In the November, 2004 issue of the journal Nature Medicine, the researchers report tumor cells that "overexpress" the protein Rab25 are more aggressive and associated with poorer outcome. Thus, Rab25 could represent a novel therapeutic target or marker of tumor behavior, they say.
The researchers matched tumor samples to outcomes in about 100 patients diagnosed with either breast or ovarian cancer and found that a low level of Rab25 protein on a patient's cancer sample was associated with a better clinical outcome in both cancer types. For example, patients with early stage (I and II) ovarian cancer who had low Rab25 tumor expression had an 80 percent survival five years after treatment, compared to 50 percent survival if Rab25 expression was high. In women with advanced breast cancer, a low level of Rab25 protein expression was associated with a 60 percent five-year survival, compared to 40 percent if Rab25 protein expression was high.
Adding this protein to other known molecular markers of progression could contribute to a "highly predictive test of outcome in breast or ovarian cancer," says the study's lead investigator, Gordon Mills, M.D., Ph.D., a professor and chair of the Department of Molecular Therapeutics at M. D. Anderson.
He adds that the protein might also, one day, be a target for cancer treatment. "We are pursuing Rab25 both as a test for outcomes and as a possible treatment."
Researchers from Lawrence Berkeley National Laboratory, the University of British Columbia, the University of California San Francisco, and Northwestern University participated in the research study, which was funded by the National Cancer Institute and the U. S. Department of Defense.