Chronic Stress Agitates Ovarian Cancer in Mice

Chronic Stress Agitates Ovarian Cancer in Mice
Reducing Stress Seems to Slow Tumor Growth

When mice with ovarian cancer are stressed, their tumors grow and spread more quickly, but that effect can be blocked using a common heart disease medication, according to new laboratory study results.

Significance of results

The findings, published online July 23 in the journal Nature Medicine, provide the first measurable link between psychological stress and the biological processes that make ovarian tumors grow and spread, says the study's principal investigator Anil Sood, M.D., associate professor in M. D. Anderson's Department of Gynecologic Oncology and Department of Cancer Biology.

Research methods

Sood's research team created a stressful environment for mice infected with ovarian cancer by confining them to a small space for zero, two or six hours during the day.

The confinement caused the mice to produce the same stress hormones as humans produce. These "fight-or-flight" hormones are released when people are fearful or threatened and also are responsible for causing the heart to beat harder and faster.

Primary results

Sood and his colleagues found that, surprisingly, cancer cells make receptors for these stress hormones on their surface and that when these receptors are activated, they help form new blood vessels that feed tumors. This process, called angiogenesis, is known to allow tumors to grow and spread more rapidly.

After three weeks, the researchers measured the number and size of tumors in the mice.

The size of tumors was:

• The same in mice who spent no time in the confined space
• 2.5 times greater in the mice confined for two hours
• 3.6 times greater in mice confined for six hours

In addition, tumors spread to the liver or spleen in half of the confined mice but did not spread in mice who spent no time in the confined space.

Additional results

The researchers also gave the stressed mice a heart drug called propranolol, also known as a "beta blocker," which completely neutralized the effect of stress on tumor growth, says Sood, M. D. Anderson's director of ovarian cancer research in the Department of Gynecologic Oncology.

"The concept of stress hormone receptors directly driving cancer growth is very new," Sood says. "Our research opens a new area of investigation."

Also, no one has studied the effect of beta blockers on chronic stress as it relates to cancer in humans, Sood adds. "There is a lot of interest now in this area of combining behavioral interventions to reduce stress, as well as using beta blockers in cancer patients."

What's next?

Sood and his team are in the process, in follow-up studies, of further refining the role of stress in cancer by examining the hormone receptor status of cancers other than ovarian cancer.

- From staff reports