The nonsteroidal antiinflammatory
drug sulindac displays chemopreventive activity in patients with
familial adenomatous polyposis (FAP).
Sulindac metabolites induce apoptosis in colon
tumor cells, in part, by a
polyamine-dependent mechanism that can be suppressed with exogenous
putrescine. To determine the relevance of this mechanism in animals, we treated Apc(Min/+) mice, a model of human FAP, with
sulindac alone or in combination with dietary
putrescine.
Sulindac increased steady-state
RNA levels and enzymatic activity of the
polyamine catabolic
enzyme spermidine/spermine N(1)-acetyltransferase and intestinal levels of monoacetylspermidine,
spermidine, and
spermine in the small intestine of mice.
Sulindac also decreased the activity of the biosynthetic
enzyme ornithine decarboxylase but not
adenosylmethionine decarboxylase (AMD). Dietary
putrescine increased intestinal
putrescine contents, whereas the combination of dietary
putrescine and
sulindac yielded the highest levels of intestinal
putrescine and correlated with a statistically significant reduction in AMD
enzyme activity. Dietary
putrescine did not statistically significantly increase
tumorigenesis, although it significantly increased the grade of
adenoma dysplasia (P < 0.05). The effectiveness of
sulindac to suppress intestinal
carcinogenesis was partially abrogated by dietary
putrescine. These data suggest that
sulindac exerts at least some of its
anticarcinogenic effects in mice via a
polyamine-dependent mechanism. Because high concentrations of
putrescine can be found in certain dietary components, it may be advantageous to restrict dietary
putrescine consumption in patients undergoing treatment with
sulindac.