Photodynamic therapy (PDT) is one of cancer treatments using a specific photosensitizer and a particular type of light. There have been many trials to improve the effectiveness of the therapy. Immunotoxin (IT), on the other hand, has been developed as a class of highly potent biopharmaceuticals designed as a molecular targeted therapy for the treatment of malignant tumor. However, the internalization of IT into cytoplasm remains as the big issue. In order to overcome this issue, NG-PDT is developed which target the cancer specific membrane protein by IT in combination of PDT. The authors challenges to develop more effective next generation-PDT.
We present here an example of NG-PDT using a saporin-conjugated antibody against the tumor specific membrane protein, Robo1, and a photosensitizer which generates reactive oxygen by light to destruct endocytic membranes. Though the treatment with IT only showed little effect on cancer cells examined, the addition of light illumination augmented the cytotoxic effect several tens of times. By longer exposure, we observed a significant effect even on a cancer cell line which has ten times less Robo1 expression.
Thus the results suggested that the NG-PDT widen the therapeutic measure both in the specific drug delivery and in the drug target.
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