True ferroelectric switching in thin films of trialkylbenzene-1,3,5-tricarboxamide (BTA).

We have investigated the ferroelectric polarization switching properties of trialkylbenzene-1,3,5-tricarboxamide (BTA), which is a model system for a large class of novel organic ferroelectric materials. In the solid state BTAs form a liquid crystalline columnar hexagonal phase that provides long range order that was previously shown to give rise to hysteretic dipolar switching. In this work the nature of the polar switching process is investigated by a combination of dielectric relaxation spectroscopy, depth-resolved pyroelectric response measurements, and classical frequency- and time-dependent electrical switching. We show that BTAs, when brought in a homeotropically aligned hexagonal liquid crystalline phase, are truly ferroelectric. Analysis of the transient switching behavior suggests that the ferroelectric switching is limited by a highly dispersive nucleation process, giving rise to a wide distribution of switching times.

The role of TRKA signaling in IL-10 production by apoptotic tumor cell-activated macrophages.

Tumor-associated macrophages (TAMs) are a major supportive component within neoplasms. Mechanisms of macrophage (MΦ) attraction and differentiation to a tumor-promoting phenotype, which is characterized by pronounced interleukin (IL)-10 production, are under investigation. We report that supernatants of dying cancer cells induced substantial IL-10 release from primary human MΦs, dependent on signaling through tyrosine kinase receptor A (TRKA or neurotrophic tyrosine kinase receptor type 1 (NTRK1)). Mechanistically, sphingosine-1-phosphate (S1P) release from apoptotic cancer cells triggered src-dependent shuttling of cytosolic TRKA to the plasma membrane via S1P receptor signaling. Plasma membrane-associated TRKA, which was activated by constitutively autocrine secreted nerve growth factor, used phosphatidylinositol 3-kinase (PI3K)/AKT and p38 mitogen-activated protein kinase (MAPK) signaling to induce IL-10. Interestingly, TRKA-dependent signaling was required for cytokine production by TAMs isolated from primary murine breast cancer tissue. Besides IL-10, this pathway initiated secretion of IL-6, tumor necrosis factor-α (TNF-α) and monocyte chemotactic protein-1 (MCP-1), indicating relevance in cancer-associated inflammation. Our findings highlight a fine-tuned regulatory system including S1P-dependent TRKA trafficking for executing TAM-like cell function in vitro as well as in vivo.

Unusual thermoelectric behavior indicating a hopping to bandlike transport transition in pentacene.

An unusual increase in the Seebeck coefficient with increasing charge carrier density is observed in pentacene thin film transistors. This behavior is interpreted as being due to a transition from hopping transport in static localized states to bandlike transport, occurring at temperatures below ∼250 K. Such a transition can be expected for organic materials in which both static energetic disorder and dynamic positional disorder are important. While clearly visible in the temperature and density dependent Seebeck coefficient, the transition hardly shows up in the charge carrier mobility.

Targeting dendritic cells with antigen via dendritic cell-associated promoters.

The induction of tumor-specific immune responses is largely dependent on the ability of dendritic cells (DCs) to present tumor-associated antigens to T lymphocytes. Therefore, we investigated the use of DC-associated promoter-driven genetic vaccines to specifically target DC in vivo. Restricted expression of vaccine-encoding genes in DC should enhance specificity and improves their safety for clinical applications. Hereto, 3-5 kb upstream sequences of the murine genes encoding CD11c, DC-SIGN, DC-STAMP and Langerin were isolated, characterized and subcloned into enhanced green fluorescent protein (EGFP) reporter constructs. Upon electroporation, EGFP was expressed in DC cell lines, but not in other cell lines, confirming DC-restricted promoter activity. When these promoters were cloned into a construct upstream of the gene for ovalbumin (OVA), it appeared that DC-STAMP promoter-driven expression of OVA (pDCSTAMP/OVA) in DC yielded the most efficient OVA-specific CD4+ and CD8+ T-cell responses in vitro. Administration of pDC-STAMP/OVA in vivo, using the tattoo gun vaccination system, evoked specific immune responses as evidenced in a mouse tumor model. Adoptively transferred pDC-STAMP/OVA-transfected DCs induced strong CD8+ T-cell proliferation in vivo. These experiments demonstrate that our DC-directed promoter constructs are potential tools to restrict antigen expression in DC and could be implemented to modulate DC function by the introduction of relevant proteins.

