Direct monitoring of molecular recognition processes using fluorescence enhancement at colloid-coated microplates

Direct monitoring of recognition processes at the molecular level is a valuable tool for studying reaction kinetics to assess affinity constants (e.g. drugs to receptors) and for designing rapid single step immunoassays. Methods currently used to gain information about binding processes predominantly depend on surface plasmon resonance. These systems use excitation with coherent light in attenuated total reflection geometry to obtain discrimination between surface-bound and free molecules in solution. Therefore labeling of the compounds is not necessary, but due to the complexity of the measuring setup the method is rather costly. In this contribution we present a simple method for performing kinetic single step biorecognition assays with fluorophore labeled compounds using the fluorescence enhancement properties of surface bound silver colloids. Silver colloids are bound to standard microplates via silanization of the plastic surface. Fluorophores close to this colloid coated surface show a significant gain in fluorescence compared to fluorophores farther away in the bulk solution. Therefore discrimination between surface bound and free fluorophores is possible and the binding of, for example, fluorophore labeled antibodies to antigens immobilized on the colloid surface results in increasing fluorescence intensity. Utilization of standard microplates makes this method fully compatible with conventional microplate processing and reading devices. Neither excitation with coherent laser light nor ATR geometry is required, the measurement is performed in a standard fluorescence microplate reader in front face geometry with a xenon flash lamp as excitation source. Methods for the preparation of colloid-coated microplates and fluorescence-enhanced biorecognition assays are presented. Additionally the dependence of the system performance on the structure and properties of the metal colloid coated surface is described. A two-component biorecognition model system shows a detection limit in the subnanomolar range. The ease of colloid-surface preparation and the high sensitivity makes fluorescence enhancement at colloid-coated microplates a valuable tool for studying reaction kinetics and performing rapid single-step immunoassays.

The interaction between wheat germ agglutinin and other plant lectins with prostate cancer cells Du-145

The bioadhesive properties of fluorescein-labeled plant lectins with different carbohydrate specificities were investigated by flow cytometry at 4 and 37 degrees C using Du-145 prostate cancer cells. At both temperatures the lectin association rate increased following the order: Dolichos biflorus agglutinin (DBA)<peanut agglutinin<Ulex europaeus isoagglutinin I<Lens culinaris agglutinin<Solanum tuberosum lectin << wheat germ agglutinin (WGA), reflecting the glycosylation pattern of Du-145 cells. Both, the BSA-binding capacity of the cells referring to nonspecific binding and inhibition studies using the complementary carbohydrate, assured specificity of the lectin-cell interactions except for DBA. The WGA-association rate of Du-145 cells was dependent on temperature indicative for cellular uptake of membrane-bound WGA. Intracellular enrichment of WGA was confirmed by confocal microscopy. As resulted from experiments in presence of ouabain active transport mechanisms were involved in cellular uptake of WGA. Equilibration of the intracellular pH with monensin pointed to accumulation of intracellular located WGA within acidic compartments of Du-145 cells such as the lysosomes or the trans-Golgi complex. Consequently the interaction of WGA with Du-145 cells at 37 degrees C is a one way process due to immediate active transport of membrane-bound lectin into acidic compartments of prostate cancer cells.

Parameters influencing the transport rate of marker compounds across Caco-2 monolayers

Performing transport experiments with Caco-2 monolayers some important parameters have to be considered. Cell layers are appropriate for transport studies after complete polarisation and differentiation. Consequently they should be used 20 - 25d after seeding. Monolayers grown for shorter time than 20d yield to high transport rates, a cultivation period longer than 25d results in layers susceptible to detachment. Additionally the material of the filter support exerts an influence on the transport data because of varying barrier functions of cell layers grown on polyester- versus polycarbonate filter inserts. By comparison of transport rates obtained with different model systems such as Transwells and Ussing chambers the influence of the unstirred water layer on permeation of markers was investigated. The results indicate that there is a noticeable difference with hydrophobic compounds only. To check the dependence of transport phenomena on energy the difference in transport rates between 4°C and 37°C as well as the cumulative transport subject to the transport direction was determined. Moreover the influence of the stirring rate on the cumulative transport in the Ussing chamber system was elucidated. For assessment of the cell associated amount of the transported substance the cell layer was dissolved in NaOH / SDS to get further valuable informations.

The bicalutamide Early Prostate Cancer Program. Demography

BACKGROUND: The optimal treatment for early prostate cancer has yet to be established. A well-tolerated hormonal therapy such as bicalutamide could be a useful treatment option in this setting, either as adjuvant or immediate therapy. A major collaborative clinical trials program was set up to investigate bicalutamide as a treatment option for local prostate cancer (localized or locally advanced disease). METHODS: The bicalutamide Early Prostate Cancer program comprises three randomized, double-blind, placebo-controlled trials of similar design that are being conducted in distinct geographical areas (North America; Australia, Europe, Israel, South Africa and Mexico; and Scandinavia). Men with T1b-4N0-1M0 (TNM 1997) prostate cancer have been randomized on a 1:1 basis to receive bicalutamide 150 mg daily or placebo. Recruitment to the program closed in July 1998, and follow-up is ongoing. Study endpoints include time to clinical progression, overall survival and tolerability. RESULTS: 8113 men aged 38 to 93 years (mean 66.9) were randomized over a 3-year period. 67.4% of the enrolled patients had localized disease (T1-2) and 66.4% had a Gleason score </=6 at study entry, while the majority of patients had node-negative (N0) disease; only 3.1% in two of the studies and none in the third study had confirmed N+ disease. Overall, 71.8% of the patients received therapy of primary curative intent within 16 weeks of randomization; the remainder received watchful waiting as their primary approach. Across the program, the two randomized groups are well balanced. CONCLUSION: This is the largest randomized clinical trial program to date in local prostate cancer and is expected to provide critical information on the role of bicalutamide as an addition to standard care for patients with local prostate cancer who have received a therapy of curative intent or are candidates for watchful waiting.

Bioavailability and metabolism of mometasone furoate following administration by metered-dose and dry-powder inhalers in healthy human volunteers

These studies were conducted to assess the systemic bioavailability of mometasone furoate (MF) administered by both the dry-powder inhaler (DPI) and the metered-dose inhaler with an alternate propellant (MDI-AP). The pharmacokinetics of single doses (400 micrograms) of MF administered by intravenous (i.v.) and inhalation routes was assessed in a randomized, three-way crossover study involving 24 healthy volunteers. In a separate study, 6 healthy subjects were administered a single dose of tritiated (3H-) MF by DPI, and the radioactivity in blood, urine, feces, and expired air was determined. Following i.v. administration, MF was detected in all subjects for at least 8 hours postdose. The half-life (t1/2) following i.v. administration was 4.5 hours. In contrast, following DPI administration, plasma MF concentrations were below the limit of quantification (LOQ, 50 pg/mL) for many subjects (10 of 24), and the systemic bioavailability by this route was estimated to be less than 1%. Only two plasma samples following MDI-AP administration had plasma concentrations of MF above the LOQ indicating no detectable systemic bioavailability in 92% of the subjects. A separate study with 6 healthy male subjects administered a single dose of 3H-MF (200 microCi) by DPI revealed that much of the dose (approximately 41%) was excreted unchanged in the feces (0-72 hours), while that which was absorbed was extensively metabolized. These results indicate that inhaled MF has negligible systemic bioavailability and is extensively metabolized and should therefore be well tolerated in the chronic treatment of asthma.

Lectin-mediated bioadhesion: preparation, stability and caco-2 binding of wheat germ agglutinin-functionalized Poly(D,L-lactic-co-glycolic acid)-microspheres

To take advantage of the cytoadhesive characteristics of Wheat germ agglutinin (WGA) for improved particulate drug delivery, the interaction between WGA-grafted poly(D,L-lactic-co-glycolic acid)-microspheres and Caco-2 monolayers was investigated using bovine serum albumin (BSA) or glycine coated microspheres as a control. Covalent immobilization of WGA by the carbodiimide/N-hydroxysuccinimide-method on 4 microm microspheres yielded a surface density of 9.67+/-1.21x10(6) molecules/particle, whereas 0.22+/-0.04x10(6) WGA-molecules were bound by physical adsorption. After storage for 21 days in HEPES-buffer and treatment of the particles with 5 M urea, 86% of covalently linked lectin was still attached to the particles. At 4 degrees C the Caco-2 binding rate of both, WGA- and BSA-modified particles increased with addition of increasing numbers of particles until saturation was reached at 38150+/-1740 (WGA) or 12066+/-1195 (BSA) microspheres bound/mm(2) Caco-2 monolayer. Inhibition of Caco-2 binding of WGA-functionalized microspheres by chitotriose indicated for specificity of the interaction. As observed by confocal laser scanning microscopy, the fluorescein-loading of the particles was accumulated intracellularly after incubation of Caco-2 monolayers with WGA-modified microspheres contrary to glycine-grafted microspheres. Additionally, in case of WGA-functionalized microspheres the amount of cell associated fluorescein was 200-fold higher than that of the free solution. In conclusion, WGA-modified microspheres are expected to enhance intestinal transport of incorporated drugs due to cytoadhesion provided by the lectin coating.

