Researchers have found that patients with ovarian cancer who experienced symptoms of depression and stress had elevated levels of an enzyme associated with the spread of cancer in macrophages, influential cells in the tumor microenvironment. The enzyme, MMP9, is a matrix metalloproteinase, which can induce cancer cells to invade and metastasize. The study included 56 women, and the findings appeared in the November 1 Clinical Cancer Research.

Dr. Susan K. Lutgendorf of the University of Iowa and her colleagues found that depressive symptoms, chronic stress, and low social support were strongly associated with increased levels of MMP9 in tumor-associated macrophages. Conversely, patients who had higher levels of social support had lower levels of MMP9 and VEGF, a growth factor that promotes the development of tumor blood vessels.

To look more closely at the mechanism by which these signals are elevated, the researchers exposed macrophages in vitro to hormones released during depression and stress, norepinephrine and cortisol, at concentrations similar to those found in vivo when a person is under stress. They found that this exposure increased production of MMP9 in the cells.

"These findings provide a new understanding of biobehavioral influences on the tumor microenvironment and may have implications for patient outcome and targeted pharmacologic and/or behavioral interventions for ovarian cancer patients," the researchers wrote.