In-vitro gastric cancer prevention by a polyphenol-rich extract from olives through induction of apoptosis

Abstract

In recent years, natural dietary agents have drawn a great deal of attention owing to their demonstrated ability to suppress cancer. We aimed to investigate the in-vitro gastric cancer preventive activity of a methanol extract obtained from table olives of Greek origin. Tested were AGS cell proliferation, induction of apoptosis and inhibition of inflammation. AGS stomach cancer cells were cultured at a density of 105 cells/ml. Methanol extract of olive was added to cultures at concentrations of 2.0, 1.6, 1.0, and 0.4 μg phenols/ml. Effect on cellular viability was evaluated via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and percentages of early and late apoptotic cells were assayed by annexin V-FITC staining on a FACS scan. Interleukin-8 (IL-8) and intercellular adhesion molecule (ICAM)-1 mRNA and protein production were measured by applying reverse transcriptase-PCR and enzyme-linked immunosorbent assay. Olive extract significantly suppressed cell proliferation at 2.0, 1.6, and 1.0 μg phenols/ml. Flow cytometric analysis of Annexin-V labeled cells indicated that 2.0 μg phenols/ml significantly induced apoptosis. Similarly, at 2.0, 1.6, and 1.0 μg phenols/ml a significant decrease of ICAM-1 and IL-8 protein levels was observed. ICAM-1, as well as IL-8, mRNA expression were decreased in the presence of 2.0 μg phenols/ml. Results indicate that the methanol extract from olives, rich in phenolic compounds, exhibits gastric cancer preventive efficacy by limiting cell proliferation, inducing cell death and suppressing inflammation in AGS cells.