Avocado extracts selectively induce apoptosis in transformed human oral cells

A132

Diets rich in fruits and vegetables has been associated with reduced risks for many types of cancers. Avocado (Persea americana) is a widely consumed fruit containing many cancer preventing nutrients, vitamins and phytochemicals. Additionally, the avocado is sodium, cholesterol and sugar free, and low in calories and fats making it a part of a healthy diet. We have shown that avocado extract D003 selectively induced apoptosis in premalignant and malignant human oral epithelial cell lines via accumulation of reactive oxygen species (ROS). To further test the potential activity of avocado extract selectively targeting precancerous cells, primary human oral epithelial cells (TE1177) were transformed with retrovirus containing HVP16/E6 or HVP16/E7. Infection of either HVP16/E6 or E7 successfully immortalized primary human oral epithelial cells. Two cell line from E6 (TE1177/E6) and five cell lines from E7 (TE1177/E7) were established. Flow cytometry analysis found that all seven cell lines harbored higher basic levels of ROS compared to the parent TE1177 cells. ROS levels rose dramatically in these transformed cell lines upon the treatment of avocado extracts for 3 hrs. Growth inhibition assay found that the transformed cells were more sensitive to the treatment of avocado extract than TE1177 cells. The addition of N-Acetyl-Cysteine (NAC) markedly reduced the levels of the ROS produced by the treatment of cells with the D003 extract and partially reversed D003-induced growth inhibition in transformed cells. Our data demonstrates that avocado extracts have potent inhibitory effect on the proliferation and selective killing of human oral transformed/premalignant and malignant cells. This inhibition appears to be mediated via ROS induced apoptosis. The further identification and characterization of the active components in avocados and their molecular targets in premalignant and malignant cells should help to better establish the nutritional components responsible for food-based chemopreventive activity.