Stress, emotion and natural killer cell antitumor activity
Neoplasia is one of the paradigmatic psychoneuroimmunology (PNI) disorders, and several studies showcased clinical associations between behavioral and emotional states and cancer and between those states and the immune system. If clinically relevant PNI effects on cancer were to be found, they would likely depend on selection of appropriate parameters: tumors susceptible to identifi ed immunologic functions; immune effects acting at appropriate points in the natural history of neoplastic disease, and effective immunomodulatory intervention. Animal studies suggest that natural killer (NK) cells are important for cancer control, especially with respect to dissemination and growth of metastasis. Surgical and psychological stress have been reported to suppress NK activity (NKCC) in animals and humans and this suppression was shown to compromise animal resistance to tumor progression. Studies published by Ben-Eliyahu showed powerful model of stressrelated NK-dependent metastasis. Metastatic progression in their MADB106 mammary adenocarcinoma model is related to surgical stress, swim stress, hypothermia or social confrontation and stress hormone-induced suppression of NKCC that is not dependent on physical dissemination of the primary tumor. Moreover, perioperative suppression of NKCC in the immediate postoperative period may contribute in part to the risk of subsequent emergence of metastasis, and perioperative interventios that reduce this risk may improve patient outcome.