Watermelon powder supplementation reduces colonic cell proliferation and aberrant crypt foci by upregulating p21Waf1/Cip1 expression

Abstract

• Watermelon supplementation inhibited colonic aberrant crypt foci (ACF) formation. • The inhibition of ACF exhibited in the proximal, middle and distal regions of colon. • Watermelon supplementation lowered colonic cell proliferation. • The decreased proliferation may related to downregulation of p21 Waf1/Cip1 expression. The objective of this study was to examine the effects of watermelon powder supplementation on colonic cell proliferation, aberrant crypt foci, and gene expression of cell cycle regulators. Thirty-two rats were randomly assigned to one of the following isocaloric diets: 0.5% watermelon powder, 0.36% l -arginine, and control for 9 weeks. All animals were injected with azoxymethane (15 mg/kg body weight s.c.). Both watermelon powder and l -arginine groups exhibited lower numbers of aberrant crypt foci (ACF) in all proximal, middle, and distal regions of the colon (P < 0.01). Both groups also showed lower proliferation index and proliferative zone (P < 0.05). In addition, watermelon powder and l -arginine supplementation upregulated p21 Waf1/Cip1 gene expression (P = 0.048). These results suggest that watermelon or l -arginine supplementation may decrease the risk of colorectal cancer as they reduced proliferation by upregulating a cyclin-dependent kinase inhibitor and inhibited ACF formation in all anatomical regions of the colon.