Cytotoxic effects of fumonisin B_(1) on the ultrastructure of a human oesophageal carcinoma cell line - an in vitro study
Mycotoxin Research Unit, Nelson R Mandela School of Medicine, Faculty of Health Sciences, University of Natal, Congella, Durban, South Africa
AIM: To determine the ultrastructural pathological effects of fumonisin B1 (FB1) on a squamous cell carcinoma cell line using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In addition, metabolised FB1 was immunochemically probed using a monoclonal antibody. METHODS: The SNO epithelial cells were grown to confluency in culture medium supplemented with 5% foetal calf serum, 1% L-glutamine and 1% penstrep fungizone. The cells were then treated with FB1 at concentrations of 1 µM, 2 µM, 4µM, 8µM and 16µM for 24 hrs. Control cells received no toxin treatment. After 24 hrs, the flasks were washed with Hank’s balanced salt solution and the cells were fixed in 1% glutaraldehyde for TEM and immunocytochemistry (ICC). Sections were cut and viewed (ultrastructure and immunolocalisation) using a JEOL-JEM 100S electron microscope. A monoclonal FB1 antibody was used to probe for metabolised toxin. SEM was accomplished using a Hitachi S520 scanning electron microscope. RESULTS: The toxin treated SNO cells displayed marked pathological changes which included plasma membrane damage, swelling or microsegregation of the nucleus, microsegregation of the nucleolus and swelling and elongation of mitochondria. These cytotoxic effects were attributed to FB1, since FB1 was actively metabolised as evidenced by immunolocalised FB1 in the SNO cells. The results also indicate the FB1 preferentially targets membranes, the nucleus and mitochondria of cells. CONCLUSIONS: The cellular pathology observed suggests that the mitochondria, the nucleus and nucleolus are important in oesophageal carcinogenesis. The high levels of FB1 label found in these organelles show that ultrastructural alterations are due to this toxin and that FB1 may exert its carcinogenic effect through covalent binding directly to these organelles.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 797 (Manifestations of cancer).