We examined the modifying effects of freeze-dried whole-leaf Aloe arborescens Miller var. natalensis Berger (Japanese name, Kidachi aloe; designated as 'ALOE') on 1,2-dimethylhydrazine (DMH)-induced colorectal tumorigenesis in mice. Female ICR mice (7-weeks old) were given a basal diet or a diet containing 1, 0.5 or 0.1% ALOE for 32 weeks. One week later, all mice were injected i.p. with DMH (20 mg/kg, once weekly for 10 weeks) or vehicle (1 mM EDTA solution, pH 6.5). At 32 weeks, animals were killed by exsanguination, and the colorectums were processed for histological examination. The administration of ALOE (1, 0.5 or 0.1% in diet) did not induce diarrhea or reduction of body weight. In mice given DMH and 1% ALOE (Group 2), the incidence and multiplicity of colorectal adenomatous hyperplasias were significantly decreased as compared with mice given DMH alone (Group 1) (both p < 0.05), whereas the incidence and multiplicity of tumors (adenoma and adenocarcinoma) in Group 2 tended to be lower than those in Group 1. In addition, the incidence and multiplicity of the colorectal proliferative lesions (the total of adenomatous hyperplasias, adenomas and adenocarcinomas in mouse colorectum) in Group 2 were significantly decreased as compared with Group 1 (both p < 0.01). No colorectal proliferative lesions were found in animals that did not receive DMH. These results indicated that ALOE reduces the incidence and multiplicity of DMH-induced colorectal proliferative lesions, especially adenomatous hyperplasia, in mice.
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