Signal Transduction: Nerves Help Tumors Evade the Immune System

Interactions between the brain, nerves and immune cells form a complex network. Researchers distinguish three levels of communication: local signaling within tissues, reflex responses at the organ level, and centralized regulation by the brain. Tumors exploit this system to survive. They release specific proteins that reach the brain and trigger the production of stress hormones. These substances shift the body toward suppressing inflammation through the so-called brain–spleen axis. As a result, the immune system receives a false signal that it is time to stand down, preventing protective T cells from effectively attacking the tumor.

Moreover, some malignant tumors can mimic nervous tissue. By appropriating the brain's signaling pathways, they acquire a kind of “immune passport” that allows them to hide from killer cells. Tumors can also directly affect a person's mood, causing depression and sleep disturbances. This creates a vicious cycle: chronic anxiety activates the sympathetic nervous system, leading to the continuous release of hormones and prompting suppressor cells to block the body's immune defenses.

These newly identified mechanisms are already being explored for practical applications. Clinical trials are investigating beta-blockers, commonly used to treat high blood pressure, in combination with immunotherapy. The goal is to prevent nerves from suppressing the immune response. Early studies in patients with breast cancer suggest promising results: blocking stress receptors may reduce the risk of metastasis.

Researchers are also testing electrical stimulation of the vagus nerve, which has been shown to help reduce inflammation in conditions such as rheumatoid arthritis and multiple sclerosis. According to the researchers, targeting specific neural circuits could pave the way for personalized treatments that spare patients the severe side effects associated with conventional therapies.