Involvement of cell surface TG2 in the aggregation of K562 cells triggered by gluten

Gluten-induced aggregation of K562 cells represents an in vitro model reproducing the early steps occurring in the small bowel of celiac patients exposed to gliadin. Despite the clear involvement of TG2 in the activation of the antigen-presenting cells, it is not yet clear in which compartment it occurs. Herein we study the calcium-dependent aggregation of these cells, using either cell-permeable or cell-impermeable TG2 inhibitors. Gluten induces efficient aggregation when calcium is absent in the extracellular environment, while TG2 inhibitors do not restore the full aggregating potential of gluten in the presence of calcium. These findings suggest that TG2 activity is not essential in the cellular aggregation mechanism. We demonstrate that gluten contacts the cells and provokes their aggregation through a mechanism involving the A-gliadin peptide 31-43. This peptide also activates the cell surface associated extracellular TG2 in the absence of calcium. Using a bioinformatics approach, we identify the possible docking sites of this peptide on the open and closed TG2 structures. Peptide docks with the closed TG2 structure near to the GTP/GDP site, by establishing molecular interactions with the same amino acids involved in stabilization of GTP binding. We suggest that it may occur through the displacement of GTP, switching the TG2 structure from the closed to the active open conformation. Furthermore, docking analysis shows peptide binding with the β-sandwich domain of the closed TG2 structure, suggesting that this region could be responsible for the different aggregating effects of gluten shown in the presence or absence of calcium. We deduce from these data a possible mechanism of action by which gluten makes contact with the cell surface, which could have possible implications in the celiac disease onset.

Changes in protein expression in two cholangiocarcinoma cell lines undergoing formation of multicellular tumor spheroids in vitro

Epithelial-to-Mesenchymal Transition (EMT) is relevant in malignant growth and frequently correlates with worsening disease progression due to its implications in metastases and resistance to therapeutic interventions. Although EMT is known to occur in several types of solid tumors, the information concerning tumors arising from the epithelia of the bile tract is still limited. In order to approach the problem of EMT in cholangiocarcinoma, we decided to investigate the changes in protein expression occurring in two cell lines under conditions leading to growth as adherent monolayers or to formation of multicellular tumor spheroids (MCTS), which are considered culture models that better mimic the growth characteristics of in-vivo solid tumors. In our system, changes in phenotypes occur with only a decrease in transmembrane E-cadherin and vimentin expression, minor changes in the transglutaminase protein/activity but with significant differences in the proteome profiles, with declining and increasing expression in 6 and in 16 proteins identified by mass spectrometry. The arising protein patterns were analyzed based on canonical pathways and network analysis. These results suggest that significant metabolic rearrangements occur during the conversion of cholangiocarcinomas cells to the MCTS phenotype, which most likely affect the carbohydrate metabolism, protein folding, cytoskeletal activity, and tissue sensitivity to oxygen.

Comparative proteomic analysis of ductal breast carcinoma demonstrates an altered expression of chaperonins and cytoskeletal proteins

The aim of the present study was to analyze the protein composition of ductal breast carcinoma and the surrounding normal tissue in individual patients using comparative 2D proteomics and mass spectrometry to detect candidate disease biomarkers for diagnosis and prognosis. Samples of normal and cancerous tissue obtained form 28 patients were analyzed. Chaperonins and cytoskeletal proteins predominated among the 11 proteins for which major changes in abundance were detected. Of these 11 proteins with an altered expression, 2 had a decreased expression and 9 had an increased expression. In addition, the abundance of a few cytokeratins was also altered; however, they were not capable of serving as specific circulatory biomarkers. The proteins which we observed to exhibit an altered expression in infiltrating ductal breast carcinoma may be exploited as novel targets for therapeutic interventions or represent novel diagnostic/prognostic markers for the early detection of aggressive tumors, particularly those with multridrug-resistant phenotypes during the earlier stages of the disease.

Antiangiogenic drugs for chemotherapy of bladder tumours

BACKGROUND

Bladder cancers have different angiogenic pathways distinguishing not only papillary from solid tumours, but even papillary superficial from papillary invasive ones, thus representing selective targets for antiangiogenic drugs.

METHODS

The bacterial wall component tecogalan, inhibiting basic fibroblast growth factor (bFGF), the fumagillin derivative TNP-470, inhibiting vascular endothelial growth factor (VEGF), the distamycin A derivative PNU153429, and the tetracycline minocycline were administered to nude mice injected with the human bladder cancer cell lines 639V, causing bFGF-expressing papillary superficial tumours, or T24, causing VEGF-expressing papillary invasive tumours.

