Regression of experimental oral carcinomas by local injection of β‐carotene and canthaxanthin

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Regression of 7,12-dimethylbenz[a]anthracene (DMBA)-induced epidermoid carcinomas of hamster buccal pouch was accomplished by local injections of beta-carotene and canthaxanthin. One-hundred male hamsters (2-3 months old) were divided into five groups of 20 animals. All animals had the right buccal pouches painted three times weekly for 14 weeks with a 0.5% solution of DMBA in mineral oil, at which time all animals exhibited gross tumors of variable size and number. Group 1 animals were then injected locally into the right buccal pouch twice weekly for 4 weeks with 250 micrograms-carotene in 0.1 ml minimal essential medium (MEM) per injection. Group 2 animals were similarly injected with 250 micrograms canthaxanthin in 0.1 ml MEM. Group 3 animals were similarly injected with 250 micrograms 13-cis-retinoic acid in 0.1 ml MEM. Group 4 animals were injected only with MEM; Group 5 animals were untreated controls. Animals were killed in a carbon dioxide chamber, and buccal pouches were photographed. Tumors were counted and measured. Tumor burden in each group was compared, and statistical significance between groups was recorded. beta-Carotene was more effective than canthaxanthin in tumor regression. 13-cis-Retinoic acid had no effect in this system.