One major problem in the treatment of cancers using chemotherapeutic agents is the occurrence of resistance against the compound used. Here we report a pilot study to investigate this problem in more detail using Pharmacomethylomics" approach. The model used in the current study consists of a set of three cell lines ("Glc4", "Tera" and "A2780") and derived cell lines showing resistance against elevated concentrations of the compounds Doxorubicin and Cisplatin in cell culture.The methylation status of promoter sequences of a set of 10 genes involved in DNA repair pathways was investigated using a highly specific SybrGreen based real-time MSP. Each promoter region was represented by two different pairs of primers. In vitro methylated DNA was used as a positive control for the technical performance (single band in agarose gels; single melting peak indicating the expected melting temperature; no signal in no template controls) of the assays applied.Using the described experimental set-up, we could show that the genes FancG (NM_004629), RAD9A (NM_004584), RecQL5 (NM_001003715), XRCC3 (NM_005432), and HUS1 (NM_004507) show at least three-fold higher level of methylation in the resistant cell lines compared to their sensitive counterparts.The findings presented here indicate that studying the methylation status of the promoters of genes involved in DNA repair pathways may contribute to a better understanding of the development of drug resistance against chemotherapy in patients.

[First AACR International Conference on Molecular Diagnostics in Cancer Therapeutic Development, Sep 12-15, 2006]