Chronic stress speeds colorectal cancer’s spread dramatically, study indicates

NEW YORK, Oct. 12 (UPI) -- Chronic stress speeds colorectal cancer's spread dramatically by disrupting gut microbiota -- the delicate balance of good and bad bacteria, a new study in mice indicates.

The study, conducted in China, will be presented Sunday at UEG Week 2024, an annual conference of United European Gastroenterology in Vienna.

Researchers demonstrated that chronic stress not only fueled tumor growth, but it also undermined beneficial gut bacteria, especially Lactobacillus genus, which are vital for mounting a healthy immune response against cancer.

To perform the experiment, investigators injected an antibiotic cocktail into two groups of mice -- those with chronic stress and those without -- to rid the gut of healthy bacteria. Both groups experienced weakening of the body's defenses in fighting cancer, researchers reported.

About 11 weeks after the injection, all mice developed tumors in their intestines. After confirming the presence of tumors, researchers euthanized the mice and used special chemical dyes to analyze the characteristics of these growths, the study's lead investigator, Dr. Qing Li, told UPI.

As for inducing a state of physical or emotional tension in the mice, "we employed chronic restraint stress, for six hours each day, until the end of the experiment," said Li, a postdoctoral researcher in the department of gastrointestinal cancer and liver diseases at West China Hospital of Sichuan University in Chengdu, Sichuan Province, China.

Chronic restraint stress -- a common model for studying rodents in scientific research -- is created by a harmful stimulus that can stem from living conditions, such as crowding and frustration.

She and her collaborators then probed deeper into how this good bacteria influences cells that protect against tumor growth and disease proliferation. To accomplish this, they transplanted the same bacteria into chronically stressed mice and witnessed less tumor formation.

Using good gut bacteria along with traditional anti-tumor medications to treat patients, particularly those who endure chronic stress, shows promise, researchers noted.

"This study highlights the crucial role of gut microbiota changes during chronic stress in promoting colorectal cancer progression," Li said.

Before launching this study, the researchers reviewed scientific literature to understand how mental turmoil affects patients with colorectal cancer. After discovering that persistent stress can alter gut bacteria, they still wondered whether these changes can accelerate worsening of colorectal cancer.

"The initial motivation for this study stemmed from our frequent observations in clinical work that the mental state of cancer patients influences their prognosis," Li said. "Patients who were excessively worried about their condition often had poorer outcomes."

She explained that "when people are diagnosed with a malignant disease like colorectal cancer, it's natural for them to experience feelings of worry and concern.

"However, these emotions are not beneficial for their condition. Our findings suggest that patients should try to adjust their mindset as much as possible to avoid further exacerbation of their disease."

The European Commission reports that colorectal cancer is a major health concern across Europe. It's the second most prevalent malignancy and the second leading cause of cancer-related death on the continent where the gastroenterology conference is taking place.

In the next decade, the incidence of this disease is expected to swell as a result of an aging population, unhealthy diets, physical inactivity and obesity, according to the British medical journal, BMJ Open.

Forging ahead in their scientific endeavor, the researchers intend to collect stool and tumor samples from patients with colorectal cancer. They plan to analyze alterations in gut microbiota among people with and without chronic stress.

The results prompted interest among the medical community.

"The study adds to the increasing body of literature showing that chronic stress negatively impacts the natural history of colorectal cancer. The authors should be congratulated for their study findings," said Dr. Olatunji Alese, director of gastrointestinal oncology at Winship Cancer Institute of Emory University in Atlanta. He was not involved in the study.

"Although this was a preclinical study, the results could have implications for medical practice," Alese said, while cautioning that potential intervention "is not yet ready for prime time."

Before then, confirming the findings in humans with colorectal cancer will be necessary, said Dr. Jeffrey Meyerhardt, co-director of the Colon and Rectal Cancer Center at Dana-Farber Cancer Institute in Boston.

"Nonetheless, these data are an important piece of the puzzle and warrant continued research to allow us to eventually translate this to patients," Meyerhardt said.

Scientists have expended a lot of effort trying to identify specific gut bacteria that may be useful for a therapeutic purpose, said William DePaolo, an immunologist and microbiologist.

But even after years of conducting research, scientists still haven't found a powerful therapeutic agent derived from gut bacteria, said DePaolo, chief executive officer of Tend Health Inc., a Seattle-based biotech startup that developed a device for gut bacteria transplants.

"The field is at such an early stage and so young, there are simple concepts that we have no idea about, let alone in these more complicated diseases," he said.