites tumour cells

Verapamil has been proposed to modulate the multidrug resistance phenotype by competitive inhibition of an energy dependent efflux of cytotoxic drug. However, the accumulation of both 14C-verapamil and 3H-verapamil was similar in wild type EHR2 and multidrug resistant EHR2/DNR+ Ehrlich ascites cells, and was much less in both cell lines in energy deprived medium than in medium containing glucose. Azidopine accumulation was also similar in both EHR2 and EHR2/DNR+ cells but, in contrast to verapamil, did not differ significantly with changes in cellular energy levels. Azidopine photolabelled a 170 kDa protein in EHR2/DHR+ plasma membrane vesicles which was immunoprecipitated by monoclonal antibody towards P-glycoprotein. Azidopine increased daunorubicin accumulation and modulated vincristine resistance in EHR2/DNR+ cells in a similar fashion to verapamil. Azidopine photolabelling was inhibited by vincristine and verapamil, but not by daunorubicin. Vincristine, but not daunorubicin, was able to increase both azidopine and verapamil accumulation in EHR2/DNR+ cells only. Finally, though both verapamil and azidopine are a substrate for P-glycoprotein in EHR2/DNR+ cells, they do not themselves appear to be transported by the multidrug resistance efflux mechanism to any significant extent in these cells.