APOPTOTIC AND ANTIPROLIFERATIVE EFFECTS OF FUMONISIN B-1 IN HUMAN KERATINOCYTES, FIBROBLASTS, ESOPHAGEAL EPITHELIAL-CELLS AND HEPATOMA-CELLS

Fumonisin B-1 is associated with various animal and human carcinomas a nd toxicoses, including leukoencelphalomalacia, hepatocarcinoma, pulmo nary edema and esophageal carcinoma, We have examined the cellular eff ects of fumonisin B-1 in vitro using cellular model systems relevant t o potential human target tissues, Although fumonisin B-1 has been desc ribed as a mitogen in Swiss 3T3 cells based on stimulation of [H-3]thy midine incorporation, in the current work it was found that fumonisin B-1 inhibited incorporation of [H-3]thymidine by cultured neonatal hum an keratinocytes and HepG2 human hepatocarcinoma cells at 10(-7) and 1 0(-4) M respectively, Fumonisin B-1 also inhibited clonal expansion of normal human keratinocytes and HET-IA human esophageal epithelial cel ls at 10(-5) M and growth in mass culture of normal human fibroblasts at 10(-7) M. The clonogenicity of normal human keratinocytes decreased to 45.5% of controls after exposure to 10(-4) M fumonisin B-1 for 2 d ays, However, no differences in the cell cycle distribution of culture d keratinocytes was noted after exposure to 10(-5) M fumonisin B-1 for 40 h., The viability of normal human keratinocytes and HET-1A cells d ecreased as a result of fumonisin B-1 treatment, as determined by a fl uorescein diacetate/propidium iodide flow cytometric cell viability as say, Fumonisin B1-treated keratinocytes released nucleosomal DNA fragm ents into the medium 2-3 days after exposure to 10(-4) M fumonisin B-1 and increased DNA strand breaks were detected in attached keratinocyt es exposed to 0-10(-4) M fumonisin B-1 using a terminal deoxynucleotid yl transferase-based immunochemical assay system, Furthermore, fumonis in B-1-treated keratinocytes and HET-1A cells developed morphological features consistent with apoptosis, as determined by phase contrast mi croscopy, fluorescent microscopy of acridine orange stained cells and electron microscopy, These results are consistent with the occurrence of fumonisin B-1-mediated apoptosis in vitro.