An extract of Spirulina-Dunaliella algae was shown to prevent tumor development in hamster buccal pouch when a 0.1% solution of 7,12-dimethylbenz[a]anthracene (DMBA) in mineral oil was applied topically three times weekly for 28 weeks. The algae extract was delivered by mouth in continued dosages of 140 micrograms in 0.4 ml mineral oil three times per week. After 28 weeks, the animals given vehicle and untreated controls all presented gross tumors of the right buccal pouch. Animals fed canthaxanthin presented a notably and statistically significant reduction in tumor number and size compared with controls. Animals fed beta-carotene demonstrated a smaller but statistically significant reduction in tumor number and size. The algae animals presented a complete absence of gross tumors. However, microscopic sections of the buccal pouch in the algae group showed localized areas of dysplasia and early carcinoma-in-situ undergoing destruction.
Previous studies have shown that beta-carotene and alpha-tocopherol can act synergistically to inhibit the growth of experimentally induced oral cancer. The initial studies on the synergistic anticancer activity of antioxidants have been extended to include reduced glutathione and ascorbic acid. Sixty male hamsters (4-5 wks old) were divided into six equal groups. Groups 1-6 were treated with 7,12-dimethylbenz[a]anthracene (DMBA) (0.5% solution). Group 2 received a mixture containing equal amounts of beta-carotene, dl-alpha-tocopherol (vitamin E), glutathione, and l-ascorbic acid (vitamin C) (12.5 micrograms) delivered orally by pipette. Groups 3-6 were treated with beta-carotene alone (50 micrograms), vitamin E alone (50 micrograms), glutathione (50 micrograms) alone, and vitamin C alone (50 micrograms). Animals were euthanized at 12 and 14 weeks. Tumors were counted and measured, and tumor burden was calculated for each experimental group. The mixture of antioxidants significantly reduced tumor burden, whereas the beta-carotene, vitamin E, and reduced glutathione treatments also reduced tumor burden. beta-Carotene and glutathione provided greater levels of chemoprevention than vitamin E as single agents. In contrast, vitamin C treatment produced no antitumor effect but increased tumor burden by Week 14. This mixture of antioxidants produced a significant synergistic chemoprevention of oral cancer.
Forty young adult Syrian hamsters (Mesocricetus auratus) were divided into four groups of 10 animals each. In Group 1 (tumor control), the right buccal pouches were painted three times per week with a 0.5% solution of 7,12-dimethylbenz[a]anthracene (DMBA) in heavy mineral oil (USP) with a no. 4 sable brush. In Group 2 (experimental group), the right buccal pouches were painted with DMBA, as in Group 1. In addition, Group 2 received 1 mg of reduced glutathione in 0.5 ml of mineral oil three times per week on days alternate to the DMBA application. The glutathione was administered systemically by mouth with a pipette. Group 3 received only glutathione, and Group 4 was untreated (control groups). Animals were sacrificed after 14 weeks, and tumors were counted and measured. Both right and left pouches were photographed, excised, fixed in formalin, sectioned in paraffin, and studied histologically. The animals receiving glutathione demonstrated significantly fewer and smaller tumors. The mean tumor burden was 315 mm3 in the glutathione-treated group and 3,040 mm3 in the untreated group. The statistical significance by Student's t test was < or = 0.0001. Histological study also revealed significantly fewer areas of dysplastic leukoplakia in the group treated with glutathione. This study represents the first demonstration of the anticancer effect of systemically administered reduced glutathione.
alpha-Tocopherol (vitamin E) and beta-carotene have been shown to be capable of regressing established epidermoid carcinomas of hamster buccal pouch when injected locally into the tumor site. Neither has yet been shown to be effective in regressing cancer when administered by oral route. However, a combination of both alpha-tocopherol and beta-carotene was shown to be effective in regressing epidermoid carcinomas of hamster buccal pouch when the mixture was administered orally in vegetable oil. The epidermoid carcinomas were induced in the right buccal pouch of 100 Syrian hamsters by painting three times weekly for 14 weeks with a 0.5% solution of 7,12-dimethylbenz[a]anthracene in mineral oil. The animals were then divided into five equal groups of 20 animals. Group 1 animals received no further treatment and represented tumor controls. Group 2 animals received 200 micrograms beta-carotene and 200 micrograms dl-alpha-tocopherol acid succinate combined in 0.2 ml vegetable oil. Animals received the mixture daily by mouth using a 1-ml syringe. Groups 3 and 4 received beta-carotene and alpha-tocopherol individually in double amounts (400 micrograms in 0.2 ml vegetable oil). Group 5 animals received only the vegetable oil (0.2 ml daily) and were controls for vehicle. The animals in Groups 1, 3, 4, and 5 were killed after 22 weeks because the tumors were extensive, large, and necrotic and the animals were weak and cachectic. After 22 weeks, the tumors in Group 2 animals were small in 15 out of 20 animals. The tumors were reduced in size compared with tumor burden at 14 weeks, the point at which the beta-carotene/alpha-tocopherol was started.
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