alpha-carotene and Skin-Neoplasms

Carotenoids and tocopherols have been hypothesized to protect against cancer.. We prospectively evaluated associations of several carotenoids and alpha-tocopherol with risk of nonmelanoma skin cancer using serum collected at baseline from 302 subjects in the Isotretinoin-Basal Cell Carcinoma Prevention Trial. All subjects had at least two BCCs in the 5 years prior to randomization. During 5 years of follow-up, 70 subjects did not develop a nonmelanoma skin cancer, 221 developed a BCC, and 85 developed a squamous cell carcinoma (SCC). Cox proportional hazards models were used to estimate risk ratios. Models were stratified by clinical center and gender and adjusted for age, solar damage, skin type, number of prior BCCs and/or SCCs, treatment group, body mass index, and serum low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol.. Risk of developing a subsequent BCC was not related to serum levels of any of the carotenoids measured or to alpha-tocopherol. Serum levels of alpha-carotene, beta-carotene, lycopene, and alpha-tocopherol also were not independently related to risk of a subsequent SCC. However, serum lutein, zeaxanthin, and beta-cryptoxanthin were positively related to SCC risk; risk ratios for subjects in the highest versus lowest tertiles of these micronutrients were 1.63 [95% confidence interval (95% CI) 0.88-3.01; P for trend = 0.01], 2.40 (95% CI 1.30-4.42; P for trend = 0.01), and 2.15 (95% CI 1.21-3.83; P for trend = 0.09), respectively.. Additional research is needed on the relationship of carotenoids to SCC risk in the general population and in subsets of the population who are at increased risk.

Topics: Adult; Age Distribution; Aged; alpha-Tocopherol; Carcinoma, Squamous Cell; Carotenoids; Female; Humans; Male; Middle Aged; Prevalence; Probability; Prognosis; Proportional Hazards Models; Prospective Studies; Reference Values; Risk Assessment; Sensitivity and Specificity; Sex Distribution; Skin Neoplasms; Treatment Outcome

Various natural carotenoids were proven to have anticarcinogenic activity. Epidemiological investigations have shown that cancer risk is inversely related to the consumption of green and yellow vegetables and fruits. Since beta-carotene is present in abundance in these vegetables and fruits, it has been investigated extensively as possible cancer preventive agent. However, various carotenoids which co-exist with beta-carotene in vegetables and fruits also have anti-carcinogenic activity. And some of them, such as alpha-carotene, showed higher potency than beta-carotene to suppress experimental carcinogenesis. Thus, we have carried out more extensive studies on cancer preventive activities of natural carotenoids in foods; i.e., lutein, lycopene, zeaxanthin and beta-cryptoxanthin. Analysis of the action mechanism of these natural carotenoids is now in progress, and some interesting results have already obtained; for example, beta-cryptoxanthin was suggested to stimulate the expression of RB gene, an anti-oncogene, and p73 gene, which is known as one of the p53-related genes. Based on these results, multi-carotenoids (mixture of natural carotenoids) seems to be of interest to evaluate its usefulness for practice in human cancer prevention.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Anticarcinogenic Agents; beta Carotene; Carotenoids; Colonic Neoplasms; Cryptoxanthins; Disease Models, Animal; Fruit; Humans; Lutein; Lycopene; Methylnitrosourea; Mice; Rats; Rats, Inbred F344; Skin Neoplasms; Tetradecanoylphorbol Acetate; Vegetables; Xanthophylls; Zeaxanthins

Although beta-carotene has been considered to be a key cancer preventive agent in green and yellow vegetables, other types of carotenoids, such as alpha-carotene, may also contribute to anticarcinogenic action, since these carotenoids usually coexist with beta-carotene and are detectable in human blood and tissues. In this study, we compared the inhibitory effect of natural alpha-carotene, obtained from palm oil, with that of beta-carotene on spontaneous liver carcinogenesis in C3H/He male mice. The mean number of hepatomas per mouse was significantly decreased by alpha-carotene supplementation (per os administration in drinking water at a concentration of 0.05%, ad libitum) as compared with that in the control group (P < 0.001, Student's t test). On the other hand, beta-carotene, at the same dose as alpha-carotene, did not show any such significant difference from the control group. Furthermore, we also compared the antitumor-promoting activity of alpha-carotene with that of beta-carotene against two-stage mouse lung carcinogenesis (initiator, 4-nitroquinoline 1-oxide; promoter, glycerol). alpha-Carotene, but not beta-carotene, reduced the number of lung tumors per mouse to about 30% of that in the control group (P < 0.001, Student's t test). The higher potency of the antitumor-promoting action of alpha-carotene compared to beta-carotene was confirmed in other experimental systems; e.g., alpha-carotene was also found to have a stronger effect than beta-carotene in suppressing the promoting activity of 12-O-tetradecanoylphorbol-13-acetate on skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated mice. These results suggest that not only beta-carotene, but also other types of carotenoids, such as alpha-carotene, may play an important role in cancer prevention.

Topics: 4-Nitroquinoline-1-oxide; 9,10-Dimethyl-1,2-benzanthracene; Administration, Oral; Animals; beta Carotene; Carotenoids; Drug Screening Assays, Antitumor; Humans; Liver Neoplasms; Lung Neoplasms; Male; Mice; Mice, Inbred C3H; Ornithine Decarboxylase; Papilloma; Skin Neoplasms; Specific Pathogen-Free Organisms; Tetradecanoylphorbol Acetate