From pollutant gas to biological messenger: the diverse actions of nitric oxide in cancer.

Nitric oxide (NO) has undergone an image change in recent years. Previously regarded as a toxic pollutant gas, it has now become the subject of intense research in many fields of medicine and science. It is a free radical, with a diverse range of actions in both physiological and pathological processes. Although over 44,000 research papers have now been written on NO, only a small number have originated from the surgical specialties. Its role in tumour biology remains incompletely understood. NO is known to have both tumour promoting and inhibitory effects, presumed to be dependent on its local concentration within the tumour. NO appears to be pivotal in the angiogenic process, and the p53 tumour suppressor gene may influence its production. This review summarises the brief history of this molecule, gives an overview of its many effects in the common solid tumours and discusses how targeting of NO production may have possible future therapeutic benefit.