Abstract 1232: Aberrant JAK/STAT signaling confers epigenetic silencing of STAT3 targets in gastric cancer by integrated microarray and bioinformatic analysis

Gastric cancer is the 2nd leading cause of cancer worldwide. One of the major risk factors of gastric cancer is infection of H. pylori. Patients infected with CagA-positive H. pylori would have increased risk of gastric cancer. Previous studies including ours have demonstrated that infection of CagA-positive H. pylori induced activation of JAK/STAT3 signaling pathway. However, the role of aberrant activation of this signaling pathway in gastric cancer is not clear understood. We hypothesized that aberrant activation of JAK/STAT signaling may lead to epigenetic silencing of STAT3 target genes in gastric cancer. In this study, we transfected a constitutively activated mouse STAT3 mutant (STAT3c) into MKN28 gastric cancer cell line in which the JAK/STAT signaling pathway is not active. STAT3c stable transfectant MKN28/STATc-16 showing hyper-phosphorylation of STAT3 demonstrated increased cell proliferation as compared to vector control MKN28/C-9. In order to identify STAT3 target genes that are epigenetically down-regulated in MKN28/STATc-16 cells, expression microarray using Agilent 44K oligonucleotide microarray coupled bioinformatic analysis were performed. Our result showed that there are 2945 genes showing at least 1.5 fold down-regulation in MKN28/STATc-16 cells as compared with vector control. By whole genome bioinformatic analysis, 397 genes with STAT3 binding sites within 5kb of a CpG island were discovered. Integrated analysis revealed that there are 18 downregulated genes with a STAT3 binding site around the promoter CpG island. Further characterization of two STAT3 target, NR4A3 and LOXL4 demonstrated that promoter hypermethylation of these 2 genes were observed in MKN28/STATc-16 cells but not the vector control. Demethylation treatment using 5azaDC also restored expression of these 2 genes in MKN28/STATc-16 cells. These phenomena may be partially related to the up-regulation of DNMT1 in MKN28/STATc-16 cells. In conclusion, our result demonstrated that aberrant JAK/STAT3 signaling may lead to epigenetic silencing of its target gene in gastric cancer. The role of STAT3 in mediating epigenetic silencing of NR4A3 and LOXL4 and its clinical significance in gastric cancer patients is currently under investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstrac