Abstract: High grade gliomas are always the research focus in the field of neurosurgery due to their poor prognosis despite the current standard therapeutic regimen of surgical resection followed by radiation therapy and chemotherapy. Alkylating agent temozolomide has been established as the  standard chemotherapy while its resistance inevitable during treatment. This phenomenon seriously influences the prognosis of patients suffering from  high grade gliomas. This review aims to elucidate temozolomide chemoresistance mechanisms through three chapters including O6-methylguanine-DNA methyltransferase (MGMT) methylation, mismatch repair mutation and epigenetic regulation consisting of p21, chromatin and histone, Y-box binding  protein-1 and microRNAs.

Key words: high&ensp, grade&ensp, glioma, &ensp, temozolomide, &ensp, resistance, &ensp, O6-methylguanine-DNA&ensp, methyltransferase, &ensp, mismatch&ensp, repair