Binding and penetration of methylated DNA into primary and transformed human cells

Tumor progression was shown to be accompanied by the circulation of aberrantly methylated DNA both in the plasma and at the surface of blood cells. As the methylated DNA of tumor suppression genes in blood is a carrier of potentially harmful genetic information, we have studied the stability of methylated DNA fragments in the extracellular space, their binding to the cell surface, and their penetration into cells. It has been shown that the methylated fragments of the RARbeta2 gene are more stable and penetrate into the primary and transformed cells at least twice as efficiently as the unmethylated fragments. The data obtained demonstrate the prevalence of methylated DNA in intracellular traffic compared to the same sequences of unmethylated DNA and, thus, a high transformation potential of methylated DNA.