A dangerous partnership between chronic stress and the growth and the spread of cancer

How the body’s nerves become accomplices in the spread of cancer? ………..
Others were studying nerves in hopes of pinning down an elusive connection between cancer and stress. One such researcher was Anil Sood, a cancer biologist at the University of Texas MD Anderson Cancer Center in Houston. He was intrigued by findings that tumors grew bigger and faster in lab animals that were stressed—for example, by being physically restrained or socially isolated. Some studies had even suggested chronic stress in people made cancer more likely to progress. But how those proposed links worked wasn’t clear, he says. Among researchers interested in stress and cancer, “There was a feeling that hardcore scientists would view these kinds of observations to be ‘soft science.’”

So Sood and others went hunting for mechanisms. The researchers focused on the sympathetic nervous system, which orchestrates our “fight or flight” response to a perceived threat. The hormones epinephrine and norepinephrine play a key role in the response, increasing heart rate and blood pressure. Sympathetic nerves, which weave through our organs and signal to them, release those hormones into nearby tissue. (The adrenal glands perched on our kidneys secrete the same hormones into the bloodstream, which distributes them widely.)

Many cells in the body, including many cancer cells, are studded with β-adrenergic receptors, to which epinephrine and norepinephrine bind. And activating those receptors on cancer cells seems to encourage them to grow. In 2006, Sood’s team reported it could prompt a mouse’s ovarian tumor to grow larger by either exposing mice to chronic stress or giving the animal a drug that activates β-adrenergic receptors. Both interventions prompted cancer cells to recruit and nourish nearby blood vessels that, in turn, fueled their growth. Blocking the receptors prevented this growth.

That study and others showed cancer cells were alert to signals from the nervous system. Then, in 2013, research oncologist Claire Magnon and colleagues in the lab of cell biologist Paul Frenette at Albert Einstein College of Medicine in New York City went further. The researchers revealed that the small nerve fibers near a tumor were, at least sometimes, essential to the tumor’s growth. The team grafted human prostate tumors into mice and then either sliced out the surrounding nerves or destroyed them with a toxic chemical. Without neighboring nerves, the tumor failed to grow. In people, the team found that the higher the density of nerves in and around a prostate tumor, the faster the tumor tended to spread outside the prostate and the faster the cancer tended to recur after surgery. Studies by other groups showed that removing nerves could also prevent gastric and pancreatic tumors from forming. And at many other sites—including the breast, colon, and lung—researchers correlated nerve density with more aggressive disease.

Gustavo Ayala has probed basic interactions between nerves and tumor cells that could lead to new therapies. DWIGHT ANDREWS/MCGOVERN MEDICAL SCHOOL AT UTHEALTH
They also began to document the ways that cancer and nerves cozy up. Nerves entwined in blood vessels can hitch a ride into a tumor as it recruits blood vessels to supply it with oxygen. Cancer cells also produce molecular signals that can prompt nearby nerves to form new projections snaking into and around the tumor. Some evidence suggests signals from cancer can even prompt the body to make brand-new neurons from stem cells.

A provocative paper published in Nature this year showed that, in mice, neural precursor cells in the brain appear to migrate to a prostate tumor to supply it with neurons. The study, by Magnon, who is now at the French biomedical research agency INSERM in Paris, and collaborators, pointed to an unexplored path of communication between cancer and the central nervous system.
For more details follow the link
https://www.sciencemag.org/news/2019/09/how-body-s-nerves-become-accomplices-spread-cancer?

Melanie