Abstract 4794: Monoamine oxidase A expression correlates with cholangiocarcinoma tumor grade and survival and is suppressed via IL-6-driven hypermethylation of the promoter
Authors: Huang Li , Frampton Gabriel , Liang Li-Jian , DeMorrow Sharon 
Published: June 2012

The metabolism of dopamine and serotonin is dysregulated in cholangiocarcinoma (CCA), which has subsequent growth promoting effects. Monoamine oxidase A (MAOA), the enzyme responsible for the degradation of serotonin and dopamine, is switched off in CCA although the mechanism by which this occurs is unknown. MAOA transcriptional activity can be suppressed by hypermethylation. IL-6 is known to be overproduced in CCA and can control hypermethylation events. The aims of this study were to 1) Correlate MAOA expression with pathophysiological parameters of CCA; 2) determine if IL-6 drivenhypermethylation of the MAOA promoter is involved in the suppression of expression. Methods: MAOA expression was assessed in biopsy samples from 84 patients with hilar CCA, or non-malignant controls by immunohistochemistry and realtime PCR and Kaplan-Meier survival analysis and Log Rank test performed. Hypermethylation of the MAOA promoter was assessed in four CCA cell lines previously shown to have suppressed MAOA expression, in two non-malignant cholangiocyte lines (H69 and HIBEC), and in human tumor samples using bisulfite modification followed by pyrosequencing analysis. Mz-ChA-1 and H69 cells were treated with a DNA methyltransferase inhibitor (5-aza; 10μM) for 4 days to inhibit the hypermethylation followed by qPCR assessment of MAOA expression. In parallel, Mz-ChA-1 cells were treated with a neutralizing IL-6 antibody (1μg/mL) for 4 days, or IL-6 expression was knocked down by stable transfection of IL-6 shRNA plasmids and MAOA expression was assessed by qPCR. Results: MAOA expression has a negative correlation with tumor differentiation (correlation coefficient: -2.68; P=0.014&lt;0.05(2-tailed)). Furthermore there was a distinct correlation between MAOA expression and total survival (10.8 ± 0.9 months for low MAOA expression vs 27.2 ± 4.3 months for moderate or strong expression group, P&lt;0.01). The MAOA promoter region was hypermethylated in CCA cells, but not H69 or HIBEC and treatment with 5-aza increased MAOA expression in Mz-ChA-1 cells, but not H69 cholangiocytes. Suppression of IL-6 expression either by neutralizing antibodies or by specific knock down of expression (to 3% of the parental cell line) reversed the hypermethylation and increased the subsequent MAOA expression. Conclusions: MAOA expression correlates with both differentiation grade and overall survival of CCA patients. Aberrant IL-6 expression seen in CCA cells may drive the suppression of MAOA expression by regulating promoter methylation and subsequent MAOA gene expression. Agents that may restore MAOA expression may have therapeutic value in the treatment of CCA.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4794. doi:10.1158/1538-7445.AM2011-4794