Protein Kinase D3 (PKD3) Requires Hsp90 for Stability and Promotion of Prostate Cancer Cell Migration.

Prostate cancer metastasis is a significant cause of mortality in men. PKD3 facilitates tumor growth and metastasis, however, its regulation is largely unclear. The Hsp90 chaperone stabilizes an array of signaling client proteins, thus is an enabler of the malignant phenotype. Here, using different prostate cancer cell lines, we report that Hsp90 ensures PKD3 conformational stability and function to promote cancer cell migration. We found that pharmacological inhibition of either PKDs or Hsp90 dose-dependently abrogated the migration of DU145 and PC3 metastatic prostate cancer cells. Hsp90 inhibition by ganetespib caused a dose-dependent depletion of PKD2, PKD3, and Akt, which are all involved in metastasis formation. Proximity ligation assay and immunoprecipitation experiments demonstrated a physical interaction between Hsp90 and PKD3. Inhibition of the chaperone-client interaction induced misfolding and proteasomal degradation of PKD3. PKD3 siRNA combined with ganetespib treatment demonstrated a specific involvement of PKD3 in DU145 and PC3 cell migration, which was entirely dependent on Hsp90. Finally, ectopic expression of PKD3 enhanced migration of non-metastatic LNCaP cells in an Hsp90-dependent manner. Altogether, our findings identify PKD3 as an Hsp90 client and uncover a potential mechanism of Hsp90 in prostate cancer metastasis. The molecular interaction revealed here may regulate other biological and pathological functions.

In Vitro Imaging and Quantification of the Drug Targeting Efficiency of Fluorescently Labeled GnRH Analogues.

GnRH analogues are effective targeting moieties and able to deliver anticancer agents selectively into malignant tumor cells which highly express GnRH receptors. However, the quantitative analysis of GnRH analogues' cellular uptake and the investigated cell types in GnRH-based drug delivery systems are currently limited. Previously introduced, selectively labeled fluorescent GnRH I, -II and -III derivatives provide great detectability, and they have suitable chemical properties for reproducible and robust experiments. We also found that the appropriate up-to-date methods with these labeled GnRH analogues could offer novel information about the GnRH-based drug delivery systems. This manuscript introduces some simple and fast experiments regarding the cellular uptake of [D-Lys6(FITC)]-GnRH-I, [D-Lys6(FITC)]-GnRH-II and [Lys8(FITC)]-GnRH-III on the EBC-1 (lung), the BxPC-3 (pancreas) and on the Detroit-562- (pharynx) malignant tumor cells. In parallel with these GnRH-FITC conjugates, the cell surface level of GnRH-I receptors was also examined on these cell lines before and after the GnRH treatment by confocal laser scanning microscopy. The cellular uptake of GnRH-FITC conjugates was quantified by fluorescence-activated cell sorting. In these experiments minor differences among GnRH analogues and major differences among cell types was observed. The significant differences among cell lines are correlated with their distinct level of cell surface GnRH-I receptors. The introduced experiments contain practical methods to visualize, quantify and compare the uptake efficiency of GnRH-FITC conjugates in a time- and concentration-dependent manner on various adherent cell cultures. These results could predict the drug targeting efficiency of GnRH conjugates on the given cell culture, and offer a good basis for further experiments in the examination of GnRH-based drug delivery systems.

Synthesis, characterization and systematic comparison of FITC-labelled GnRH-I, -II and -III analogues on various tumour cells.

