MGMT and neoplasm: However, if MGMT is expressed in tumor cells, it will directly remove the methyl group from O6‐meG, causing the cells to become TMZ‐resistant.13 Every methyl group removed from O6‐meG is transferred to a cysteine residue within the active site of MGMT in a stoichiometric reaction, and this MGMT molecule is then inactivated and finally degraded.