5-hydroxy-6-8-11-14-eicosatetraenoic-acid and Stomach-Neoplasms

Recent studies highlight the regulatory role of arachidonate lipoxygenase5 (Alox5) and its metabolite 5-hydroxyeicosatetraenoic acid (5-HETE) in cancer tumorigenesis and progression. In this study, we analyzed the expression, biological function and the downstream signaling of Alox5 in gastric cancer.. Alox5 protein levels were measured using IHC and ELISA. Growth, migration and survival assays were performed. Phosphorylation of molecules involved in growth and survival signaling were analyzed by WB. Analysis of variance and t-test were used for statistic analysis.. Alox5 and 5-HETE levels were upregulated in gastric cancer patients. ALOX5 overexpression or 5-HETE addition activates gastric cancer cells and reduces chemotherapy's efficacy. In contrast, ALOX5 inhibition via genetic and pharmacological approaches suppresses gastric cancer cells and enhances chemotherapy's efficacy. In addition, Alox5 inhibition led to suppression of ERK-mediated signaling pathways whereas ALOX5-5-HETE activates ERK-mediated signaling in gastric cancer cells.. Our work demonstrates the critical role of ALOX5-5-HETE in gastric cancer and provides pre-clinical evidence to initialize clinical trial using zileuton in combination with chemotherapy for treating gastric cancer.

Topics: Analysis of Variance; Antineoplastic Agents; Arachidonate 5-Lipoxygenase; Cell Proliferation; Cell Survival; Disease Progression; Humans; Hydroxyeicosatetraenoic Acids; Hydroxyurea; Lipoxygenase Inhibitors; MAP Kinase Signaling System; Phosphorylation; Stomach Neoplasms; Up-Regulation

Our recent studies documented that red ginseng extract (RGE, isolates from steamed and dried Panax ginseng, C.A. Meyer) can inhibit Helicobacter pylori-induced mitogen-activated protein kinase (MAPK) signaling with repressing either nuclear factor (NF)-kappaB-DNA binding activity or releases of IL-8 and COX-2 in gastric epithelial cells (Dig Dis Sci 50:1218-1227, 2005). We extended the experiment to prove whether RGE influences 5-lipoxygenase (5-LOX) pathway, thereby suppressing the biosynthesis of 5(S)-HETE. The 5-LOX enzyme activities were measured by thin layer chromatography using (14)C-labeled arachidonic acid (AA) and quantified by reverse phase-high performance liquid chromatography in human gastric adenocarcinoma (AGS) cells cocultured with H pylori (ATCC 43504 strain) with or without pretreatment of RGE. Western blotting analyses for MAPK signaling and 5-LOX, reverse transcriptase polymerase chain reaction for interleukin-8, and electrophoretic mobility shift assay for NF-kappaB-DNA binding were done, respectively. H pylori infection increased exclusively 5-LOX enzyme activity and RGE inhibited H pylori-stimulated 5-LOX activity, resulting in suppression of 5(S)-HETE generations from AA. RGE inactivated c-jun phosphorylation and repressed redox-sensitive transcriptional activation, led to reduced expression of IL-8 and 5-LOX mRNA in gastric mucosal cells, of which action was very similar to known LOX inhibitor, 200 mumol of geraniin. RGE could be phytoceutical against H pylori infection-associated gastric inflammation through its LOX-inhibiting actions, inhibitory 5-LOX enzyme activity, and attenuating its expression.

Topics: Adenocarcinoma; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Cyclooxygenase 2; Epithelial Cells; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Humans; Hydroxyeicosatetraenoic Acids; Lipoxygenase Inhibitors; Mitogen-Activated Protein Kinases; Panax; Plant Extracts; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Stomach Neoplasms; Tumor Cells, Cultured