Chemical and biochemical composition of caviar from different sturgeon species and origins

The chemical and biochemical composition of caviar in 22 specimens of wild caught and of 2 farmed animals were measured. The results include grain size, protein and fat content, fatty acid composition of triglycerides and phospholipids, as well as the concentrations of relevant heavy metals and chlorinated hydrocarbons. The average protein content varied between 26.2 and 31.1% (wet weight) and fat from 10.9 to 19.4% (wet weight) with lowest values for caviar from farmed sturgeon. The triglycerides and phospholipids contained more n-3 fatty acids, especially eicosapentaenoic and docosahexaenoic acid than n-6 fatty acids. The copper and zinc concentrations varied between 1.20 and 1.69 and 10.3 and 12.4 mg/kg (wet weight), respectively. These values reflect the elevated requirement of sturgeons for these components. Lead content varied between 0.06 and 0.15 mg/kg (wet weight). The cadmium concentrations were less than 5 micrograms/kg (wet weight) leading to the conclusion that no accumulation took place in the eggs. The concentrations of sigma DDT and sigma PCB were extremely high in caviar from Huso huso compared to the samples of the other species thus reflecting the different food habits leading to increased bio-accumulation.

[Early detection of prostatic carcinoma in urologic practice with digital rectal examination and prostate-specific antigen. Early Detection Project Group]

For the early detection of prostate cancer, a patient should undergo digital rectal examination (DRE) and PSA investigation. Follow-up of increased PSA levels detects nearly 80% of cancers. Positive predictive value of suspicious DRE and PSA is about 50%. Whereas in the first evaluation of this case-finding trial about 70% of the patients had organ-confined cancers, nearly all of the detected cancers in the follow-up investigation were organ confined. The increased number of organ-confined cancers detected in early periodical examinations can lead to a reduction of mortality and morbidity from prostate cancer.

Development of a self-inactivating, minimal lentivirus vector based on simian immunodeficiency virus

In contrast to oncoviruses, lentiviruses do not require target cell division for integration into the host genome. Lentiviral vectors can therefore expand the spectrum of target cells susceptible to retroviral gene transfer. To analyze whether vectors based on simian immunodeficiency viruses (SIVs) could be used for gene transfer, a three-plasmid vector-packaging system was developed, in which Gag-Pol and the vector itself are of SIV origin, while Env is derived either from SIV, amphotropic murine leukemia virus (MuLV), or the G glycoprotein of vesicular stomatitis virus (VSV-G). To increase the safety of the SIV vector system, a self-inactivating SIV vector was constructed. After optimization of the SIV gag-pol expression plasmid, a minimal SIV vector, which contained only SIV sequences present on the multiply spliced nef transcript, could still be produced at titers of 2 x 10(5) infectious units/ml. Growth-arrested cells could be transduced with this vector even if vif, vpr, vpx, and nef had been deleted from the packaging construct and the vector.

[PSA rise after radical prostatectomy]

Approximately 18 % of patients will experience PSA failure only after radical prostatectomy. The rate of clinical (local or systemic) recurrence is in the same range. Clinical recurrence is accompanied by an increasing PSA in almost all cases. Altogether, the 10-year risk of PSA recurrence after radical prostatectomy for clinically localized prostate cancer is about 35 %. PSA relapse precedes the development of metastases by a median time of 8 years. The median survival after the manifestation of metastases is about 4-5 years. To differentiate the reasons of PSA failure, recurrence-free interval, Gleason score and PSA doubling time deliver important information. Patients with a high probability of isolated local failure (PSA relapse later than two years after radical prostatectomy) should undergo a biopsy, if a local radiotherapy is considered. The results of current clinical trials are eagerly awaited to answer the question weather immediate, delayed or intermittent hormonal therapy offer best results in individual cases.

