Alcohol Consumption and Risk of NHL: Role of MTOR Dysfunction

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The incidence of Non-Hodgkin's lymphoma (NHL) in the USA has dramatically increased over the past two decades. Diffuse large B-cell lymphoma (DLBCL) is the most frequently diagnosed lymphoma in the REAL international study accounting for approximately a third of all cases. Unfortunately, despite aggressive chemotherapy for DLBCL the still high fatality rate illustrates the urgent need for innovative approaches. Most advances in NHL in recent years have come from development of disease-specific molecular targeted agents. Chronic alcohol consumption is associated with an increased risk for cancers of various organs. Interestingly, in contrast to solid tumors, there has been epidemiologic evidence indicating that alcohol decreases the risk for most types of non-Hodgkin's lymphoma. The mechanisms accounting for such paradoxical and alcohol-induced decrease in the incidence of NHL remain largely unknown. Previous work from others has shown that ethanol decreases protein synthesis in cells, although the underlying regulatory mechanisms of this process are not fully understood. There is recent evidence suggesting that chronic alcohol intake is associated with suppression of the mTOR/p70 S6K signaling pathway, a pathway that plays key roles in the control of important cellular processes, including cell survival and growth. It is therefore possible that alcohol- dependent inhibition of mTOR and its effectors in human lymphocytes is associated with decreased incidence of lymphomagenesis. The central hypothesis of this proposal is that alcohol directly inhibits mTOR and/or its effectors, resulting in suppression of cap-dependent mRNA translation and protein synthesis in human lymphocytes; and that such a mechanism accounts for the anti-lymphoma properties of alcohol. Understanding the underlying molecular and biochemical mechanisms by which chronic alcohol consumption suppresses lymphoma development may be important for developing novel strategies for the prevention and treatment of lymphoma. Towards this end we will pursue several lines of investigation: 1) Does alcohol suppress mTOR activity in human lymphocytes directly or indirectly? What are the effects of mTOR on upstream mTOR regulators such as the PI 3' kinase and the akt kinase? 2) Does alcohol inhibit p70 S6K activity and its downstream effectors S6 ribosomal protein and eukaryotic initiation factor 4B? 3) What are the effects of alcohol on the phosphorylation of the translational repressor 4E-BP1 and the formation of 4E-BP1-eIF4E complexes? What are the effects of alcohol on cap-dependent translation in normal human lymphocytes and malignant lymphoma cells? The specific aims are: Specific Aim 1: To determine whether alcohol exhibits suppressive effects on the activation of the mTOR pathway in lymphocytes and malignant lymphoma cells and to identify the mechanisms by which it exhibits such effects. Specific Aim 2: To examine the effects of alcohol on the activation and function of downstream effectors of the mTOR pathway, including S6 ribosomal protein, eIF4B and 4E-BP1. Specific Aim 3: To examine the ability of chronic ethanol exposure on lymphoma xenografts as well as its capacity to attenuate the development of lymphomas in a p53 +/- mouse model. Altogether, these studies should help us understand the mechanisms by which alcohol inhibits malignant lymphomas and may form the basis for the development of innovative approaches to block lymphoma growth, including the future design of more selective and specific pharmacological agents that target similar pathways.