Visinets: a web-based pathway modeling and dynamic visualization tool.

In this report we describe a novel graphically oriented method for pathway modeling and a software package that allows for both modeling and visualization of biological networks in a user-friendly format. The Visinets mathematical approach is based on causal mapping (CMAP) that has been fully integrated with graphical interface. Such integration allows for fully graphical and interactive process of modeling, from building the network to simulation of the finished model.

Tenascin C interacts with ecto-5'-nucleotidase (eN) and regulates adenosine generation in cancer cells.

Tenascin C is expressed in invasive human solid tumors; however its specific role in cancer biology remains obscure. Previously, we have found that ecto-5'-nucleotidase (eN) is a marker of ER (-) breast carcinoma and elevated expression correlates with invasive mesenchymal cell phenotype. To investigate for the potential relationship between eN and protein components of the extracellular matrix (ECM) we measured adenosine generation from AMP in cells incubated with soluble ECM proteins.

Expression of ecto-5'-nucleotidase (eN, CD73) in cell lines from various stages of human melanoma.

Ecto-5'-nucleotidase is a GPI-anchored enzyme localized in cell membrane lipid rafts. Although it is highly expressed in many tumour cells, its specific function during tumorigenesis is unclear. We have found that, among different melanoma cells, upregulated expression of ecto-5'-nucleotidase is associated with a highly invasive phenotype.

Lipid rafts remodeling in estrogen receptor-negative breast cancer is reversed by histone deacetylase inhibitor.

Recently, we have found dramatic overexpression of ecto-5'-nucleotidase (or CD73), a glycosylphosphatidylinositol-anchored component of lipid rafts, in estrogen receptor-negative [ER-] breast cancer cell lines and in clinical samples. To find out whether there is a more general shift in expression profile of membrane proteins, we undertook an investigation on the expression of selected membrane and cytoskeletal proteins in aggressive and metastatic breast cancer cells. Our analysis revealed a remarkably uniform shift in expression of a broad range of membrane, cytoskeletal, and signaling proteins in ER- cells.

Enforced expression of cytosolic 5'-nucleotidase I confers resistance to nucleoside analogues in vitro but systemic chemotherapy toxicity precludes in vivo selection.

Purpose: Retroviral transfer of cDNA sequences that confer drug resistance can be used to protect against chemotherapy-induced hematopoietic toxicity and for the selective expansion of gene-modified cells. To successfully expand genetically engineered cells in vivo, an appropriate balance must be achieved between systemic toxicity induced by the selecting agent and the expansion of modified cells.

Method: In this study, we investigate retroviral transfer of cytosolic 5'-nucleotidase I (cN-I) for protection and selection of gene-modified cells when treated with 2-chloro-2'-deoxyadenosine (2-CdA) and 5-fluorouracil (5-FU) alone and in combination.

The 5'-nucleotidases as regulators of nucleotide and drug metabolism.

The 5'-nucleotidases are a family of enzymes that catalyze the dephosphorylation of nucleoside monophosphates and regulate cellular nucleotide and nucleoside levels. While the nucleoside kinases responsible for the initial phosphorylation of salvaged nucleosides have been well studied, many of the catabolic nucleotidases have only recently been cloned and characterized. Aside from maintaining balanced ribo- and deoxyribonucleotide pools, substrate cycles that are formed with kinase and nucleotidase activities are also likely to regulate the activation of nucleoside analogues, a class of anticancer and antiviral agents that rely on the nucleoside kinases for phosphorylation to their active forms.

Molecular characterization of recombinant mouse adenosine kinase and evaluation as a target for protein phosphorylation.

The regulation of adenosine kinase (AK) activity has the potential to control intracellular and interstitial adenosine (Ado) concentrations. In an effort to study the role of AK in Ado homeostasis in the central nervous system, two isoforms of the enzyme were cloned from a mouse brain cDNA library. Following overexpression in bacterial cells, the corresponding proteins were purified to homogeneity.

Wnt and beta-catenin signaling target the expression of ecto-5'-nucleotidase and increase extracellular adenosine generation.

Solid tumors, which routinely experience necrosis and ischemia, release and degrade adenine nucleotides. This process may lead, depending on the expression of enzymes that regulate adenosine, to the generation of extracellular adenosine. Since genes encoding ecto-5'-nucleotidase (eN) and adenosine deaminase (ADA) contain TCF/LEF consensus binding sites, we asked whether Wnt/beta-catenin signaling, a pathway that is deregulated in several human tumors, targets the expression of these genes and thus influence extracellular adenosine generation.

Role of estrogen receptor in the regulation of ecto-5'-nucleotidase and adenosine in breast cancer.

Purpose: The purpose is to understand the expression of ecto-5'-nucleotidase (eN), an adenosine producing enzyme with potential roles in angiogenesis, growth, and immunosuppression, in estrogen receptor (ER)-negative and -positive breast cancer.

Experimental Design: We investigated the regulation of eN expression at the mRNA and protein levels by alpha in a panel of breast cancer cell lines that differ in ER status and invasive and metastatic potential. We also determined rates of adenosine formation in cells with high and low eN expression and in ER+ cells treated with estradiol.

Cyclosporin A and FK506 decrease adenosine kinase activity and adenosine uptake in T-lymphocytes.

Adenosine is a potent modulator of immune function, and adenosine kinase (AK), a rate-limiting enzyme for adenosine uptake and metabolism, is a potential mediator of adenosine regulation. We have found that adenosine uptake increased six- to 18-fold during T-lymphocyte activation. This increase correlated with an increase in AK activity but not in AK protein.

The evidence for two opposite, ATP-generating and ATP-consuming, extracellular pathways on endothelial and lymphoid cells.

Extracellular purines are important signalling molecules in the vasculature that are regulated by a network of cell surface ectoenzymes. By using human endothelial cells and normal and leukaemic lymphocytes as enzyme sources, we identified the following purine-converting ectoenzymes: (1) ecto-nucleotidases, NTP diphosphohydrolase/CD39 (EC 3.6.