Virgin Olive Oil Phenols Inhibit Proliferation of Human Promyelocytic Leukemia Cells (HL60) by Inducing Apoptosis and Differentiation

Abstract

Although epidemiologic evidence and animal studies suggest that olive oil may prevent the onset of cancer, the components responsible for such an effect and their mechanisms of action remain largely unknown. In the present study, we investigated the effect of a virgin olive oil phenol extract (PE) on proliferation, the cell cycle distribution profile, apoptosis, and differentiation of the human promyelocytic cell line HL60. PE inhibited HL60 cell proliferation in a time- and concentration-dependent manner, as demonstrated by the viable cell count and 3-[4,5-dimethyl(thiazol-2-yl)]-3,5-diphenyltetrazolium bromide (MTT) metabolism. Cell growth was completely blocked at a PE concentration of 13.5 mg/L; apoptosis was also induced as detected by fluorescence microscopy and flow cytometry. Determination of the cell cycle distribution by flow cytometry revealed an accumulation of cells in the G(0)/G(1) phase. Two compounds isolated from PE, the dialdehydic forms of elenoic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) and to tyrosol (pHPEA-EDA), were shown to possess properties similar to those of PE; they account for a part of the powerful effects exerted by the complex mixture of compounds present in PE. The concentrations of the different compounds in PE were determined by HPLC, and the purity of 3,4-DHPEA-EDA and pHPEA-EDA was ascertained by NMR. Treatment with PE induced a differentiation in HL60 cells, which subsequently acquired the ability to produce superoxide ions and reduce nitroblue tetrazolium to formazan. These results support the hypothesis that polyphenols play a critical role in the anticancer activity of olive oil.

Inhibitory effects of olive oil phenolics on invasion in human colon adenocarcinoma cells in vitro

“…The dialdehydic form of elenolic acid, linked to hydroxytyrosol or to tyrosol, has been shown to account, in part, for the antiproliferative and apoptotic effects of virgin olive oil phenol extract in human promyelocytic leukemia cells. 33 Strong antioxidant activity of 3,4-dihydroxyphenylethanol-elenolic acid was also reported. 26 The higher concentration of the linked forms of hydroxytyrosol and tyrosol present in our OVP extract 7 may account for the effects shown by OVP as compared with the isolated compounds studied.…”

Involvement of Hydrogen Peroxide Formation on Apoptosis Induction by Olive Oil Phenolic Compounds

“…Hydroxytyrosol (3, and tyrosol (p-HPEA) are the most representative olive oil phenols present both as free compounds and linked to the dialdehydic form of elenoic acid (3,4-DHPEA-EDA and p-HPEA-EDA) . Previous studies carried out in our laboratory have showed that these compounds exert a pro-apoptotic activity toward cancer cell lines (Fabiani et al 2002(Fabiani et al , 2006. In particular, we have found that 3,4-DHPEA at high concentrations (100µM) induces apoptosis on HL60 cells through an oxidative stress caused by the extracellular production of hydrogen peroxide (H 2 O 2 ) (Fabiani et al 2008).…”

“…3,4-DHPEA was obtained from Cayman Chemicals Ltd; protocatechuic, vanillic, ferulic, 3,4-dihydroxy-hydrocinnamic, o-coumaric and syringic acids were obtained from Fluka Co. (Buchs, Switzerland); gallic acid was from Carlo Erba (Milan) while oleuropein was purchased by Extrasynthese (Genay, France). 3,4 DHPEA-EDA and p-HPEA-EDA were purified by semi-preparative HPLC from a methanolic extract obtained from a virgin olive oil containing 650 mg/kg of total phenols as previously reported (Fabiani et al 2006). Tyrosol (p-HPEA) and all other reagents were purchased from Sigma-Aldrich (Irvine, UK) unless differently specified Cell treatment and apoptosis analysis.…”

“…The cells were seeded at a density of 0.25 × 10 6 /ml and incubated for 24 h at 37°C and 5% CO 2 with the different phenolic compounds (100µM) in the absence and in the presence of catalase (CAT: 100 U/ml). The percentage of apoptotic cells was determined by a fluorescent microscopy assay as previously described (Fabiani et al 2006).…”

Synthesis of novel phospholipids that bind phenylalkanols and hydroquinone via phospholipase D-catalyzed transphosphatidylation

“…1), which contained olive oil extracts, exhibit antioxidant activity [8] and apoptosis induction against colon cancer cells [9], and induce the differentiation of leukemia cells [10]. 4-Hydroxybenzyl alcohol (4HBA; 2) is a component of Gastrodia elata Blume (Orchidaceae) that has an anxiolytic-like effect on mice [11], and tyrosinase inhibitory activity [12].…”