Scientists provide explanation for how cancer spreads

I came across an interesting research paper about the possible origins of metastasis; bone marrow-derived cells fuse with normal and transformed intestinal stem cells.  The research by John Pawelek's team at Yale seems to indicate that metastasis begins when a cancer cells merges with a white blood cell, which then enters the bloodstream and moves to another part of the body.  Via after cancer, now what, who comment:

The fusion theory was first proposed in the early 1900s and has attracted a lot of scientific interest over the years. Pawelek and his colleagues began their research several years ago by fusing white blood cells with tumor cells. These experimental hybrids the researchers observed, were remarkably metastatic and lethal when implanted into mice. In addition, the scientists noted, some of the molecules the hybrids used to metastasize originated from white blood cells, and these molecules were the same as those used by metastatic cells in human cancers. Pawelek and his team then validated previous findings that hybridization occurs naturally in mice, and results in metastatic cancer.

This could be a really import finding, as it may direct development of drugs which inhibit metastasis when a tumor has been detected.