Apple polyphenols modulate expression of selected genes related to toxicological defence and stress response in human colon adenoma cells

Abstract

Apples contain significant amounts of flavonoids that are potentially cancer risk reducing by acting antioxidative or antiproliferative and by favorably modulating gene expression. The purpose of this study was to investigate whether polyphenols from apples modulate expression of genes related to colon cancer prevention in preneoplastic cells derived from colon adenoma (LT97). For this, LT97 cells were treated with effective concentrations of apple extracts (AEs). RNA was isolated and used for synthesis and labeling of cDNA that was hybridized to cDNA-arrays. Gene expression studies were performed using a commercial cDNA-array from Superarray that contains a limited number of genes (96 genes) related to drug metabolism, and a custom-made cDNA microarray that contains a higher number of genes (300 genes, including some genes from Superarray) related to mechanisms of carcinogenesis or chemoprevention. Real-time PCR and enzyme activity assays were additionally performed to confirm selected array results. Treatment of cells with AE resulted in 30 and 46 genes expressed over cut-off values (>or=1.5- or <or=0.7-fold) in Superarray and custom array, respectively. Of 87 genes spotted on both arrays, 4 genes (CYP3A7, CYP4F3, CHST7, GSTT2) were regulated with similar directional changes. Expression of selected phase II genes (GSTP1, GSTT2, GSTA4, UGT1A1, UGT2B7), regulated on either array, was confirmed by real-time PCR. The enzyme activities of glutathione S-transferases and UDP-glucuronosyltransferases were altered by treatment of LT97 cells with AE. The observed altered gene expression patterns in LT97 cells, resulting from AE treatment, points to a possible protection of the cells against some toxicological insults.