Targeted tumour therapy is the focus of recent cancer research. Gonadotropin-releasing hormone (GnRH) analogues are able to deliver anticancer agents selectively into tumour cells, which highly express GnRH receptors. However, the effectiveness of different analogues as targeting moiety in drug delivery systems is rarely compared, and the investigated types of cancer are also limited. Therefore, we prepared selectively labelled, fluorescent derivatives of GnRH-I, -II and -III analogues, which were successfully used for drug targeting. In this manuscript, we investigated these analogues' solubility, stability and passive membrane permeability and compared their cellular uptake by various cancer cells. We found that these labelled GnRH conjugates provide great detectability, without undesired cytotoxicity and passive membrane permeability. The introduced experiments with these conjugates proved their reliable tracking, quantification and comparison. Cellular uptake efficiency was studied on human breast, colon, pancreas and prostate cancer cells (MCF-7, HT-29, BxPC-3, LNCaP) and on dog kidney cells (Madin-Darby canine kidney). Each of the three conjugates was taken up by GnRH-I receptor-expressing cells, but the different cells preferred different analogues. Furthermore, we demonstrated for the first time the high cell surface expression of GnRH-I receptors and the effective cellular uptake of GnRH analogues on human pharynx tumour (Detroit-562) cells. In summary, our presented results detail that the introduced conjugates could be innovative tools for the examination of the GnRH-based drug delivery systems on various cells and offer novel information about these peptides. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Novel compounds reducing IRS-1 serine phosphorylation for treatment of diabetes.

Activation of various interacting stress kinases, particularly the c-Jun N-terminal kinases (JNK), and a concomitant phosphorylation of insulin receptor substrate 1 (IRS-1) at serine 307 play a central role both in insulin resistance and in ß-cell dysfunction. IRS-1 phosphorylation is stimulated by elevated free fatty acid levels through different pathways in obesity. A series of novel pyrido[2,3-d]pyrimidin-7-one derivatives were synthesized as potential antidiabetic agents, preventing IRS-1 phosphorylation at serine 307 in a cellular model of lipotoxicity and type 2 diabetes.

Targeting vascular endothelial growth factor receptor 2 and protein kinase D1 related pathways by a multiple kinase inhibitor in angiogenesis and inflammation related processes in vitro.

Emerging evidence suggests that the vascular endothelial growth factor receptor 2 (VEGFR2) and protein kinase D1 (PKD1) signaling axis plays a critical role in normal and pathological angiogenesis and inflammation related processes. Despite all efforts, the currently available therapeutic interventions are limited. Prior studies have also proved that a multiple target inhibitor can be more efficient compared to a single target one. Therefore, development of novel inflammatory pathway-specific inhibitors would be of great value. To test this possibility, we screened our molecular library using recombinant kinase assays and identified the previously described compound VCC251801 with strong inhibitory effect on both VEGFR2 and PKD1. We further analyzed the effect of VCC251801 in the endothelium-derived EA.hy926 cell line and in different inflammatory cell types. In EA.hy926 cells, VCC251801 potently inhibited the intracellular activation and signaling of VEGFR2 and PKD1 which inhibition eventually resulted in diminished cell proliferation. In this model, our compound was also an efficient inhibitor of in vitro angiogenesis by interfering with endothelial cell migration and tube formation processes. Our results from functional assays in inflammatory cellular models such as neutrophils and mast cells suggested an anti-inflammatory effect of VCC251801. The neutrophil study showed that VCC251801 specifically blocked the immobilized immune-complex and the adhesion dependent TNF-α -fibrinogen stimulated neutrophil activation. Furthermore, similar results were found in mast cell degranulation assay where VCC251801 caused significant reduction of mast cell response. In summary, we described a novel function of a multiple kinase inhibitor which strongly inhibits the VEGFR2-PKD1 signaling and might be a novel inhibitor of pathological inflammatory pathways.

Discovery and Biological Evaluation of Novel Dual EGFR/c-Met Inhibitors.

Activating mutations in the epidermal growth factor receptor (EGFR) have been identified in a subset of non-small cell lung cancer (NSCLC), which is one of the leading cancer types worldwide. Application of EGFR tyrosine kinase inhibitors leads to acquired resistance by secondary EGFR mutations or by amplification of the hepatocyte growth factor receptor (c-Met) gene. Although several EGFR and c-Met inhibitors have been reported, potent dual EGFR/c-Met inhibitors, which can overcome this latter resistance mechanism, have hitherto not been published and have not reached clinical trials. In the present study we have identified dual EGFR/c-Met inhibitors and designed novel N-[4-(quinolin-4-yloxy)-phenyl]-biarylsulfonamide derivatives, which inhibit the c-Met receptor and both the wild-type and the activating mutant EGFR kinases in nanomolar range. We have demonstrated by Western blot analysis that compound 10 inhibits EGFR and c-Met phosphorylation at cellular level and effectively inhibits viability of the NSCLC cell lines.

