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Lipopolyamine treatment increases the efficacy of intoxication with saporin and an anticancer saporin conjugate
Author(s) -
Geden Sandra E.,
Gardner Richard A.,
Fabbrini M. Serena,
Ohashi Masato,
Phanstiel IV Otto,
Teter Ken
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.06008.x
Subject(s) - saporin , immunotoxin , endocytosis , endosome , ribosome inactivating protein , ricin , microbiology and biotechnology , chemistry , endocytic cycle , biology , biochemistry , pharmacology , cytotoxicity , cell , toxin , in vitro , ribosome , rna , gene
Saporin is a type I ribosome‐inactivating protein that is often appended with a cell‐binding domain to specifically target and kill cancer cells. Urokinase plasminogen activator (uPA)‐saporin, for example, is an anticancer toxin that consists of a chemical conjugate between the human uPA and native saporin. Both saporin and uPA‐saporin enter the target cell by endocytosis and must then escape the endomembrane system to reach the cytosolic ribosomes. The latter process may represent a rate‐limiting step for intoxication and would therefore directly affect toxin potency. In the present study, we document two treatments (shock with dimethylsulfoxide and lipopolyamine coadministration) that generate substantial cellular sensitization to saporin/uPA‐saporin. With the use of lysosome‐endosome X (LEX)1 and LEX2 mutant cell lines, an endosomal trafficking step preceding cargo delivery to the late endosomes was identified as a major site for the dimethylsulfoxide‐facilitated entry of saporin into the cytosol. Dimethylsulfoxide and lipopolyamines are known to disrupt the integrity of endosome membranes, so these reagents could facilitate the rapid movement of toxin from permeabilized endosomes to the cytosol. However, the same pattern of toxin sensitization was not observed for dimethylsulfoxide‐ or lipopolyamine‐treated cells exposed to diphtheria toxin, ricin, or the catalytic A chain of ricin. The sensitization effects were thus specific for saporin, suggesting a novel mechanism of saporin translocation by endosome disruption. Lipopolyamines have been developed as in vivo gene therapy vectors; thus, lipopolyamine coadministration with uPA‐saporin or other saporin conjugates could represent a new approach for anticancer toxin treatments.