Chemopreventive Effects of Bovine Lactoferrin on N‐Butyl‐N‐(4‐ hydroxybutyl)nitrosamine‐induced Rat Bladder Carcinogenesis

Chemopreventive effects of bovine lactoferrin (bLF), which is found at high concentrations in colostrum, on rat bladder carcinogenesis were investigated using a rat bladder medium‐term bioassay. In experiment 1, a total of 80 F344 male rats, 6 weeks old, were divided into 5 groups. Groups 1 and 2 were treated with 0.05%N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN) in the drinking water for 8 weeks and after a 1‐week interval, received dietary supplementation with 2% and 0.2% bLF, respectively. Group 3 received 0.05% BBN for 8 weeks and then no treatment. Group 4 was administered 2% bLF alone from week 9, without prior carcinogen exposure. Group 5 was maintained without any treatment throughout the experiment. All rats were killed at the end of week 36. Group 1 demonstrated a significantly decreased multiplicity of the bladder tumors (carcinomas and papillomas) as compared with group 3, Maximum cut surface areas of bladder tumors were also significantly decreased in groups 1 and 2 compared with group 3. No bladder tumors were observed in groups 4 or 5. In experiment 2, a total of 60 rats were divided into two groups (30 rats each); both were treated with 0.05% BBN for 4 weeks and after a 1‐week interval, one received 2% bLF (group 1) and the other, basal diet (group 2) for 4 weeks. Group 1 demonstrated a tendency for decrease of the 5‐bromo‐2′‐deoxyuridine (BrdU) labeling index. bLF was detected in the urine of rats fed bLF by ELISA as well as western blot analysis. The findings indicate that 2% bLF can inhibit BBN‐induced rat bladder carcinogenesis, and that this may be due to bLF in the urine.