beta-carotene and Tracheal-Neoplasms

In recent intervention studies, beta-carotene failed to reduce or even increased the incidence of lung cancers in smokers. In the present investigation, the modifying effects of beta-carotene at various doses on the development of upper respiratory tract tumors were investigated in Syrian hamsters treated with diethylnitrosamine (DEN) and cigarette smoke. A total of 120 male 5-week-old hamsters were divided into 4 groups, each consisting of 30 animals. After a single subcutaneous (s.c.) injection of 100 mg/kg DEN, hamsters in groups 1-4 were respectively administered diets supplemented with beta-carotene at doses of 0.5%, 0.05%, 0.005% or 0% during experimental weeks 1 to 13, and simultaneously exposed to cigarette smoke. The duration of cigarette smoke exposure was 9 min twice a day, 5 days a week. Because of a marked reduction of body weight in group 1, the highest dose of beta-carotene was changed to 0.25% after 10 days. In all groups, epithelial hyperplasias and/or papillomas were induced in the larynx and trachea. However, the incidence and multiplicity of papillomas in group 1 were significantly (P < 0.05) lower than the group 4 values. Moreover, the beta-carotene treatments significantly (P < 0.05 or 0.01) reduced both the incidence and multiplicity of hyperplasias in a dose-dependent manner. The levels of retinol and beta-carotene in the serum, and the retinol level in the liver, were also elevated with dose dependence. Our results thus indicate that beta-carotene inhibits tumorigenesis, even at the high dose of 0.25%, under the present experimental conditions.

Topics: Animals; Anticarcinogenic Agents; Antioxidants; beta Carotene; Cricetinae; Diethylnitrosamine; DNA Damage; Laryngeal Neoplasms; Male; Mesocricetus; Nicotiana; Plants, Toxic; Smoke; Tracheal Neoplasms

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Agents; beta Carotene; Carotenoids; Case-Control Studies; Confounding Factors, Epidemiologic; Diet; Fruit; Humans; Lung Neoplasms; Male; Middle Aged; Risk; Smoking; Surveys and Questionnaires; Tracheal Neoplasms; Vegetables