Sodium-dependent phosphate transporter NaPi2b as a potential predictive marker for targeted therapy of ovarian cancer.

The high mortality rate from ovarian cancer is due to the asymptomatic nature of the course of the disease, which leads to the diagnosis of ovarian cancer in later stages. The sodium-dependent phosphate transporter NaPi2b encoded by SLC34A2 gene is expressed in 80-90% of epithelial ovarian cancers and used as a target for therapeutic antibodies XMT-1536, and XMT-1592, which are derived from MX35 antibodies and used in clinical trials for the treatment of ovarian and lung cancers. In this work, we aimed to evaluate NaPi2b as a molecular marker for diagnostics and predicting the course and outcome of ovarian cancer disease. Quantitative analysis of SLC34A2 gene expression in ovarian tumor tissue was performed at the level of transcription and translation using real-time PCR, droplet digital PCR and Western blot analysis respectively. Statistical analysis was performed taking into account various clinicopathological characteristics of the ovarian cancer patients, including the stage of the disease, the tumor grade, the applying of neoadjuvant chemotherapy and the presence of ascites. In this work, we demonstrated that the expression of the human NaPi2b (hNaPi2b) transporter is downregulated in the tumors of patients receiving neoadjuvant therapy and during the development of disease. The data suggest that the level of expression of the SLC34A2 gene can serve as a potential marker for the monitoring and predicting responses to neoadjuvant and targeted therapy in patients with ovarian cancer.

Application of serex-analysis for identification of human colon cancer antigens.

BACKGROUND: Colorectal, lung and breast tumors are the most devastating and frequent malignances in clinical oncology. SEREX-analysis of colon cancer leads to identification of more than hundred antigens which are potential tumor markers. With idea that immunoscreening with pool of allogeneic sera is more productive for antigen isolation, SEREX-analysis was applied to four cases of stages II-IV primary colon tumor and 22 new antigens were isolated. OBJECTIVE: To characterize 22 primary colon cancer antigens isolated by SEREX-technique. MATERIALS AND METHODS: Allogenic screening, real-time PCR analysis. RESULTS: After allogeneic immunoscreening, for 5 of 22 (22%) isolated antigens were confirmed colon cancer restricted serological profile solely positive for 14% of tested colon cancer sera. Through these five antigens, KY-CC-17/ß-actin has cytoskeleton function; KY-CC-14/ACTR1A and KY-CC-19/TSGA2 participate in chromosome segregation; KY-CC-12/FKBP4 regulates steroid receptor function and KY-CC-15/PLRG1 is a component of spliceosome complex. For the last four antigens tested were found aberrant mRNA expression in some cases of colon tumor. CONCLUSION: The exploration of identified antigens may define suitable targets for immunotherapy or diagnostic of colon cancer.

Biologic activities of recombinant human-beta-defensin-4 toward cultured human cancer cells.

AIM: The aim of the study was in vitro analysis of biological activity of recombinant human beta-defensin-4 (rec-hBD-4). METHODS: hBD-4 cDNA was cloned into pGEX-2T vector, and recombinant plasmid was transformed into E. coli BL21(DE3) cells. To purify soluble fusion GST-hBD-4 protein, affinity chromatography was applied. Rec-hBD-4 was cleaved from the fusion protein with thrombin, and purified by reverse phase chromatography on Sep-Pack C18. Effects of rec-hBD-4 on proliferation, viability, cell cycle distribution, substrate-independent growth, and mobility of cultured human cancer cells of A431, A549, and TPC-1 lines were analyzed by direct cell counting technique, MTT assay, flow cytofluorometry, colony forming assay in semi-soft medium, and wound healing assay. RESULTS: Rec-hBD-4 was expressed in bacterial cells as GST-hBD-4 fusion protein, and purified by routine 3-step procedure (affine chromatography on glutathione-agarose, cleavage of fusion protein by thrombin, and reverse phase chromatography). Analysis of in vitro activity of rec-hBD-4 toward three human cancer cell lines has demonstrated that the defensin is capable to affect cell behaviour in concentration-dependent manner. In 1-100 nM concentrations rec-hBD-4 significantly stimulates cancer cell proliferation and viability, and promotes cell cycle progression through G2/M checkpoint, greatly enhances colony-forming activity and mobility of the cells. Treatment of the cells with 500 nM of rec-hBD-4 resulted in opposite effects: significant suppression of cell proliferation and viability, blockage of cell cycle in G1/S checkpoint, significant inhibition of cell migration and colony forming activity. CONCLUSION: Recombinant human beta-defensin-4 is biologically active peptide capable to cause oppositely directed effects toward biologic features of cancer cells in vitro dependent on its concentration.