[Development and biochemical characterization of EGFR/c-Met dual inhibitors]. / EGFR/c-Met kettosgátlók fejlesztése és biokémiai vizsgálata.

The epidermal growth factor receptor (EGFR) family has been well-known for more than ten years as the target of non-small lung carcinoma (NSCLC) which is one of the leading cause of mortality among the cancer types. The receptor tyrosine kinase inhibitors (gefitinib, erlotinib, lapatinib) which have been applied in the therapy, are not able to inhibit the progression of this disease perfectly because of resistance. It has been demonstrated that the amplification of mesenchymal-epithelial transition factor (c-Met) or secondary mutation of EGFR kinase causes the resistance against EGFR inhibitors in 18-20 percent of the cases. Clinical candidates inhibiting both of EGFR and c-Met kinases are unknown in the literature. We have developed quinoline-based inhibitors in our research project, which inhibit both kinases in submicromolar range in enzymatic assays, moreover we have demonstrated by western blot analysis that these compounds inhibit the autophosphorylation in vivo. The binding of the effective compounds was examined by in silico and docking simulations.

Dasatinib inhibits proinflammatory functions of mature human neutrophils.

Dasatinib is a tyrosine kinase inhibitor used to treat imatinib-resistant chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia. At present, little is known about how dasatinib influences nonmalignant cells. In the present study, we tested the effect of dasatinib on functional responses of normal mature human neutrophils. Dasatinib completely blocked integrin- and Fc-receptor-mediated neutrophil functions, with the lowest IC(50) values below 10nM under serum-free conditions. Dasatinib caused a partial inhibition of neutrophil responses triggered by G-protein-coupled receptors and had a moderate effect on neutrophil responses triggered by microbial compounds. Whereas dasatinib inhibited neutrophil chemotaxis under static conditions in 2 dimensions, it did not affect migration under flow conditions or in 3-dimensional environments. Dasatinib did not have any major effect on phagocytosis or killing of bacteria by neutrophils. Adhesion of human neutrophils in the presence of whole serum was significantly inhibited by 50-100nM dasatinib, which corresponds to the reported serum concentrations in dasatinib-treated patients. Finally, ex vivo adhesion of mouse peripheral blood neutrophils was strongly reduced after oral administration of 5 mg/kg of dasatinib. Those results suggest that dasatinib treatment may affect the proinflammatory functions of mature neutrophils and raise the possibility that dasatinib-related compounds may provide clinical benefit in neutrophil-mediated inflammatory diseases.

Optimization of important early ADME(T) parameters of NADPH oxidase-4 inhibitor molecules.

Through their reactive oxygen species (ROS) producing function, NADPH oxidase (NOX) enzymes have been linked to several oxidative stress related diseases. In our recently published paper [1] we have already shown the NOX4 inhibitory effect of diverse, molecule sub-libraries and their biological importance. We also presented our work connected to potential anti-tumour molecules and the relationship between their biological activity and physico-chemical properties [2]. As an extension of these studies further physico-chemical and biological investigation has been carried out on a molecule group included NOX4 inhibitory chromanone compounds. Here we describe the optimization of early ADME(T) parameters determining lipophilicity, phospholipophilicity and permeability linked to structure-activity relationship. We prove that optimal lipo- and phospholipophilicty can be also determined in case of NOX4 inhibitors and a comparison will be made between the chemically similar isochromanone and chromanone molecular libraries. It will be also shown how to predict the effect of different substituents on permeability, lipo- and phospholipophilicity and also the biological differences between anti-tumour molecules and NOX4 inhibitors according to their penetration ability.

PLGA:poloxamer blend micro- and nanoparticles as controlled release systems for synthetic proangiogenic factors.

