COLOCALIZATION OF SURAMIN AND SERUM-ALBUMIN IN LYSOSOMES OF SURAMIN-TREATED HUMAN COLON-CANCER CELLS

Suramin is a polysulfonated compound currently under investigation for the treatment of various types of cancer, Pharmacokinetic studies fro m clinical trials in humans have shown that most of the circulating dr ug is associated with serum albumin. The objective of the present stud y was to investigate the intracellular localization of suramin and ser um albumin in human colon cancer cells (HT-29-D4) upon suramin treatme nt. For this purpose, combined gold labeling and autoradiographic meth ods were performed on HT-29-D4 cells grown in serum free medium contai ning both [H-3]suramin and colloidal gold-albumin, These morphological experiments demonstrated for the first time that suramin and serum al bumin were co-localized in the same cellular compartment (i.e. the lys osomal system) of the suramin-treated HT-29-D4 cells. The albumin-dire cted targeting of suramin in lysosomes may allow the drug to inhibit t he activity of several lysosomal hydrolases, resulting in a lysosomal storage disorder.