Lei Cao, PhD - US grants

DESCRIPTION (provided by applicant): Environmental factors and lifestyle have profound effects in the initiation, promotion and progression of cancer. Our recent work on environmental enrichment (EE), a housing environment boosting mental health, has revealed a novel phenotype characterized by a robust reduction in adiposity, resistance to diet-induced obesity, lower leptin level, higher adiponectin level, enhanced immune functions, and marked inhibition in melanoma and colon cancer growth. One key underlying mechanism is the activation of the hypothalamic- sympathoneural-adipocyte (HSA) axis whereby the physical, social and cognitive 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. The long-term goal of this project is to further characterize the role of HSA axis in cancer development and progression. Specifically we propose to generalize HSA activation to additional cancer models particularly the cancers with the strongest association with obesity such as breast cancer, and evaluate its long-term preventive effects. In addition we plan to determine whether genetically activating HSA axis by BDNF gene therapy can alleviate obesity and inhibit tumor growth in melanocortin receptor 4 (MC4R) deficient mice. Moreover we will evaluate whether long-term BDNF gene therapy using an autoregulatory vector can prevent the premature mortality in MC4R mice, a model representing the most common monogenic form of obesity. These studies will further characterize the HSA axis, elucidate underlying mechanisms, identify potential therapeutic targets, and provide the preclinical data to assess the potential to ultimate clinical intervention for cancer.

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.

DESCRIPTION (provided by applicant): The worldwide epidemic of obesity and global incidence of cancer are both rising. Obesity is linked to an increased risk of certain types of cancer including postmenopausal breast, renal, ovarian, esophagus, pancreas, prostate, hepatobiliary, colorectal, and melanoma. Our recent research on environmental enrichment (EE), a housing condition boosting mental health, has revealed a novel phenotype characterized by a robust reduction in adiposity, white to brown adipocyte phenotypic switch, enhanced insulin sensitivity, resistance to diet-induced obesity (DIO), lower leptin level, higher adiponectin level and marked inhibition in melanoma and colon cancer growth. One key underlying mechanism is the activation of the hypothalamic- sympathoneural-adipocyte (HSA) axis with brain-derived neurotrophic factor (BDNF) as the upstream mediator in the brain and leptin as the key peripheral component mediating the anticancer phenotype. These data support the link between adipose remodeling and cancer progression. However obesity is not always linked to insulin resistance or adverse metabolic profile. There is considerable interest in the role of the healthy expansion of adipose tissue in improving insulin sensitivity. Human adenovirus type 36 (Ad-36) can serve as a novel model dissociating adipose expansion from the common adverse health consequences of obesity including diabetes and cancer. Ad-36 has been causatively and correlatively linked with obesity in animals and humans, respectively. However Ad-36 infection paradoxically improves glycemic control, increases adiponectin level, and decreases leptin level. These are the features resemble those closely related to the anticancer phenotype induced by the activation of the HSA axis, although HSA axis activation causes leanness. The goal of this project is to study the effects of healthy expansion of adipose tissue on cancer growth. Specifically we propose to use the adipogenic Ad-36 as a model of a subset of obesity that is derived from metabolically favorable remodeling of adipose tissue and is insulin sensitive. We plan to comprehensively characterize the effects of Ad-36 infection on adipose remodeling, metabolism, hypothalamic gene expression, and cancer progression in both normal weight animals and conventional DIO model. Accomplishing the proposed studies may help to better understand the role of adiposity in cancer progression, clarify the contribution of altered adipokine profiles (specifically the adiponectin/leptin ratio) versus expansion of adipose tissue per se to cancer risk, and stimulate studies to harness certain properties of microbes for beneficial purposes.

DESCRIPTION (provided by applicant): The face of aging in the United States is changing dramatically with the projection of 70 million Americans age 65 or older in the next 25 years. As life expectancy increases, the incidence of diseases such as cancer, cardiovascular disorders and neurodegeneration rises. It is vital, therefore, that we understand more about the dynamics of aging, how they interact with various environmental and lifestyle factors, and the connections between disease processes and aging in order to develop more effective ways to prevent, diagnose and treat age-related diseases. Our recent work on environmental enrichment, a housing environment boosting mental health, has revealed a novel phenotype characterized by a robust reduction in adiposity, resistance to diet-induced obesity, enhanced insulin sensitivity, enhanced immune function, and inhibition in cancer growth. Moreover the anti-cancer and anti-obesity phenotypes are mediated by the activation of a brain-fat axis, the hypothalamic-sympathoneural-adipocyte (HSA) axis. In this regulatory network, the key component in the brain is BDNF, which is highly responsive to activity and the environment, and it controls the HSA activity and thereby regulates fat. Fat, as the principal responsive organ in the periphery, subsequently influences multiple organ systems. The key features of activation of the HSA axis are shared by those environmental and genetic factors known to increase lifespan such as calorie restriction and fat-specific insulin receptor knockout mice. However the role of the HSA axis in the aging process has not been investigated. The long-term goal of this study is to understand how a physically, mentally, and socially active environment may influence healthspan and lifespan and to define the underlying mechanisms. Specifically, we propose to utilize a multidisciplinary approach to characterize the role of HSA axis in healthy aging. We plan to investigate the effects of short-term activation of the HSA axis via environmental intervention or gene transfer of BDNF on aging markers (adiposity, metabolism, hormonal and growth factor alteration, insulin sensitivity, and immune function), as well as the effects of long term HSA axis activation on healthspan and lifespan in both normal animals and obesity and diabetes models. Accomplishing the proposed experiments will assess the role of this newly characterized brain-fat axis in healthy aging and the effects of manipulating a single gene in the brain to regulate healthspan, and furthermore may reveal potential targets for the prevention and treatment of age-related diseases.