Colorectal cancer triggers nerve inflammation in mice and primates, study finds

Colorectal cancer does more than destroy tissue. New research suggests it reaches into the nervous system itself, triggering inflammation that damages the delicate fibers responsible for sensation and movement. The finding, demonstrated in both mice and primates, reveals a pathway to chronic pain and neurological dysfunction that may begin long before a patient ever receives chemotherapy or radiation.

Clinicians have long noticed that colorectal cancer survivors report nerve problems at higher rates than the general population. Peripheral neuropathy—damage to the nerves that carry signals from the limbs and organs back to the brain—is common enough among cancer patients that it's often attributed to treatment side effects. But researchers wanted to know whether the cancer itself, independent of therapy, might be the culprit. They built a mouse model of colorectal cancer and watched what happened to the animals' peripheral nerves.

What they found was striking. Mice bearing colorectal tumors developed measurable nerve damage without any obvious pain hypersensitivity. The animals showed subtle problems with movement and coordination, the kind of deficits easy to miss unless you're looking for them. When the researchers examined the peripheral nerves under the microscope, they saw widespread inflammation. Pro-inflammatory molecules called cytokines were elevated throughout the nerve tissue. Lipid metabolites—the building blocks of cell membranes—were disrupted in ways that suggested the nerves were struggling to maintain their structure.

At the cellular level, the damage was even more specific. Macrophages, immune cells that normally help clear debris, had accumulated in the nerves. The myelin sheaths that insulate nerve fibers had begun to break down and decompress. Inside the sensory neurons themselves, calcium regulation had gone haywire. A protein called the ryanodine receptor, which controls calcium flow, had become oxidized and dysfunctional. The result was that sensory neurons could no longer fire with their normal strength. Their electrical signals were dampened, weakened.

To test whether this pattern held beyond rodents, the team examined rhesus macaques with colorectal cancer. The primates showed the same signature: elevated inflammatory markers in their blood, disrupted lipid metabolites, macrophage infiltration in peripheral nerves, and evidence of nerve damage. The consistency across species suggested something fundamental about how cancer cells communicate with the nervous system.

The researchers propose that colorectal cancer triggers a form of chronic inflammatory demyelinating polyneuropathy—a condition in which the immune system attacks nerve insulation. But unlike typical autoimmune neuropathy, this version is driven by the tumor itself. The inflammation appears to be a direct consequence of cancer's presence, not a side effect of treatment. That distinction matters enormously. It means the nerve damage may have already begun by the time a patient receives their diagnosis and starts chemotherapy or radiation. Those treatments might compound an injury that was already underway.

The clinical implications are sobering. If neuropathy develops before treatment, then screening and monitoring protocols might need to start earlier in the disease course. Survivors might benefit from interventions designed to dampen this tumor-driven inflammation, not just manage pain after the fact. The study suggests that what has been dismissed as an unfortunate side effect of cancer therapy may actually be an underreported but significant consequence of the disease itself—one that deserves its own attention, its own research agenda, and its own place in how we care for people living with and beyond colorectal cancer.