MicroRNA-190 and Oxidative Stress in Arsenic carcinogenesis

Our previous research has clearly demonstrated that trivalent arsenic (As3+) can induce generation of reactive oxygen species (ROS) and preliminary data showed that As3+ is also capable of inducing malignant transformation of the human bronchial epithelial cells. The goal of this application is to determine how As3+ induces ROS generation from the cells and what role of ROS played on the transformation of the cells induced by arsenic. Major emphasis will be on the ROS-mediated production of an abnormal cell cycle regulatory protein that interrupts the checkpoint mechanisms of the cell cycle and causes cell transformation. Our preliminary data have shown that (a) inhibition of As3+-induced ROS generation reduces transformation potential of the bronchial epithelial cells; (b) As3+ induces generation of G15á, [a protein derived from Gadd45á with a molecular weight of 15 kDa] due to alternative splicing of the gadd45á pre-mRNA; and (c) overexpression of the As3+-induced G15á causes cell transformation. Based on these preliminary studies, we hypothesize that As3+-induced ROS are responsible for the generation G15á protein, an inhibitor of the cell cycle checkpoint protein Gadd45á, leading to inhibition of Gadd45á-mediated cell cycle control, and consequently, the cell transformation and carcinogenesis. Three specific aims will be pursued: Specific Aim 1 will investigate how As3+ induces ROS generation with emphasis on the role of NADPH oxidase in human bronchial epithelial cell line, BEAS-2B. We will identify each of the reactive oxygen species induced by As3+; Specific Aim 2 will determine the effects of As3+-induced ROS on the generation of abnormal cell cycle regulating protein, G15á; Specific Aim 3 will using overexpression and orthotopic tumorigenesis strategies to study the role of ROS and G15á in As3+-induced carcinogenesis by overexpression of the antioxidant enzymes and G15á in human bronchial epithelial. We will establish stable transfectants and determine the effects of overexpression of G15á or antioxidant enzymes on either basal or As3+-induced cell transformation and carcinogenesis by assays of colony formation and inoculation of the cells in nude mice orthotopically. The completion of this project will establish the mechanism of As3+- induced G15á generation and its role in As3+ carcinogenesis.