Inhibition of intestinal tumorigenesis in Apc^Min/+ mice by a combination of (-)-epigallocatechin-3-gallate (EGCG) with fish oil or calcium

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In the present study, we sought to determine the effect of a combination of EGCG with fish oil or adequate calcium on tumorigenesis in Apc^Min/+ mice, a widely used model for chemoprevention that spontaneously develops small intestinal tumors due to truncation of the Adenomatous Polyposis Coli gene. The control “basic” diet was a high-fat, low calcium diet, formulated to mimic the average American diet, consisting of 20% mixed lipid and 1.4 mg calcium/g diet.The combination of 0.32% EGCG with adequate calcium (5.2 mg/g diet) for 8 weeks significantly reduced total tumor intestinal multiplicity (58%, p<0.05) in comparison to control mice. EGCG alone also inhibited total tumor multiplicity (47%, p<0.05), but the degree of inhibition was less than the combination group. The number of large and medium-sized tumors in the combination EGCG and calcium group was reduced by >50% (p<0.05), whereas EGCG alone had no effect on tumor size. Combination of 0.16% EGCG with 12% fish oil (which displaced 12% of the mixed lipid in the basic diet) reduced total tumor number by >50% (p<0.01) as compared to control, whereas EGCG alone had no significant effect. The effect of the fish oil and EGCG combination yielded a similar trend on the number of large-sized tumors. Cell proliferation index (PI) in adenomas as measured by immunohistochemistry (IHC) for Ki-67 was significantly reduced (54% reduction from controls, p<0.005) by the combination EGCG and fish oil to a greater extent than either EGCG or fish oil alone (39% and 29% reduction from controls, respectively, p<0.05), Nuclear expression of β-catenin in adenomas from the EGCG and fish oil combination group was 67% lower (p<0.0005) than seen in controls. This was a greater reduction than what was observed in the EGCG group (58% reduction from controls, p<0.005), implicating modulation of the Wnt pathway as a potential mechanism of inhibition of tumorigenesis by EGCG and fish oil. These data suggest that EGCG in combination with both calcium or fish oil can inhibit tumor multiplicity in Apc^Min/+ mice to a greater extent than EGCG alone (Supported by NIH Grant CA88961).