Epigenetic Control of Estrogen Receptor Expression and Tumor Suppressor Genes Is Modulated by Bioactive Food Compounds

Abstract

BACKGROUND: The tumor suppressor genes p15(INK)⁴(b) and p16(INK)⁴(a) as well as the estrogen receptor-α (ESR1) gene are abnormally methylated and expressed in colon cancer. The cancer-preventative abilities of several bioactive food components have been linked to their estrogenic and epigenetic activities. METHODS: The effect of folic acid, zebularine, resveratrol, genistein and epigallocatechin-3-gallate (EGCG) on tumor cell growth, promoter methylation of ESR1, p15(INK)⁴(b) and p16(INK)⁴(a) and gene expression of ESR1 and ESR2 was analyzed in Caco-2 cells. Gene expression was measured using real-time PCR, and promoter CpG methylation was assessed using bisulfite conversion and methylation-specific PCR. RESULTS: After exposure to a high concentration of folic acid (20 μmol/l), enhanced cancer cell growth and concomitant increased methylation of the ESR1 (3.6-fold), p16(INK)⁴(a) and p15(INK)⁴(b) promoters was observed. A lower concentration of folic acid (2 μmol/l) decreased cell growth. The phytoestrogens genistein and resveratrol enhanced expression of ESR1 (genistein 200 μmol/l: 2.1-fold; resveratrol 50 μmol/l: 6.3-fold) and ESR2 (2.6- and 3.6-fold, respectively). Genistein and resveratrol treatment increased promoter methylation of ESR1 (genistein 200 μmol/l: 2.9-fold; resveratrol 50 μmol/l: 1.4-fold). For p16(INK)⁴(a), increased methylation was found after exposure to 10 μmol/l resveratrol, but for p15(INK)⁴(b), decreased methylation was found. Both components showed growth-inhibitory activities. For EGCG, growth inhibition at 100 μmol/l and suppressed promoter methylation of tumor suppressor genes (p16(INK)⁴(a): 0.9-fold; p15(INK)⁴(b): 0.6-fold) was seen. CONCLUSIONS: Our results show that these food compounds regulate ESR and tumor suppressor gene expression by multiple mechanisms including epigenetic processes. An improved understanding of these epigenetic effects could therefore support specific dietary concepts of epigenetic cancer prevention and intervention.