tolcapone and Neuroblastoma

Currently, peripheral COMT inhibitors have an important role in the treatment of Parkinson's disease, and central COMT inhibitors have a potential role in the treatment of various neuropsychiatric disorders, such as attention deficit hyperactivity disorder. Adverse reactions, low bioavailability and short elimination half-lives have prompted the development of new selective COMT inhibitors. The objective of this study was to evaluate the pharmacodynamic properties of novel tight-binding COMT inhibitors (NC, NE, NDE, NCAPE, CNCAFBn, CNCAPE, NCAFBn, CNCAPA, CNCABA and CNCAHA) and compared to standard inhibitors tolcapone and entacapone. The activity of soluble (S) and membrane bound (MB) COMT from rat liver and brain was assessed in the presence of varying concentrations of each inhibitor. NE and NC behaved most potently against liver S-COMT, and CNCAPE was the most potent inhibitor against brain MB-COMT. The cytotoxicity of tolcapone and CNCAPE in human neuroblastoma SK-N-SH cells and human liver adenocarcinoma SK-HEP-1 cells was also assessed. At lower concentrations, CNCAPE did not reduce cell viability, suggesting that CNCAPE may have a potential therapeutic role as a centrally active COMT inhibitor.

Topics: Animals; Brain; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Catechols; Cell Line, Tumor; Cell Survival; Enzyme Inhibitors; Humans; Liver; Liver Neoplasms; Neuroblastoma; Nitriles; Parkinson Disease; Rats; Tolcapone

Catechol-O-methyltransferase (COMT) is an enzyme that inactivates dopamine and other catecholamines by O-methylation. Tolcapone, a drug commonly used in the treatment of Parkinson's disease, is a potent inhibitor of COMT and previous studies indicate that Tolcapone increases the bioavailability of dopamine in cells. In this study, we demonstrate that Tolcapone kills neuroblastoma (NB) cells in preclinical models by inhibition of COMT. Treating four established NB cells lines (SMS-KCNR, SH-SY5Y, BE(2)-C, CHLA-90) and two primary NB cell lines with Tolcapone for 48 h decreased cell viability in a dose-dependent manner, with IncuCyte imaging and Western blotting indicating that cell death was due to caspase-3-mediated apoptosis. Tolcapone also increased ROS while simultaneously decreasing ATP-per-cell in NB cells. Additionally, COMT was inhibited by siRNA in NB cells and showed similar increases in apoptotic markers compared to Tolcapone. In vivo xenograft models displayed inhibition of tumor growth and a significant decrease in time-to-event in mice treated with Tolcapone compared to untreated mice. These results indicate that Tolcapone is cytotoxic to neuroblastoma cells and invite further studies into Tolcapone as a promising novel therapy for the treatment of neuroblastoma.

Topics: Animals; Antineoplastic Agents; Apoptosis; Benzophenones; Caspase 3; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Cell Line, Tumor; Cell Proliferation; Cell Survival; Female; Humans; Mice, Nude; Neuroblastoma; Nitrophenols; Oxidative Stress; Reactive Oxygen Species; Tolcapone; Tumor Cells, Cultured

Tolcapone and entacapone are catechol-O-methyltransferase (COMT) inhibitors used as adjuncts to levodopa in the treatment of Parkinson's disease (PD). The use of tolcapone has been limited by its hepatotoxicity, the cause of which remains uncertain. Tolcapone compound is an uncoupler of mitochondrial respiration in isolated mitochondria and this action may be relevant to its effect on liver function. We have examined the actions of COMT inhibitors on cultured cells, comparing them with those of the classical uncoupler carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), in order to provide insight into their mechanism of potential toxicity. Tolcapone and FCCP were shown to be toxic to human neuroblastoma SH-SY5Y cells and caused a profound reduction in ATP synthesis. Entacapone was not toxic to SH-SY5Y. Tolcapone and FCCP were shown to be equally toxic to cells depleted of mtDNA and thus devoid of a functional respiratory chain. This study demonstrates that tolcapone markedly inhibits ATP synthesis in cultured cells mirroring the effects of a classical uncoupler. However its toxicity may also involve a mechanism independent of its effects upon oxidative phosphorylation.

Topics: Benzophenones; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Catechols; Cell Survival; DNA, Mitochondrial; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Neuroblastoma; Nitriles; Nitrophenols; Tolcapone; Tumor Cells, Cultured