GI Cancer Chemoprevention Potential

ANIMAL STUDIES

ScFOS: Animal studies using dietary fiber in chemically induced colon carcinogenesis have provided conflicting results and for the most part may reflect the amount and type of dietary fiber used in the studies. One study (1) demonstrating such a difference in dietary fiber was conducted in Min mice – a genetically relevant animal model mimicking human intestinal carcinogenesis and used extensively in chemoprevention studies. These animals develop more than 50 tumors throughout the entire intestinal tract until they die of bowel obstruction and intestinal bleeding at 150 to 170 days of age.

Study diets consisted of a control (CD) containing low fiber cellulose, and three high fiber diets: retrograded high amylose corn starch (RS); wheat bran treated to remove entrapped starch (WB), and scFOS. Due to short animal life spans, diets were administered over a 42-day period only, animals sacrificed and small intestines and colons removed surgically for microscopic examination.

The results showed a significant reduction (P < 0.01) in colon tumors in mice receiving the scFOS-supplemented diet versus other treatments. Of special interest is the fact that four animals out of 10 in this group were totally free of colon tumors versus zero for the other three diets. A second major finding was that none of the diets, including scFOS, had any effect on the occurrences of small intestinal tumors.

EGCG: The same Min-mice model was used in experiments involving EGCG . In this study (2) different EGCG concentrations, and a single caffeine concentration representing that found in green tea, were introduced into the animal’s drinking water as a sole source of drinking fluid for the duration of the study. Small intestines and colons were removed after animal sacrifices and microscopically examined for tumor incidences. Significant reductions (37 & 47%) in small intestinal tumor formation were found for EGCG drinking fluid concentrations of 0.08 and 0.16% respectively, but caffeine had no inhibitory activity against intestinal tumorigenesisi. The incidences of colon tumors were similar for all treatments, including controls.

HUMAN STUDY:

GREEN TEA – CHRONIC GASTRITIS & STOMACH CANCER: The protective effect of drinking green tea against chronic gastritis and stomach cancer was conducted in Yangzhong City, an island in southeast China with one of the highest rates of alimentary cancer in the world. The study (3) was a collaborative one involving American-Chinese researchers associated with UCLA, Columbia University, Sloan-Kettering Cancer Center, Shanghai Medical University and University of Massachusetts Cancer Center.

Eligible cases of the two disease groups were selected with pathologically confirmed diagnoses. In addition, healthy and cancer-free eligible controls were selected from the same region. Demographic variables consisted of age, gender, education, BMI (kg/m2), smokers, pack-years of smoking and alcohol drinkers. Further breakdown included green tea drinking, number of cups per week, tea drinking history in years and non-tea drinkers.

The authors found that green tea drinkers had a 48% reduced risk of stomach cancer than non-tea drinkers. This risk was further reduced with increasing frequency and duration of drinking tea. Similarly, green tea drinkers had a 51% lower risk of chronic gastritis than non-drinkers, and again a decreased risk with frequency and duration of drinking tea.

 

[1] Pierre F et al (1997) Short chain fructooligosaccharides reduce the occurrence of colon tumors and develop gut-associated lymphoid tissue in Min mice. Cancer Research 57:225-228.

[2] Ju J et al (2005) Inhibition of intestinal tumorigenesis in Apcmin/+ Mice by epigallocatechin-3-gallate, the major catechin in green tea. Cancer Research 65(22):10623-10631.

[3] Setiawan VW et al (2001) Protective effect of green tea on the risks of chronic gastritis and stomach cancer. International Journal of Cancer 92:600-604.