Dr Weiming Xu, Dept of Molecular Biology and Biotechnology, University of Sheffield
The role of nitric oxide and other apoptosis associate genes in cancer and cardiovascular diseases
Nitric oxide (NO) is a pleiotropic regulator, which has an important role in many biological processes including vasodilatation, neurotransmission, and macrophage-mediated immunity. The family of nitric oxide synthases (NOS) comprises inducible NOS (iNOS), endothelial NOS (eNOS), and neuronal NOS (nNOS). Various studies have shown that all three isoforms can be implicated in promotion or inhibition of the development of human cancer. High amounts of iNOS expression - e.g., those generated by activated macrophages - might be cytostatic or cytotoxic for tumour cells, whereas low activity could have the opposite effect and promote tumour growth.
NO has both genotoxic and angiogenic properties, so increased NO production could select mutant p53 cells and contribute to tumour angiogenesis by upregulation of vascular endothelial growth factor and provide radiation and multidrug resistance by upregulation of DNA-dependent protein kinase catalytic subunit. These dual functions can be partly explained by the dose-dependency of NO in physiological and pathological conditions. In order to investigate the effects of different concentrations of NO we have developed two recombinant iNOS cell expression systems with promoters regulated by either insect hormone ecdysone (figure) or tetracycline. These cell lines can generate NO in a dose-dependent and time-dependent manner at concentrations found in human cancer cells. We are currently using several cDNA microarray systems and proteomic approaches to dissect NO-mediated inhibition of the mitochondrial respiration pathway, which could have an important role in cytotoxicity and hypoxia adaptation in tumour cells and endothelium cells. Our findings could help us to understand the fundamental roles of NO in tumour biology.
Recently we have expanded our research on the other apoptosis associate genes, such as glucose-regulated protein 78(GRP78), which mediates cytoprotection against apoptosis in cancer development and cellular inhibitors of apoptosis protein in cancer and cardiovascular diseases. The elucidations of the signal transduction pathways of these genes will help us to develop new diagnostic tool and novel treatments for human cancer and cardiovascular diseases.
Legend: Fluorescence image of microencapsulated nitric oxide - producing cell.
Selected publications and references
Xu W, Liu L, Brown NJ, Christian S & Hornby DP. 2012 Quantum dot-conjugated anti-GRP78 scFv inhibits cancer growth in mice. Molecules 17(1):796-808, doi:10.3390/molecules17010796
Xu W & Liu L. 2010 The E3 ubiquitin ligase c-IAP1 regulates PCSK9-mediated LDLR degradation: Linking the TNF-α pathway to cholesterol uptake. Nature Precedings http://hdl.handle.net/10101/npre.2010.4554.1
Liu L & Xu W 2009 Targeting Nitric oxide mediated upregulation of membrane-bound glucose regulated-protein 78 by subtractive single chain variable fragment (scFv) phage display. Am J. Biomed. Sci 1(4), 321-335.
Liu L, Huq S and Xu W 2009 Targeting Cyclooxygenase and nitric oxide pathway cross-talk: a new signal transduction pathway for developing more effective anti-inflammatory drugs. Current Signal Transduction Therapy 4(1), 66-75.
Lamb, H.K., Mee, C., Xu, W., Liu, L., Blond, S., Cooper, A., Charles, I.G. Hawkins AR. 2006 The affinity of a major Ca2+ binding site on GRP78 is differentially enhanced by ADP and ATP. J Biol Chem, 281 (13), 8796-8805.
Xu, W., Charles, I.G., Moncada, S. 2005. Nitric oxide: orchestrating hypoxia regulation through mitochondrial respiration and the endoplasmic reticulum stress response. Cell Res 15(1), 63-65.
Xu, W., Liu, L., Charles, I.G., Moncada, S. 2004. Nitric oxide induces coupling of mitochondrial signalling with the endoplasmic reticulum stress response. Nat Cell Biol 6(11), 1129-1134.
Xu W, Liu LZ, Loizidou M, Ahmed M, Charles IG.2002.The role of nitric oxide in cancer. Cell Res.12, 311-20.
Xu W, Liu L. & Charles IG. 2002 Microencapsulated iNOS-expressiong ceels cause tumor suppression in mice. FASEB J, 16, 213-215.
Xu W, Liu L, Smith GC, Charles IG. 2000. Nitric oxide upregulates expression of DNA-PKcs to protect cells from DNA-damaging anti-tumour agents. Nat Cell Biol. 2(6), 339-345.