Identification of phosphorylase kinase as a novel therapeutic target through high-throughput screening for anti-angiogenesis compounds in zebrafish.

Angiogenesis is essential for development and tumor progression. With the aim of identifying new compound inhibitors of the angiogenesis process, we used an established enhanced green fluorescent protein-transgenic zebrafish line to develop an automated assay that enables high-throughput screening of compound libraries in a whole-organism setting. Using this system, we have identified novel kinase inhibitor compounds that show anti-angiogenic properties in both zebrafish in-vivo system and in human endothelial cell in-vitro angiogenesis models. Furthermore, we have determined the kinase target of these compounds and have identified and validated a previously uncharacterized involvement of phosphorylase kinase subunit G1 (PhKG1) in angiogenesis in vivo. In addition, we have found that PhKG1 is upregulated in human tumor samples and that aberrations in gene copy number of PhK subunits are a common feature of human tumors. Our results provide a novel insight into the angiogenesis process, as well as identify new potential targets for anti-angiogenic therapies.

Morphological device model for organic bulk heterojunction solar cells.

We present a numerical model for calculating current-voltage characteristics of polymer:fullerene bulk hetrojunction solar cells at different degrees of nanoscale phase separation. We show that the short-circuit current enhancement with finer phase separation is due to a reduction in bimolecular recombination caused by lateral movement of photogenerated electrons to the fullerene-rich phase. At high bias, vertical electron transport is enhanced and lateral movement is reduced, causing a significant field-dependent carrier extraction for coarse morphologies.

Conjugation-length dependence of spin-dependent exciton formation rates in pi-conjugated oligomers and polymers.

We have measured the ratio, r = sigma(S)/sigma(T) of the formation cross section, sigma of singlet and triplet excitons from polarons in pi-conjugated oligomer and polymer films, using a spectroscopic technique we developed recently. We discovered a universal relation between r and the conjugation length (CL): r(-1) depends linearly on CL-1, irrespective of the chain structure. Since r is directly related to the maximum possible electroluminescence quantum efficiency in organic light emitting diodes (OLED), our results indicate that polymers have an advantage over small molecules in OLED applications.

Real-space measurement of the potential distribution inside organic semiconductors.

We demonstrate that the soft nature of organic semiconductors can be exploited to directly measure the potential distribution inside such an organic layer by scanning-tunneling microscope (STM) based spectroscopy. Keeping the STM feedback system active while reducing the tip-sample bias forces the tip to penetrate the organic layer. From an analysis of the injection and bulk transport processes it follows that the tip height versus bias trace obtained in this way directly reflects the potential distribution in the organic layer.

Radicicol suppresses transformation and restores tropomyosin-2 expression in both ras- and MEK-transformed cells without inhibiting the Raf/MEK/ERK signaling cascade.

The antibiotic radicicol suppresses transformation in a variety of transformed cells. The antineoplastic effects of the drug have been attributed to the degradation of Raf and the inactivation of the Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling cascade. Here we demonstrate that radicicol induces cell spreading, suppresses anchorage-independent cell growth, and increases the expression of the high-molecular weight tropomyosin isoform TM-2 in cells stably expressing a constitutively active form of MEK-1 as well as in ras-transformed cells. Furthermore, the reverting effects of the drug are achieved at concentrations below those required to deplete Raf from the cell or to inhibit the phosphorylation of ERK or its substrates Elk and pp90(RSK). In contrast, low concentrations of radicicol significantly inhibited activator protein (AP-1) and serum response factor (SRF)-mediated transcription. The lack of correlation between the effects of radicicol on cell phenotype and on the signaling activities of the Raf/MEK/ERK pathway indicate that Raf depletion or disruption of proximal signaling events in the mitogen-activated protein kinase pathway are not the predominant mechanisms by which the drug suppresses the transformed phenotype. Our observation that low concentrations of radicicol block transcriptional activities mediated by AP-1 and SRF suggests that interference with signaling upstream of these transcription factors may contribute to the reverting effects of the drug.

