Heavy alcohol consumption increases the risk of human breast cancer by up to 50% and is associated with a worse outcome and a higher incidence of relapse in those where a diagnosis is already made. These observations suggest that alcohol may function both at the initiation and progression stages. Approximately 75% of breast cancer cases are sporadic, stressing the need to identify and modulate environmental and/or nutritional risk factors responsible for disease initiation and progression. The mechanism by which alcohol contributes to an increased breast cancer risk is not clear. Prolonged alcohol consumption primarily mediates its effects in various organ systems via inflammation and oxidative stress. Initiation and progression of breast cancer is linked to a local inflammatory cytokine environment and it is likely that alcohol exerts its affect via a pro-inflammatory effect n the breast tissue. Cancer progression and the tumor microenvironment are characterized by an imbalance in oxidative stress and protein homeostasis. Alcohol activates stress induced heat shock transcription factor (HSF1) and its target genes, heat shock proteins (hsps) which are important in proteostasis, in macrophages and in breast cancer epithelial cells. Hsps serve as molecular chaperones in inflammatory processes and HSF1 may also directly induce unique gene sets such as cytokines and chemokines to stimulate tumor initiation and promote invasion thus contributing to a more aggressive phenotype. The central hypothesis of this grant is that alcohol directly - via activation of stress mediated HSF1 and/or induction of hsps - orchestrates an inflammatory microenvironment conducive to initiation and progression of human breast cancer in vivo. We will use a combination of in vitro cell culture studies and novel mouse model of human breast cancer ex-plants to determine the effects of chronic alcohol consumption on human cancer growth, progression and metastasis. The unique aspects of this mouse model is the ability to accept human tumor xenografts which maintain architectural structure, human immune cells, human stroma a tumor microenvironment similar to the original parent tumor. This powerful model will allow manipulation of single factors (such as alcohol) in a functioning mammalian system, while controlling other confounding factors common to human studies. To determine mechanisms, we will examine HSF1 activation, HSF1 target hsp genes as well as identify unique induction of cytokine and chemokine genes crucial to maintain inflammatory environment during breast tumorigenesis. These studies will establish a novel in vivo animal model to investigate the effects of alcohol on human breast cancer and will also uncover stress- mediated novel mechanisms regulating inflammation in breast cancer.