Tissue engineering is one of the most promising research areas in bioregenerative medicine. However, the restoration of biological functionalities by implanting bioartificially engineered tissues is still highly limited because of their lack of vascular networks. The use of proangiogenic molecules delivered from a controlled release device is a promising strategy to induce tissue vascularization. Indeed, the controlled release system can enhance the therapeutic effect in vivo of many short half-life drugs, while circumventing the need for repeated administrations. In this work, PLGA:poloxamer blend based micro- and nanoparticles have been developed for the sustained delivery of a recently developed synthetic proangiogenic compound: SHA-2-22. Drug-loaded PLGA:poloxamer blend microparticles were prepared by an oil-in-oil solvent extraction/evaporation technique. Drug-loaded PLGA:poloxamer nanoparticles were prepared by a modified solvent diffusion technique. These drug carriers were characterized with regard to their physicochemical properties, morphology, drug encapsulation efficiency and release kinetics in vitro. The results show that by adjusting the formulation conditions, it is possible to obtain PLGA:poloxamer micro- and nanoparticles with very high drug loadings, and with the capacity to release the active compound in a controlled way for up to one month. In vitro cell assays performed in an endothelial cell model confirmed the bioactivity of SHA-22-2 encapsulated in PLGA:poloxamer microparticles.

Small-molecule inhibitors of NADPH oxidase 4.

NOX enzymes are the major contributors in many oxidative damage related diseases. Unfortunately, at present no specific NOX inhibitor is available. Here, we describe the discovery and development of novel NOX4 inhibitors. Compound libraries were tested in a cell-based assay as a primary screen, monitoring H2O2 production. Twenty-four compounds inhibited Nox4 activity with low-micromolar IC(50) values of which three were selected for further drug development.

Nanoparticles based on PLGA:poloxamer blends for the delivery of proangiogenic growth factors.

New blood vessel formation is a critical requirement for treating many vascular and ischemia related diseases, as well as for many tissue engineering applications. Angiogenesis and vasculogenesis, in fact, represent crucial processes for the functional regeneration of complex tissues through tissue engineering strategies. Several growth factors (GFs) and signaling molecules involved in blood vessels formation have been identified, but their application to the clinical setting is still strongly limited by their extremely short half-life in the body. To overcome these limitations, we have developed a new injectable controlled release device based on polymeric nanoparticles for the delivery of two natural proangiogenic GFs: platelet derived growth factor (PDGF-BB) and fibroblast growth factor (FGF-2). The nanoparticle system was prepared by a modified solvent diffusion technique, encapsulating the GF both in presence and in the absence of two stabilizing agents: bovine serum albumin (BSA) and heparin sodium salt (Hp). The developed nanocarriers were characterized for morphology, size, encapsulation efficiency, release kinetics in vitro and GF activity in cell cultures. The results have indicated that the coencapsulation of stabilizing agents can preserve the GF active structure and, in addition, increase their encapsulation efficiency into nanoparticles. Through this optimization process, we were able to raise the encapsulation efficiency of FGF-2 to 63%, and that of PDGF-BB to 87%. These PLGA:poloxamer blend nanoparticles loaded with GFs were able to release PDGF-BB and FGF-2 in a sustained fashion for more than a month. This work also confirms other positive features of PLGA:poloxamer nanoparticles. Namely, they are able to maintain their stability in simulated biological medium, and they are also nontoxic to cell culture models. Incubation of nanoparticles loaded with FGF-2 or PDGF-BB with endothelial cell culture models has confirmed that GFs are released in a bioactive form. Altogether, these results underline the interest of PLGA:poloxamer nanoparticles for the controlled delivery of GFs and substantiate their potential for the treatment of ischemic diseases and for tissue engineering applications.

Detection of hydrogen peroxide by lactoperoxidase-mediated dityrosine formation.

The aim of this work was to study the dityrosine-forming activity of lactoperoxidase (LPO) and its potential application for measuring hydrogen peroxide (H2O2). It was observed that LPO was able to form dityrosine at low H2O2 concentrations. Since dityrosine concentration could be measured in a simple fluorimetric reaction, this activity of the enzyme was utilized for the measurement of H2O2 production in different systems. These experiments successfully measured the activity of NADPH oxidase 4 (Nox4) by this method. It was concluded that LPO-mediated dityrosine formation offers a simple way for H2O2 measurement.

