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.
Fini
Lucia
L
GI Cancer Research Laboratory, Department of Internal Medicine, Sammons Cancer Center, Dallas, TX 75246, USA.
Selgrad
Michael
M
Fogliano
Vincenzo
V
Graziani
Giulia
G
Romano
Marco
M
Hotchkiss
Erin
E
Daoud
Yahya A
YA
De Vol
Edward B
EB
Boland
C Richard
CR
Ricciardiello
Luigi
L
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics*; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors; D019175:DNA Methylation / Q000187:drug effects*; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D020868:Gene Silencing / Q000187:drug effects; D016147:Genes, Tumor Suppressor; D006801:Humans; D027845:Malus / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry / Q000494:pharmacology*; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D059808:Polyphenols; D025521:Tumor Suppressor Proteins / Q000235:genetics; D000097584:DNA Methyltransferase 3B
D000972:Antineoplastic Agents, Phytogenic; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D005419:Flavonoids; D010636:Phenols; D010936:Plant Extracts; D059808:Polyphenols; D025521:Tumor Suppressor Proteins; D000097584:DNA Methyltransferase 3B