Improvement of the primary metabolism of cell cultures by introducing a new cytoplasmic pyruvate carboxylase reaction

Continuous mammalian cell lines are important hosts for the production of biological pharmaceuticals. However, these cell lines show some severe disorders in primary metabolism, which they have in common with many cancer cells. This leads to a high throughput of substrates giving a low energy yield and ample toxic side products such as lactate and ammonia. Because the enzymatic connection between glycolysis and the tricarboxylic acid cycle (TCA) is very poor, glucose is mainly degraded via oxidative glycolysis. It will be shown that introducing a pyruvate carboxylase gene expressed in the cytoplasma into a continuous BHK-21 cell line, and thus reconstituting the missing link between glycolysis and TCA, can reduce this problem. Thus, glucose consumption could be reduced by a factor of four and glutamine utilization up to a factor of two, compared with control. Moreover, a 1.4-fold-higher adenosine triphosphate (ATP) content was achieved. The flux of labeled [(14)C]-glucose into the TCA is shown to be enhanced, indicating a higher rate of oxidative glucose degradation. Host cell lines with an improved energy metabolism will therefore result in better exploitation of substrates, an increasing yield by the more efficient use of carbon source, and higher product integrity combined with lower production costs.

A review of studies of hormonal adjuvant therapy in prostate cancer

There is increasing interest in the use of adjuvant hormonal therapies, which are given after the resection or destruction of all gross disease, in early-stage prostate cancer, as a significant proportion of patients experience progression and/or die from the disease despite undergoing therapy with curative intent. Several retrospective studies suggest that adjuvant hormonal therapy may improve long-term outcome after radical surgery in men with positive lymph nodes, although this approach has yet to be studied in a prospective setting. No studies of adjuvant therapy for patients with extracapsular extension at surgery have been completed, but in an interim analysis of an open controlled trial, adjuvant flutamide significantly improved progression-free survival at 4 years. Three prospective studies in the radiotherapy setting have shown that adjuvant luteinizing hormone-releasing hormone (LH-RH) agonist therapy significantly improves progression-free and/or overall survival. Future studies need to define patient subgroups who will benefit most from adjuvant therapy. The side effects of the different therapeutic options also need to be compared. It is hoped that many of the outstanding questions concerning adjuvant hormonal therapy will be answered by the ongoing Bicalutamide Early Prostate Cancer Programme.

Cell lines with reduced UDP-N-acetylhexosamine pool in the presence of ammonium

The glycosylation of pharmaglycoproteins from recombinant cell lines can be affected by an uncontrolled accumulation of ammonium in the medium. Glucosamine-6-phosphate isomerase (GPI) has been proposed as the key enzyme responsible for elevating the intracellular UDP-N-acetylhexosamine pool (UDPGNAc) by accepting ammonium from the medium of cultured mammalian cells. As previously reported, the increased UDPGNAc pool then affects the N-glycan complexity in glycoproteins. To understand the entry of extracellular ammonium into the cellular metabolism, GPI has been isolated to homogeneity from BHK-21 cells and characterized. Thus, the complete pathway by which ammonium enters the cellular metabolism was elucidated. To reduce the negative effects of ammonium, GPI was inhibited using two different strategies. First, the addition of mannose to the culture media and, second, antisense RNA expression. In both cases, the cellular UDPGNAc pool was suppressed in the presence of high ammonium concentrations in the medium. However, constant suppression of the UDPGNAc pool could not be achieved by antisense RNA expression because antisense clones were apparently unstable. Further studies showed that the main reason for instability was the inducibility of GPI by its substrate ammonium. GPI was induced to a factor of two under ammonium-containing medium conditions. We propose gene knockout technology for GPI repression to obtain cell lines consisting of an UDPGNAc pool unaffected by the presence of ammonium.

Poly(D,L-lactic-co-glycolic acid) microspheres for sustained delivery and stabilization of camptothecin

Camptothecin (CPT) and its water-insoluble derivatives are known as topoisomerase-I inhibitors exhibiting high antitumoral activity against a wide spectrum of human malignancies. Until now clinical application of CPT is restricted by insolubility and instability of the drug in its active lactone form resulting in less antitumor potency and poor bioavailability. For these reasons CPT-loaded-microspheres were prepared by the solvent evaporation method using the H-series of poly(D,L-lactide-co-glycolide) (H-PLGA), which contain more carboxylic acid end chains and hydrate faster than the non-H-series. At 1.2% CPT-payload the drug was molecular dispersed throughout the matrix whereas at higher CPT-payload the amount of crystalline CPT-islets increased with the CPT content. The release pattern of CPT was biphasic comprising a first burst effect delivering 20-35% of the payload and increasing with drug-loading. This phase was followed by sustained delivery of CPT releasing 40-75% of the payload within 160 h. In comparison to PLGA-microspheres, the CPT-release rate from H-PLGA was twofold higher and accelerated. The active CPT-lactone was maintained during preparation, storage and release due to hindered diffusion of acidic oligomers among other mechanisms. Thus stabilization and sustained release of CPT from PLGA-microspheres might reduce local toxicity combined with prolonged efficacy offering new perspectives in CPT chemotherapy.