FGF-2 protects small cell lung cancer cells from apoptosis through a complex involving PKCepsilon, B-Raf and S6K2.

Patients with small cell lung cancer (SCLC) die because of chemoresistance. Fibroblast growth factor-2 (FGF-2) increases the expression of antiapoptotic proteins, XIAP and Bcl-X(L), and triggers chemoresistance in SCLC cells. Here we show that these effects are mediated through the formation of a specific multiprotein complex comprising B-Raf, PKCepsilon and S6K2. S6K1, Raf-1 and other PKC isoforms do not form similar complexes. RNAi-mediated downregulation of B-Raf, PKCepsilon or S6K2 abolishes FGF-2-mediated survival. In contrast, overexpression of PKCepsilon increases XIAP and Bcl-X(L) levels and chemoresistance in SCLC cells. In a tetracycline-inducible system, increased S6K2 kinase activity triggers upregulation of XIAP, Bcl-X(L) and prosurvival effects. However, increased S6K1 kinase activity has no such effect. Thus, S6K2 but not S6K1 mediates prosurvival/chemoresistance signalling.

Identification of novel binding partners for tuberous sclerosis complex 2 (TSC2) by yeast two-hybrid approach.

AIM: To identify novel tuberous sclerosis complex (TSC2) binding partners by yeast two-hybrid screening. METHODS: The yeast two-hybrid system DupLEX-A developed by OriGene Technologies and Mouse embryo and HeLa cells cDNA libraries were used in this study. The "bait" constructs, containing full-length and truncated form of TSC2 were prepared. The expression of all constructs in yeast was confirmed by immunoblotting with specific anti-LexA antibodies. The suitability of generated constructs for screening was tested in autoactivation and nuclear translocation assays. Screening of mouse embryo and HeLa cDNA libraries with selected baits was carried out according to manufacturer's recommendations. Positive clones were selected using double selection procedure and further confirmed in mating assay. Isolated cDNA clones were identified by automated DNA sequencing and database searching. RESULTS: Extensive screening of two cDNA libraries from mouse embryo and HeLa cells with TSC2 baits led to the isolation of 102 positives clones. The specificity of interaction between TSC2 and binding proteins of selected clones was confirmed by mating assay for 83 clones. Sequencing of these clones indicated that they encode already known and novel TSC2-binding partners. CONCLUSION: The isolation of several known TSC2-binding partners, such as several isoforms of 14-3-3, demonstrates the validity of generated bait constructs and screening conditions. In addition, we have found a number of novel interactors, which encode cytoskeletal proteins and signaling molecules, such as Ser/Thr phosphatases.

Molecular chaperone, HSP60, and cytochrome P450 2E1 co-expression in dilated cardiomyopathy.

Physiological stresses (heat, hemodynamics, genetic mutations, oxidative injury and myocardial ischemia) produce pathological states in which protein damage and misfolded protein structures are a common denominator. The specialized proteins family of antistress proteins - molecular chaperons (HSPs) - are responsible for correct protein folding, dissociating protein aggregates and transport of newly synthesized polypeptides to the target organelles for final packaging, degradation or repair. They are inducible at different cell processes such as cell division, apoptosis, signal transduction, cell differentiation and hormonal stimulation. HSPs are involved in numerous diseases including cardiovascular pathologies, revealing changes of expression and cell localization. We studied the possible changes in expression level of abundant mitochondrial chaperon Hsp60 and main human cytochrome P450 monooxygenase (2E1 isoform) at dilated cardiomyopathy (DCM) progression at the end stage of heart failure using Western blot analysis. The ischemic and normal humans' hearts were studied as control samples. We observed the decrease of Hsp60 level in cytoplasmic fraction of DCM- and ischemia-affected hearts' left ventricular and significant increase of Hsp60 in mitochondrial fractions of all hearts investigated. At the same time we detected the increase of P450 2E1 expression level in ischemic and dilated hearts' cytoplasmic fractions in comparison with normal myocardium and no detectable changes in microsomal fractions of hearts investigated which could be linked with increased level of oxidative injury for DCM heart muscle. In addition, all the changes described are accompanied by significant decrease of ATPase activity of myosin purified from DCM-affected heart in comparison with normal and ischemic myocardia as well. The data obtained allow us to propose a working hypothesis of functional link between antistress (HSPs) and antioxidative (cytochromes) systems at DCM progression.

