adenosine-kinase and Brain-Neoplasms

The aim of the present study was to investigate adenosine deaminase (ADA) and adenosine kinase (ADK) expression in human glioma and to explore its correlation with glioma‑associated epilepsy. Tumor tissues (n=45) and peritumoral tissues (n=14) were obtained from glioma patients undergoing surgery. Normal control tissues (n=8) were obtained from brain trauma patients. The disease grade was determined by histological evaluation and the degree of tumor invasion was evaluated using immunofluorescence analyses. mRNA and protein expression of ADA and ADK were evaluated using reverse transcription quantitative polymerase chain reaction or western blot analysis, respectively. Based on histological evaluations, four cases were classified as Grade I gliomas, 18 cases as Grade II, 17 cases as Grade III and six cases were considered Grade IV. Increased ADA and ADK expression was observed in tumor tissues. ADA was predominantly distributed in the cytoplasm of tumor cells, whereas ADK was detected in the cytoplasm as well as in the nuclei. ADA and ADK levels were upregulated in patients with Grade II and Grade III gliomas compared to those in control subjects (p<0.05). In addition, tumor invasion was detected in peritumoral tissues. The number of ADA‑positive or ADK‑positive cells in tumor tissues was similar between glioma patients with and without epilepsy (p>0.05). However, ADA and ADK expression was upregulated in peritumoral tissues derived from patients with epilepsy compared to that in glioma patients without epilepsy. The results of the present study suggested that ADA and ADK are involved in glioma progression, and that increased ADA and ADK levels in peritumoral tissues may be associated with epilepsy in glioma patients.

Topics: Adenosine Deaminase; Adenosine Kinase; Adolescent; Adult; Aged; Brain Neoplasms; Case-Control Studies; Cell Nucleus; Child; Child, Preschool; Cytoplasm; Disease Progression; Epilepsy; Female; Gene Expression Regulation, Neoplastic; Glioma; Humans; Male; Middle Aged; Neoplasm Grading

Adenosine kinase (ADK), a largely astrocyte-based metabolic enzyme, regulates adenosine homeostasis in the brain. Overexpression of ADK decreases extracellular adenosine and consequently leads to seizures. We hypothesized that dysfunction in the metabolism of tumor astrocytes is related to changes in ADK expression and that those changes might be associated with the development of epilepsy in patients with tumors.. We compared ADK expression and cellular distribution in surgically removed tumor tissue (n = 45) and peritumoral cortex (n = 20) of patients with glial and glioneuronal tumors to normal control tissue obtained at autopsy (n = 11). In addition, we compared ADK expression in tumor patients with and without epilepsy. To investigate ADK expression, we used immunohistochemistry and Western blot analysis. ADK activity measurement was performed in surgical specimens of astrocytomas World Health Organization (WHO) grade III (n = 3), peritumoral cortex (n = 3), and nonepileptic cortex (n = 3).. Immunohistochemistry predominantly showed cytoplasmic labeling in tumors and peritumoral tissue containing infiltrating tumor cells. ADK immunoreactivity was significantly stronger in tumor and peritumoral tissue compared to normal white matter and normal cortex, especially in astrocytoma WHO grade III, as confirmed by Western blot analysis and ADK activity measurements. Importantly, we found a significantly higher expression of ADK in the peritumoral infiltrated tissue of patients with epilepsy than in patients without epilepsy.. These results suggest a dysregulation of ADK in astrocytic brain tumors. Moreover, the upregulation of ADK observed in peritumoral infiltrated tissue of glioma patients with epilepsy supports the role of this enzyme in tumor-associated epilepsy.

Topics: Adenosine Kinase; Adolescent; Adult; Aged; Astrocytoma; Brain Neoplasms; Cerebral Cortex; Child; Epilepsy; Female; Humans; Immunohistochemistry; Male; Middle Aged; Up-Regulation; Young Adult

In C6 glioma cells, adenine nucleotides, especially AMP, and adenosine inhibited cell proliferation in time- and concentration-dependent manners. alpha,beta-methylene-ADP, an ecto-5'-nucleotidase inhibitor, suppressed the hydrolysis of AMP and reversed the inhibition of cell growth induced by AMP but not by adenosine. Adenosine deaminase eliminated both AMP- and adenosine-mediated growth inhibitions. 5'-N-ethylcarboxamidoadenosine, an adenosine receptor agonist, had little effect on the cell growth. Equilibrative nucleoside transporters, ENT-1 and ENT-2, were expressed in C6 cells by determining their mRNAs. ENT inhibitors, nitrobenzylthioinosine and dipyridamole, suppressed the uptake of [(3)H]adenosine into C6 cells, and attenuated AMP- or adenosine-mediated growth inhibition. Furthermore, an adenosine kinase inhibitor 5-iodotubercidin reversed the growth inhibition induced by AMP and adenosine. When uridine was added in the extracellular space, AMP- or adenosine-induced cell growth inhibition was completely reversed, suggesting that intracellular pyrimidine starvation would be involved in their cytostatic effects. These results indicate that extracellular adenine nucleotides inhibit C6 cell growth via adenosine, which is produced by ecto-nucleotidases including CD73 at the extracellular space and then incorporated into cells by ENT2. Intracellular AMP accumulation by adenosine kinase after adenosine uptake would induce C6 cell growth inhibition through pyrimidine starvation.

Topics: 5'-Nucleotidase; Adenine Nucleotides; Adenosine; Adenosine Deaminase; Adenosine Diphosphate; Adenosine Kinase; Adenosine Monophosphate; Animals; Brain Neoplasms; Cell Count; Cell Line, Tumor; Cell Proliferation; Cyclic AMP; Dipyridamole; Equilibrative Nucleoside Transporter 1; Equilibrative-Nucleoside Transporter 2; Glioma; Hydrolysis; Rats; Reverse Transcriptase Polymerase Chain Reaction; Tetrazolium Salts; Thiazoles; Thioinosine; Uridine