New cyclic somatostatin analogues containing a pyrazinone ring: importance of Tyr for antiproliferative activity.

Novel somatostatin analogues containing a pyrazinone ring, compounds 1 and 2, exhibited good antiproliferative activity on A431 tumor cells. To increase antitumor activity and binding affinity on somatostatin receptors (SSTRs), we substituted Tyr in the critical sequence, Tyr-D-Trp-Lys, with more hydrophobic aromatic residue. The substituted compounds dramatically lost antitumor activity, indicating that Tyr residue was an essential residue.

Synthesis of somatostatin analogues containing C-terminal adamantane and their antiproliferative properties.

On the basis of the structure of somatostatin analogue TT-232 (1), which exhibited a highly potent antitumor activity, we synthesized small linear peptide derivatives and evaluated their antitumor and apoptotic activity. Of them, Boc-Tyr-D-Trp-1-adamantylamide (5) had the most potent cell antiproliferative activity in SW480 and A431 cell lines, which was supported in A431 cell lines by FACS analysis that demonstrated a major increase in DNA fragmentation in the subG1 fraction.

Doxorubicin-induced activation of protein kinase D1 through caspase-mediated proteolytic cleavage: identification of two cleavage sites by microsequencing.

Recent studies have demonstrated the importance of protein kinase D (PKD) in cell proliferation and apoptosis. Here, we report that in vitro cleavage of recombinant PKD1 by caspase-3 generates two alternative active PKD fragments. N-terminal sequencing of these fragments revealed two distinct caspase-3 cleavage sites located between the acidic and pleckstrin homology (PH) domains of PKD1. Moreover, we present experimental evidence that PKD1 is an in vitro substrate for both initiator and effector caspases. During doxorubicin-induced apoptosis, a zVAD-sensitive caspase induces cleavage of PKD1 at two sites, generating fragments with the same molecular masses as those determined in vitro. The in vivo caspase-dependent generation of the PKD1 fragments correlates with PKD1 kinase activation. Our results indicate that doxorubicin-mediated apoptosis induces activation of PKD1 through a novel mechanism involving the caspase-mediated proteolysis.

Protein kinase D: a family affair.

The protein kinase D family of enzymes consists of three isoforms: PKD1/PKCmu PKD2 and PKD3/PKCnu. They all share a similar architecture with regulatory sub-domains that play specific roles in the activation, translocation and function of the enzymes. The PKD enzymes have recently been implicated in very diverse cellular functions, including Golgi organization and plasma membrane directed transport, metastasis, immune responses, apoptosis and cell proliferation.

Protein kinase D: an intracellular traffic regulator on the move.

Recent research has identified protein kinase D (PKD, also called PKCmu) as a serine/threonine kinase with potentially important roles in growth factor signaling as well as in stress-induced signaling. Moreover, PKD has emerged as an important regulator of plasma membrane enzymes and receptors, in some cases mediating cross-talk between different signaling systems. The recent discovery of two additional kinases belonging to the PKD family and the plethora of proteins that interact with PKD point to a multifaceted regulation and a multifunctional role for these enzymes, with functions in processes as diverse as cell proliferation, apoptosis, immune cell regulation, tumor cell invasion and regulation of Golgi vesicle fission.

Getting to know protein kinase D.

The protein kinase D (PKD) enzymes represent a new family of second messenger stimulated kinases, with diacylglycerol as a prime, but not the sole, mediator of activation. Their molecular architecture features a catalytic domain, unrelated to that of all PKC family members, and a large inhibitory, regulatory domain, comprised of two Zinc fingers, and a pleckstrin homology domain. These different sub-domains play distinctive roles in the activation, translocation and biological functions of the kinase. The enzymes have been implicated in signalling mechanisms controlling cell proliferation and programmed cell death and in metastasis, immune responses, and Golgi restructuring and function. A variety of proteins specifically interact with the different sub-domains of the enzymes and direct their wide range of cellular functions.