MGMT and neoplasm: In contrast, no additive effects of 6-MP and TMZ combination on the levels of O6-mG than TMZ treatment alone were observed in the tumor-adjacent or normal brain tissues (Supplementary Fig. 11n, o), probably due to the expression of MGMT which effectively removes O6-mG in normal brain tissues, therefore protecting normal brain tissues from damaging by 6-MP and TMZ combination treatment.