MGMT and glioblastoma: There is also evidence that defects in the mismatch repair (MMR) pathway can confer increased resistance to temozolomide independent of MGMT methylation status (31) with mutations in mutS homolog 6 (MSH6) (32) and aberrant expression of MMR proteins MSH6, mutS homolog 2 (MSH2), PMS2 postmeiotic segregation increased 2 (PMS2), and mutL homolog 1 (MLH1) reported in some glioblastoma specimens (33, 34).