New breast cancer gene found

ANN ARBOR, Mich., July 27 (UPI) -- FOXP3, a gene that blocks the HER-2 protein linked to aggressive breast cancer, has been uncovered by U.S. researchers. Yang Liu and his colleagues at the University of Michigan Comprehensive Cancer Center were exploring FOXP3's role in autoimmune disease when they noticed that 90 percent of the female mice they had bred for their experiments and which lacked the FOXP3 gene were developing breast cancer. They also had high levels of ErbB2, the mouse equivalent of HER-2 in humans. Since breast cancer is rare in mice, they thought the gene must be responsible and decided to look at human breast cancer tissue to see if FOXP3 was present or absent. They examined 600 human breast cancer tissue samples and discovered that 80 percent of them did not contain FOXP3 and the gene was mutated in the rest. FOXP3 is located on the X chromosome, which means that a single mutation can effectively silence the gene and allow levels of HER-2 to rise. "FOXP3 defects promote cancer development," said Yang. "We do not know whether this is a genetic defect that puts women at higher risk. For treatment, this gene could be quite important, but for diagnosis, it's too early to tell." A report on the study was published in the current issue of the journal Cell.