They were looking for drugs to treat the inflammation seen in Crohn's disease and ulcerative colitis. They tested a compound called a PPAR-gamma modulator. It would never normally have been thought of as a cancer drug, or in fact a drug of any kind. They ran several tests and found the compound killed pretty much every epithelial tumor cell lines they have seen. Epithelial cells line organs such as the colon, and also make up skin.
They reported in the journal International Cancer Research that it killed colon tumors in mice without making the mice sick. The compound worked in much the same way as the taxane drugs, including Taxol, which were originally derived from Pacific yew trees. It targets part of the cell cytoskeleton called tubulin. Tubulin is used to build microtubules, which in turn make up the cell's structure.
Destroying it kills the cell, but cancer cells eventually evolve mechanisms to pump out the drugs that do this, a problem called resistance. Resistance to anti-tubulin therapies, like Taxol, is a huge problem in many cancers. They see this as another way to get to the tubulin. The PPAR-gamma compound does this in a different way from the taxanes, which might mean it could overcome the resistance that tumor cells often develop to chemotherapy.
Most of the drugs like Taxol affect the ability of tubulin to form into microtubules. This doesn't do that -- it causes the tubulin itself to disappear. They do not know why. They planned to do more safety tests in mice. As the compound is already patented, the team will probably have to design something slightly different to be able to patent it as a new drug.
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http://cancerfocus.org/forum/showthread.php?t=3440