DNA Methylation and Soy Phytoestrogens: Quantitative Study in DU-145 and PC-3 Human Prostate Cancer Cell Lines

Abstract

Aim: DNA hypermethylation is an epigenetic mechanism which induces silencing of tumor-suppressor genes in prostate cancer. Many studies have reported that specific components of food plants like soy phytoestrogens may have protective effects against prostate carcinogenesis or progression. Genistein and daidzein, the major phytoestrogens, have been reported to have the ability to reverse DNA hypermethylation in cancer cell lines. The aim of this study was to investigate the potential demethylating effects of these two soy compounds on BRCA1, GSTP1, EPHB2 and BRCA2 promoter genes. Methods&materials: Prostate cell lines DU-145 and PC-3 were treated with genistein 40 µM, daidzein 110 µM, budesonide (methylating agent) 2 µM and 5-azacytidine (demethylating agent) 2 µM. In these two human prostate cancer cell lines we performed methylation quantification by using Methyl Profiler DNA methylation analysis. This technique is based on a methylation-specific digestion followed by quantitative PCR. We analyzed the corresponding protein expression by western blotting. Results: Soy phytoestrogens induced a demethylation of all promoter regions studied except for BRCA2, which is not methylated in control cell lines. An increase in their protein expression was also demonstrated by western blot analysis and corroborated the potential demethylating effect of soy phytoestrogens. Conclusion: This study showed that the soy phytoestrogens, genistein and daidzein, induce a decrease of methylation of BRCA1, GSTP1 and EPHB2 promoters. Therefore, soy phytoestrogens may have a protective effect on prostate cancer. However, more studies are needed in order to understand the mechanism by which genistein and daidzein have an inhibiting action on DNA methylation.

KEYWORDS::

• DNA hypermethylation
• prostate cancer
• soy phytoestrogens

Financial&competing interests disclosure

M Adjakly is the recipient of a grant from ARTP (Association pour la Recherche sur les Tumeurs de la Prostate) in 2010. The authors received financial support from La Ligue Contre Le Cancer (Comité du Puy de Dôme). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Additional information

Funding

M Adjakly is the recipient of a grant from ARTP (Association pour la Recherche sur les Tumeurs de la Prostate) in 2010. The authors received financial support from La Ligue Contre Le Cancer (Comité du Puy de Dôme). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.