Generation of reactive oxygen species by Nox4 in human colorectal cancer cells: role of nitric oxide in the regulation of Nox4 by s-nitrosylation

• Grant number: 18/04860-8
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2018
• End date: May 31, 2020
• Field of knowledge: Biological Sciences - Biochemistry - Metabolism and Bioenergetics
• Agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
• Principal Investigator: Hugo Pequeno Monteiro
• Grantee: Ana Caroline de Souza Teodoro
• Host Institution: Centro de Terapia Celular e Molecular. Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Cancer is the denomination attributed to a set of more than 200 diseases, of which genesis and progression are complex processes with multiple stages that leads to the conversion of a normal cell into a malignant state. Colorectal cancer (CCR) is among the leading causes of death in a worldwide scenario, and encompasses tumors affecting a segment of the large intestine (the colon) and the rectum. About 30 to 50% of patients with CCR can die within five years of the advanced disease. It is known that reactive oxygen species (ROS), at higher levels, can induce senescence, apoptosis and cell death due to their mutagenic and cytotoxic potential. However, lower levels of ROS provide regulatory characteristics on growth, differentiation and cellular apoptosis. Studies have highlighted that these species may be associated with human carcinogenesis. The isoforms 1,2,4 and 5 of NADPH oxidase (Nox) enzymes are a major source of ROS in cancer. Specifically, Nox4 has been identified with more prominence in cancer and its elevated expression found in several types of solid tumors, including those of CCR. Nitric oxide (NO) is synthesized by three isoforms of the NO synthase enzymes. Among them is inducible NO synthase (iNOS or NOS2). This isoform has been shown to be an important component of the progression of CCR tumors. Local NO concentrations, duration, and exposure to these concentrations determine the effects of NO on tumor cells. Higher concentrations induce apoptosis, while lower levels stimulate tumor progression. Evidence in the literature and obtained in our laboratory point to differential levels of NO in CCR. In the early stages of tumor development, NO production is reduced and in subsequent stages, where tumor cells detach from their primary site and migrate to metastasis sites, higher NO concentrations prevail. Relatively recent studies have demonstrated a negative modulatory role of NO on Nox4 in vascular cells. In this interaction, NO can negatively modulate ROS production by s-nitrosylation, reducing O2- levels significantly. Thus, the aims of this project will be: (1) To determine the presence and activity of Nox4 in human cell lines of colon tumors at various stages of development: SW480 (Duke's stage B), SW620 (Duke's C stage) and HCT-116 (Duke's D stage); (2) To study the modulation of Nox4 activity by the levels of NO produced by these cells and (3) To verify if the regulation of Nox4 is associated with the stage of tumor development represented by each of the cell lines studied. (AU)