Nitric oxide co-ordinates early defence responses through mitochondrial regulation

Cancer is one of the major killers in the developed world, and breast and prostate cancer in particular have been highlighted as areas of concern. Although survival rates have improved over the last few years there is still an urgent need to improve our understanding of the disease, particularly in the way cancers can be rapidly diagnosed and effectively treated. This study uses a novel technology to find markers specifically associated with cancer cells. Importantly, these markers may also be used as targets for the development of new treatments, and so the overall approach is designed to find new methods of diagnosis and treatment. The research we have undertaken has already identified successfully one such marker and the funding will be used to progress this work further. The marker can be used to identify cancer cells by cross-reacting with an antibody - that is a protein used by our bodies as part of the general defence mechanism ? and we are already evaluating this antibody in a breast and prostate cancer screen. Treatment for cancers generally falls into two main categories: patients are given either radiotherapy or chemotherapy. The last few years has seen a change in the regime for some cancers because of new successful therapies based on antibodies. The antibody we have used as a diagnostic for breast and prostate cancer also seems to be able to kill cancer cells and this study will be used to evaluate further how this process works. Of course not all the markers found will ultimately be of clinical use, however by studying the pathway we hope to gain a greater understanding of the disease, and ultimately to learn how to control it.

Nitric oxide (NO) plays an important role as an inter- and intra-cellular messenger, acting in the cardiovascular system, in the nervous system and as a component of the immune system. NO is a diatomic free radical which is a gas at room temperature, making it highly diffusible within the vasculature. One of its major targets is the soluble guanylyl cyclase (sGC). The binding of NO to Fe2+ in the haem group of sGC activates the enzyme and increases the concentration of cGMP (guanosine 3?, 5?-cyclic monophosphate). For many years we have focused on NO/cGMP signalling and the importance of this pathway to a wide range of biological systems, including blood pressure regulation, platelet aggregation, smooth muscle relaxation and peripheral and central neurotransmission. More recently we have been involved in understanding how NO can signal via a completely different pathway that has equally important pleiotropic biological consequences. We have shown that NO, in the nanomolar concentration range that activates sGC, can also bind to the mitochondrial enzyme cytochrome c oxidase (complex IV) and inhibit it in a manner that is reversible and in competition with oxygen. This inhibition can prevent the enzyme from using any available oxygen, resulting in what we have termed ?metabolic hypoxia?. We aim to further our understanding of how this NO-mediated inhibition of cellular respiration results in signalling to transduction pathways that ultimately control the fate of the cell. In order to do this we have developed a series of biochemical techniques, cell lines and reagents that permit the highly regulated generation of NO in a dose- and time?dependent manner.