DESCRIPTION (provided by applicant): Cancer is influenced by an individual's interaction with its physical and social environment, yet the underlying mechanisms are poorly defined. Epidemiological studies have revealed that social support is linked to improved health outcomes among cancer patients whereas social isolation predicts risk for mortality. Mechanistic studies in chronic stress models suggest that prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic-adrenal medullary (SAM) axis may promote cancer progression. Our recent work has shown that environmental enrichment (EE), a housing environment boosting mental health, inhibits tumor growth by activating the hypothalamic- sympathoneural-adipocyte (HSA) axis. The stimulations provided in EE stimulate brain- derived neurotrophic factor (BDNF) expression in the hypothalamus leading to preferential sympathoneural activation of white fat. The elevated sympathetic drive activates adipocyte ss-adrenergic receptors inhibiting leptin expression and release, and thereby suppresses cancer growth. In contrast, social isolation (SI) is linked to increased tumor burden. However, both EE and SI increase the classical stress hormones, glucocorticoids and catecholamines, and ss-adrenergic blockers may abrogate their effects on cancer. This apparent paradox may in part lie in the lack of recognition of the difference between "eustress" (positive stress) and "distress" (negative stress) and their opposing health outcomes. The long-term goal of this project is to understand how the eustressful and distressful events trigger distinct molecular changes in the brain leading to an orchestrated differential activation of the three neuroendocrine axes: HPA, SAM and HSA, and subsequent opposite influences on cancer. Specifically we propose to use a multidisciplinary approach to provide a comprehensive and explicit comparison between the eustress model EE versus distress model SI on cancer progression, metabolism, and fat physiology. The analysis of the nature and magnitude of the 3 axes will help to elucidate the mechanisms underlying eustress-associated anticancer versus distress-associated pro- cancer phenotype. In addition we plan to profile the gene expression in the laser-capture microdissected hypothalamus nuclei to identify molecular mediators distinguishing eustress and distress. Furthermore we will investigate the role of hypothalamic BDNF in mediating SI impact on cancer. These studies may reveal novel therapeutic targets for cancer prevention and treatment.
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