The antagonistic effects of temozolomide and trichostatin a combination on MGMT and DNA mismatch repair pathways in Glioblastoma

Glioblastoma is the most aggressive and fatal form of brain cancer. Despite new advancements in treatment, the desired outcomes have not been achieved. Temozolomide (TMZ) is the first-choice treatment for the last two decades and has improved survival rates. Emerging studies have shown that targeting epigenetics in glioblastoma can be beneficial when combined with clinically used treatments. Trichostatin A (TSA), a histone deacetylase inhibitor, has anti-cancer properties in various cancers. No data concerning the TMZ and TSA relationship was shown previously in glioblastoma therefore, we aimed to determine the likely therapeutic effect of the TMZ and TSA combination in glioblastoma. The T98G and U-373 MG, glioblastoma cell lines, were used in this study. TMZ and TSA cytotoxicity and combination index were performed by MTT assay. The expression of DNA repair genes (MGMT, MLH-1, PMS2, MSH2 and MSH6) was detected using RTPCR. One-way analysis of variance (ANOVA) was used for statistical analysis. Combination index calculations revealed antagonistic effects of TMZ and TSA in terms of cytotoxicity. Antagonistic effects were more apparent in the T98G cell line, which is expressing MGMT relatively higher. MGMT and DNA Mismatch Repair (MMR) genes were upregulated in the T98G cell line, whereas downregulated in the U373-MG cell lines under TMZ and TSA combination treatment. It is concluded that MGMT might be playing a more active part than MMR genes in TMZ resistance to TMZ and TSA antagonism. This is the first study elucidating the TMZ and TSA relationship in cancer cell lines