[Features of fibronectin-dependent activation of ribosomal protein S6 kinase (S6K1 and S6K2)]. / Osoblyvosti fibronektynzalezhnoï aktivatsiï kinaz rybosomnoho bilka S6 (S6K1 i S6K2).

Integrin family of adhesion receptors play an important role in organizing the actin cytoskeleton and in signal transduction from the extracellular matrix. The previous studies have shown that exposure of fibroblast cells to extracellular matrix proteins activates ribosomal S6 kinase 1 (S6K1) pathway in a ligand dependent manner. Recently, a new, highly homologous ribosomal S6 kinase, termed S6K2, was identified. It has 70% amino acid identity in the overall sequence with S6K1, and the potential phosphorylation sites of S6K1 are conserved in S6K2. However, the N- and C-terminal domains of S6K2 are quite different from those of S6K1. In this study we have examined dynamics of fibronectin-induced activation of these two kinases, transiently expressed in human HEK 293 cells. Differences between profiles of activation of S6K1 and S6K2 were observed in the early period of fibronectin stimulation. Fibronectin-induced changes in S6K2 activity were closely correlated with phosphorylation at Ser423, which is homologues to Ser 434 of S6K1. Although we didn't observe considerable changes in phosphorylation of S6K1 at Ser434, suggesting potential differences in the regulation of these homologous kinases upon fibronectin stimulation.

Compartmentalization of certain components of the protein synthesis apparatus in mammalian cells.

A comparative study on the localization of free cytosolic tryptophanyl-tRNA synthetase (TrpRS) and several components of the multi-aminoacyl-tRNA synthetase (ARS) complex (glutamyl-prolyl-tRNA synthetase (GluProRS), arginyl-tRNA synthetase (ArgRS)), and two non-synthetase polypeptides p38 and p43 has been carried out on ultrathin sections of cultured rabbit kidney cells by the immunogold technique using monoclonal antibodies raised against appropriate polypeptides. It has been shown that GluProRS, ArgRS and p38 polypeptide are distributed in the cells similarly to TrpRS and are located mainly in the vicinity of ribosomes. A smaller but significant portion of these proteins has been observed in the nuclei in the diffuse chromatin regions and in the vicinity of interchromatin granules. On the contrary, the main part of p43 protein was found in the cell nuclei; this indicates that this protein may exist in the cell separately from the cytoplasmic multi-ARS complex. Our results argue in favor of compartmentalization of both free ARS (such as TrpRS) and the multi-ARS complex in the vicinity of ribosomes. At the same time, the detection of some ARS in the diffuse chromatin regions in the nucleus implies that these enzymes may exhibit some non-canonical functions in addition to their role in protein synthesis.

Evidence for similar structural organization of the multienzyme aminoacyl-tRNA synthetase complex in vivo and in vitro.

Although aminoacyl-tRNA synthetases from higher eukaryotic cells are routinely isolated as components of a multienzyme complex, it has remained unclear how closely the isolated complex reflects a structure that exists within the cell. To answer this question, we have used chemical cross-linking and immunological detection to identify the nearest neighbor(s) of arginyl-tRNA synthetase both in the isolated, purified complex and in saponin-permeabilized cells, which retain much of the structural organization of intact cells. Our results show that arginyl-tRNA synthetase is cross-linked primarily both in vitro and in vivo to a single protein, an as yet uncharacterized 38-kDa polypeptide known to be present in synthetase complexes from many sources. These data demonstrate that the isolated, multienzyme amino-acyl-tRNA synthetase complex reflects a defined structure that also pre-exists in the cell and that the 38-kDa polypeptide is an integral component of this complex.

Immunoelectron microscopic location of tryptophanyl-tRNA synthetase in mammalian, prokaryotic and archaebacterial cells.

