Mechanisms of As-Induced Carcinogenesis

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DESCRIPTION (provided by applicant): Arsenic remains a top environmental concern in the United States as well as world-wide because of its global existence and serious health impacts. Epidemiological studies provide ample evidence that arsenite exposure is associated with the increased incidence of skin and lung cancers. The scope of the parent grant addresses the relation of reactive oxygen species (ROS) generation and skin carcinogenesis due to arsenite exposure in both the human keratinocytes and the mouse skin models. While the scope of current competitive revision seeks to evaluate the contribution and molecular mechanisms of linking the arsenite-induced chronic inflammation to lung carcinogenesis both in vitro and in vivo, this competitive revision seeks to expand the original scope of study from ROS generation in the mediation of skin carcinogenesis, to identification of the molecular mechanisms that link arsenite-induced chronic inflammation to lung tumorigenicity in vitro and in vivo in cellular as well as animal response to arsenite exposure. Although both the parent grant and the current competitive revision propose to study the mechanisms implicated in the carcinogenic effects of arsenite exposure, this revision is specifically intended to identify the contribution of key inflammatory mediators TNF-1 and COX-2 to arsenite-induced development of tumorigenicity of human bronchial epithelial cells (HBECs) in vitro and in vivo, as well as the molecular mechanisms involved in this tumorigenic process. The main hypothesis of this revision is that TNF-1 plays a central role in the formation and maintenance of sustained chronic lung inflammation and subsequently results in the induction of lung epithelial cell tumorigenicity due to arsenic exposure. The overall goal of this proposal is to determine role of TNF-1 and COX-2 in arsenite-induced HBECs' tumorigenicity, as well as the central role of TNF-1 in the maintenance of lung chronic inflammation during arsenic exposure both in vitro and in vivo. There are two Specific Aims proposed for this investigation: 1) To determine the contribution of TNF-1 and COX-2 to the development of tumorigenicity of HBECs due to arsenic exposure; 2) To assess the central role of TNF-1 in arsenic-induced lung chronic inflammation and its mechanisms in vivo. Success of the revision will facilitate our understanding of the molecular mechanism(s) of the formation and maintenance of the chronic lung inflammatory microenvironment, and its role in lung cancer development induced by arsenic exposure. A better understanding of those issues may provide valuable information that is needed for the designing more effective agents for the prevention of and therapy for inflammation-associated lung cancers. Furthermore, funding of this competitive revision will save two jobs, one part-time for Dr. Jianxiu Yu and one for Dongyun Zhang, both of whom provide valuable expertise and are crucial for the proposed studies. The finding will also create new training opportunity for two postdoctoral fellows in the proposed research field. Since we have most of research tools, and research animals are either available in our laboratory or commercially, we believe that the proposed studies will be achieved within two years. PUBLIC HEALTH RELEVANCE: Arsenic remains the top environmental concern in United States as well as world wide, and the existence of a sustained lung chronic inflammatory microenvironment is thought to be a major driving force for the development of lung cancers due to arsenite exposure, however, the molecular mechanisms linking arsenite exposure to lung chronic inflammation are totally unknown. This application is to test the hypothesis that TNF-1 plays a central role in the formation and maintenance of sustained chronic lung inflammation and induction of lung epithelial cell tumorigenicity due to arsenic exposure. Success of the revision will facilitate our understanding of the molecular mechanism(s) of the formation and maintenance of the lung chronic inflammatory microenvironment, and its role in lung cancer development induced by arsenic exposure. A better understanding of those issues may provide valuable information needed for designing more effective agents for prevention and therapy of the inflammation-associated lung cancers.