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N Onogi

Publications and source records attributed to N Onogi.

6 recordsLinked to original sources
PubMed1998

Antiproliferative effect of carotenoids on human colon cancer cells without conversion to retinoic acid.

The present study employed two human colon cancer cell lines, DLD-1 and Colo 320DM, to investigate whether the provitamin A activity of carotenoids is necessary for their antitumor effect on colon cancer. Carotenoids, including alpha- and beta-carotene and canthaxanthin, significantly suppressed cell viability [measured by tetrazolium (MTT) assay], DNA synthesis (measured by [3H]thymidine uptake), and cell proliferation (measured by cell counting) and thus showed growth-inhibitory effects on both cancer cell lines. Because canthaxanthin does not have provitamin A activity, these results suggest that the carotenoid directly inhibited the cell growth. Moreover, the effective dose of retinoic acid, an active metabolite of vitamin A, was much higher than that of alpha- or beta-carotene. A retinoic acid-inducible gene, retinoic acid receptor-beta, was not enhanced in either type of cancer cell by treatment with alpha- or beta-carotene. Therefore, like canthaxanthin, alpha- and beta-carotene might also exert their tumor-suppressing effects without being converted to retinoids. These results suggest that a certain antitumor activity of carotenoids may not necessarily require their provitamin A activity.

Carotenoids↗
PubMed1996

Suppression of mouse skin papilloma by canthaxanthin and beta-carotene in vivo: possibility of the regression of tumorigenesis by carotenoids without conversion to retinoic acid.

Using mouse skin papilloma as a model system, we examined whether the antitumorigenic activity of carotenoids was related to their provitamin A activity. Oral administration of canthaxanthin (CX) or beta-carotene at 200 mg/kg/day for 14 days significantly reduced the cumulative size of papillomas induced on the skin by 9,10-dimethyl-1,2-benzanthracene (p < 0.05), after the accumulation of these carotenoids in the tumors. The levels of a protooncogene, c-myc, were simultaneously suppressed in papillomas in carotenoid-treated mice. Because CX cannot be converted metabolically to retinoids, these results suggested that CX directly inhibited the growth of papillomas. Neither the accumulation of retinoids nor the expression of a retinoic acid-inducible gene, retinoic acid receptor-beta, was found in papillomas of CX- and beta-carotene-treated mice, suggesting that, like CX, beta-carotene might exert the tumor-suppressing effect without being converted to retinoids. Thus a certain antitumorigenic activity of carotenoids appears not necessarily to require their provitamin A activity.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Suppressing effect of perilla oil on azoxymethane-induced foci of colonic aberrant crypts in rats.

We have investigated the modulatory effect of dietary perilla oil which is rich in the n-3 polyunsaturated fatty acid, alpha-linolenic acid, on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in male F344 rats. Animals were given three weekly subcutaneous injections of AOM (15 mg/kg body weight) to induce ACE. The rats were fed a basal diet containing either 12% olive oil, 12% safflower oil, 12% perilla oil, 6% perilla oil plus 6% olive oil, or 3% perilla oil plus 9% olive oil for 5 weeks, starting 1 week before the first dosing of AOM. All rats were sacrificed 2 weeks after the last AOM injection. The amount of food consumed and body weight gain were identical among every dietary group. The frequency of ACF was significantly lower in the rats fed 12% perilla oil than in those fed 12% olive oil or 12% safflower oil (P < 0.01 and P < 0.05, respectively). The suppressive effect of perilla oil was dose-dependent, as the number of ACF was 20.7, 40.7 and 47.4% of those of the 12% olive oil-fed controls in rats fed 12% perilla oil, 6% perilla oil plus 6% olive oil and 3% perilla oil plus 9% olive oil, respectively. Perilla oil significantly reduced ras expression as well as the AgNORs count (cell proliferation biomarkers) in the colonic mucosa, as compared with olive oil or safflower oil (P < 0.01, respectively). Marked increases in n-3 polyunsaturated fatty acids in membrane phospholipid fractions and decreased PGE2 levels were observed in colonic mucosa of perilla oil-fed rats. These results suggest that perilla oil, even in small amounts, suppresses the development of aberrant crypt foci, and is therefore a possible preventive agent in the early stage of colon carcinogenesis.

Animals↗
PubMed1996

Synergistic suppression of azoxymethane-induced foci of colonic aberrant crypts by the combination of beta-carotene and perilla oil in rats.

The modulating effect of the combined dietary feeding of beta-carotene and perilla oil, which is rich in alpha-linolenic acid, on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) was investigated in male F344 rats. Rats received oral administration of beta-carotene (0, 50 or 200 mg/kg body weight/day) and fed a basal diet containing either 12% olive oil, 3% perilla oil plus 9% olive oil, or 12% perilla oil. A dose-dependent suppressive effect of perilla oil was found. The numbers of ACF were 42.0 and 18.4% of those of the 12% olive oil-fed controls in the rats fed 3% perilla oil plus 9% olive oil and 12% perilla oil, respectively. The development of ACF was also reduced significantly by the addition of dietary beta-carotene in each of the oil-fed groups (P < 0.05, respectively). The suppression by the combination of beta-carotene and perilla oil was synergistic, as the numbers of ACF were 12.9 and 8.9% of those of the 12% olive oil-fed controls in beta-carotene-treated rats fed 3% perilla oil plus 9% olive oil and 12% perilla oil, respectively. beta-carotene plus perilla oil also suppressed the numbers of silver-stained nucleolar organizer regions and the expression of ras mRNA in the colonic mucosa (cell proliferation biomarkers). Following administration of beta-carotene, a significant increase in the concentration of intact beta-carotene molecules was found in the colonic mucosa, livers, and sera. However, no accumulation of retinoids was observed in the colonic mucosa, suggesting that the inhibitory effect may not be related to the provitamin A activity. These results suggest that the combination of beta-carotene and perilla oil may be useful in the prevention of colon cancer.

Administration, Oral↗
PubMed1995

[Carotenoids].

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Adult↗