`Stress can cause breast cancer to spread to bone`

Washington: Stress or depression following primary treatment in breast cancer patients can make it more favourable for cancer cells to spread to the bone.

The study published in PLoS Biology journal found that both stress and depression activate the sympathetic nervous system, which increases bone levels of a signalling molecule called RANKL.

The researchers from Vanderbilt Centre for Bone Biology found that breast cancer cell migration to the bone depends on RANKL, which is known to promote the formation of osteoclasts, bone cells that break down bone tissue.

"We came to the hypothesis that sympathetic activation might remodel the bone environment and make it more favourable for cancer cells to metastasise there," said Florent Elefteriou, director of the Vanderbilt Centre for Bone Biology.

"Metastasis, the spread of cancer cells to distant organs, including bone is more likely to kill patients than a primary breast tumour," Elefteriou said.

The researchers studied cancer cell metastasis in mice. They followed fluorescently "tagged" human breast cancer cells that were injected into the mouse heart to model the stage of metastasis when breast cancer cells leave the primary site and move through the circulation.

They found that treating the mice with a drug that mimics sympathetic nervous system activation caused more cancer lesions in bone.