The nitrone compound PBN, α-phenyl-tert-butylnitrone, and closely related 
nitrones have anti-cancer activity in several experimental cancer models. The 
three experimental models most extensively studied include A) the rat choline 
deficiency liver cancer model, B) the rat C6 glioma model and C) the mouse 
APC(Min/+) colon cancer model. The two PBN-nitrones mostly studied are PBN and a 
PBN derivative 2,4-disulfophenyl-tert-butylnitrone, referred as OKN-007. OKN-007 
is a proprietary compound that has had extensive commercial development 
(designated as NXY-059) for another indication, acute ischemic stroke, and after 
extensive clinical studies was shown to lack efficacy for this indication but 
was shown to be very safe for human use. This compound administered orally in 
the rat glioma model has potent activity in treating fully formed gliomas. In 
this report observations made on the PBN-nitrones in experimental cancer models 
will be summarized. In addition the experimental results will be discussed in 
the general framework of the properties of the compounds with a view to try to 
understand the mechanistic basis of how the PBN-nitrones act as anti-cancer 
agents. Possible mechanisms related to the suppression of NO production, 
S-nitrosylation of critical proteins and inhibition of NF-κB activation are 
discussed.