AN-7, a prodrug of butyric acid, induced histone hyperacetylation and 
differentiation and inhibited proliferation of human prostate 22Rv1 cancer cells 
in vitro and in vivo. In nude mice implanted with these cells, 50 mg/kg AN-7 
given orally thrice a week led to inhibition of tumor growth and metastasis, 
tumor regression in >25% of animals and increased survival. Median time to the 
experimental end point (tumor volume 2 cm3 or death) in the untreated was 52 
days, and average tumor volume was 0.8 +/- 0.18 cm3. At the same time, 94.4% of 
AN-7-treated mice survived and had average tumor volumes of 0.37 +/- 0.1 cm3. 
PSA expression was a useful marker for 22Rv1 lung metastasis detection. Sizeable 
metastases positively stained for PSA and limited air gaps were found in lungs 
of untreated mice. In animals treated with AN-7, lung morphology appeared 
normal. Primary tumors of treated animals were highly positive for PSA and had 
an elevated level of p21 and the proapoptotic protein Bax. Sections taken from 
AN-7-treated animals, examined under an electron microscope, exhibited condensed 
chromatin and apoptotic bodies. PSA serum levels were higher in untreated 
compared to treated animals and correlated with tumor volume. Since prolonged 
oral administration with 50 mg/kg or a single oral dose of 1.2 g/kg AN-7 did not 
cause adverse effects and the former exhibited significant anticancer activity, 
AN-7 is likely to display a high therapeutic index and may be beneficial for 
prostate cancer patients.