Highlights of the fifth international workshop on nitric oxide and cancer

Nitric oxide (NO) is an endogenous molecule that performs key physiological signaling functions. The overall biological effect exerted by NO strongly depends on its concentration. Indeed, at a low concentration NO acts as a signal transducer affecting many physiological processes, such as blood flow regulation, iron homeostasis, and neurotransmission, while at a high concentration it preferentially exerts cytotoxic effects. Gaining knowledge about the molecular pathways involved in the NO-tumor response represents a great scientific and clinical challenge for developing novel anticancer strategies based on either endogenous or exogenous NO regulation and induction. This review summarizes the most recent advances in the pathological and therapeutic roles of NO in cancer achieved by prominent experts in the field. In particular, the following topics are reviewed: the role of inducible nitric oxide synthase (iNOS) in chronic inflammation and tumorigenesis; the connection between NOS and IL-10 and their function in immunity at the tumor site; the role of NO in photodynamic therapy; and the role of S-nitrosylation in cancer. Finally, an overview of NO-mediated therapies for cancer treatment is provided, including iNOS inhibitors, NO-releasing compounds, and molecular conjugates and nanoparticles that induce NO formation upon irradiation with light.