Monoclonal antibody Am1 against conservative epitope of tryptophanyl-tRNA synthetase (WRS) was labeled with colloidal gold particles and used to localize the enzyme on ultrathin sections of eubacteria (Escherichia coli), archaebacteria (Methanococcus halophilus), rat pancreas tissue and rat fibroblasts (cell line RAT1). In all cell types immunoelectron microscopy revealed predominant cytoplasmic location of gold particles, as this could be expected from known biochemical data. In particular, in mammalian cells intensive labeling was observed in cytoplasmic regions rich in polysomes and free ribosomes. At the same time, the label was virtually absent in cytoplasmic regions where microfilament bundles were present. Significant concentrations of gold particles were found in mitochondria and nuclei. In the latter case, gold particles were located over diffuse chromatin regions and were virtually absent over compact chromatin. The density of diffuse chromatin in labeling may amount to about 50% of that found in the cytoplasm. Distribution of labeled antibodies over E. coli cells looks rather similar to that found for M. halophilus: gold particles are preferably concentrated over the cytoplasm and "boundary zone", i.e., a 30 nm wide cytoplasmic zone adjacent to the nucleoid border, while the label over nucleoid is virtually absent. Two main conclusions are drawn: (i) although in the animal cell homogenates WRS is recovered mainly as a soluble cytosolic enzyme, in intact cells it is associated with defined cellular organelles and compartments; this may be an evolutionarily acquired feature probably typical for multicellular organisms; (ii) the considerable density of labeling in diffuse (not compact) chromatin regions may be indicative of WRS involvement in the active chromatin functions (transcription, processing, transfer of gene products, etc.).

[Comparative study of localization of tryptophanyl-tRNA-synthetase and components of high molecular weight aminoacyl-tRNA-synthetase complex in animal cells]. / Sravnitel'noe izuchenie lokalizatsii triptofanil-tRNK-sintetazy i komponentov vysokomolekuliarnogo aminoatsil-tRNK-sintetaznogo kpmpleksa v kletkakh zhivotnykh.

A comparative study on the localization of cytosolic Trp-tRNA synthetase (TrpRS), aminoacyl-tRNA synthetases associated in a multienzyme complex (Glu-tRNA synthetase (GluRS), and Arg-tRNA synthetase (ArgRS)) and polypeptides p37 and p43 from the multienzyme complex was carried out on ultrathin sections of cultured rabbit cells RK-1 by means of immunogold technique. It is shown that GluRS, ArgRS, and polypeptide p43 have approximately the same distribution in the cell as TrpRS. The data obtained evidences in favour of a multienzyme structure of most (or, may be all) aminoacyl-tRNA synthetases in intact cells. A statistical analysis of enzyme distribution in different cell organelles showed nonrandom, compartmentalized distribution of studied synthetases in the mammalian cell. Aminoacyl-tRNA synthetases were found in the cell nucleus in the vicinity of interchromatin granules and in the regions of diffused chromatin. This fact points to a role which these proteins may play in active chromatin functions (transcription, processing, transfer of gene products, etc.) and needs special attention. Detection of ArgRS and GluRS in the nucleus allows one to suggest that either multienzyme synthetase complexes are present not only in the cytoplasm, but also in the nucleus, or these enzymes can dissociate from the complex and pass to the nucleus as individual proteins.

[Immunoelectron-microscopic determination of the localization of tryptophanyl-tRNA synthetase in eubacterial cells of Escherichia coli and Methanococcus halophilus archaebacteria]. / Immunoélektronno-mikroskopicheskoe opredelenie lokalizatsii triptofanil-tRNK-sintetazy v kletkakh éubakterii Escherichia coli i arkhebakterii Methanococcus halophilus.

Localization of tryptophanyl-tRNA-synthetase (TRS) was studied in halophilic archaebacterium Methanococcus halophilus and eubacterium E. coli. Ultrathin sections of the cells, fixed with glutaraldehyde and embedded in "Lowicryl K4M" at -35 degrees C, were treated with colloidal gold complexes containing monoclonal antibodies Aml against TRS. The latter bind specifically to TRS isolated both from eucaryotes, archae- and eubacteria. According to the label distribution three zones in M. halophilus and E. coli can be distinguished: (i) about 75% of the whole amount of gold particles are localized in the cytoplasm, the distribution of label being more or less homogeneous; (ii) cytoplasmic regions, adjacent to nucleoid, are intensively labelled (about 20% of the whole amount of label); (iii) very few gold particles (not more than 10% of the whole amount) are present in the nucleoid. The data obtained show, that the distribution of TRS in the nucleoid and cytoplasm of archaebacterium M. halophilus is close to the distribution of TRS, found in E. coli. It supports our previous conclusion that the structural organization of transcription-translation apparatus in methanogen and halophilic archaebacteria is similar to that in eubacteria.

[Immunochemical study of tryptophanyl-tRNA-synthetase]. / Immunokhimicheskoe izuchenie triptofanil-tRNK-sintetaz.