Separation and characterization of oligomers by reversed-phase high-performance liquid chromatography: a study on well-defined oligothiphenes.

Reversed-phase high-performance liquid chromatography (RP-HPLC) was used for the separation of 3-hexylthiophene oligomers in the range of 3 to 30 monomeric units, while systematically varying stationary and mobile phases. A set of different columns was chosen, covering a broad range of silica types, pore sizes and bonding chemistry. Mobile phases of tetrahydrofuran (THF) combined with water, acetonitrile (ACN) or methanol (MeOH) were used. Although differences between columns were small, a higher selectivity correlated with a lower hydrophobicity parameter from the Galushko column test. The model of Jandera, based on the linear solvent strength model of Snyder, was used to describe the retention of the oligomers in gradient mode. This gave information about selectivities on different stationary phases similar to the hydrophobicity parameter. Contrary to the stationary phase, the mobile phase had a major influence on the selectivity. The THF-water combination gave much higher selectivities compared to THF combined with MeOH or ACN. Using the aqueous mobile phase even enabled separation of different isomers. Determination of thermodynamic parameters for the model compounds showed that retention of the different isomers was mainly determined by the orientation of the side chains at both ends of the chain. An additional repeating unit in the middle of the polymer backbone gave a similar contribution to retention, irrespective of the orientation of its side chain. Three model isomers were separated by preparative RP-HPLC and identified by proton nuclear magnetic resonance spectroscopy. The combination of subsequent preparative size-exclusion chromatography, RP-HPLC and matrix-assisted laser desorption ionization time-of-flight mass spectrometry enabled the identification of the two major oligomeric series in the sample as the regioregular product with one bromine end group and, in smaller amounts, a regioirregular product with two bromine end groups. reserved.

Ras- and Raf-induced down-modulation of non-muscle tropomyosin are MEK-independent.

Transformation is accompanied by the down-regulation of the high molecular weight isoforms of non-muscle tropomyosin. Several lines of evidence suggest that tropomyosin down-regulation may be essential for ras-induced tumorigenicity. It is unclear which of the many signaling pathways downstream of Ras are involved in tropomyosin down-regulation. Here we demonstrate that Raf activation induces tropomyosin down-regulation comparable to that induced by Ras. Expression of the effector-domain mutant Ras-G12V,Y40C, which is unable to bind Raf, induced only modest down-modulation of tropomyosin. Treatment with the MEK-specific inhibitor PD98059 had little effect on tropomyosin levels in ras- or raf-transformed cells. In contrast, a mutant form of MEK-1, MEK-1-S218A,S222A, restored tropomyosin levels in ras-transformed NIH3T3 cells almost to the levels observed in non-transformed cells. MEK-1-S218A,S222A does not inhibit MEK phosphorylation and is a poor inhibitor of ERK phosphorylation. These data suggest that this mutant form of MEK-1 interferes with a yet uncharacterized pathway controlled by Raf. We conclude that the ras-induced down-modulation of tropomyosin is predominantly Raf-mediated, but MEK-independent, and that a novel pathway exists downstream of Raf which may play an important role in regulation of the cytoskeleton.

Tropomyosin-2 cDNA lacking the 3' untranslated region riboregulator induces growth inhibition of v-Ki-ras-transformed fibroblasts.

