RETROVIRAL GENE-TRANSFER IS INHIBITED BY CHONDROITIN SULFATE PROTEOGLYCANS GLYCOSAMINOGLYCANS IN MALIGNANT PLEURAL EFFUSIONS

Gene therapy may be an important adjuvant for treating cancer in the p leural space. The initial results of retroviral gene transfer to cance r cells in malignant pleural effusions revealed that transduction was markedly inhibited, and studies to characterize the inhibitory factor( s) were performed. The inhibition was contained within the soluble, ra ther than cellular, components of the effusions and was demonstrated w ith amphotropic, gibbon ape leukemia virus, and vesicular stomatitis v irus-glycoprotein pseudotyped retroviral vectors. After excluding comp lement proteins, a series of studies identified chondroitin sulfates ( CSs) as the inhibitory substances. First, treatment of the effusions w ith mammmalian hyaluronidase or chondroitinases, but not Streptomyces hyaluronidase, abolished the inhibitory activity, Second, addition of exogenous CS glycosaminoglycans mimicked the inhibition observed with pleural effusions. Third, immunoassays and biochemical analyses of mal ignant pleural effusion specimens revealed CS in relevant concentratio ns within pleural fluid. Fourth, proteoglycans/glycosaminoglycans isol ated from the effusions inhibited retroviral gene transfer. Analyses o f the mechanism of inhibition indicate that the chondroitin sulfates i nteract with vector in solution rather than at the target cell surface . These results suggest that drainage of the malignant pleural effusio n, and perhaps enzymatic pretreatment of the pleural cavity, will be n ecessary for efficient retroviral vector mediated gene delivery to ple ural metastases.