Fumonisin B₁ induces global DNA hypermethylation in human glioblastoma U87MG cells

Fumonisin B₁ (FB₁) is a common maize contaminant known to induce toxicity and carcinogenesis in humans and animals; however, its epigenetic mechanisms remain poorly understood. DNA methylation is an epigenetic modification that controls gene expression through DNA methyltransferase and demethylase activities. In this study, the effect of FB₁ on DNA methylation in brain glioblastoma U87MG cells was evaluated. FB₁ cytotoxicity was determined by the MTT assay and an IC₅₀ value of 880 µM FB₁ was obtained. The ELISA-based global DNA methylation assay displayed an increase in 5-methylcytosine levels. qPCR and western blot revealed a significant increase in DNA methyltransferase expressions (DNMT1, DNMT3A, and DNMT3B) and a significant decrease in demethylase expression (MBD2). This data indicates that FB₁ induces global DNA hypermethylation, through increased DNA methyltransferase expressions and DNA demethylase suppression in U87MG cells, thus suggesting an alternative mechanism of toxicity.