DIETARY LIGNIN, AN INSOLUBLE FIBER, ENHANCED UTERINE-CANCER BUT DID NOT INFLUENCE MAMMARY-CANCER INDUCED BY N-METHYL-N-NITROSOUREA IN RATS

Previous investigations suggested potential breast cancer-preventive p roperties of dietary fiber from cabbage. The purpose of the present in vestigation was to determine whether lignin, a component of cabbage fi ber, would protect against mammary carcinogenesis by N-methyl-N-nitros o-urea (MNU) in Sprague-Dawley rats. A six-week study was conducted us ing diets containing 0.5-5% dietary wood lignin (a readily.available, purified source). These diets were well tolerated by the rats, and a c arcinogenesis study using 5 mg MNU/100 g body wt iv at 50 days of age was conducted, with the 2.5% lignin diet fed from 6 through 8 weeks of age followed by 5% lignin diet until 20 weeks after MNU. Dietary lign in and MNU treatment increased food consumption (p < 005), and body we ight was slightly reduced at 10 and 20 weeks after MNU in the MNU-5% l ignin diet group (p < 0.05). Serum estradiol was not altered by dietar y lignin or MNU treatment, but uterine weights were highest in the MNU -control diet group 4 and 12 weeks after MNU. Expression of creatine k inase B, an estrogen-responsive gene, was lower in the uteri of the MN U-lignin diet group than in other groups at 20 weeks. Mammary carcinog enesis was not altered by dietary lignin. However, uterine endometrial adenocarcinoma was observed only in the MNU-lignin diet group (4 carc inomas/40 effective rats) (p < 005).