Cancer is considered both a genetic and epigenetic disease. The best studied epigenetic mechanism in carcinogenesis is DNA methylation, a mechanism which inactivates tumor suppressor genes by methylating their promoters. A subclass of tumor suppressor genes that are often methylated in the process of carcinogenesis are the DNA repair genes. Accumulation of DNA damage is associated with cancer and thus inactivation of DNA repair genes promotes cancer formation. Methylation of DNA repair genes seems to be unique compared to the methylation of other tumor suppressor genes in that it not only promotes tumorigenesis, but at the same time influences the sensitivity of tumors to chemotherapies that are based on agents that damage DNA to kill cancer cells. This literature study summarizes the current knowledge regarding epigenetic inactivation of DNA repair genes and the subsequent progress that has been made coping with the acquired chemotherapy resistances.
Keywords: DNA repair, methylation, cancer, MGMT, BRCA1, MLH1