MGMT and cancer: Even though DNMT inhibitors, such as 5-Aza and decitabine, have proven effective in re-expressing MGMT in cancer cells, the clinical advantage of the restored MGMT expression is doubtful [58-60] since tumors with the unmethylated promoter of MGMT gene appear significantly less susceptible to the cytotoxic effects of alkylating drugs [56,57,60].