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Using Anthrax To Fight Cancer
StarEmperor writes "According to this BBC news article, scientists have used a version of the anthrax toxin to kill tumors in mice. The toxin was so effective that after just one treatment tumours were reduced in size by up to 92%."
The authors of the study have managed to modify the anthrax toxin (or one of its associated proteins?? I'm still reading the article) to specifically target the toxin to urokinase, a protein that is expressed on the cell surface. In cancerous cells, expression of this protein is dramaticly increased so the modified anthrax toxin will preferentially bind to and kill cancerous cells. Like any chemotherapy, some noncancerous cells will likely also be hit by the poison but hopefully less than in traditional chemotherapy.
Anthrax is a complex of three proteins: anthrax protective antigen, edema factor, and lethal factor. Anthrax works by binding onto the surface of a cell, then an endogenous protease cleaves the protective antigen, which allows the lethal factor to enter the cell where it acts as a protease chopping up the cell's proteins (notably those involved with cellular signaling) which kills the cell. The authors of the above study have replaced the old cleavage site in the anthrax protective antigen with one that is recognized and specifically cut by urokinase, which is dramaticly upregulated in cells that are cancerous. The result is that the anthrax toxin binds cells but is only cleaved by urokinase, not by whatever was cutting it before. So cells that are making lots of urokinase (cancer cells) cut more of the anthrax protective antigen which allows more of the anthrax lethal factor to enter the cell and chop up more proteins, which kills the cell. The down side is that all cells produce some level of urokinase, so a few noncanerous cells will also be killed by the anthrax toxin, but this sounds like it could be less than traditional chemotherapy. Anyway, this is an incredibly slick idea for combating cancer!