Quantification of PCNA staining showed 65.5% (p<0.001), 62.2% (p<0.001), 65.1% (p<0.001) and 67.0% (p<0.001) reduction in proximal, middle, distal portions of small intestine and colon polyps by Riccardin D. Quantitative data showed that Riccardin D treatment resulted in increases of TUNEL-positive cells in intestinal polyps by 51.9% (p<0.001) in proximal, 57.9% (p<0.001) in middle, and 48.2% (p<0.001) in distal portions of small intestine and 54.1% (p<0.001) in polyps of colon (Fig. 5B). This evidence concerns the gene PCNA and digestive system cancer.