Potent Cancer Chemopreventive Activity of α-Carotene Against Carcinogenesis

Abstract

Although ß-carotene has been considered to be a key cancer-preventive agent, other types of carotenoid, such as (X-carotene, mayaIso contribute to anticarcinogenic action. These carotenoids usually coexist with ß-carotene in green and yellow vegetables and daily food stuffs and are detectable in human blood and tissues. We compared the antitumor-promoting activity of (X-carotene from palm fruit oil, with that of ß-carotene against two-stage mouse lung carcinogenesis (initiator was 4-nitroquinoline-1-oxide; promoter was glyc-erol). The mean number oflung tumors per mouse was signifi-cantly decreased by (X-carotene supplementation (per os administration in drinking water at a concentration of 0.05% ad libitum) compared with that in the control group (P < 0.001, Student's t-test). ß-Carotene, at the same dose as (X-carotene, did not show any significant difference from the control group. The higher potency of the antitumor-promoting action of (X-carotene compared to that of ß-carotene was confirmed in other experimental systems; for example, (X-carotene was also found to have astronger effect than ß-carotene in sup-pressing the promoting activity of 12-0-tetradecanoyl phorbol-13-acetate on skin carcinogenesis in 7,12-dimethylbenz(a)anthracene-initiated mice. We further com-pared the inhibitory effect of (X-carotene with that of ß-carotene on spontaneous liver carcinogenesis in C3H/He male mice. (X-Carotene, but not ß-carotene, reduced the num-ber ofhepatomas per mouse significantly (P < 0.001, Student's t-test). These results suggest that not only ß-carotene, but other types of carotenoids as well, such as (X-carotene, may play an important role in cancer prevention.