In vitro effects of polyphenols on colorectal cancer cells

AIM: To investigate the effects of quercetin and genistein on colon cancer cell proliferation and their estrogen receptor beta( ER beta) expression. METHODS: Colon cancer cells were stably transfected with a mammalian expression vector to overexpress ER beta ( HCT8-beta 8-expressing cells) or a control vector ( HCT8-pSV2neo-expressing cells). The proliferation of these cells was examined after treatment with quercetin or genistein (5-100 mu mol/L), or 10 nmol/L 17 beta-estradiol (17 beta-E2). Cell viability was examined by acridine orange staining following treatments for 48 or 144 h. Effects of quercetin and genistein on ER beta transcriptional transactivation were examined by luciferase activity in HCT8-beta 8-expressing cells transiently transfected with a pEREtkLUC reporter vector. In addition, the regulation of ER beta transcription by phytoestrogens and 17 beta-E2 was examined by quantitative polymerase chain reaction. RESULTS: Proliferation of HCT8-beta 8-expressing cells was not reduced low doses (5 mu mol/L) of quercetin and genistein, while it was reduced at 25-50 mu mol/L with an effect similar to 10 nmol/L 17 beta-E2. Treatment with doses of phytoestrogens >= 75 mu mol/L completely blocked cell growth and reduced overall cell counts, however no effects at any dose were observed in HCT8-pSV2neoexpressing cells. These results were supported by viability staining that revealed acridine orange-stained lysosomes with high doses or extended treatment periods. Genistein and quercetin (50 mu mol/L) significantly increased ER-responsive luciferase activity similar to 10 nmol/L 17 beta-E2 (P < 0.05). Furthermore, genistein and quercetin (50 mu mol/L), as well as 10 nmol/L 17 beta-E2 significantly increased ER beta mRNA levels in HCT8-beta 8expressing cells (P < 0.05). In addition, treatment of HCT8-pSV2neo-expressing cells with 50 mu mol/L quercetin or 10 nmol/L 17 beta-E2 significantly increased ER beta mRNA levels compared to untreated controls (P < 0.05), though the absolute levels were much lower than in HCT8-beta 8-expressing cells. CONCLUSION: The antitumorigenic effects of the phytoestrogenic compounds quercetin and genistein on colon cancers cells occur through ER beta activity and expression. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.