The levels of high molecular weight isoforms of tropomyosin (TM) are markedly reduced in ras-transformed cells. Previous studies have demonstrated that the forced expression of tropomyosin-1 (TM-1) induces reversion of the transformed phenotype of ras-transformed fibroblasts. The effects of the related isoform TM-2 on transformation are less clear. To assess the effects of forced expression of the TM-2 protein on ras-induced tumorigenicity, we introduced a TM-2 cDNA lacking the 3' untranslated region riboregulator into ras-transformed NIH 3T3 fibroblasts. TM-2 expression resulted in a flatter cell morphology and restoration of stress fibers. TM-2 expression also significantly reduced growth rates in low serum, soft agar, and nude mice. The reduced growth rates were associated with a prolongation of G0-G1. To identify the mechanism of TM-2-induced growth inhibition, we analyzed the effects of TM-2 reexpression of ERK and c-jun N-terminal kinase (JNK) activities. Levels of ERK phosphorylation and activity in TM-2-transfected tumor cells were comparable to those in mock-transfected tumor cells. JNK activity was only modestly increased in ras-transformed cells relative to untransformed NIH 3T3 cells and only slightly reduced as result of forced TM-2 expression. We conclude that the partially restored expression of the TM-2 protein induces growth inhibition of ras-transformed NIH 3T3 cells without influencing ERK or JNK activities. Furthermore, the 3' untranslated region riboregulator of the alpha-tropomyosin gene is not needed for the inhibition of ras-induced growth.

Bispecific monoclonal antibodies for intravenous treatment of carcinoma patients: immunobiologic aspects.

Immunobiologic parameters measured during a phase I trial of intravenously (i.v.) administered bispecific monoclonal antibodies (BsmAb) in renal cell carcinoma (RCC) patients are described. The BsmAb used, BIS-1, is reactive with a pancarcinoma-associated 38 kDa transmembrane glycoprotein, EGP-2, as well with the CD3 complex. Patients received during a 2 h i.v. infusion F(ab')2 fragments of BIS-1 at doses of 1, 3, or 5 micrograms/kg body weight during concomitantly applied subcutaneous (s.c.) IL-2 treatment. Acute but transient BIS-1 F(ab')2-related toxicity was observed at the 3 and 5 micrograms/kg dose level, and the maximum tolerated dose (MTD) was set at 5 micrograms/kg. A dose-dependent binding of BIS-1 F(ab')2 to circulating T lymphocytes was found. The in vivo occupancy of CD3 molecules on T lymphocytes was highest at teh end of the infusion period and then rapidly decreased, as shown by flow cytometry. A much slower decrease of BIS-1 F(ab')2 binding was observed in vitro, suggesting migration of BIS-1 F(ab')2-loaded T lymphocytes from the circulation. A strong but transitory leukopenia was observed, in which LFA-1 alpha bright, CD3/CD8 double positive T cells left the circulation preferentially. This phenomenon was most likely induced by elevated TNF-alpha and IFN-gamma plasma levels, which were at a maximum shortly after the end of the infusion. Isolated peripheral blood mononuclear cells obtained from patients directly after treatment with BIS-1 F(ab')2 at the 3 and 5 micrograms/kg dose level showed increased EGP-2-directed antitumor activity.

Immunomodulatory effects of intravenous BIS-1 F(ab')2 administration in renal cell cancer patients.

We report the immunomodulatory effects of an intravenous treatment with F(ab')2 fragments of the bispecific monoclonal antibody BIS-1 during subcutaneous recombinant interleukin 2 (rIL-2) therapy of renal cell cancer (RCC) patients. BIS-1 is directed against both the CD3 antigen on T cells and the EGP-2 molecule on carcinoma cells and some normal epithelia. The amount of BIS-1 F(ab')2 bound to peripheral blood lymphocytes (PBLs) increased dose-dependently. This occupation degree was highest at the end of the 2 h infusion and rapidly decreased subsequently. During the first hour of BIS-1 F(ab')2 infusion the number of PBLs decreased slowly. This was followed by an increase in serum tumour necrosis factor alpha (TNF-alpha) concentrations and a rapid decrease in the numbers of peripheral blood lymphocytes, monocytes and eosinophils. In our view, the most likely explanation for the observed decrease in occupation degree of BIS-1 F(ab')2 and the rise in TNF-alpha levels is based on the assumption that BIS-1-carrying T cells leave the circulation. The CD3 antigens on these extravasated T cells become cross-linked by EGP-2 antigens, inducing TNF-alpha secretion. This results in an enhanced decrease in the numbers of PBLs, monocytes and eosinophils. These preliminary results suggest that BIS-1 F(ab')2 treatment during IL-2 therapy may induce local T-cell activation.

