UVM Theses and Dissertations
Format:
Print
Author:
Sham, Derek
Dept./Program:
Pathology
Year:
2012
Degree:
MS
Abstract:
Reactive oxygen species (ROS) were once thought to be harmful byproducts produced by cells. Today, however, ROS are considered to play a vital role in signaling and innate immunity, especially in the lung. It has been shown that the concentration of ROS is a determinant in the progression of lung diseases such as lung inflammation and cancer; however, cells have developed several enzymatic mechanisms (most notably the NADPH oxidase (NOX) family) that can utilize oxygen as an electron acceptor-to mediate host defense and cellular signaling events. Amongst the NOX family, DUOX1 is one of the most prominent NOXs expressed in the lung. The role of DUOX1 in the lung has been noted to contribute to innate immune responses as well as cell migration and wound closure. Although many published studies focus on the role of NOXs in homeostasis and the development of diseases, only a fraction have highlighted the importance of targeted oxidation by ROS.
Some studies, which address the role of DUOX1, have linked it to the activation of the epidermal growth factor receptor (EGFR), yet the exactly signaling mechanism in normal lung epithelium is still unclear. Furthermore, little is known of its role in lung cancer. The work presented in this thesis outlines how DUOX1 mediates EGFR activation through redox-sensitive proteins as well as how DUOX1 may act as a tumor suppressor in H292 airway epithelial cells. We show that ATP stimulation results in EGFR phosphorylation, which in turn causes ligand independent and dependent mechanisms by a non-tyrosine kinase, c-Src. In addition, we show that DUOX1 plays a role in the oxidation of c-Src and TACE (Tumor necrosis factor alpha converting enzyme), which are mediators of EGFR activation. We also characterize the morphological changes and cell signaling events that occur when DUOX1 is silenced from a lung epithelial cancer cell line.
Due to specific structural changes and physiological features, we conclude that the suppression of DUOX1 may cause Epithelial to Mesenchymal Transition (EMT). Furthermore, DUOX1 silenced celIs exhibited hallmark features of EMT such as suppressed expression of E-cadherin and elevated expression of vimentin. We also demonstrate that a lack of DUOX1 causes an increase in wound closure but is not dependent upon the purinergic signaling pathway. Overall, our findings introduce a novel redox signaling role for DUOX1, which may act as a marker for EMT and drug sensitivity. These studies open the door for future aims at understanding oxidative mechanisms and the strategies to combat against cancer.
Some studies, which address the role of DUOX1, have linked it to the activation of the epidermal growth factor receptor (EGFR), yet the exactly signaling mechanism in normal lung epithelium is still unclear. Furthermore, little is known of its role in lung cancer. The work presented in this thesis outlines how DUOX1 mediates EGFR activation through redox-sensitive proteins as well as how DUOX1 may act as a tumor suppressor in H292 airway epithelial cells. We show that ATP stimulation results in EGFR phosphorylation, which in turn causes ligand independent and dependent mechanisms by a non-tyrosine kinase, c-Src. In addition, we show that DUOX1 plays a role in the oxidation of c-Src and TACE (Tumor necrosis factor alpha converting enzyme), which are mediators of EGFR activation. We also characterize the morphological changes and cell signaling events that occur when DUOX1 is silenced from a lung epithelial cancer cell line.
Due to specific structural changes and physiological features, we conclude that the suppression of DUOX1 may cause Epithelial to Mesenchymal Transition (EMT). Furthermore, DUOX1 silenced celIs exhibited hallmark features of EMT such as suppressed expression of E-cadherin and elevated expression of vimentin. We also demonstrate that a lack of DUOX1 causes an increase in wound closure but is not dependent upon the purinergic signaling pathway. Overall, our findings introduce a novel redox signaling role for DUOX1, which may act as a marker for EMT and drug sensitivity. These studies open the door for future aims at understanding oxidative mechanisms and the strategies to combat against cancer.