Nitric oxide releasing nanomaterials for cancer treatment: current status and perspectives. Nitric oxide (NO) is known to have dichotomous effects on cancer biology, acting as a pro- or antineoplastic agent. Low concentrations of NO are reported to promote tumor growth, whereas high NO influx acts as a potent tumor repressor, leading to cytotoxicity and apoptosis. There is increasing interest in developing NO-releasing materials as potent tumoricidal agents in which high and localized concentrations of NO may be directly released in a sustained manner to the tumor site. Nanomaterials allied to NO donors have emerged as a promising strategy in cancer treatment. In this context, this review summarizes the roles of NO in cancer biology and highlights the therapeutic potential effects of NO-releasing nanomaterials based on polymeric nanoparticles, dendritic polymers, liposomes, silica nanoparticles, metallic nanoparticles and quantum dots in combating tumor cells.