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Jozef Spychala

Publications and source records attributed to Jozef Spychala.

4 recordsLinked to original sources
PubMed2004

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. RESULTS: ER-negative cells express high eN protein and mRNA levels and produce up to 104-fold more adenosine from AMP and ATP. Estradiol and antiestrogen treatments confirm that eN mRNA and protein expression and adenosine generation are negatively regulated through the ER. Endogenous expression of eN in ER- cells transfected with ERalpha and phorbol ester-induced eN expression in ER+ cells was strongly suppressed by estradiol, suggesting a dominant function of ER. Finally, an examination of 18 clinical breast cancer samples that were analyzed for both ER status and eN expression by Martin et al. (Cancer Res., 60: 2232-2238, 2000) revealed a significant inverse correlation between ER and eN status. CONCLUSIONS: Our results show for the first time that eN is negatively regulated by ERalpha in dominant fashion and suggests that eN expression and its generation of adenosine may relate to breast cancer progression. Additionally, increased expression of eN in a subset of ER-negative cells may serve as a novel marker for a subset of more aggressive breast carcinoma.

5'-Nucleotidase↗
PubMed2002

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 3.6.1.5) and ecto-5'-nucleotidase/CD73 (EC 3.1.3.5); (2) ecto-nucleotide kinases, adenylate kinase (EC 2.7.4.3) and nucleoside diphosphate kinase (EC 2.7.4.6); (3) ecto-adenosine deaminase (EC 3.5.4.4). Evidence for this was obtained by using enzyme assays with (3)H-labelled nucleotides and adenosine as substrates, direct evaluation of gamma-phosphate transfer from [gamma-(32)P]ATP to AMP/NDP, and bioluminescent measurement of extracellular ATP synthesis. In addition, incorporation of radioactivity into an approx. 20 kDa surface protein was observed following incubation of Namalwa B cells with [gamma-(32)P]ATP. Thus two opposite, ATP-generating and ATP-consuming, pathways coexist on the cell surface, where basal ATP release, re-synthesis of high-energy phosphoryls, and selective ecto-protein phosphorylation are counteracted by stepwise nucleotide breakdown with subsequent adenosine inactivation. The comparative measurements of enzymic activities indicated the predominance of the nucleotide-inactivating pathway via ecto-nucleotidase reactions on the endothelial cells. The lymphocytes are characterized by counteracting ATP-regenerating/adenosine-eliminating phenotypes, thus allowing them to avoid the lymphotoxic effects of adenosine and maintain surrounding ATP at a steady-state level. These results are in agreement with divergent effects of ATP and adenosine on endothelial function and haemostasis, and provide a novel regulatory mechanism of local agonist availability for nucleotide- or nucleoside-selective receptors within the vasculature.

5'-Nucleotidase↗
PubMed2002

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 immunosuppressive drugs cyclosporin A (CsA) and FK506 inhibited both adenosine uptake and AK activity in a concentration-dependent manner. Among several nucleosides and bases, the inhibition of uptake was selective for adenosine. Immunosuppressive drug treatment also caused a twofold increase in the level of extracellular adenosine but not of inosine, suggesting that the effect is not related to the general toxicity of drugs. Inhibitors of calcineurin did not inhibit adenosine uptake, suggesting that this protein phosphatase does not mediate the effect. These data demonstrate that CsA and FK506 enhance adenosine concentrations in T-lymphocytes by way of a mechanism that involves AK inhibition.

Adenosine↗