Courtesy of pathologist Richard Klemke of the University of California, San Diego.

Zebrafish are showing scientists how cancer spreads to other parts of the body. By injecting the tiny, transparent fish with human breast cancer cells, researchers can watch blood vessels (green) grow toward a tumor (red)-a key step in cancer metastasis. The technique has helped them identify two proteins needed for cancer cells to invade the bloodstream and may aid the search for medicines that slow or stop the spread of the disease.

This work also was supported by NIH's National Cancer Institute.

Featured in the November 21, 2007, issue of Biomedical Beat.