Impact of PKCε downregulation on autophagy in glioblastoma cells.

Background: Several efforts have been focused on identification of pathways involved in malignancy, progression, and response to treatment in Glioblastoma (GB). Overexpression of PKCε was detected in histological samples from GB, anaplastic astrocytoma, and gliosarcoma and is considered an important marker of negative disease outcome. In multiple studies on GB, autophagy has been shown as a survival mechanism during cellular stress, contributing to resistance against anti-cancer agents.

Zapotin (5,6,2',6'-tetramethoxyflavone) Modulates the Crosstalk Between Autophagy and Apoptosis Pathways in Cancer Cells with Overexpressed Constitutively Active PKCϵ.

Autophagy is important in the regulation of survival and death signaling pathways in cancer. PKCϵ revealed high transforming potential and the ability to increase cell migration, invasion, and metastasis. Zapotin (5,6,2',6'-tetramethoxyflavone), a natural flavonoid, showed chemopreventive and anticancer properties.

Synthesis, cytotoxic, and antitumor activities of 2-pyridylhydrazones derived from 3-benzoylpyridazines.

A series of 2-pyridylhydrazones derived from phenyl-pyridazin-3-yl-methanones were prepared in search for potential novel antitumor agents. The stereochemistry of these compounds was established by means of NMR spectroscopy. Whereas hydrazones derived from 3-benzoylpyridazines (IC50  = 0.

Thienoquinolines as novel disruptors of the PKCε/RACK2 protein-protein interaction.

Ten protein kinase C (PKC) isozymes play divergent roles in signal transduction. Because of sequence similarities, it is particularly difficult to generate isozyme-selective small molecule inhibitors. In order to identify such a selective binder, we derived a pharmacophore model from the peptide EAVSLKPT, a fragment of PKCε that inhibits the interaction of PKCε and receptor for activated C-kinase 2 (RACK2).

Telomerase downregulation induces proapoptotic genes expression and initializes breast cancer cells apoptosis followed by DNA fragmentation in a cell type dependent manner.

The aim of the study was to analyze the consequence of silencing genes coding for the key subunits of the telomerase complex, i.e. TERT, TERC and TP1 in human breast cancer MCF7 and MDA-MB-231cells.

The tetramethoxyflavone zapotin selectively activates protein kinase C epsilon, leading to its down-modulation accompanied by Bcl-2, c-Jun and c-Fos decrease.

Zapotin, a tetramethoxyflavone, is a natural compound with a wide spectrum of activities in neoplastic cells. Protein kinase C epsilon (PKCε) has been shown to be oncogenic, with the ability to increase cell migration, invasion and survival of tumor cells. Here we report that zapotin inhibits cell proliferation.

Oleanolic acid derivative methyl 3,11-dioxoolean-12-en-28-olate targets multidrug resistance related to ABCB1.

Multidrug resistance (MDR) in leukemia patients is a great incentive to the development of new drugs. In a search for potential multidrug resistance modulators we tested a group of oleanolic acid (OA) analogues modified at C-3, C-11, C-12 and C-28 using an experimental model consisting of three human acute lymphoblastic leukemia cell lines (CCRF-CEM and the multidrug resistant sublines CCRF-VCR1000 and CCRF-ADR5000). The most effective compound, methyl 3,11-dioxoolean-12-en-28-olate (DIOXOL) was more potent in cell viability inhibition than its precursor - OA, and showed similar or even higher activity in the drug resistant than in the wild-type cells.

Modulators of protein-protein interactions: novel approaches in targeting protein kinases and other pharmaceutically relevant biomolecules.

In recent years the development of small organic molecules modulating protein-protein interactions (P-PIs) has drawn major attention in both academic and industrial research. Despite the appreciable progress being made, targeting such extensive interaction areas with comparatively small, drug-like agents has proven to be an ambitious objective. This review highlights the reasons rendering this task highly challenging and provides an overview on the latest developments in rational design approaches for P-PI modulators.

Barbituric acid derivative BAS 02104951 inhibits PKCε, PKCη, PKCε/RACK2 interaction, Elk-1 phosphorylation in HeLa and PKCε and η translocation in PC3 cells following TPA-induction.

Protein kinase C (PKC) is a family of at least 10 isozymes involved in the activation of different signal transduction pathways. The exact function of these isozymes is not known at present. Isozyme-selective inhibitors would be important to explain the function of the different PKCs and are anticipated to have pharmaceutical potential.

Protein kinase Cgamma in colon cancer cells: expression, Thr514 phosphorylation and sensitivity to butyrate-mediated upregulation as related to the degree of differentiation.

Protein kinase C (PKC) isoenzymes are expressed and activated in a cell type-specific manner, and play an essential role in tissue-specific signal transduction. The presence of butyrate at millimolar concentrations in the colon raises the question of whether it affects the expression of PKC isoenzymes in the different cell types of the colonic epithelium. We investigated the protein expression levels of PKCgamma, Thr(514)-phosphorylated PKCgamma (pPKCgamma-Thr(514)), and their subcellular distribution as affected by butyrate in a set of colon cancer cell lines.