RESULTS

Tecogalan had no effect even on 639V tumour growth, where bFGF was unaffected. TNP-470 only had an effect on T24 tumours, delaying tumour appearance and growth and lowering VEGF; these effects were augmented by adding minocycline. PNU153429 had no effect on 639V tumours, and a slight effect on T24 tumours.

CONCLUSION

TNP-470 may represent a selective drug for the treatment of VEGF-expressing invasive papillary bladder tumours.

Tumor and metastasis suppression by the human RNASET2 gene

The region 6q27 from human chromosome 6 has been reported to contain one or more tumor suppressor genes on the basis of cytogenetic, molecular and functional studies. We have recently carried out a detailed analysis of a candidate gene from 6q27 to evaluate its putative role as a tumor suppressor gene involved in ovarian cancer pathogenesis. The RNASET2 gene was shown to behave as a class II tumor suppressor and abolish the tumorigenic potential of an ovarian cancer-derived cell line. In this study, we have started the cellular and biochemical characterization of RNASET2 and showed that it is a secreted glycoprotein. Moreover, we have extended our previous studies by evaluating the effect of RNASET2 on the metastatic behavior of the highly-invasive ovarian cancer cell line HEY3MET2. From such analysis, RNASET2 was found to significantly decrease the metastatic potential of this cell line in vivo. Moreover, RNASET2-mediated suppression of tumorigenesis and metastasis was not affected by a double point mutation targeted to the putative ribonuclease catalytic sites, suggesting that tumor suppression by RNASET2 is not mediated by its ribonuclease activity. The potential biological implications of this unexpected finding are discussed in relation to the current evolutionary models.

The role of peroxisome proliferator-activated receptor gamma in bladder cancer in relation to angiogenesis and progression

Peroxisome proliferator-activated receptor gamma (PPAR gamma) immunohistochemical expression was analyzed in 75 human bladder tumor specimens, where the expression of some angiogenic factors, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived endothelial cell growth factor (PDECGF), and tumor progression markers, such as epidermal growth factor receptor (EGFr), p16, mutated p53, and normal pRB, were also analyzed. The results were then compared to the clinical and pathological characteristics of the disease. PPAR gamma was expressed more significantly in papillary tumors than in solid cancers, and its presence was associated with statistical significance to low incidence of tumor recurrence or progression. This significant association was observed also when PPAR gamma was expressed in the presence of PDECGF, which resulted, when considered alone, to an angiogenic factor typical of solid cancers and appeared related to poor prognosis. In the presence of bFGF, on the contrary, PPAR gamma expression no longer resulted to a significant association with low incidence of tumor recurrence or progression, suggesting a possible worsening role of this angiogenic factor, typical of papillary cancers, in its interaction with PPAR gamma.

Reorganization of contractile systems and protein tyrosine phosphorylation in platelet aggregation

Platelet aggregation is accompanied with reorganization of contractile systems. This event involves tyrosine phosphorylation of various proteins. When tyrosine phosphorylation is induced by an intracellular trigger as vanadate, a phosphorylated cytosolic 60 Kd protein acts as a nucleating center on which new actin filaments grow. When aggregation is induced by an extracellular signal as ristocetin, actin filaments of the membrane-associated skeleton and the 60 Kd protein bound to this structure migrate toward the cytosol and only in this soluble state the 60 Kd protein undergoes tyrosine phosphorylation and consequently triggers reorganization of contractile systems.

Production of reactive oxygen-derived species by redox reactions between Fe(II)cytochrome c and oxygen. A kinetic study

In aerated water solutions Fe(II)Cytochrome c is slowly oxidized to Fe(III)Cytochrome c by molecular oxygen, from which superoxide anion radicals are produced (kobs = 2.7 x 10(-4) min-1 at 37 degrees C and pH = 7.3). The biological importance of this reaction has been evidenced by kinetic investigations in the presence of scavengers. In the presence of Superoxide dismutase the oxidation rate is strongly enhanced (kobs = 3 x 10(-3) min-1 at 37 degrees C). Catalase and mannitol reduce the rate constant values by 50% and 25% respectively either in the presence or in the absence of Superoxide dismutase: differences between rate constants correspond to the differences in stoichiometric redox ratios indicating that hydrogen peroxide and hydroxyl radicals are formed subsequently to the production of superoxide anion radicals.

