MRC1 and glioblastoma: While the loss of the MMR pathway will lead to microsatellite instability (MSI), in GBM, the importance of MMR is primarily defined by three aspects: resistance to alkylating chemotherapy is driven by MMR defects, MSI might predict immunotherapeutic response, and important proteins involved in MMR mediate TMZ sensitivity, especially in patients who lack MGMT expression [151].