Advantages and Disadvantages of Drug Combination Treatment: Riluzole, Metformin and Dexamethasone Effect on Glioblastoma Cell.

Background/aim: In glioblastoma multiforme (GBM), a deadly brain tumor, glucose is one of the main fuels for accelerated growth. Patients with GBM are also exposed to excess glucose through hyperglycemia in diabetes mellitus. In addition, dexamethasone (Dex), a corticosteroid commonly administered for controlling cerebral oedema, causes additional excess glucose. Therefore, targeting glucose metabolism is an attractive therapeutic intervention for GBM treatment. We have recently shown that riluzole (Ril), a drug used to treat amyotrophic lateral sclerosis (ALS), has an effect on some detrimental Dex-induced metabolic changes in GBM. Therefore, we examined the effect of the combination of metformin (Met), widely used to treat type 2 diabetes, and Ril on GBM cells.

Materials and methods: The 3-(4, 5-dimethylthiazol)-2, 5-diphenyltetrazolium bromide (MTT) assay was used to determine cell viability of U87MG after treatment with Ril, Met, Ril plus Met (Ril+Met) and the addition of Dex to this co-treatment. Cell migration was assessed by the xCELLigence system, matrix metalloproteinase 2 (MMP2) activation by zymography assay and gene expression by real-time polymerase chain reaction (RT-PCR).

Results: Co-treatment with Ril and Met was effective in killing GBM cells and reducing the expression of genes involved in glucose and stem cell metabolism. Furthermore, combination of Ril and Met reduced MMP2 activation. But co-administration increased the migration of U87MG cells. The addition of Dex to this combination reversed the unfavorable effects of Ril+Met on cell migration.

Conclusion: Ril+Met co-treatment had a positive effect in terms of GBM cell death, decreased expression of genes involved in glucose metabolism and stemness, and reduced MMP2 activation. Disadvantage of Ril+Met treatment was increased cell migration. Taken together, these drug combinations may also allow the reduction of the concentration of Dex to minimize its side effects.