Carcinogenic cells establish themselves in the brain and form new tumors as they cling to capillary blood vessels and synthesize proteins that block the brain's natural defenses against them, according to a study published in Cell magazine.

The research, carried out at the Memorial Sloan Kettering Cancer Center and led by Spanish scientist Joan Massague, thus explains how metastasis works in the brain, and the process by which some carcinogenic cells escape from the original tumor and install themselves in other tissues and organs.

Metastasis is the most common cause of deaths from cancer, and brain tumors born of this process are 10 times more common than primary cancers.

Carcinogenic cells separate from the tumor where they originated and enter the blood flow to reach the brain, where many are killed by a protein emitted by cells called astrocytes.

The only ones that survive manage to produce another protein - Serpin - which acts as an antidote, according to Massague, who is also director of the Sloan Kettering Institute in New York.

After observing images of carcinogenic cells in mice brains, the researchers ascertained that the surviving cells grow clinging to capillary blood vessels "like a panda bear hugging a tree trunk," Massague said.

"This hugging is clearly essential," Dr. Massague said. "If a tumor cell detaches from its vessel, it gets killed by nearby astrocytes. By staying on, it gets nourished and protected, and may eventually start dividing to form a sheath around the vessel."

The discovery could convert these cells into the target of new drugs designed to diminish the risk of metastasis. EFE