Photochemical internalization of scFvCD133/rGelonin, a novel CD133-targeting immunotoxin

What is it about?

In this work we developed and explored a novel CD133-targeting immunotoxin (IT) for use in combination with the endosomal escape method photochemical internalization (PCI). scFvCD133/rGelonin was recombinantly constructed by fusing a gene (scFvCD133) encoding the antibody-fragment (scFv) that targets both non-glycosylated and glycosylated forms of both human and murine CD133/prominin-1 to a gene encoding the ribosome-inactivating protein (RIP) gelonin (rGelonin). Selective binding and intracellular accumulation of scFvCD133/rGelonin was confirmed by using flow cytometry and fluorescence microscopy. PCI of scFvCD133/rGelonin was explored in CD133high and CD133low cell lines and a CD133neg cell line, where cytotoxicity was evaluated by the MTT assay. scFvCD133/rGelonin exhibited superior binding to and a higher accumulation in CD133high cells compared to CD133low cells. No cytotoxic responses were detected in either CD133high or CD133low cells after 72 h incubation with <100 nM scFvCD133/rGelonin alone. PCI of scFvCD133/rGelonin induced strong reduction of viability compared to PCI of rGelonin. Strikingly, PCI of scFvCD133/rGelonin exceeded the cytotoxicity of PCI of rGelonin also in CD133low cells. In conclusion, PCI promotes strong cytotoxic activity of the per se non-toxic scFvCD133/rGelonin in both CD133high and CD133low cancer cells.

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Why is it important?

CD133 is expressed in cancer stem cells but also in normal stem cells. The PCI technology can be used for light-controlled activation of CD133-targeting therapeutics that alone is non-toxic.

Perspectives