Apoptotic and anti-proliferative effects of fumonisin B sub(1) in human keratinocytes, fibroblasts, esophageal epithelial cells and hepatoma cells

Fumonisin B sub(1) is associated with various animal and human carcinomas and toxicoses, including leukoencelphalomalacia, hepatocarcinoma, pulmonary edema and esophageal carcinoma. We have examined the cellular effects of fumonisin B sub(1) in vitro using cellular model systems relevant to potential human target tissues. Although fumonisin B sub(1) has been described as a mitogen in Swiss 3T3 cells based on stimulation of [ super(3)H]thymidine incorporation, in the current work it was found that fumonisin B sub(1) inhibited incorporation of [ super(3)H]thymidine by cultured neonatal human keratinocytes and HepG2 human hepatocarcinoma cells at 10 super(-7) and 10 super(-4) M respectively. Fumonisin B sub(1) also inhibited clonal expansion of normal human keratinocytes and HET-1A human esophageal epithelial cells at 10 super(-5) M and growth in mass culture of normal human fibroblasts at 10 super(-7) M. The clonogenicity of normal human keratinocytes decreased to 45.5% of controls after exposure to 10 super(-4) M fumonisin B sub(1) for 2 days. However, no differences in the cell cycle distribution of cultured keratinocytes was noted after exposure to 10 super(-5) M fumonisin B sub(1) for 40 h. The viability of normal human keratinocytes and HET-1A cells decreased as a result of fumonisin B sub(1) treatment, as determined by a fluorescein diacetate/propidium iodide flow cytometric cell viability assay. Fumonisin B sub(1)-treated keratinocytes released nucleosomal DNA fragments into the medium 2-3 days after exposure to 10 super(-4) M fumonisin B sub(1) and increased DNA strand breaks were detected in attached keratinocytes exposed to 0-10 super(-4) M fumonisin B sub(1) using a terminal deoxynucleotidyl transferase-based immunochemical assay system. Furthermore, fumonisin B sub(1)-treated keratinocytes and HET-1A cells developed morphological features consistent with apoptosis, as determined by phase contrast microscopy, fluorescent microscopy of acridine orange stained cells and electron microscopy. These results are consistent with the occurrence of fumonisin B sub(1)-mediated apoptosis in vitro.