The immunochemical approach used extensively in medicine and in some fields of biology has not yet been systematically applied to enzymology, in particular, to the study of a large, functionally significant group of enzymes, such as aminoacyl-tRNA synthetases (EC 6.1.1). The present investigation was aimed at the analysis of applicability of polyclonal and monoclonal antibodies against bovine tryptophanyl-tRNA synthetase in the study of functional properties of this enzyme as well as of its distribution inside the cell and among organs and tissues of various animals. The general conclusions one may draw from these data are as follows. i) Tryptophanyl-tRNA synthetase of eukaryotes, eubacteria and archaebacteria share one common structural element (antigenic determinant) that is not essential for the catalytic activity. The evolutionary conservative nature of this element suggests that the enzyme may implement functions other than catalysis of tryptophanyl-tRNA formation. ii) Tryptophanyl-tRNA synthetase shows an anomalous distribution among mammalian organs: its content is far greater in the exocrine part of the ruminant animal pancreas in comparison with their other organs (liver) or with other mammalian orders. This finding suggests that the enzyme or its fragments may play a role in the digestive function of ruminant animals. iii) Tryptophanyl-tRNA synthetase was found in considerable quantities in diffuse chromatin of mammalian cell nuclei. This fact indicates that the enzyme may participate in such processes in the nucleus as transcription, processing, transport, etc. It may thus be concluded that tryptophanyl-tRNA synthetase of higher organisms, besides catalyzing the formation of aminoacyl-tRNAs can exert some other, yet unknown, noncanonical functions.

Monoclonal antibodies to the components of the high-molecular-mass aminoacyl-tRNA synthetase complex.

Six monoclonal antibodies to the components of the rabbit multienzyme aminoacyl-tRNA synthetase complex were generated and characterised. Two, F7 and F31 were directed against arginyl-tRNA synthetase, two, F8 and F25 against glutamyl-tRNA synthetase, and two, F6 and F12 recognised 38 and 43 kDa polypeptides, respectively. All antibodies were species-specific and failed to affect the activity of the respective enzymes.

[Express method of isolation of mammalian phenylalanine-tRNA-synthetase and preparation of monoclonal antibodies against this enzyme]. / Bystryi metod vydeleniia fenilalanil-tRNK-sintetazy iz mlekopitaiushchikh i poluchenie monoklonal'nykh antitel k étomu fermentu.

A rapid and efficient procedure for isolating homogeneous beef liver phenylalanyl-tRNA synthetase (EC.6.1.1) was developed that enables to purify the enzyme 5000 fold and to achieve the activity of 8 e.a.u. per mg of protein. The molecular mass of the native enzyme was estimated to be 260 kDa, for alpha subunit - 59 kDa, and for beta - 72 kDa. Two cellular clones were derived by means of hybridization of immunised splenocytes with myeloma cells. They secrete monoclonal antibodies, designated P6 and P1 2, that bind to human placental and bovine liver phenylalanyl-tRNA synthetases but not to the same enzymes from E. coli and T. thermophilus. P6 and P1 2 antibodies do not affect the aminoacylation capacity of human or bovine phenylalanyl-tRNA synthetases. By immunoblotting, it was shown that P6 antibodies recognize the alpha subunit of the enzyme.

[Mechanisms of verapamil prevention of disorders of cardiac contractile function during ischemia and reperfusion]. / Mekhanizmy preduprezhdeniia verapamilom narushenii sokratitel'noi funktsii serdtsa pri ishemii i reperfuzii.

A dog heart isolated according to Langendorf was used to study the effect of verapamil, used as a preventive measure, on the contractile function of the heart, its work and oxygen consumption, and the coronary blood flow in modelled coronary insufficiency and after restoration of blood supply to the myocardium. The results provide evidence that verapamil prevents significant decrease of the efficacy of myocardial functioning in ischemia, owing to which the heart maintains a higher level of performance under conditions of inadequate blood supply, the development of acidosis is prevented, and reperfusion disorders of cardiac function are removed completely. This effect is mediated to a great measure by maintenance of high economy of heart performance due to verapamil.

Bovine tryptophanyl-tRNA synthetase and glyceraldehyde-3-phosphate dehydrogenase form a complex.

Bovine tryptophanyl-tRNA synthetase is able to form a complex with glyceraldehyde-3-phosphate dehydrogenase. The complex formation (i) does not influence the tryptophan-dependent PPi-ATP exchange reaction and (ii) involves predominantly the N-terminal dispensable domain of the synthetase. Glyceraldehyde-3-phosphate dehydrogenase was shown to be capable of interacting simultaneously with tryptophanyl-tRNA synthetase and with ribosomal RNA to form a ternary complex. It is proposed that compartmentation of some aminoacyl-tRNA synthetases in certain cases might be achieved via 'adapter' molecules which can bind at once to ribonucleic acids and to aminoacyl-tRNA synthetases.