Dehydroepiandrosterone sulfate directly activates protein kinase C-beta to increase human neutrophil superoxide generation.

Dehydroepiandrosterone sulfate (DHEAS) is the most abundant steroid in the human circulation and is secreted by the adrenals in an age-dependent fashion, with maximum levels during the third decade and very low levels in old age. DHEAS is considered an inactive metabolite, whereas cleavage of the sulfate group generates dehydroepiandrosterone (DHEA), a crucial sex steroid precursor. However, here we show that DHEAS, but not DHEA, increases superoxide generation in primed human neutrophils in a dose-dependent fashion, thereby impacting on a key bactericidal mechanism.

Signal transduction of constitutively active protein kinase C epsilon.

The protein kinase C (PKC) family is the most prominent target of tumor-promoting phorbol esters. For the PKCepsilon isozyme, different intracellular localizations and oncogenic potential in several but not all experimental systems have been reported. To obtain information about PKCepsilon-signaling, we investigated the effects of constitutively active rat PKCepsilon (PKCepsilonA/E, alanine 159 is replaced by glutamic acid) in HeLa cells in a doxycycline-inducible vector.

Human platelets attenuate Aspergillus species via granule-dependent mechanisms.

Using laser scanning microscopy, we investigated whether platelets are capable of internalizing Aspergillus conidia and examined Aspergillus-platelet adherence. The influence of platelets on fungal growth was evaluated by assessing galactomannan (GM) release, hyphal elongation, and colony size. A secretion assay with [(3)H]-serotonin (5-hydroxytryptamine [5-HT]) was performed.

N-benzoxazol-2-yl-N'-1-(isoquinolin-3-yl-ethylidene)-hydrazine, a novel compound with antitumor activity, induces radicals and dissipation of mitochondrial membrane potential.

The novel compound N-benzoxazol-2-yl-N'-1-(isoquinolin-3-yl-ethylidene)-hydrazine (EPH136) has been shown to exhibit antitumor activity in vitro and in vivo. A COMPARE analysis showed that the patterns of cellular effects of EPH136 are not related to any of 175 standard antitumor agents with a known mechanism of action. In order to help identify the mechanism of action we employed a bioinformatics approach called partial least squares modelling in latent variables in which the expression levels of approximately 8,000 genes in each of 56 untreated NCI panel cell lines were correlated with the respective IC(50) values of each cell line following treatment with EPH136.

Synthesis, structure-activity relationships, and antitumor studies of 2-benzoxazolyl hydrazones derived from alpha-(N)-acyl heteroaromatics.

Recently we have described the antitumor activities of 2-benzoxazolylhydrazones derived from 2-formyl and 2-acetylpyridines. In search of a more efficacious analogue, compounds in which the 2-acetylpyridine moiety has been replaced by 2-acylpyridine and alpha-(N)-acetyldiazine/quinoline groups have been synthesized. The 2-acylpyridyl hydrazones inhibited in vitro cell proliferation in the nM range, whereas the hydrazones derived from the alpha-(N)-acetyldiazines/quinolines inhibited cell growth in the muM range.

Novel boronated derivatives of 5,10,15,20-tetraphenylporphyrin: synthesis and toxicity for drug-resistant tumor cells.

We have developed the synthesis of boronated porphyrins for potential application in cancer treatment, based on the functional derivatives of 5,10,15,20-tetraphenylporphyrin. Boronated amide derivatives starting from 5,10,15,20-tetra(p-aminophenyl)porphyrin and 9-o- and 9-m-carborane carboxylic acid chlorides were prepared. Also, the reaction of 2-formyl-5,10,15,20-tetraphenylporphyrin with closo-C-lithium-o- and m-carboranes, as well as with closo-C-lithium monocarbon carborane, yielded neutral and anionic boronated hydroxy derivatives of 5,10,15,20-tetraphenylporphyrin, respectively.

A cold-active extracellular metalloprotease from Pedobacter cryoconitis--production and properties.

An extracellular protease from Pedobacter cryoconitis, isolated from alpine cryoconite on glacier ice, was purified and characterized. Despite high cell densities at a temperature range of 1-25 degrees C, the optimum temperature for protease production was 15 degrees C. Maximum enzyme production was achieved when the strain was grown in a pH-neutral medium containing soybean meal, wheat flour and citrate over 72 h.

Protein kinase C isozymes as potential targets for anticancer therapy.

Protein kinase C (PKC) comprises a family of isozymes (alpha, betaI, betaII, gamma, delta, epsilon, theta, eta, lambda/iota [mouse/human], and zeta) which are involved in signal transduction from membrane receptors to the nucleus. Activation of PKC by phorbol esters promotes tumor formation, and from that it was concluded that inhibitors of PKC might prevent carcinogenesis or inhibit tumor proliferation. However, the situation is more complicated because the exact function of the different PKC isozymes is not known at present.