Chemopreventive Effects of Magnesium Hydroxide on Colon Carcinogenesis

Abstract

The suppression by magnesium hydroxide (Mg(OH)2) of rat colon carcinogenesis was examined in two different experiments. The modification by Mg(OH)2 of cell proliferation in the colon mucosa was also analyzed. Mg(OH)2 reduced the number of colon tumors induced by methy-lazoxymethanol (MAM) acetate or 1,2-dimethylhydrazine. In both experiments, the relationship between the dose of Mg(OH)2 and the tumor-suppressing effect was not strong. Mg(OH)2 suppressed MAM-acetate-induced 5-bromo-2’-deoxyuridine (BrdU) labeling in colon mucosa. The decrease in BrdU labeling indices was more prominent in the proximal segment than in the distal segment. A clear relationship between the dose of Mg(OH)2 and the BrdU labeling index was not found. Mg(OH)2 suppressed the MAM-acetate-induced expression of the c-myc proto-oncogene, and also reduced the increased proliferating cell nuclear antigen (PCNA) labeling induced by carcinogen in colon mucosa, in the same way as with BrdU labeling. The elevation in the BrdU labeling index induced by cholic acid was also suppressed by Mg(OH)2 or by calcium lactate. The inhibitory effect on cell proliferation by Mg(OH)2 may be related to the suppressive action of magnesium on carcinogen-induced colon carcinogenesis. Mg(OH)2 could be a promising chemopreventive agent for human colon neoplasia.