Phospholipids metabolism in platelets stimulated with collagen

Collagen addition to platelets suspended in Calcium-free medium induces slow shape change followed by fast aggregates formation. Time courses of membrane phospholipids metabolism and arachidonic acid oxidative metabolism indicate that phospholipase C is the immediate target of the stimulus, and subsequently phospholipase A-2 is activated by synergistic action of released calcium and protein kinase C.

Two distinct mechanisms of inhibition of platelets aggregation by acetylsalicylic acid

The von Willebrand Factor-Ristocetin adduct activates Platelets aggregation and secretion. Acetylsalicylic acid inhibits Platelets activation by two distinct mechanisms indicating that the adduct activates Platelets by triggering at least two distinct intraplatelet metabolic pathways. The first starts from the activation of Phospholipase A-2 that produces Arachidonic acid, which, in turn, undergoes the metabolic pathway leading to Thromboxane A-2; this pathway can be blocked by the intraplatelet Acetylsalicylic acid by irreversible inactivation of Cyclooxygenase but it is insensitive to the extra-platelet Acetylsalicylic acid. The second pathway is triggered by intact von Willebrand Factor, but not by the Acetylsalicylic acid-treated one; it is insensitive to intraplatelet Acetylsalicylic acid and therefore unrelated to the Arachidonic acid metabolism.

[Effect of ASA on the interaction of von Willebrand factor with the platelet membrane]

Ristocetin induces a conformational change on von Willebrand Factor (vWF) similar to that due to the interaction with the subendothelium, by which the former can interact with the Glycoprotein-1 B (GPIB) of the platelet membrane and trigger aggregation and granule content secretion. Platelet Rich Plasma (PRP) treated with Acetyl Salicylic Acid (ASA) loses completely the aggregability induced by addition of Ristocetin whereas ASA-treated and successively Washed Platelets (AWP) supplemented with normal plasma (PPP) give an aggregation and a secretory response to Ristocetin similar to that given by PRP; similarly normal Washed Platelets (WP) supplemented with ASA-treated plasma (APPP) give identical aggregation, and secretion by Ristocetin addition. Ours results indicate that the Ristocetin-vWF complex can trigger two distinct intraplatelet metabolic pathways. A first well known way starts from the activation of Phospholipase A-2 (PL-A2), by which arachidonic acid is produced, that, in turn, undergoes the metabolic pathway leading to Thromboxane A-2; this pathway can be blocked by the intraplatelet ASA by irreversible inactivation of Cyclooxygenase, but it is insensitive to the extra-platelet ASA. A second, independent metabolic pathway, can be triggered by intact vWF, but not by the ASA treated one. It is insensitive to intraplatelet ASA and therefore unrelated to the arachidonic acid metabolism. This pathway could start from the activation of Phospholipase C (PL-C).

Cloning of DNA fragments complementary to tobacco nitrate reductase mRNA and encoding epitopes common to the nitrate reductases from higher plants

Messenger RNAs encoding the nitrate reductase apoenzyme from tobacco can be translated in a cell-free system. Poly(A)+ mRNA fractions from the 23-32 S area of a sucrose gradient were used to build a cDNA library in the expression vector gt11 with an efficiency of cloning of approximately 10(4) recombinants/ng mRNA. Recombinant clones were screened with a rabbit polyclonal antibody directed against the corn nitrate reductase, which cross reacts specifically with the nitrate reductases from dicotyledons. Among 240000 recombinant plaques, eight clones were isolated containing inserts of sizes ranging from 1.6 kb to 2.1 kb and sharing sequence homologies. Seven of these clones contained a common internal 1.6 kb EcoRI fragment. The identity of these clones was confirmed as follows. A fusion protein of 170 kDa inducible by IPTG and recognized by the rabbit nitrate reductase antibody was expressed by a lysogen derived from one of the recombinants. The antibodies binding the fused protein were eluted and shown to be inhibitory to the catalytic activity of tobacco nitrate reductase. Two monoclonal antibodies directed against nitrate reductase were also able to bind the hybrid protein. The 1.6 kb EcoRI fragment was sequenced by the method of Sanger. The open reading frame corresponding to a translational fusion with the -galactosidase coding sequence of the vector shared strong homology at the amino acid level with the heme-binding domain of proteins of the cytochrome b5 superfamily and with human erythrocyte cytochrome b5 reductase. When the 1.6 kb EcoRI fragment was used as a probe for Northern blot experiments a signal corresponding to a 3.5 kb RNA was detected in tobacco and in Nicotiana plumbaginifolia mRNA preparations but no cross-hybridization with corn mRNAs was detected. The probe hybridized with low copy number sequences in genomic blots of tobacco DNA.