Protein triggers aggressive breast cancer

NEW YORK (Reuters Health) - Scientists have found that a gene called SATB1, which is crucial to the development of the immune system, reprograms the expression of more than 1000 other genes to fuel the growth and spread of breast cancer.

According to the scientists, breast cancer cells need SATB1 to become "metastatic" -- the stage when cancer cells break away from the original tumor and spread to other parts of the body.

Previous research has identified global changes in gene expression that occur during cancer progression, the team reports in the journal Nature this week. The mechanisms responsible for these changes, however, are poorly understood.

The new research suggests that SATB1 is a key contributing factor in the most aggressive forms of breast cancer.

In its normal role, SATB1 is a protein that acts as a genome organizer, which is critical for the development of infection-fighting T cells. The new findings indicate that SATB1 is expressed in breast cancer cells and once this occurs, it coordinates the expression of numerous genes to promote the spread of breast cancer to other parts of the body.

"SATB1's role in breast cancer is a new paradigm for the way tumors progress," study investigator Dr. Terumi Kohwi-Shigematsu, from the University of California at Berkeley, said in a statement.

In a mouse model, she and colleagues showed that knocking out SATB1 expression restored a more normal cell appearance and inhibited tumor growth and spread. By contrast, SATB1 expression in non-aggressive cells led to a more aggressive type capable of spreading.

"An important question is what turns on SATB1 during breast cancer progression," Kohwi-Shigematsu stated. "That's just the beginning of the things we really want to know."

"SATB1 may be useful as a therapeutic target for metastatic breast tissue," the scientists conclude.

SOURCE: Nature, March 13, 2008.