Specific Silencing of Inducible Nitric Oxide Synthase Alternative Splicing variants by siRNA technology in tumor cell lines

• Grant number: 09/06864-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2009
• End date: August 31, 2011
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Hugo Pequeno Monteiro
• Grantee: Pedro Paulo Moraes Mathias
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Inducible nitric oxide synthase (iNOS/NOS2) is the synthase isoform most commonly associated with tumors. Accumulating experimental evidence points to a major role of this isoform in tumor progression and metastasis. iNOS was initially characterized in macrophages. The enzyme is capable of generating large amounts of nitric oxide (NO) which in association with other reactive nitrogen species, promotes damage to DNA and to the DNA repair enzymatic machinery. In addition, high concentrations of NO are pro-apoptotic and potentially may lead to inhibition of tumorigenesis and tumor progression. On the other hand, physiologic levels of NO have been associated with cell proliferation. Therefore, negative regulatory mechanisms have been proposed to account for a reduced production of NO by iNOS in tumor cells. Post transcriptional based mechanisms such as alternative splicing for its mRNA may be operative. Alternative isoforms of the enzyme could be translated from these alternative mRNAs. These isoforms would be important as generators of adequate concentrations of NO resulting in the stimulation of tumorigenesis and resistance to toxic concentrations of this radical. To understand the negative regulation of NO production and its importance on tumor progression we will develop specific siRNAs for the alternative splicing isoforms. Silencing the alternative isoforms will stimulate the tumor to produce NO in cytotoxic concentrations. Such development may represent a new therapeutic strategy for cancer treatment.