Author(s): Mawussi Adjakly 1 2 3 , Rémy Bosviel 1 2 3 , Nadège Rabiau 1 2 3 , Jean-Paul Boiteux 2 3 4 , Yves-Jean Bignon [**] 5 , Laurent Guy 2 3 4 , Dominique Bernard-Gallon 1 2 3
DNA hypermethylation; prostate cancer; soy phytoestrogens
Prostate cancer is the leading cause of cancer-related death in males and the second cause of death by cancer in the world  . In Europe, the number of prostate cancer cases detected in 2008 was 3.4 million among which there were 70,800 deaths reported. In France, it represented 65,860 new cases of cancer in 2008  . The incidence of prostate cancer is increasing in numerous western countries; however, the specific mortality remains stable in these countries where there is an early diagnosis  . The incidence of hormone-dependent cancers, such as those of the breast and prostate, is much lower in eastern countries such as China and Japan in comparison with the western world. Several studies suggested that that soy food consumption could be associated with a lower risk of prostate cancer [4-6] . Diet is believed to have a major effect on disease risk and one group of compounds, the phytoestrogens, which are consumed in large amounts in Asian populations, have been implicated in cancer protection. As the soy isoflavones, genistein and daidzein have been the most widely studied, these compounds are believed to be a potent anticancer agent and have been shown to possess anticancer properties. Genistein and daidzein have been found to inhibit the growth and survival of cancer cells derived from the human prostate  . The growth-inhibitory effects of these compounds may be linked to their ability to induce apoptosis and activation of the caspase pathway  . It has been shown that genistein and daidzein decrease the expression of many genes implicated in the cell cycle and angiogenesis  . DNA methylation is an example of one of the epigenetic events that occurs, in the human genome on cytosine bases in a CpG dinucleotide. The methylation of CpG located in the promoters of genes has important effects on gene expression. Several studies reported that promoter methylation induce a silencing of oncosuppressors in prostate cancer cell lines [10-13] . Inactivation of many genes by DNA methylation has been also observed in the serum and urine from prostate cancer patients [14-18] .
It has been found that soy phytoestrogens, genistein and daidzein, have the ability to modulate the expression of many genes by epigenetic mechanisms. Several works have reported that prostate cancer cell line treatment with genistein induces a re-expression of many genes such as BTG3 , RAR [beta]Î² and MGMT [19,20] . A recent study, in our laboratory, has showed that genistein and daidzein induced a reversion of hypermethylation of GSTP1 , RASSF1A , EPHB2 and BRCA1 genes observed on prostate cancer cell lines  .
In order to clarify the capacity of soy phytoestrogens to modulate the expression of genes by DNA hypermethylation reversion, we studied their effects on the promoters of GSTP1, EPHB2, BRCA1 and BRCA2. Using a quantitative technique which is based on DNA digestion followed by real-time...