Recent findings have illuminated the method by which malignant growths promote their expansion. They enlist sensory neurons and exploit them for their own benefits. These nerve cells establish connections with the cancerous cells, transmitting signals toward the brain. In response, the brain deactivates the immune cells tasked with combating the malignancy. Consequently, these rampant cells are enabled to proliferate unchecked.
Researchers meticulously examined this communication sequence running from the tumor to the brain and back again. Anna-Maria Globig, an immunologist-oncologist at the Allen Institute for Immunology in Seattle, observed that the tumor co-opts this mechanism, putting it to its own advantage. Her colleague, Chengcheng Jin from the University of Pennsylvania, reported that tumor growth could be significantly retarded—by over 50%—if the sensory neurons were inhibited via genetic engineering.
It has long been understood that neural elements exist within tumor masses, yet their precise role in tumor progression remained unclear. Previously, genetic tools were insufficient for accurately probing neuronal activity, and biopsy samples yield poor data concerning these cells, given they represent the body’s longest cellular structures.
Jin’s group analyzed microscopic imagery showing neurons enveloping and infiltrating lung tumors. Initial attempts to dampen the activity of these neurons using pharmacological or genetic approaches proved fruitless.
A breakthrough emerged serendipitously. They collaborated with Ruikang Chang, a neurobiologist from Yale University renowned for his expertise in genetic gene knockout techniques. Collectively, they managed to block the sensory neurons of the vagus nerve, which links the brain with various organs, including the heart and lungs. This blockade successfully unveiled the signaling channel between the brain and lung tumors in murine models.
It was discovered that the tumor hijacks this pathway, with neurons originating from the brainstem relaying signals back to the tumor. These neurons release norepinephrine, a chemical that suppresses the anti-cancer immune cells. The scientists expressed surprise; they had anticipated that these neurons would warn the brain about the tumor, thus aiding in its elimination. Isaac Chiu, an immunologist at Harvard Medical School, explained that macrophages respond to these neural signals by initiating tissue repair. This suppressive route likely functions as a defense against detrimental inflammation. Neuro-oncologist Claire Manion remarked, “I’m pleased the community is no longer viewing this with skepticism. We are only just beginning to grasp how these nerves develop.”
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