Ps. Carlton et al., Inhibition of N-nitrosomethylbenzylamine-induced tumorigenesis in the rat esophagus by dietary freeze-dried strawberries, CARCINOGENE, 22(3), 2001, pp. 441-446
In the present study, we examined the ability of dietary freeze-dried straw
berries to inhibit N-nitrosomethylbenzyl-amine (NMBA)-induced tumorigenesis
in the rat esophagus, Initially, we conducted a bioassay to determine the
effects of dietary freeze-dried strawberries on esophageal tumor developmen
t. Two weeks prior to NR IBA treatment, animals were placed on a control di
et or diets containing 5 and 10% freeze-dried strawberries. NMBA treatment
was once per week for 15 weeks. At 30 weeks, 5 and 10% freeze-dried strawbe
rries in the diet caused significant reductions in esophageal tumor multipl
icity of 24 and 56%, respectively. Based on these results, we conducted stu
dies to determine potential mechanisms by which freeze-dried strawberries i
nhibit tumorigenesis, In a short-term bioassay, we evaluated the effects of
dietary freeze-dried strawberries on the formation of O-6-methylguanine in
the rat esophagus, Animals were placed on control diet or diets containing
5 and 10% freeze-dried strawberries for two weeks. At the end of this peri
od, animals received a single subcutaneous dose of NMBA and were killed 24
h later. A significant decrease in O-6-methylguanine levels was observed in
the esophageal DNA of animals fed strawberries, suggesting that one or mor
e components in strawberries influence the metabolism of NMBA to DNA-damagi
ng species. Finally, in order to evaluate post-initiation effects, we condu
cted a study where freeze-dried strawberries were administered in the diet
only following NMBA treatment. Animals were placed on control diet and dose
d with NMBA three times per week for 5 weeks. Immediately following NMBA tr
eatment, animals were placed on control diet or diets containing 5 and 10%
freeze-dried strawberries. At 25 weeks, 5 and 10% freeze-dried strawberries
in the diet significantly reduced tumor multiplicity by 38 and 31%, respec
tively. Our data suggest that dietary: freeze-dried strawberries effectivel
y inhibit NMBA-induced tumorigenesis in the rat esophagus.