A new study confirms that stress can contribute to the rapid growth of cancer, particularly in women experiencing anxiety and depression. The findings, published in the Journal of Clinical Investigation, shows that chronic stress and depression cause the release of a hormone known as epinephrine, which then triggers biochemical reactions that boost breast cancer growth and spread, EurekAlert reported on Monday. Previous studies already suggested the link between stress and cancer. However, most findings did not determine how the condition directly affects cancer. In the new study, researchers discovered cancer stem cells’ reaction to stress through tests on mice that involved animal and human breast cancer cells. The team induced chronic stress in mice for a week before having either human or mouse breast cancer cells. They found that those mice that experienced chronic stress showed behavioral changes consistent with anxiety and depression and had bigger, faster-growing tumors at the same time. The researchers then analyzed the underlying biochemical underpinnings that caused stress to increase the growth of cancer. They then found that epinephrine levels were significantly high in mice that experienced stress and faster tumor growth. The stress hormone triggers the release of an enzyme called lactate dehydrogenase that boosts activities of cancer-causing genes. “These data provide a novel pathway that explains how elevated epinephrine caused by chronic stress promotes breast cancer progression by acting directly on cancer stem cells,” said Quentin Liu, lead researcher from the Institute of Cancer Stem Cell at Dalian Medical University in China. To confirm how the study applies to humans, the researchers measured epinephrine in the blood of 83 human breast cancer patients. Women with high levels of stress hormones also had high levels of cancer-activating lactate dehydrogenase in their biopsied breast cancer tissue. In a separate test, the team found that vitamin C suppressed lactate dehydrogenase production when injected into stressed mice. They also found that it helped reduce the size of tumors. “A better understanding of the biochemistry that causes stress to increase the growth of cancer cells could lead us toward targeted drug interventions, one of which we discovered in this work,” Liu said. Source
