Statins and bisphosphonates are epigenetically active drugs

Epigenetics is an evolving research area having tremendous influence on the understanding of human health and disease. It was found that epigenetic processes, especially changes of DNA-methylation, have far reaching effects on fetal development, aging, the development of chronic diseases and tumors. Epigenetic DNA-methylation affects the cytosines of cytosine/guanosine dinucleotides (CpG), which can be methylated at the carbon-5 position of the pyrimidine ring. The methyl-moiety is transferred from S-adenosylmethionine to the cytosine by DNA (cytosine-5- )-methyl-transferases, usually during replication. Although the regulation of the methylation process is still an open question, the involvement of the RAS-RAF-MAPK-pathway is most likely. Methylation of the cytosines affects not only gene transcription and therewith the phenotype of cells and tissues but also the stability of the genome, which is of great importance for tumor progress. Statins as well as bisphosphonates are two of the most used drugs at all. Statins were developed for treatment of lipid disorders, while bisphosphonates were designed for treatment of osteoporosis. Both drugs influence, albeit in different sections, the synthesis of isoprene-moieties, which are required to anchor the "small GTP-binding proteins" at the cell membrane; only then a proper function of the proteins can be expected. The small GTP binding proteins, which include RAS and RAF, are central regulators of cell multiplication, behavior, differentiation and apoptosis. However, because statins affect the same cellular synthetic pathway as bisphosphonates, statins may not only improve lipid metabolism but also ameliorate bone metabolism. While the benefit of bisphosphonates for bone is well established, the impact of statins on bone metabolism is still an open question. The aim of the project is to show that bisphosphonates and statins, which both modulate the RAS/RAF-signal transduction pathway, can influence the epigenetic status of cells. To show this, we will study cell multiplication and apoptosis using biochemical techniques and differentiation by genome-wide gene expression. We assume that interruption of signal transduction by these drugs attenuates the expression of the DNA methylation machinery, leading to changes in the methylation status of the regulatory regions of genes. We expect promoter demethylation of the apoptosis-promoting gene FAS, the regulator of the osteoblastic differentiation DLX5 and the collagen cross-linker protein and tumor suppressor lysyl oxidase (LOX) as well as a concomitant increased expression of these genes. By use of these drugs as well as by other inhibitors of the RAS/FAF-pathway we will learn how epigenetic DNA-methylation is regulated. In addition, recent studies suggest that the methylation status of individual CpGs is important for gene regulation. Therefore, we intend to study the DNA methylation pattern at the level of individual nucleotides and how it is altered by the various drugs. A proof that the two drugs are epigenetically active would have far-reaching consequences. On the one hand, it will lead to a new understanding of the mechanisms of action and secondly a new risk assessment will become necessary as epigenetic modifications can have long-term effects. This is particularly important because both drugs are used for a longer period and minor epigenetic changes may accumulate in tissues. The accumulated epigenetic modifications might lead to significant changes in gene expression and, therefore, might influence physiological metabolic processes.

Epigenetics contributes significantly to the understanding of diseases. Epigenetic DNA methylation is the modification of cytosines by methyl-moieties in the context of cytosine/guanosine-dinucleotides (CpG). The transfer of the methyl-moiety from S-adenosyl-methionine to cytosines at the position 5 of the pyrimidine ring is accomplished DNMT1 (DNA-(cytosine-5-)-Methyl-transferase 1), usually during replication.Statins and bisphosphonates are widely used drugs. Statins are administered for the treatment of disordes of the lipid metabolism, while bisphosphonates are used to treat and prevent bone fracture diseases. However, far-reaching epidemiologic studies suggest that both medications have beneficial effects for the treatment and prevention of neoplastic diseases, although their potency may be restricted to specific neoplasms. Many neoplasms are characterized by mutations or changes in the activity of small-GTP-binding proteins, i.e. RAS and RAF that play a central role in the regulation of cell multiplication, cell function, differentiation and apoptosis. These proteins may contribute to an aberrant DNA-methylation of promoters from tumor suppressor genes. As a consequence, these genes will be inactivated.