beta-carotene and Salivary-Gland-Neoplasms

The effects of individual and multiple antioxidant vitamins on growth and morphology of human nontumorigenic (2HPC8) and tumorigenic (2HP1G) parotid acinar cells in culture have not been investigated. Our study showed that tumorigenic acinar cells were more sensitive than nontumorigenic acinar cells to individual vitamins such as vitamin C, beta-carotene (BC), d-alpha-tocopheryl succinate (alpha-TS), and retinoic acid (RA) and a mixture of four vitamins (vitamin C, BC, alpha-TS, and RA). The effect of individual vitamins on tumorigenic acinar cells depended on the dose and the type of vitamins. Vitamin C at a low concentration stimulated growth, but at a high concentration it inhibited growth. BC was most effective in reducing growth, and it alone caused extensive morphological changes in tumorigenic acinar cells. A mixture of four vitamins at appropriate doses was more effective than a mixture of two or three vitamins at the same doses in reducing the growth of tumorigenic acinar cells. The extent of growth inhibition depended on the dose and the type of vitamins. Our results suggest that the use of multiple antioxidant vitamins is essential for a maximal reduction in cancer incidence among a high-risk population. The use of one or two vitamins may be ineffective or even harmful.

Topics: Antioxidants; Ascorbic Acid; beta Carotene; Cells, Cultured; Humans; Parotid Gland; Salivary Gland Neoplasms; Tocopherols; Tretinoin; Vitamin E; Vitamins

The effects of feeding semipurified diets supplemented with excess retinyl palmitate (20,000 and 100,000 IU/kg), beta-carotene (250 mg/kg), and canthaxanthin (250 mg/kg) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced salivary gland tumors were studied in rats. None of the dietary supplements had a significant effect on tumor incidence. Tumor weights, however, tended to be lower in rats fed the dietary supplements compared with the controls. The incidence of tumor-bearing rats with large tumors was significantly lower in rats fed canthaxanthin than in the control rats. At termination of the experiment, the levels of vitamin A were higher in plasma, liver, normal salivary glands, and the tumor of rats fed diets supplemented with the higher level of retinyl palmitate. Feeding the canthaxanthin-supplemented diet had the opposite effect on tissue and plasma vitamin A levels. beta-Carotene supplementation was associated with higher vitamin A concentrations in the liver but not in plasma, salivary glands, or the tumor. The levels of beta-carotene were increased in tissues and plasma of rats fed the beta-carotene-supplemented diet. The results suggest that in this experimental model, the diet-induced modification of tissue or plasma vitamin A levels did not have an effect on tumor incidence.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; beta Carotene; Canthaxanthin; Carotenoids; Diterpenes; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Salivary Gland Neoplasms; Tissue Distribution; Vitamin A

Different levels of beta-carotene (0, 5, 25, 125, and 250 mg/kg diet) were tested for their chemoprevention effects using 9,10-dimethyl-1,2-benzanthracene-induced salivary gland tumor model in rats. Tumor incidence and tumor weights were slightly lower in rats fed diets supplemented with 25 mg or more beta-carotene/kg diet. Hepatic vitamin A and beta-carotene levels were increased in a dose-dependent fashion, reaching a plateau at 125 mg beta-carotene/kg diet. In plasma, beta-carotene concentrations were also increased with an increase in dietary beta-carotene. Vitamin A levels in plasma were not affected. The normal salivary glands had higher concentrations of beta-carotene than did the tumors. The results suggest that the decreases in tumor incidence and tumor weight may be related to the increase in plasma and tissue levels of beta-carotene as a result of feeding high levels of beta-carotene.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; beta Carotene; Carotenoids; Diet; Dose-Response Relationship, Drug; Liver; Male; Rats; Rats, Inbred Strains; Salivary Gland Neoplasms; Salivary Glands; Vitamin A

The chemopreventive effects of beta-carotene and 13-cis-retinoic acid (RA) on chemically induced salivary gland tumors were studied in rats. Young male Sprague-Dawley rats were injected in one of the submandibular salivary glands with 1 mg of dimethylbenzanthracene (DMBA) dissolved in olive oil. The contralateral gland was injected with the vehicle alone. Rats were divided into four groups and were fed ad libitum a semisynthetic diet supplemented with 0 or 100 mg beta-carotene/kg diet, or 20 or 100 mg RA/kg diet. Rats were killed at 22 weeks after the DMBA treatment, and tumors were examined histologically. Tumors were generally found to be squamous cell carcinomas or poorly differentiated neoplasms resembling squamous cell carcinomas. The tumor incidence was slightly lower in rats fed the diet supplemented with beta-carotene. RA had no appreciable effect on tumor incidence. A high activity of gamma-glutamyl transpeptidase was histochemically demonstrated in the tumors. There were some mortalities in the beta-carotene and RA supplemented groups, especially in the group fed high levels of RA. This mortality appeared to be related to vitamin K becoming somewhat limited.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; beta Carotene; Butylated Hydroxytoluene; Carotenoids; Diterpenes; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Salivary Gland Neoplasms; Submandibular Gland Neoplasms; Time Factors; Tretinoin; Vitamin A