Chemopreventive properties of pinoresinol-rich olive oil involve a selective activation of the ATM-p53 cascade in colon cancer cell lines.

UNLABELLED: The Mediterranean diet is rich in extra virgin olive oil (EVOO) and associated with a lower incidence of colorectal cancer. EVOO contains phenolic extracts with potential anticarcinogenic activity. AIM: To assess the anticancer properties of EVOO phenolic extracts using in vitro models. METHODS: Phenolic profiles of two different EVOOs (A and B) were determined. RKO and HCT116 (both p53 proficient), SW480 (p53 mutant) and HCT116(p53-/-) (p53 knocked out) cell lines were treated with EVOO extracts and assessed for cell viability. Apoptosis was determined by terminal deoxynucleotidyl transferase nick end labeling (TUNEL) assay and changes in Bax transcript levels. Cell cycle analysis was determined by flow cytometry and western blots. To confirm the data, analysis of cell viability and cell cycle was performed with purified pinoresinol. RESULTS: Chemical characterization showed that pinoresinol is the main phenol in EVOO-A, and oleocanthal predominates in EVOO-B. Only EVOO-A affected cell viability, which was significantly more pronounced in p53-proficient cells. At a concentration of 200 nM, p53-proficient cells showed increased apoptosis and G(2)/M arrest. In p53-proficient cells, ataxia telangiectasia mutated (ATM) and its downstream-controlled proteins were upregulated after treatment, with a parallel decrease of cyclin B/cdc2. Identical results on cell viability and cell cycle were obtained with purified pinoresinol, but this required a higher concentration than in EVOO-A. CONCLUSION: Our results demonstrate that pinoresinol-rich EVOO extracts have potent chemopreventive properties and specifically upregulate the ATM-p53 cascade. This result was achieved at substantially lower concentrations in EVOO than with purified pinoresinol, indicating a possible synergic effect between the various polyphenols in olive oil.

Annurca apple polyphenols have potent demethylating activity and can reactivate silenced tumor suppressor genes in colorectal cancer cells.

The CpG island methylator phenotype is characterized by DNA hypermethylation in the promoters of tumor suppressor genes with silencing of transcription. Hypermethylation of the promoter of hMLH1 and subsequent microsatellite instability occurs in approximately 12% of sporadic colorectal cancers (CRC). Annurca apple, a variety of southern Italy, is rich in polyphenols that are associated with anticancer properties. Populations in southern Italy have lower incidences of CRC than elsewhere in the western world. We evaluated the mechanisms of putative anticancer effects of Annurca polyphenol extract (APE) in in vitro models of CRC. We extracted polyphenols from Annurca apples and treated RKO, SW48, and SW480 cells with APE and assessed the cell viability, apoptosis, and cell cycle. DNA methylation of selected tumor suppressor genes was evaluated after treatment with APE and was compared with the synthetic demethylating agent 5-aza-2'deoxycytidine (5-aza-2dC). DNA methyltransferase (DNMT)-1 and -3b levels were evaluated. Decreased cell viability and induction of apoptosis was evident after treatment. We found no significant changes in cell cycle dynamics. We observed significant increases of p53 protein expression in RKO after treatment. APE treatment strongly reduced DNA methylation in the promoters of hMLH1, p14(ARF), and p16(INK4a) with consequent restoration of normal expression. These effects were qualitatively comparable with those obtained with 5-aza-2dC. We observed a significant reduction in expression of DNMT proteins after treatment without changes in messenger RNA. In conclusion, APE have potent demethylating activity through the inhibition of DNMT proteins. The lack of toxicity in Annurca extracts makes them excellent candidates for the chemoprevention of CRC.