University of California-San Francisco researchers, led by Professor Konstantin Stoletov, said finding a way to suppress the newly identified proteins might stop the movement of cancer cells into the blood vessels and, therefore, the cancer's subsequent metastasis.

The scientists developed a zebrafish that makes a green fluorescent protein only in its blood vessels, allowing scientists to view tumor-induced blood vessel formation. They injected the fish with inflammatory breast cancer cells that were tagged in different colors to study the tumor progression.

The researchers found the two proteins work together to allow cancerous breast tumors to enter the blood vessels, thus promoting metastasis. The first stimulates new blood vessel formation; the second promotes cell movement or migration.

The scientists determined neither protein by itself allows the cancerous tumor to enter the blood vessels.

The study appears in the early online edition of the Proceedings of the National Academy of Science.