Abstract
Gangliosides are sialic acid-containing glycolipids expressed on plasma membranes from nearly all vertebrate cells. The expression of ganglioside GD3, which plays essential roles in normal brain development, decreases in adults but is up regulated in neuroectodermal and epithelial derived cancers. R24 antibody, directed against ganglioside GD3, is a validated tumor target which is specifically endocytosed and accumulated in endosomes. Here, we exploit the internalization feature of the R24 antibody for the selective delivery of saporin, a ribosome-inactivating protein, to GD3-expressing cells [human (SK-Mel-28) and mouse (B16) melanoma cells and Chinese hamster ovary (CHO)-K1 cells]. This immunotoxin showed a specific cytotoxicity on tumor cells grew on 2D monolayers, which was further evident by the lack of any effect on GD3-negative cells. To estimate the potential antitumor activity of R24-saporin complex, we also evaluated the effect of the immunotoxin on the clonogenic growth of SK-Mel-28 and CHO-K1GD3+ cells cultured in attachment-free conditions. A drastic growth inhibition (>80–90%) of the cell colonies was reached after 3 days of immunotoxin treatment. By the contrary, colonies continue to growth at the same concentration of the immuntoxin, but in the absence of R24 antibody, or in the absence of both immunotoxin and R24, undoubtedly indicating the specificity of the effect observed. Thus, the ganglioside GD3 emerge as a novel and attractive class of cell surface molecule for targeted delivery of cytotoxic agents and, therefore, provides a rationale for future therapeutic intervention in cancer.
Highlights
Gangliosides are a heterogeneous family of sialic acid-containing glycosphingolipids present on plasma membranes, where they participate in cell-surface events such as modulation of growth factor receptors and cell-to-cell and cell-to matrix interactions [1]
We demonstrated that the R24 antibody is rapidly endocytosed after binding to the disialo ganglioside GD3, sorted to early endosomes, latter accumulated in the recycling endosome and transported back to the plasma membrane [8]
Similar binding and internalization of R24 antibody bound to GD3 was observed in human SK-Mel-28 melanoma cells, which mainly express the ganglioside GD3 and GM3 (Fig. 1)
Summary
Gangliosides are a heterogeneous family of sialic acid-containing glycosphingolipids present on plasma membranes, where they participate in cell-surface events such as modulation of growth factor receptors and cell-to-cell and cell-to matrix interactions [1]. Aberrant glycosilation occurs in essentially all types of experimental and human cancers, and many glycosil epitopes constitute tumor-associated antigens [2]. Especially those of neuroectodermal origin (like melanoma and neuroblastoma), often result in elevated expression of gangliosides such us GM2, GD2, GD3 and 9-O-acetyl-GD3 [3,4]. Several types of targeted therapy need that the antibody remains at the cell surface to mediate cytotoxicity, but other therapies need internalization and drug release into the cell [5]. Anti-ganglioside antibodies are available, like anti-GD2 for neuroblastoma [6] and anti-GD3 for melanoma [7]. Mouse monoclonal R24 antibody (IgG3), directed against ganglioside GD3, is a validated tumor targeting agent that shows strong cell surface reactivity with a range of human melanoma cell lines and other epithelial cancer tumor cells [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
