“The relationship between a person’s emotional state and cancer has been demonstrated in the past, but mainly in relation to negative feelings such as stress and depression and without a physiological map of the mechanism of action within the brain,” says prof. Asya Rolls. Prof. Rolls is based at the Faculty of Medical Rappaport at the Technion-Israel Institute of Technology in Haifa. She and her colleagues were puzzled by the idea that emotions, processed by the brain, could somehow influence the breakthrough that tumors can take once deposited inside the body. It is intuitive to consider that stress, anxiety and depression could have a negative impact on the body’s ability to fight diseases. But can positive emotions or a simulation of these emotions reinforce the immune response? Several researchers have shown that an improvement in the patient’s emotional state can influence the course of the disease. But it is not clear how it happened. Thus, Prof. Rolls and the team decided to conduct a study to explore these mechanisms and learn more about how emotions in the brain can affect the way the immune system responds to cancer. In an article published in the journal Nature Communications, the researchers report what they have found through their recent study, presenting a physiological model that can explain at least some of these effects.
Immunotherapy, which aims to strengthen the immune system’s response to cancer cells, has gained ground in cancer research in recent years. However, the involvement of immune cells in cancerous processes is a double-edged sword because some components of these cells also support tumor growth. They do this by blocking the immune response and creating a growth friendly environment. But, as the researchers explain, existing studies have suggested that activity in the brain reward system can help regulate the way the immune system works. Based on these notions, Prof. Rolls and his colleagues conducted a preclinical study in which they experimented with manipulating the brain reward system in mouse models of melanoma (skin cancer) and lung cancer. Specifically, they “targeted” the dopamine-releasing neurons found in the ventral tegmental area (VTA) of the brain, a key region of the reward system. The VTA communicates with the limbic system, a brain structure responsible for processing emotions, among other things. And this, as the team has discovered, interacts with the sympathetic nervous system, the network of neurons and nerves that is found partly in the central nervous system and partly in the peripheral nervous system, which is known to regulate the combat or escape response.
This interaction, therefore, seemed to extend to the immune system. “By artificially activating VTA,” explains Prof. Rolls, “we can influence the nervous system and, therefore, the immune system”. Furthermore, once the immune system is activated in this way, it also seems to create a more resilient “memory” of the foreign agents to which it has been exposed, which enables it to respond more efficiently to such pathogens. When they tested these effects in mouse models of melanoma and lung cancer, the team revealed that by stimulating VTA, the immune system seemed to respond more effectively to tumors. The researchers found that after 14 days of repeated VTA activation, the tumor size was reduced by 46.5%, on average, while the tumor’s weight decreased by 52.4%, on average. Although this study is preclinical, and has only examined the effects of VTA stimulation in two types of cancer using mouse models, researchers believe that their findings could influence the way health professionals view the role of mental state and emotional well-being. both in the development and in the treatment of diseases such as cancer.
It is long known that depression flattens immune system; traumas can do the same by the chronic release of cortisol and steroid in the bloodstream. These would, in turn, cause immune suppression, leaving hte potential “primed” or “promoted” cells free to escape the immune surveillance. Dopamine, on the contrary, is a “tonic” modulator of lymphocytes and keep the in alert. Given the established relationships between mind, immune and nervous system (PsychoNeuroEndocrinoImmunology or PNEI), there is no wonder that positive emotions can fight cancer cells through immune system and, perhaps, in still-unknown mechanisms. Prof. Rolls and colleagues studied the role of emotional states and of the brain reward system, in modulating immune responses for some time. He said: “Understanding the brain’s influence on the immune system and its ability to fight cancer will allow us to use this mechanism in medical treatments. Different people react differently and we will be able to take advantage of this enormous healing potential, only if scientists acquire a thorough understanding of the mechanisms”.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Ben-Shaanan TL et al. Nat Commun. 2018 Jul 13; 9(1):2723.
Ben-Shaanan TL et al. Nature Med. 2016 Aug; 22(8):940-44.