The present study was designed to investigate the modifying effects of dietary 5-hydroxy-4-(2-phenyl-(E)-ethenyl)-2(5H)-furanone (KYN-54), a new synthetic retinoidal butenolide, during the post-initiation phase on azoxymethane (AOM)-induced rat intestinal carcinogenesis, The number of aberrant crypt foci (ACF) in rat colon, colonic ornithine decarboxylase (ODC) activity and bromodeoxyuridine (BrdUrd) labeling index in rat colonic epithelium were also assessed, At 7 weeks of age, male F344 rats (except the KYN-54 alone and control groups) were given weekly s.c. injections of AOM at 15 mg/kg body wt for 3 weeks, Starting 1 week after the last injection of AOM, rats (except the control group) were fed a diet containing KYN-54 at concentrations of 100 or 200 p.p.m. throughout the experiment, All animals were necropsied at 32 weeks after the start of the experiment, Compared with the AOM alone group, KYN-54 at both doses reduced the incidence and multiplicity of tumors in entire intestine (small and large intestines), In the 200 p.p.m. KYN-54 fed group especially, tumor incidence and multiplicity in the entire intestine were lower compared with the AOM alone group (P < 0.005 and P < 0.05 respectively). Also, the number of ACF/cm(2) colon in the groups of rats treated with AOM and KYN-54 at both doses were significantly lower than that of rats treated with AOM alone (P < 0.05), Colonic ODC activity and BrdUrd labeling index in the groups of rats treated with AOM and KYN-54 at both doses were slightly lower than those treated with AOM alone, KYN-54 at 200 p.p.m. significantly lowered BrdUrd labeling index induced by AOM (P < 0.005), These results suggest that KYN-54 might be a promising chemopreventive agent for intestinal neoplasia.