Phase I study of intravenously applied bispecific antibody in renal cell cancer patients receiving subcutaneous interleukin 2.

In a phase I trial the toxicity and immunomodulatory effects of combined treatment with intravenous (i.v.) bispecific monoclonal antibody BIS-1 and subcutaneous (s.c.) interleukin 2 (IL-2) was studied in renal cell cancer patients. BIS-1 combines a specificity against CD3 on T lymphocytes with a specificity against a 40 kDa pancarcinoma-associated antigen, EGP-2. Patients received BIS-1 F(ab')2 fragments intravenously at doses of 1, 3 and 5 micrograms kg-1 body weight during a concomitantly given standard s.c. IL-2 treatment. For each dose, four patients were treated with a 2 h BIS-1 infusion in the second and fourth week of IL-2 therapy. Acute BIS-1 F(ab')2-related toxicity with symptoms of chills, peripheral vasoconstriction and temporary dyspnoea was observed in 2/4 and 5/5 patients at the 3 and 5 micrograms kg-1 dose level respectively. The maximum tolerated dose (MTD) of BIS-1 F(ab')2 was 5 micrograms kg-1. Elevated plasma levels of tumour necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) were detected at the MTD. Flow cytometric analysis showed a dose-dependent binding of BIS-1 F(ab')2 to circulating T lymphocytes. Peripheral blood mononuclear cells (PBMCs), isolated after treatment with 3 and 5 micrograms kg-1 BIS-1, showed increased specific cytolytic capacity against EGP-2+ tumour cells as tested in an ex vivo performed assay. Maximal killing capacity of the PBMCs, as assessed by adding excess BIS-1 to the assay, was shown to be decreased after BIS-1 infusion at 5 micrograms kg-1 BIS-1 F(ab')2. A BIS-1 F(ab')2 dose-dependent disappearance of circulating mononuclear cells from the peripheral blood was observed. Within the circulating CD3+ CD8+ lymphocyte population. LFA-1 alpha-bright and HLA-DR+ T-cell numbers decreased preferentially. It is concluded that i.v. BIS-1 F(ab')2, when combined with s.c. IL-2, has a MTD of 5 micrograms kg-1. The treatment endows the T lymphocytes with a specific anti-EGP-2-directed cytotoxic potential.

Poor induction of interleukin-2 receptor expression on CD8bright+ cells in whole blood cell cultures with CD3 mAb. Implications for immunotherapy with CD3 mAb.

To induce better stimulation of T cells during recombinant interleukin-2 (rIL-2) therapy of renal cell carcinoma patients, pretreatment with low-dose CD3 monoclonal antibody (mAb) has been proposed. However, in our clinic, such a treatment did not induce additional activation of T cells. To investigate this we performed whole blood cell cultures with rIL-2 or CD3 mAb as a stimulant. Cultures using isolated blood mononuclear cells were used as a control. When stimulated by the addition of rIL-2, the lymphocyte composition and activation of whole blood cultures did not differ from those of mononuclear cell (MNC) cultures. However, when stimulation was performed with CD3 mAb, CD8bright+ cells in whole blood cultures were not or only minimally induced to express CD25 or IL-2 receptor beta (IL-2R beta). This is in contrast to the situation found in MNC cultures where all CD8bright+ cells expressed CD25 or IL-2R beta to a high extent at the end of culture. When rIL-2 or recombinant interferon gamma (rIFN gamma) was added to whole blood cultures together with CD3 mAb, significantly more CD8bright+ cells were induced to express CD25 or IL-2R beta. These results suggest that whole blood cultures represent the in vivo situation better than MNC cultures. In addition, the results suggest that, also in vivo, administration of low-dose CD3 mAb alone might not be sufficient to induce IL-2R expression on CD8bright+ cells, and would therefore not induce additional specific T cell activation in rIL-2-based immunotherapy. The presented results suggest that in vivo simultaneous administration of rIFN gamma or rIL-2 with low-dose CD3 mAb might induce better stimulation of CD8+ T cells than CD3 mAb only.