The Effect of Ascorbic Acid over the Etoposide- and Temozolomide-Mediated Cytotoxicity in Glioblastoma Cell Culture: A Molecular Study

Abstract

AIM: Glioblastoma (GBM) is one of the lethal central nervous system tumors. One of the widely used chemical agents for the treatment of glioblastoma is temozolomide. It is an orally administered, deoxyribonucleic acid (DNA) alkylating agent. DNA alkylation triggers the death of tumor cells. However, some tumor cells are able to repair this type of DNA damage and thus lower the therapeutic effect of temozolomide. Laboratory and clinical studies indicate that temozolomide's anticancer effects might be strengthened when combined with other chemotherapeutic agents like etoposide or antioxidant agents like ascorbic acid. In this study, we aimed to evaluate the cytotoxic and oxidative stress effects of ascorbic acid (1000 mu M), temozolomide (100 mu M) and etoposide (25 mu M) agents alone and in dual and triple combinations in a glioblastoma U87 MG cell culture. MATERIAL and METHODS: The cytotoxic and oxidative stress effects were investigated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis methods. RESULTS: Cytotoxicity tests showed that etoposide, temozolomide, "etoposide+ascorbic acid", "temozolomide+ascorbic acid", "temozolomide+etoposide" and "temozolomide+etoposide+ascorbic acid" combinations have anti-proliferative effects. The maximum anti-proliferation response was observed in the "temozolomide+etoposide+ascorbic acid"-added group. Similarly LCMS/MS analyses showed that minimum oxidative DNA damage occurred in the "temozolomide+etoposide+ascorbic acid"-added group. CONCLUSION: Ascorbic acid decreases the cytotoxic and genotoxic effect of etoposide and etoposide-temozolomide combination but it has no meaningful effect on temozolomide's toxicity.