Abstract B168: Dietary polyphenols inhibit pepsin and prevent airway epithelial cell hyperproliferation associated with laryngeal cancer.

Abstract

Abstract A number of otolaryngologic inflammatory and neoplastic diseases are associated with gastric reflux extending proximal to the esophagus. Extraesophageal reflux, also known as laryngopharyngeal reflux (LPR), increases the risk of developing laryngeal cancer by approximately two-fold and analyses of neoplastic development in patients with prior gastrectomy suggest that nonacid components of refluxate promote laryngeal carcinogenesis as well. Clinical and basic science research implicates gastric pepsin as a key deleterious agent of LPR. Our previous research demonstrates that pepsin at pH7 induces hyperproliferation and inflammatory and cell cycle regulatory gene expression changes in airway epithelial cells in vitro. Acid suppression therapy through proton-pump inhibitors (PPI's), the most commonly prescribed therapeutic for reflux, has demonstrated minimal efficacy in resolution of LPR-attributed disease. Phytochemicals derived from algae, pine, and most recently Noni fruit, however, have been shown to not only attenuate reflux-attributed lesions and inflammation in rat models of disease but also directly inhibit peptic activity. This study examines the potential of plant polyphenols curcumin, ecabet sodium (ES) and an anthocyanin-enriched fraction of freeze-dried black raspberry (BRB) to inhibit peptic activity and pepsin-mediated cell damage and proliferative changes in cultured human laryngeal and pharyngeal cells. Cultured human laryngeal epithelial cells from punch biopsy, pharyngeal carcinoma (FaDu) and gastric adenocarcinoma (AGS) cells were pre-treated with/without curcumin (10uM), ES (125ug/ml) and BRB (100ug/ml) for 30 minutes, rinsed and subsequently treated with/without nonacid pepsin (0.1mg/ml, pH7.0) for 1 hour. Morphological changes were examined by transmission electron microscopy and proliferative changes by cell count assay and realtime PCR array (curcumin only). Direct inhibition of peptic activity was determined by in vitro kinetic assay. Curcumin, ES and BRB significantly inhibited peptic activity (p<0.05) in a dose-dependent manner at uM or ug/ml concentrations. Curcumin, ES and BRB abrogated mitochondrial damage and significantly reduced hyperproliferation elicited by pepsin in human laryngeal and pharyngeal cells. Curcumin attenuated 28 of the 31 changes in cell cycle regulatory gene expression induced by pepsin in pharyngeal cells. Gastric cells, which would not be expected to exhibit sensitivity to pepsin-mediated damage, displayed neither mitochondrial damage nor hyperproliferation following treatment with pepsin. These data demonstrate that plant polyphenols curcumin, ES and BRB are protective against pepsin-mediated airway epithelial cell damage and hyperplasia and implicate dietary modification/supplementation with plant polyphenols as a novel pepsin-protective therapeutic modality for diseases associated with proximal reflux including laryngeal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B168.